[iv] ACKNOWLEDGEMENT I am highly grateful to Fadi Nader, promoter, IFP Energies nouvelles, Rueil (Fance) for his generous guidance throughout the present studies and for his critical review of the thesis. I also appreciated his approach in providing every help, which was necessary for the present study.

Special thanks are due to Daniel Garcia of the Ecole des Mines, Saint Etienne who was my Thesis supervisor. I am highly acknowledged to him for giving me the chance to carry out this research project, and his helpful suggestions. I am also grateful to Rudy Swennen Katholieke Universiteit Leuven (Belgium), my cosupervisor for his precious time, which he spared for me from his busy schedule. His contagious enthusiasm, useful advice and frequent critics were of inestimable help for me, especially during the write up stage of my manuscript. To Brigitte Doligez of the IFP Energies Nouvelles, Rueil (France) for constantly pushing me towards the end of the manuscript in the absence of my promoter. Her interest and help during the final moments of my thesis helped in finishing it during the allocated time.

To Christophe Renac of the University of Jean Monnet, Saint Etienne (France) who helped me with the analyses and interpretation of the isotope geochemistry during my stay in Saint Etienne. I am grateful to Marta Gasparrini, IFP Energies nouvelles, Rueil (France) for fruitful discussions in the office as well as during the fieldwork. To Michael Joachimski of the University of Erlangen (Germany) and for measuring the stable isotopes of my carbonates. Thanks are due to Rob Ellam of Scottish Universities Environmental Research Centre (United Kingdom) for radiogenic isotope analyses. To Herman Nijs (Geology, K. U. Leuven) and Chantal Perrache (Geology, University of Jean Monnet, Saint Etienne) for the preparation of thin-sections for petrographic studies and double-polished wafers for fluid inclusion analyses.

To all of my colleagues in IFP Energies nouvelles for the friendly working environment and above all to Gilberto Albertao for his availability in solving most of my everyday life problems. To Hamon Youri, Julian Schmitz, Yannick Sentarre, Fakher Maktouf, Pierre Weill, and Ali Piriyai: this work would have never been finished without their psychological (psychiatric?) support and practical help. I am in depth grateful to Reine Garcia (wife of Daniel Garcia) for her hospitality during the two month stay in Saint Etienne, which is unforgettable. To my wife Maryam whose affection and comprehension during this study period gave a deeper sense to my stay in France and encouraged me to go through the worst moments. Special affection to my daughter Hooriya, whose arrival during the last stage of my work made me joyful in the tense period. Last but not least, to my parents and my brothers, who are patiently waiting for me back home.

[v]

EXTENDED ABSTRACT

This study documents the temporal and lateral variation in petrographic and geochemical signatures of fault-related dolomite bodies in the Ranero and El-Moro areas (Karrantza valley, Cantabrian mountains; NW Spain). The aim of this work is to reconstruct the main episodes of late diagenesis in the Albian carbonates and to define the causes of the dolomitisation as well as the origin of the dolomitising fluids. The research project also looked at the impact of such hydrothermal dolomitization and associated diagenesis on reservoir properties. The studied area is part of Basque Cantabrian Basin, which underwent three phases of rifting and two periods of fault-controlled regional subsidence. The last phase of early Cretaceous rifting created or reactivated major faults and fractures in NW-SE, E-W and NE-SW directions, where late Cretaceous fault-controlled regional subsidence resulted in deposition of lower Aptian-upper Albian platform rudist limestone, basinal marls and mudstone, and upper Albian-lower Cenomanian fluvial siliciclastics to turbidites. The NW-SE trending Pozalagua fault and other faults/fractures, related to early Cretaceous (early Albian) rifting, appear to have been (re)activated through sinistral strike-slip motion. These and similar faults have been selectively associated with hydrothermal activity during late Albian to Turonian times. The presence of linear (fracture-filled) dolomite bodies supports the idea that the dolomitising fluids migrated and spread through the sedimentary pile along such vertical discontinuities.

Petrography, mineralogical and geochemical systematics (XRD, ICP, XRF, stable and Sr isotopes) along sections cutting the dolostone bodies document successive hydrothermal stages, which resulted in two contrasting dolomite and calcite formations. Four phases of calcite pre-and post-date dolomitization event, where initial phase of calcite precipitation (CC-I & CC-II) restricted to infilling of paleo-karsts in the host limestone and predate dolomitisation. Early dolomites are ferroan, locally associated with MVT mineralisation, 18 O depleted (-14 to -10‰ V-PDB) and locally replace limestone producing abundant zebra lithotypes. Later dolomites are non-ferroan, severely 18 O depleted (-19 to -15‰ V-PDB), and do not replace limestones but rather previous dolomites as observed in the field, where nonferroan dolomite restricted to veins in host limestone but these veins appeared as expanded bodies in the precursor, ferroan dolomite. Dolomites are generally stoichiometric (49.76 to 51.59 M% CaCO 3 ). The dolomitisation events are believed to have occurred during the late Albian, as they are pre-and post-dated by bed-parallel stylolites. Post-dolomite white calcite (WC) shows highly depleted δ 18 O values (-20 to -16‰ V-PDB) that may indicate increase in temperature during precipitation and/or recrystallization. Sr isotope analyses indicate that the [vi] calcite and dolomite phases contain radiogenic signatures, probably derived from fluids that interacted with siliciclastic sediments (invoking the flow of the hydrothermal fluids through siliciclastics).

Fluid inclusions analyses of primary inclusions show high homogenization temperatures (120 -200°C) and salinities (12 -21 eq. wt% NaCl). The estimated salinity of the primary inclusions of these dolomite phases, which are up to six times higher than the average seawater salinity and their high homogenization temperature (reaching 200°C) may provide a possible explanation for the depleted δ 18 O values. Integration of fluid inclusion data with isotope and geochemical analyses show that these dolomites formed at temperatures higher than the ambient temperature, hence hydrothermal in origin.

The first episode of pervasive ferroan dolomitisation probably resulted from compactional dewatering of basinal fluids from the nearby Basque trough and hydrodynamic fluid flow along the NW-SE and NE-SW trending faults and fractures in the Albian carbonate platform. These early fluids must have been Mg-and Fe-rich and slightly acidic (limestonereplacive). The second episode of very hot and localized dolomitisation may be related to a thermal anomaly and/or convective flow of Fe-poor fluids. Such high temperature fluids could be related to igneous activity and convective flow induced by the high temperature magmatic activity and associated with flexuring in the Aptian-Albian limestone due to the presence of diapiric structures in the area and their coeval deformation.

The dolomite fabric and its petrophysical properties are variably altered through cataclastic deformation and late (meteoric) dedolomitisation. Dissolution during dolomitization and precipitation of dolomite cement are considered responsible for positive or negative effects on porosity development, respectively. The initial phase of dolomitisation (CCD-I) exhibited a wide porosity range (1.6 to 7.0%) and permeability values (0.3 to 1.23mD), while average porosity of zebra dolomite (ZD) and dolomite sand (DS) ranges up to 3.7%. The present study revealed that selective dissolution and dedolomitization in CCD-I resulted in the enhancement of porosity (6.0 to 6.6%) but not the permeability values (0.12 to 0.22mD). It is also observed that those CCD-II dolomite that showed considerably high porosity (8.28 to 11.6%) and permeability values (0.9 to 1.64mD), were related to postdolomite brecciation. Post-dolomite calcite (WC) mostly occurred as pore-fillings and occludes the intercrystalline porosity. To conclude, the porosity enhancement is mostly related to post-dolomite alterations, which considerably increase the reservoir character of these dolomite phases.

[vii]

LIST OF FIGURES AND TABLES

INTRODUCTION

Dolomites are Mg-rich carbonate minerals CaMg(CO 3 ) 2 , with variation in Ca/Mg compositions and trace elements such as Fe (Land, 1985). They are formed by Ca-replacement with Mg within the calcite mineral lattice CaCO 3 (Fig. 1.1A). This ionic replacement also affects the mineral volume and crystalline form of the produced dolomite. Mineral volume reduces due to replacement of limestone by dolomite, which increases porosity [START_REF] Weyl | Porosity through dolomitization: Conservation of mass requirements[END_REF]. Dolomite crystal form (rhombic) enables their rock texture to withstand compaction during burial with lesser effect on the intercrystalline pore spaces (Fig. 1.1B). These factors distinguish dolostone from limestone with respect to the rates of porosity variation with burial and molar volume, making them often good hydrocarbon reservoir (Fig. 1.1;[START_REF] Murray | Origin of porosity in carbonate rocks[END_REF].

(A) (B)

Fig. 1.1(A). Dolomite mineral formation and effect of mineral volume on porosity as porosity increases with the decrease in mineral volume. (B) Rate of change of porosity in limestone and dolostone with respect to depth. Note that a sudden decrease in porosity with increase in depth in limestone, while dolostone porosity remains rather constant (modified from [START_REF] Weyl | Porosity through dolomitization: Conservation of mass requirements[END_REF][START_REF] Murray | Origin of porosity in carbonate rocks[END_REF].

The "hydrothermal" origin for dolomite is controversial, since the term "hydrothermal" has at least three partially contradictory definitions [START_REF] Machel | Hydrothermal dolomite-a product of poor definition and imagination[END_REF]. These workers recommend the generalized and most acceptable definition proposed by (White, 1957), who related the term "hydrothermal" to "aqueous solutions that are warm or hot relative to the surrounding environment". This implies that a dolomite should be called "hydrothermal" only if it can be demonstrated to have formed at higher temperatures compared to the surrounding rocks at the time of dolomitisation, regardless of the absolute temperature of origin [START_REF] Machel | Chemistry and environments of dolomitization: a reappraisal[END_REF][START_REF] Machel | Hydrothermal dolomite-a product of poor definition and imagination[END_REF]. Davies (2006) defined hydrothermal dolomitization as "dolomitization under shallow burial depths (less than 500m) by saline water at temperature and pressure greater than the ambient temperature and pressure of the host limestone, emplaces under conditions of shear stress and abrupt pressure transients resulting in hydrofracturing, preferentially along or peripheral to extensional or transtensional (strike-slip) faults". Facies and pre-dolomitization diagenesis of the host limestone are key elements in stratal flow of the dolomitizing brine, dolomite textural type, pore types and pore volume. [START_REF] Smith | Hy dro ther mal al te ra tion of car bo nate re ser voirs: How com mon is it?[END_REF] also described that hydrothermal dolomitization occurs when hot (75-250˚C) Mg-rich brines flow up along active faults, hit sealing shales, evaporites or other low permeability strata and flow laterally in to permeable carbonates that are typically less than 1km from the surface. This distinguishes it from "deep burial" or "geothermal" dolomitization. Thermal convection flow model is driven by buoyancy [START_REF] Wilson | Spatial patterns of diagenesis during geothermal circulation in carbonate plateforms[END_REF], which explains that the water rises upon heating and sinks upon cooling. A heat source, such as geothermal gradient is necessary to generate onset of convection cells. [START_REF] Smith | Hy dro ther mal al te ra tion of car bo nate re ser voirs: How com mon is it?[END_REF] proposed that hydrothermal dolomitization must involve some sort of episodic convection. According to him, fluids flow up within the rock through active faults and alter the formation and then recycled back down through inactive faults and fractures. This whole process is not a slow, steady convection cycle, but an episodic convection driven by fault movement. Thermal convection flow models are also accomplished by [START_REF] Machel | General constraints on extensive pervasive dolomitizationand their application to the Devonian carbonates of western Canada[END_REF] in Devonian carbonate rocks of western Canada and Gasparrini et al., (2006) in SW Cantabrian zone, Spain. Thermal convection may account for more efficient dolomitization than other mechanisms because the Mg-rich fluids can be recycled many times through the precursor carbonates [START_REF] Wilson | Spatial patterns of diagenesis during geothermal circulation in carbonate plateforms[END_REF].

Fault-related dolomites are of interest in the fact that they include about 50% of the known carbonate oil and gas reservoirs (80% in North America; [START_REF] Zenger | Concepts and models of dolomitization[END_REF]. The world's largest oil field (Ghawar, Saudi Arabia) containing one-eighth of the world's proven reserves, taps the Khuff reserve, which made up of Permian shallow shelf limestones and dolostones (Cantrell et al., 2004).

In general, there are two major factors which made interest in fault-related. These include: (i) Recent integrated studies suggest that hydrothermal dolomite exists in many forms and are likely to be far more common than previously thought (Berger and Davies, 1999;Cantrell et al., 2004;Nader et al., 2004;Davies and Smith., 2006;Nader et al., 2007;López-Horgue et al., 2010;Conliffe et al., 2010;[START_REF] Ronchi | Multistage dolomitization and distribution of dolomitized bodies in Early Jurassic carbonate platforms (Southern Alps, Italy)[END_REF], and ( ii) some of the known oil and gas carbonate reservoirs consists of porous dolomites that are believed to have been affected by hydrothermal fluids -whether genetically or diagenetically (e.g. North field, Arabian Gulf; Sudrie et al., 2006). Besides this, most of the reservoirs in the Appalachian and Michigan basins of North America consisted of hydrothermal dolomites (Keith, 1989).

Together with calcite and aragonite, dolomite constitutes the main carbonate rock forming minerals. Large volumes of replacement dolostone have been documented worldwide, while dolomite as cement is less frequent. Dolomitization is mainly a process of replacement (dissolutionprecipitation; [START_REF] Lucia | Carbonate reservoir characterization[END_REF], in which significant fluid flow is generally considered to be an essential requirement. This is controlled by the permeability of the host-rock, the quantity and chemical signature of dolomitizing fluids, and the hydraulic gradient. Eventually, the position and geometry of almost any dolostone body are the result of the coeval hydrogeological setting (e.g. Wilson et al., 1990;Warren, 2000). In addition, time during which all the variables have to be tuned positively for dolomitization, remains an essential and critical factor. Dolomitization does not always produce higher rock porosity [START_REF] Lucia | Porosity evolution through hypersaline reflux dolomitization[END_REF]. It is the permeability enhancement through the redistribution of porosities due to dissolution-precipitation during dolomitization that makes the importance of these rocks with regard to reservoir capacities [START_REF] Lucia | Carbonate reservoir characterization[END_REF]; especially when this occurs in early diagenesis (i.e. before burial). Dolostones are also associated with the Mississipi

Valley Type (MVT) mineralization (e.g. Warren, 2000 andDavies, 2006), providing incentive for learning more about dolomitization.

Several previous studies of hydrothermal dolomite fronts focused on the analysis of their geometry to explain the dolomitization fluid flow (Davies & Smith, 2006, Wilson et al. 1990), sometimes in parallel, illustrating the diagenetic facies heterogeneity (e.g., [START_REF] Braithwaite | The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland[END_REF]Nader et al., 2007). The topic of my PhD addresses the classic sedimentology and diagenetic studies of the fault-related dolomite bodies and early Albian host limestone, which occur in the Basque-Cantabrian inverted basin. In order to understand the processes controlling the formation of these dolomites (evolution of dolomitizing fluids), I will provide original descriptive informations regarding the depositional/diagenetic aspects, geochemical characteristics, porosity/permeability analyses and fluid inclusion studies. Although various workers (Lopéz-Horgue et al., 2010;Rosales and Pérez-Garcia, 2010) carried out a sedimentological analysis of the host limestone and dolomite bodies, they did not report detailed investigations regarding the diagenetic history related to faultrelated dolomite bodies and nature and origin of dolomitizing fluids. Besides this, it was believed that hydrothermal reservoirs are homogeneous but bore hole studies revealed very complex heterogeneities (i.e., various dolomite phases with different porosity and permeability values). In order to overcome these problematic issues, i performed following scheme of studies.

The objective of this thesis is indeed to characterise, define and model dimensions and distributions of hydrothermal dolomite bodies. In order to better understand the genesis of the dolomite bodies, it is important to know the possible source of dolomitizing fluids. Besides this, the present studies focussed on the controlling factors for their extension and porosity/permeability modifications. To conclude, i will propose a comprehensive conceptual model to explain the timing and mode of formation of these dolomite bodies.

In order to achieve the above stated objectives, field investigations (mapping, logging and sampling) of quality exposures of hydrothermal dolomite fronts were carried out in the study area.

Conventional, cathodoluminescence, fluorescence and scanning electron microscope techniques were used in order to achieve the petrographic characterization of the various dolomite phases.

Major and trace element composition of the whole rocks and dolomite phases was achieved through XRF, ICP-AES and micro-probe analyses. Stable oxygen and carbon isotope and radiogenic Sr isotope analyses helped in defining the geochemical signatures of the dolomite phases and related fluids. The study of dolomite stoichiometry and crystal ordering was carried out by means of X-ray diffraction technique. Finally, fluid inclusions analyses were performed in order to constrain the temperature and nature of the dolomitising fluids. Meanwhile porosity and permeability analyses were also performed.

The study area is located at the boundary of Basque country and the province of Cantabria in the north-western part of Spain. It is easily accessible as it is about 15 km from the town of Laredo (situated on main highway), tourist site between Bilbao and Santander. The studied sites occur in the Karrantza valley near the Ranero village and the town of Ramales (Fig. 1.2). The two studied sites were selected in order to understand the variations in the distribution and/or dimensions of dolomite bodies, dolomite phases and associated mineralization. Spatial distribution (vertical and lateral) indicate that the two studied sites do not occur at the same stratigraphic level, hence vertical variations of various dolomite phases may be observed in these studied sections.

In the study area, the presence of excellent outcrops of large hydrothermal dolomite allows a detailed multidisciplinary study of an outcrop analogue of this type of hydrocarbon reservoir rocks.

In the Aptian and Albian rock units of the Ramales Carbonate Platform several dolomite bodies related to faults and fractures originated in a time of intense synsedimentary tectonic activity during the mid-Cretaceous (López-Horgue et al., 2010). The dolomites in the study area can be considered as the best outcrop analogues of hydrothermal dolomites. They can serve to better understand the controlling factors on hydrothermal dolomitisation, the morphology of dolomite lithosomes and porosity/permeability variations (e.g., [START_REF] López-Horgue | Fault-related hydrothermal dolomite bodies in early Cretaceous platform carbonates, Karrantza area (North Spain): outcrop analogs for dolomite reservoir characterization[END_REF]& 2010;[START_REF] Caline | Fault-related hydrothermal dolomites of Cretaceous platform carbonatesoutcropping in the Karrantza area (North Spain): lessons learned for a better characterisation of subsurface dolomite reservoirs[END_REF]Sudrie et al., 2006;[START_REF] Schröder | Characterization of fault-related dolomites bodies from outcrop analogs: application to carbonate reservoirs[END_REF], which are all matters of prime interest in oil and mineral resources exploration and production.

The present manuscript consists of six chapters, which include this introductory chapter. The second chapter consists of brief description of various methodologies adopted in the field as well as in the laboratory. In the third chapter, regional tectonic evolution of the Basque-Cantabrian basin with special emphasis to the study is discussed. Besides this, the stratigraphic succession in relation with fault-related dolomite bodies is also described in detail. Chapter four contains the detailed description of field observations, petrographic and geochemical investigations, isotopic studies, fluid inclusion studies and porosity/permeability analyses of the Ranero and El-Moro areas. Chapter five deals with the interpretation and discussion of the data described in chapter four. This chapter also contains the two research articles (Shah et al., 2010 and Shah et al., in press). Ultimately, chapter six consists of conclusions and recommendations of the present studies. Besides the above stated six chapters, five annexes are attached containing bibliography, two research articles, geochemistry data and porosity/permeability data of the study areas. Chapter: 2

GEOLOGICAL SETTINGS

GEODYNAMIC EVOLUTION

Three main tectonic stages (from Upper Carboniferous to Recent) are identified in the Iberian peninsula. These include the Varsican orogeny (late Carboniferous), Mesozoic (Permianearly Cretaceous) rifting and Alpine orogeny (late Cretaceous to present). The Iberian peninsula comprises rocks ranging from Precambrian to Quaternary age. The Variscan orogeny is recorded in numerous Iberian massifs, i.e., from central, western and northern sectors of Iberia.

Mesozoic polyphase continental rifting (Middle Permian to Early Cretaceous) resulted in different fragments of Pangea supercontinent [START_REF] Jabaloy | Palaostress evolution of the Iberian Peninsula (Late Carboniferous to present day)[END_REF]. During this stage, the Iberian micro-plate was differentiated as an independent element surrounded by marine basins and separated from Europe, Africa and North America (Fig. 2.1). In-depth studies revealed that Early and Middle Jurassic rifting observed in the Iberian peninsula was followed by detachment of part of the Laurasia from Gondwana, resulting in the westward extension of the Tethys and creation of the south Iberian margin [START_REF] Jabaloy | Palaostress evolution of the Iberian Peninsula (Late Carboniferous to present day)[END_REF]. Oceanic crust was produced in the central Atlantic and between Iberia and Gondwana, where Maghrebian flysches were deposited [START_REF] Durand-Delga | Situation structurale et nature ophiolitique de roches basiques jurassiques associées aux flyschs maghrébins du Rif (Maroc) et de Sicile (Italie)[END_REF]. The Late Jurassic to Early Cretaceous rifting produced the separation of Iberia from North America and Europe, and was followed by the development of western and northern margins of Iberia.

Fig. 2.1. Tectonic reconstruction of the evolution of the Iberian peninsula during Early Cretaceous age. (modified from [START_REF] Jabaloy | Palaostress evolution of the Iberian Peninsula (Late Carboniferous to present day)[END_REF].

In the Basque-Cantabrian mountains, the first rifting stages are detected in the Kimmeridgian rocks [START_REF] Hernaiz | Evolución estructural del margen SO de la Cuenca Vasco -Cantábrica (in English: Structural Evolution of the SO margins of the Cretaceous Basque-Cantabrian Basin)[END_REF]Rat, 1988). At the end of the Aptian age, the rifting ended in the northern and western margins of the peninsula with the onset of seafloor spreading in the North Atlantic and Bay of Biscay [START_REF] Jabaloy | Palaostress evolution of the Iberian Peninsula (Late Carboniferous to present day)[END_REF]. The spreading began in the southern part of the margin and propagated northwards in the Atlantic and westwards into the Bay of Biscay (Boillot & Malod, 1988). This spreading process produced the counter clockwise rotation of Iberia [START_REF] Olivet | Cinématique des plaques et paléogéographie[END_REF][START_REF] Ziegler | Evolution of the Arthic-North Atlantic and the western Tethys[END_REF], accompanied by strike-slip faults in the Pyrenees [START_REF] Souquet | Evolución del margen noribérico en los Pirineos durante el Mesozóico[END_REF][START_REF] Ziegler | Evolution of the Arthic-North Atlantic and the western Tethys[END_REF].

Alpine orogeny resulted in the convergence among Europe, Iberia and Africa. In the Late Cretaceous, Africa started to collide with Europe, causing the progressive closure of the Tethys (Le-Pichon et al., 1988;[START_REF] Ziegler | Evolution of the Arthic-North Atlantic and the western Tethys[END_REF][START_REF] Dewey | Kinematics of the Western Mediterranean[END_REF]. The compressive deformations during Paleogene initiated with the collision between Iberia and Europe in the Pyrenees and the subduction of the oceanic crust in the Bay of Biscay beneath the northern Iberian margin [START_REF] Jabaloy | Palaostress evolution of the Iberian Peninsula (Late Carboniferous to present day)[END_REF].

Later the deformation propagated within the peninsula and resulted in the formation of the Catalan coastal Ranges, Basque Cantabrian ranges and Iberian chain. Afterwards, the collision occurred between Iberia and Africa during the Neogene that continues to the present day. In the present day, Iberia is docked to Europe in the Pyrenees and the subduction of the Iberian lithosphere below Europe seems to be inactive.

REGIONAL TECTONICS

The BCB developed in central northern Spain as a result of Mesozoic extensional movements that were related to the opening of the North Atlantic Ocean and the Bay of Biscay [START_REF] Le Pichon | Une hypothèse d'évolution tectonique du Golfe de Gascogne[END_REF]. As many as three phases of rifting (early Triassic, late Jurassic and early Cretaceous rift phases) and two periods of fault-controlled regional subsidence (from middle Triassic to middle Jurassic and Albian) occurred in the region, whereas flexural subsidence developed during the late Cretaceous and Paleogene farther east in the foreland of the Pyrenees (Rat, 1959;Pujalte, 1977;[START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]Olivet, 1996;Lopéz-Horgue et al., 2010). Early Triassic rifting resulted in the formation of the Cantabrian early Triassic graben, which was bounded by east-trending normal faults and northwest-southeast oriented strike-slip faults. This extensional basin formed by simple shear was coupled to sinistral strike-slip movement along the principle Bilbao and Ventaniella transform faults (Fig. 2.2A; Garcia-Mondéjar et al., 1986). Left lateral slip motion resulted in the Triassic phase of extension, which coincides with the sinistral strike-slip movements in the east-west oriented Bay of Biscay rift [START_REF] Ziegler | Geological atlas of western and central Europe: Amsterdam[END_REF]. Besides the sinistral slip model, a short-lived and localized dextral transpressional strike-slip model has been proposed for the late Triassic phase of compression linking the pre-Jurassic episode of folding to the overall extensional regime (Fig. 2.2B; Garcia-Mondéjar et al., 1986). Late Jurassic rifting of the Iberian and European plates created the Bay of Biscay and was followed by the deposition of Cretaceous successions, which created the Bay of Biscay (Fig. 2.2). This also resulted in the breakup of Jurassic carbonate ramps and emergence and erosion of former marine areas (Gibbons and Moreno, 2002). Basement faults (E-W and NWSE) were reactivated due to Late Jurassic rift activation in the northern Iberian continental margin, which developed elongated grabens where huge amounts of synrift deposits began to accumulate [START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]Gibbons and Moreno, 2002). These initially isolated grabens progressively expanded, with onlap and overstep of the graben margins by faults. This evolution is recorded by the successive development of two major depositional units bounded by regional unconformities (Late Tithonian-Early Valanginian and Late Valanginian-Barremian; Pujalte, 1977[START_REF] Pujalte | Sedimentary succession and paleo-environments within a fault-controlled basin: the Wealden of the Santander area, Northern Spain[END_REF]Herenandez et al., 1999).

During the early Cretaceous rifting period the BCB underwent NNE-SSW direction of simple stretching perpendicular to the axis of the main NW-SE structural trend (Montadert et al., 1979;Grimaud et al., 1982;Boillot & Malod, 1988;Malod & Mauffret, 1990). Later on, this NNE-SSW direction of simple stretching changed to NW-SE direction as the simple extension was replaced by left lateral strike-slip motion along the main NW-SE faults as evidenced in the study area (Ranero and Güenes faults). This change in the direction was accompanied by the anticlockwise rotation of the Iberian plate with respect to European plate, as evident by the spreading documented in the western part of the Bay of Biscay (Montadert et al., 1979;Boillot & Malod, 1988). Trans-tensional movements along these younger NW-trending faults produced oblique slip and pull-apart basins, where thick sedimentary accumulations took place. Paleomagnetic data also suggest that the Iberian plate was separated from European plate during late Aptian to Santonian times (Montadert et al., 1979;Boillot & Malod, 1988;Olivet, 1996). On the other hand, the slicken-slides preserved on the Albian syn-sedimentary fault planes suggest instead that rift-related NE-SW extensional tectonism persisted until mid-Albian time [START_REF] Lepvrier | Kinematics of Aptian-Albian synsedimentary faults in the Basque basin (N. Spain), as related to the rifting of the Bay of Biscay: 14e Reunion des Sciences de la Terre[END_REF]. Later on, the Iberian plate rotated back northward and collided with the European plate, causing the culmination of the plate movement during Campanian to Maastrichtian time (Gibbons and Moreno, 2002). Zumaya and San Sebastian belongs to the European plate [START_REF] Van Der Voo | Paleomagnetic evidence for the rotation of the Iberian Peninsula[END_REF][START_REF] Vandenberg | New paleomagnetic data from the Iberian peninsula[END_REF][START_REF] Schott | Paleomagnetism of the lower Cretaceous red beds from northern Spain, evidence for a multistage acquisition of magnitization[END_REF], while the area south of the fault zone (Bilbao and its surroundings) belongs to Iberian plate (Olivet, 1996; see Fig. The study area and surrounding region contain NW-SE, E-W, N-S, and NE-SW trending faults, which record the extensional history of the study area (Fig. 2.4). Major structures include NW-SE oriented (Güenes and Ranero faults), N-S oriented (Ramales fault), E-W oriented (Arredondo and Hornijo faults) and other small scale NE-SW directed faults and fault splays (see Fig. 2.4). The Güenes fault contains oblique-slip and horsetail splay features and formed during

Early-Mid Albian (Aranburu et al., 1994), while Ranero fault (left lateral strike slip) is believed to be the splay of the Güenes fault, which contains dolomite bodies along its extension [START_REF] Garcia-Mondéjar | Aptian-Albian tectonic pattern of the Basque-Cantabrian basin (northern Spain)[END_REF] as well as along minor faults and horse-tail splays. So, these NW-SE oriented faults are related to early Cretaceous rifting in the BCB (Grimaud et al., 1982;Boillot & Malod, 1988;Olivet, 1996). N-S faults (e.g., Ramales fault) are basement-involving listric faults (Garcia-Mondéjar and Pujalte, 1975). The E-W oriented Arredondo and Hornijo faults (Early-Mid Albian) are deeply rooted in the basement and control the carbonate platform margins, which post-date NW-SE oriented faults and fractures [START_REF] Garcia-Mondéjar | Carbonate platform-basin transitions in the Soba reef area (Aptian-Albian of western Basque-Cantabrian region northern Spain). In: Sedimentation and Tectonics in the Western Basque-Cantabrian area (northern Spain) during Cretaceous and Tertiary Times[END_REF].

PALEOGEOGRAPHIC EVOLUTION

According to Fernandez-Mendiola and Garcia- [START_REF] García-Mondéjar | The Aptian-Albian carbonate episode of the Basque-Cantabrian basin (northern spain): general characteristics, controls and evolution[END_REF] and Aranburu et al., (1996), the Aptian-Albian stratigraphic record allows a systematic sequential reconstruction of the central part of the Basque-Cantabrian basin. During the late Jurassic, mostly siliciclastic influx prevailed, while continental to deltaic and marine environments dominated in the BCB. Marine conditions were never fully established due to the occurrence of sedimentary barriers formed during rift tectonics in the Bay of Biscay. During the early Aptian period, sea-level rise resulted in a marine transgression within the basin as evidenced from its litho-and biofacies. Terrigeneous influx due to transgression resulted in the development of sandstone-and siltstone-bearing platforms containing dominantly tidal and wave ripple marks (Fernandez-Mendiola and Garcia-Mondéjar, 1990).

During early to late Aptian stage, the shift from siliciclastic bearing platforms to extensive carbonate platforms indicates a change in source material (Fig. 2.5). The siliciclastic material was usually trapped within the shallow water carbonate build-ups (Pascal, 1985 andGarcia-Mondéjar, 1982). These carbonate build-ups mostly consisted of rudists with some corals, calcareous algae, orbitolinids and other benthic foraminifera (Rosales et al., 2010;Lopez-Horgue et al., 2009). The platform edges indicate gentle slope and small bathymetrical differences within the surrounding basins, while shallowing upward cycles are commonly observed (Fig. 2.5). Due to gentle slope and small bathymetrical differences, which acted as inlets for the siliciclastic material and hence inhibiting platform growth in a similar way as what can be observed in the Virgin Islands (Hubbard, 1986) and Egyptian coast of Red sea [START_REF] Purser | Carbonate-siliciclastic transitions in an arid climate: Holocene sedimentation on the Egyptian coast of the Red sea[END_REF][START_REF] Purser | Décharges silicodétritiques et sédimentation récifale récente, NW Mer Rouge, Egypte[END_REF]. The occurrence of fine marls and siltsones containing ammonites at the top of the carbonate platforms indicates an erosive surface, hence suggesting periods of emersion before the drowning event (Garcia-Mondéjar, 1990). During the late Aptian, the growth rate of carbonate platforms increased tremendously as the influx of deltaic sandstone was limited and restricted to interplatform areas (Fig. 2.6) (Fernandez-Mendiola and Garcia-Mondéjar, 1990). The Aptian-Albian boundary is marked by increased differential subsidence, accentuating differences in bathymetry between platforms and basins, which represented close association with the onset of spreading in the Bay of Biscay (Wilson, 1975;[START_REF] Soler | Petroleum Geology of the Bay of Biscay[END_REF]Wiedmann et al., 1983). The lower Albian of the Basque Cantabrian basin shows similarities with other well developed carbonate platforms in the World e.g., middle Cretaceous of Mexico [START_REF] Enos | Reefs, platforms and basins of middle Cretaceous in northeastern Mexico[END_REF]. Due to the rare occurrence of Albian platforms in Europe as compared to central America, this area attracted a lot of scientists for their studies.

The lateral short spanned platform to basin transition (i.e., less than 500m of slope deposits)

in the Basque region is similar to the Capitan Formation of the Guadalupe mountains (New Mexico), where the basinal facies mostly consists of terrigenous clastics to pure carbonate in contrast to the siliciclastics and marls deposited in the Basque Cantabrian basin [START_REF] Hileman | Upper Guadalupian facies, Permian reef complex, Guadalupe Mountains, New Mexico and west Texas[END_REF]. During the early Albian period, intense tectonic activity resulted in deepening of the Bilbao intraplatform basin (Fig. 2.7). Various carbonate platforms emerged (Lemona, Gorbea and Duranguesado), while lateral accretion has been also documented [START_REF] Eberli | Segmentation and coalescence of Cenozoic carbonate platforms, northwestern Great Bahama Bank[END_REF].

Along the platform margins, clinoforms show high slope angles (up to 40°), between the platform margins and deep basins. Megabreccias resulting from gravitational processes are commonly observed along the slope aprons. Platform margin erosional features produced by slope failure are commonly observed throughout the basin [START_REF] Mullins | Scalloped bank margins: Beginning of the end for carbonate platform[END_REF]. Such failures may result from earthquake activity [START_REF] Mullins | Catastrophic collapse of the west Florida carbonate platform[END_REF], dissolution of calcite below calcite compensation depth [START_REF] Paull | Continental margin brine seeps : Their geological consequences[END_REF] and/or shelf erosion [START_REF] Schlager | Submarine slope angles, drowning unconformities and self erosion of limestone escarpments[END_REF]. NW-SE and SW-NE trending structural features are generally observed in the basin. During middle Albian time, slow differential subsidence resulted in more or less homogeneous sedimentation and a decrease of the differential sea-floor topography (Fernandez-Mendiola and Garcia-Mondéjar, 1990). In this period, progradation of the Valmaseda deltaic system in the northward direction resulted in the demise of most carbonate platforms (Rat, 1959;Reitner, 1982;[START_REF] Pujalte | A tide-dominated delta system in a rapidly subsiding basin : the middle Albian-lower Cenomanian Valmaseda Formation of the Basque-Cantabrian region, northern Spain[END_REF].

Lithostratigraphy and depositional environments of the Albian series

The Basque-Cantabrian basin underwent two periods of subsidence resulting in faultbounded depocenters, which received high rates of sedimentation until the subsidence stopped. This resulted in accumulation of a thick sedimentary succession from the Upper Jurassic to the Lower Cretaceous (Rat, 1959(Rat, & 1988;;[START_REF] Voort | Zum Flysch Problem in den West Pyrenean[END_REF][START_REF] Feuillee | Structures et paleogeographies Pyreneo-Cantabriques[END_REF][START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]Rosales, 1995). The Basque-Cantabrian basin is sub-divided into the Iberian margin, the Landes massif and the Basque trough on the basis of facies groups (from SW to NE; Fig. 2.8). It extends from the Duero-Ubierna margin in the SW up to the North Vizcaya anticlinorium in the NE (Gibbons and Moreno, 2002). Laterally (from SW to NE), surface exposures of upper Albian to late Cenomanian rocks change from braided river (fluvial sandstones and shales) and deltaic siliciclastic deposits to platform carbonates (shallow platform limestone), which are succeeded by deep basinal turbidites (marls and shales). These turbidites are followed by shallow platform carbonate successions (see Fig. 2.8;[START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]. The Basque-Cantabrian basin records a sea level lowstand during the early Albian, which resulted in transportation of siliciclastic materials in continental areas, deltaic sedimentation at the shoreline, re-sedimentation on submarine slopes and carbonate platform emersion and karstification [START_REF] Garcia-Mondéjar | Pulsating subsidence during a rift episode: Stratigraphic and tectonic consequences (Aptian-Albian, northern Spain)[END_REF]. Ramales platform deposits to Basque trough deposits are observed (modified from Gibbons and Moreno, 2002).

Stratigraphy of the study area:

The Ramales platform (where the study area is located) belongs to the Iberian margin. It contains a sedimentary succession ranging from the Upper Jurassic to the Upper Cretaceous (Gibbons and Moreno, 2002). Rat, (1959) divided this sedimentary succession into various groups on the basis of their litho-facies, which include: [START_REF]Insti tut Fran çais du Pé trole (IFP)[END_REF] Wealden facies (Kimmeridgian -Barremian), [START_REF] Logie | Ka tho lieke Uni ver si teit Leu ven, Ce les tij nen laan 200E, B-3001 He verlee, Bel gium 3[END_REF] Urgonian facies (lower Aptian -upper Albian), and Supra-Urgonian facies (upper Albian -lower Cenomanian; Fig. 2.9). The study area (Karrantza valley) is part of the Ramales platform, which contains Aptian-Albian carbonate buildups. At the foot of these reefal and back reef carbonate buildups, slope and basinal deposits also occur (see Fig. 2.9).

The study area contains Aptian-Albian platform carbonates of the Ramales Formation, consisting of massive, micritic limestones containing Orbitolinas, corals, oysterlike Chondrodonta, and rudists as the most characteristic fauna (Rat, 1959;[START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF][START_REF] Pascal | Les systèmes biosédimentaires urgoniens (Aptien-Albien) sur la marge Nord-Ibérique[END_REF].

These Aptian-Albian carbonate buildups record two main building phases, which include an early Aptian phase and a late Aptian to middle Albian phase. The early Aptian phase is characterized by micritic rudistid limestones localized on incipient highs, and sandy marls and sandstones filling adjacent troughs (Fig. 2.10). During the late Aptian to middle Albian phase, the initial carbonate ramps and the evolving platform-to-basin tracts indicate increasing differential subsidence. Later on, during the Albian, platform margins with large mud-mounds several tens of meters high appeared at platform margins, whereas thick megabreccias were deposited on slope aprons as sealevel felt because of tectonic processes and eustatic lowstands [START_REF] Garcia-Mondéjar | Carbonate platform-basin transitions in the Soba reef area (Aptian-Albian of western Basque-Cantabrian region northern Spain). In: Sedimentation and Tectonics in the Western Basque-Cantabrian area (northern Spain) during Cretaceous and Tertiary Times[END_REF].

Terrigeneous sediments arrived from the surrounding eroded Paleozoic massifs (Fig. 2.10). Aptian-Albian rocks show cyclic development characterized by unconformity surfaces and the alteration of terrigenous and carbonate deposits [START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]. Four main depositional sequences were identified, which include (S 1 to S 4 ): lower Aptian, upper Aptian-lower Albian, lower Albianmiddle Albian, and middle Albian-upper Albian (Figs. 2.9 & 2.10;[START_REF] Garcia-Mondéjar | Carbonate platform-basin transitions in the Soba reef area (Aptian-Albian of western Basque-Cantabrian region northern Spain). In: Sedimentation and Tectonics in the Western Basque-Cantabrian area (northern Spain) during Cretaceous and Tertiary Times[END_REF]. Each of these sequences indicates long episode of sea-level rise, followed by still-stand and short episode of sea-level retreat. The unconformities and sequence stratigraphy pattern are attributed to episodic tectonism that also resulted in relative sea-level changes [START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]. The short distance between the platform carbonates and the basinal deposits suggests the formation of an intra-platform trough rather than a deep basin, which is also shown in the early-middle Albian paleogeographic map of [START_REF] Garcia-Mondéjar | Plate reconstruction of the Bay of Biscay[END_REF]see Fig. 2.10). Fig. 2.10. Lateral depositional facies variations in the study area, where platform to slope carbonates (left) changes into shales, siltstones and basinal marls (modified from Rosales et al., 2010).

Chapter: 3 METHODOLOGY

FIELDWORK

The spatial distribution of the dolomite bodies in the Ranero, El-Moro and El-Mazo areas are studied. For this purpose, dolomite bodies were delineated by means of aerial photographs and later on confirmed during fieldwork.

220 rock samples were plugged from different sites in the Ranero, El-Moro and El-Mazo areas. Field characteristics of the sampled dolomite bodies were observed, which were verified by petrography, geochemistry and petrophysical characteristics. Precursor limestone rock samples were also collected.

THIN-SECTION MICROSCOPY

177 thin-sections from different representative samples of dolomite and calcite facies as well as the precursor limestone were prepared in the University of Jean Monnet, Saint Etienne and Katholieke Universiteit, Leuven. These thin-sections were stained using modified staining technique (Dickson, 1966), which helped in distinguishing calcite (red colored) from dolomite.

Thin-sections were studied with the conventional (Nikon ECLIPSE LV 100 POL) and cathodoluminescence microscope (CL: Nikon ECLIPSE ME 600, Cathodyne OPEA Cathdoluminescence; operating conditions were 12 to 17 kV gun potential, 350 to 600 µA beam current, 0.05 Torr vacuum, Vacuum accelerator TURBOTRONIK NT 10 attached with Cathodyne OPEA). Photomicrography was done with mounted camera ProgRes C10 Plus . Cathodoluminescence is simply the luminescent light emitted by minerals when they are excited with radiation caused by an electron beam [START_REF] Machel | Causes and emission of luminescence in calcite and dolomite[END_REF]. Cathodoluminescence microscopy was done for selected thin sections in order to better characterize the growth features (dolomite cement) and relations of the different dolomite phases. Different calcite phases were also distinguished on the basis of their characteristic luminescence.

GEOCHEMISTRY

Sample selection and preparation

The analysed material corresponds either to whole rocks, or to micro drillings. Unless stated, the material is washed (for oil and salts), dried at 70°C overnight, and crushed down to 40

µm in an agate mill. A loss on ignition (LOI) is measured by burning 1g of sample at 960°C during 4 hours.

Depending on the amount of available powder, different analytical techniques may (or may not) be used. In the following, we describe first the full (and redundant) procedure that is applied on standard samples at the Centre SPIN, Ecole des Mines de Saint-Etienne; it involves the use of both X-Rays Fluorescence (XRF) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Depending on their composition and/or their abundance, the samples were processed using either or both of these methods.

X-Ray Fluorescence analyses

All the measurements are performed on a Bruker SRS3400 spectrometer (WDS) with a rhodium target X-Ray tube. For major element analysis, 0.3 g of the calcinated sample is mixed with 0.3 g of LiNO 3 and 5.4 g of Li 2 B 4 O 7 . This mixture is fused in a platinum alloy crucible at 1100°C in a muffle furnace. A glass disc is obtained by pouring the molten mixture in a 30 mm diameter platinum mould. A routine analytical program is used for the determination of 10 oxides:

SiO 2 , Al 2 O 3 , Fe 2 O 3 (total Fe as Fe 2 O 3 ), MnO, MgO, CaO, Na 2 O, K 2 O, TiO 2 and P 2 O 5 . The "fundamental parameters" method is used to determine the matrix correction coefficients. The measured intensities are calibrated against natural geochemical standards. The relative uncertainty is about 1-2% for the most abundant elements (Si, Al, Fe, K in most cases, but also Ca when carbonates are present) but the light elements Na and Mg are analysed with a lower accuracy (5%).

The method is rather precise (5%) for minor elements (Mn, Ti, P) and detection limits are in the range 0.05-0.02%.

For trace elements, XRF analysis is performed on pressed powder pellets when enough (10 g) material is available. Mass absorption effects are estimated from Compton peak intensities.

These intensities are corrected from element interferences and calibrated against natural geostandards. The relative uncertainty is about 5% for the most abundant elements (Zn, Rb, Sr, Zr, Ba) and about 10% for the remaining ones (Ni, Ga, Y, Nb, Sn, Ce, Pb, Th) with a detection limit of a few ppm for most elements. U contents are much less reliable (20% and detection limit at 10ppm).

ICP-AES analysis and cross-calibrations

250 mg of calcinated powders are digested using a standard multiacid preparation to produce 25cc HCl2M solutions (dilution 1/100) for analysis by ICP-AES on a HORIBA Jobin-Yvon Activa. Due to the high dilution and the previous removal of organic matter, there is generally no solid residue in the solutions. Analyses are performed for both major elements (Al, Fe, Mn, Mg, Ca, Na, K, Ti, P) and for the trace elements (Sc, V, Cr, Ni, Y, Sr, Nb, Ba, La, Ce, Eu, Yb and Th) on the same solution. Si contents cannot be measured since this element is reacted out (as fluorides)

during the digestion procedure. The relative uncertainty is about 5% for the most sensitive elements (major elements and Sr, Ba, Sc, Y) and about 10% for the remaining ones. Detection limits are in the range 5-20 ppb in solution, which translate into 0.5-2 ppm using a 1/100 dilution.

When elements are analysed twice, several cross-calibrations between the results obtained by XRF and ICP-AES are possible and some choices can be made, depending on the relative merits (and drawbacks) of each method:

-XRF analysis is highly reproducible and precise, but detection limits are higher;

-ICP-AES is generally more sensitive, but the short range variability of the plasma source limits the reproducibility, hence the quality of calibrations.

For major elements at high solute concentrations, the ICP-AES signal may be curved, hence the XRF value is always preferred. Conversely, ICP-AES is more accurate than XRF at low concentrations, i.e. for minor elements (Mn, Ti, P) and low MgO and Na 2 O contents (<1%). For Zn, Ga, Rb, Sr, Zr, Ba, Pb the selected value is that given by XRF while for Sc, V, Ni, Cr, Y, Nb, La, Ce, Eu, Yb and Th, the ICP value is usually retained.

STABLE C & O AND Sr ISOTOPE ANALYSES

For stable isotope (O and C) and Sr isotope analyses, following methods were adopted to know the geochemistry of the studied samples. Various diagenetic phases were micro-sampled using dentist drill for O, C and Sr isotope analyses. 106 samples were analyzed in University of Erlangen -Germany (Institute of Geology and Mineralogy) and Jean Monnet Université, Saint-Etienne (France) respectively. The carbonate powder was reacted with 100% phosphoric acid (density>1.9; Wachter & Hayes, 1985) at 70°C using Gasbench II connected to a Thermo Finnigan Five Plus mass-spectrometer. All values are reported in permil relative to Vienna Pee Dee Belemnite (V-PDB) by assigning δ 13 C values of +1.95‰ and a δ 18 O values of -2.20‰ to NBS19.

Oxygen isotopic compositions of dolomites were corrected using the fractionation factors given by Rosenbaum & Sheppard (1986). Reproducibility was checked by replicate analyses of laboratory standards is better than ±0.14‰ for δ 13 C and ±0.17‰ for δ 18 O.

15 carbonate samples were analyzed for Sr isotope analyses at the Scottish Universities Environmental Research Centre. Isotope measurements were performed on Sr extracted from HCl solution using standard cation exchange procedures [START_REF] Baadsgaard | Geochronology of the Gloserneia pegmatite, Froland, southern Norway[END_REF]. In preparation for mass spectrometry, Sr samples were loaded onto single Ta filaments with 1M phosphoric acid. Sr samples were analyzed in a VG sector 54-30 multiple collector mass spectrometer. A 88 Sr intensity of 1V (1×10 -11 A) ±10% was maintained and 87 Sr/ 88 Sr = 0.1194 and an exponential law. The VG Sector 54-30 mass spectrometer was operated in the peak-jumping mode with data collected as15 blocks of 10 ratios. For this instrument NIST SRM987 gave 0.710260 ± 0.000011 (1SD,n = 17) during the course of study.

Scanning electron microscope (SEM) equipped with an energy dispersive detector (EDX)

was used for detailed observations and qualitative chemical analyses at Ecole des Mines, Saint-Etienne. Operation conditions were 12 kV beam voltage, 10mm working distance (WD).

X-ray diffraction (XRD) technique was used on the selected twenty samples to determine (a)

bulk mineralogy; (b) amounts (%) of calcite and dolomite in a rock, and (b) know the dolomite nonstoichiometry and crystal ordering. Limestone and dolostone samples were crushed and powdered before mineralogical analyses by X-ray diffraction using PANalytical X'Pert PRO machine. Powdered samples of different dolomite phases as well as calcite were prepared. In the preparation of sample for XRD, 20% of Al 2 O 3 and 80% of the rock powder was taken and mixed (IFP internal report;Guillet et al., 2007). Cu-Kα radiation (45kV, 40mA) was used. The scan speed was set at 0.2˚θ min -1 and sampling interval at 0.001˚θ per step.

FLUID INCLUSION ANALYSES (FI)

Microthermometry was performed on two double-polished sections using Linkam THMSG 600 heating cooling stage. This method is used to infer the nature of the prevailing fluids and temperature during precipitation (or formation) of certain diagenetic phases. About 25 dolomite crystals containing primary inclusions were observed, and about 34 measurements of homogenization temperature (T H ) were achieved. First melt (T M ) was also measured where possible. Measurement accuracy is in the order of 1°C for T H values and 0.2°C for T M values.

POROSITY AND PERMEABILITY ANALYSES

Seventy two samples were selected for petrophysical analyses (porosity, permeability) to assess any petrophysical variations as a function of dolomite textures (or facies). For porosity determination, micromeritics GeoPycTM 1360 and micromeritics AccuPyc 1330 was used in the Reservoir Characterization Department of IFP, which is easy to use, fully automatic gas displacement pycnometer, while the analysis was initiated with a keystroke. For permeability analysis, the standard technique of vacuum generation using Boyle's Law was used.

Chapter: 4

STUDY SITES AND ANALYTICAL RESULTS

RANERO AREA

In this section, the detailed description of the field observations, petrographic characteristics, mineralogical/geochemical analyses, microthermometry and porosity/permeability analyses of the observed dolomite and calcite facies besides host limestone in various studied sites/sections in the Ranero area are given. These studied sites/sections include the Pozalagua quarry site, Ranero fault section, Ranero front section, Ranero vein section and Ranero breccia site (Fig. 4.1). In order to understand the dolomite facies variations, sampling of the selected dolomite and calcite phases was carried randomly and along sections across the dolomite body and dolomite tongue.

The Pozalagua quarry site is located along the main Ranero fault and at the margin of the carbonate slope (Fig. 4.1). It represents a "mega thin-section" view whereby various petrographic aspects could be studied macroscopically (Fig. Although the dolomite bodies are restricted to the faults and fractures in the slope carbonates, their lateral extensions are also observed in the platform area which is beyond the scope of the present studies.

Sedimentology and petrography

The Aptian-Albian slope carbonates are mostly composed of grey to dark grey colored limestone (miliolid and orbitolinid wackestones, floatstones and bioclastic packstones), described in detail by various authors [START_REF] García-Mondéjar | The Aptian-Albian carbonate episode of the Basque-Cantabrian basin (northern spain): general characteristics, controls and evolution[END_REF]Rosales & Pérez-García, 2010;and López-Horgue et al., 2010). Various calcite cements are recognized on the basis of their petrographic characteristics (including cathodoluminescence), which include various phases of fibrous dark grey, Various dolomite facies were distinguished on the basis of the shape of the crystal characteristics (uni-/polymodal; planar/nonplanar) and crystal size distribution using the classification of [START_REF] Sibley | Classification of dolomite rock textures[END_REF]. Due to the absence of concrete classification on size range of dolomite, these are termed as coarse (˃ 700µm), medium (300 -700µm) and/or fine Petrography: Excellent exposures on the quarry walls acted as "mega thin-section" and helped in identifying the various dolomite and calcite phases in the host limestone and their inter-relationship.

Petrographic observations revealed that limestone ranges from mudstone to packstone [START_REF] Dunham | Classification of carbonate rocks according to depositional texture[END_REF], whereas fossils include molds of tabular corals, debris of rudists and forams (Fig. 4.5A). In the host limestone, cavity/karst filling, coarse crystalline calcite cement (CC-I) pre-dates dolomitisation as evidenced by cross-cutting relationship on the quarry walls (Fig. 4.5A). It is observed that partial dolomitisation of the host limestone took place at the contact between limestone and coarse crystalline calcite (CC-II), indicating that such contact zones are vulnerable to dolomitization (Fig. 4.5A).

Massive dolomite mostly consists of nonplanar, medium to coarse-crystalline dolomite (CCD-I) that shows undulose extinction typical of saddle dolomite (Fig. 4.5B; Radke & Mathis, 1980). Zebra dolomite (ZD) exhibits alternating bands of replacive and cement phases (Fig. Such dedolomitisation may result in the enhancement of vuggy porosity as evident in CCD-I (Fig.

4.5F).

At the margin of carbonate slope deposits in the southwestern part of Pozalagua quarry

b) RANERO FAULT SECTION

This section is located the Ranero fault and was sampled on the uphill side i.e., at the margin of the depositional carbonate slope and platform, which also corresponds to the present day transition of the slope to plateau (Fig. 4.7). Sampling was carried out across the dolomite body and exhibited a width of about 30m (Fig. 4.8).

Field observations:

In the Ranero fault up-slope site, various dolomite facies were sampled along with host limestone (Fig. 4.8). Dolomite bodies show a distinct color contrast as compared to host limestone as dolomite exhibited dirty brown to dark grey colors, while limestone shows off-white color on weathered surface (Figs. 4.9 A&B). On fresh surface, these fault-controlled dolomite bodies show coarse to very coarse crystalline, interlocking saddle dolomite facies (CCD-II), which exhibit milky white appearance with curved crystal faces. They show negligible inter-crystalline porosity. Zebra-like dolomite facies (ZD) also occur in this section.

4.10B

), which shows compositional variations within the calcite crystals [START_REF] Emery | Zoned calcite cements: has analysis outpaced interpretation?[END_REF].

Medium to coarse crystalline, planar to nonplanar dolomite (CCD-I) consists of subhedral to euhedral crystals (200-500µm), while pyrite mostly confined to fractures in CCD-I dolomite (Fig.

4.10C

). Intercrystalline pore spaces in dull red luminescent dolomite (CCD-I) are commonly filled by dull orange luminescent calcite (WC; Fig. 4.10D). Coarse crystalline (300 to 700µm), nonplanar dolomite (CCD-II) often occurs adjacent to the planar to nonplanar dolomite (CCD-I) and exhibits an interlocking pattern and undulose extinction typical of Baroque dolomite [START_REF] Zhang | Formation of saddle dolomites in Upper Cambrian carbonates, western Tarim Basin (northwest China): Implications for fault-related fluid flow[END_REF][START_REF] Spotl | Saddle (baroque) dolomite in carbonates and sandstones: A reappraisal of a burial-diagenetic concept[END_REF]. Nonplanar dolomite cement (CCD-II) shows different zonations of dull to bright red colours with red rims under CL. It is evident that the size of these nonplanar dolomite crystals increased from east to west (300 to 900µm) in the Ranero fault section.

Zebra and/or zebra-like dolomites (ZD; Fig. 4.10E) are composed of coarse crystalline dolomite cement (400 to 700µm) alternating with fine crystalline dolomite matrix (20 to 100µm).

Intercrystalline porosity (7 to 10%) is mostly evident in matrix phase, while cement phase exhibits negligible porosity (Fig. 4.10E). Post-dolomite alteration resulted in occluding of pore spaces by late stage calcite (TC), while dedolomitization of the precursor dolomite is also observed (Fig.

4.10F).

A B LS Dol. Dol.

Field observations:

The irregular distribution of dolomite bodies in the host limestone, such as the Ranero front section is generally dependent upon the nature of the host rock and dolomitizing fluids. Various dolomite phases are observed in this section. Dominant facies include dirty grey to purple colored dolomite (CCD-I) containing reddish, weathered color pore-filling calcite in the inter-crystalline pore spaces and dark grey, coarse crystalline dolomite (CCD-II). E-W oriented fault observed in the northern part of the studied section, which is also evident by the brecciation of dolomite phases.

CCD-II

Petrography: In the Ranero breccia site, the host limestone mostly consisted of orbitolinid wackstone and bioclastic packstones (Fig. 4.25A) (cf. Rosales and Pérez-Garcia, 2010). The host limestone and the medium to coarse crystalline, planar to nonplanar dolomite exhibit sharp contact.

This contact is always rimmed by a dark colored dolomite of about 1cm width (Fig. 4.25A&B).

This rim is very often dedolomitized (rich is calcite), which may suggest that it originated as a nonstoichiometric, Fe-rich, CCD-I dolomite. Limestone clasts engulfed in dolomite denote the intensity of fracturation and the abundance of dolomite cement as compared to replacive dolomite (Fig.

. Dolomite stoichiometry

The stability of the dolomite crystals depends upon the nonstoichiometry expressed in mole percent (M%) CaCO 3 , as most stable dolomite crystals have a nonstoichiomtery values ranging from 50.0 and 52.0 M% CaCO 3 , while less stable crystals range from 49.0 to 50.0 and 52.0 to 58.0 M% CaCO 3 (Lumsden & Chimahusky, 1980). Stoichiometry is independent of the petrographic parameter, which includes rock type, dolomite crystal size, porosity, fossil component and insoluble residue (Lumsden & Chimahusky, 1980). Besides this, dedolomitization was also related to nonstoichiometry of dolomites (Dorobek et al., 1993). Dolomite nonstoichiometry was determined through the application of Lumsden's equation (1979).

NCaCO 3 = Md + B (Where N is the mole % of CaCO 3 in the dolomite lattice, d is the observed dspacing in Angstrom units, M is 333.33, and B is -911.99).

All of the dolomite samples analysed for nonstoichiometry exhibit sharp diffraction peaks.

The d104 spacing is quite constant and range between 2.8863 and 2.8912 Å. These d104 spacing values correspond to a Ca-content between 50.1 and 51.7 mol % (Appendix-IV).

Mineralogy

The SEM studies helped in understanding the mineralogical variation within the dolomite crystals (Figs. The Fe content of replacive dolostones may be substantially larger than that of the presentday Fe content of their exclusive carbonate fraction: this simply means that their mineralogy includes pyrite and/or silicates in addition to dolomite, and that the corresponding rocks have a multi-stage history.

Geochemistry

A wide spectrum of geochemical parameters (major and trace element composition, δ 18 Oδ 13 C results, and 87 Sr/ 86 Sr values) are used to distinguish between different dolomite types, and subsequently to obtain general information about the nature of the dolomitising fluids (cf. [START_REF] Brand | Chemical diagenesis of a multi-component carbonate system. I. Trace elements[END_REF][START_REF] Land | The isotopic and trace element geochemistry of dolomite: the state of the art[END_REF]Kertz, 1982;[START_REF] Veizer | Chemical diagenesis of carbonates: theory and application of trace element technique[END_REF][START_REF] Machel | Fluid flow direction during dolomite formation as deduced from traceelement trends[END_REF], Gasparrini, 2003;Machel, 2004). In the Ranero area (Pozalagua quarry site, Ranero fault section, Ranero front section, Ranero vein section and Ranero breccia site), the data obtained are grouped on the basis of already distinguished phases, which include cavity-and karst-filling calcite (CC-I & CC-II), medium to coarse crystalline dolomite (CCD-I), coarse crystalline, pore-and vein-filling dolomite (CCD-II), zebra dolomite (ZD), internal sediments (int. sed) also termed as dolomite sands (DS), coarse to very coarse crystalline, white calcite (WC), coarse crystalline, pore-filling transparent calcite (TC), Ba-ore carbonates and dedolomitised parts of CCD-I dolomite.

a) MAJOR AND TRACE ELEMENT COMPOSITION

In the study area, various elemental compositions (Fe, Mn, Ti and Al) showed considerable variations with respect to previously identified dolomite and calcite phases. The crossplot of Feand Mn contents of various dolomites with their δ 18 O values helped in differentiating their corresponding phases (Fig. 4.30 A&B). In the CCD-Ia (core, un-zoned and dull luminescent) and CCD-Ib (marginal, zoned and luminescent) dolomite facies, FeO contents cluster around 1-1.5% and 0.5-0.7% respectively and this difference is also well correlated with δ 18 O values of the respective CCD-Ia and CCD-Ib facies. So, the more Fe-rich dolomites (CCD-Ia) have slightly less depleted oxygen isotope ratios (-16 to -12‰ V-PDB). It is noteworthy that the coarse crystalline dolomite (CCD-II) have very low FeO contents (<0.2%) and have very depleted δ 18 O values (-16 to -19‰ V-PDB; Fig. 4.30A).

The FeO-and MnO-contents display similar correlations with δ 18 O values, as medium to coarse crystalline dolomite (CCD-I) is enriched in both Fe-and Mn-, while coarse to very coarse crystalline dolomite (CCD-II) exhibits low Fe-and Mn-contents (Fig. 4.30 A&B). While mineral chemistry may fingerprint hydrothermal stages from a fluid-based point of view, the rock's bulk compositions keep some track of their origin, particularly through the nature and the amount of non-carbonate impurities.

Al content can be used as an index, which allows the Fe initial content to be estimated and the Fe enrichment in dolomite to be calculated -since the original Fe content is proportional to Al concentrations (Fig. 4.31A). Since the Ti/Al ratios in the dolomite are almost constant and identical to those of claystones in the surrounding areas (Cuatros de Canales), hence much of the noncarbonate material has a clayey origin. Seemingly, both Al and Ti contents of dolomite are inherited from the more or less abundant clayey impurities in their precursor rocks (Fig. 4.31B). The relative TiO 2 variations may also relate to compositional differences in the source lithologies (basement rocks), which could include a Ti-rich component as also documented in the Mesozoic-early Cenozoic Newfoundland rifted margin, Northwest Atlantic (Robertson, 2007).

On the basis of macroscopic aspect and geochemical inheritance of the selected dolomite phases, true precipitates (i.e. growing crystals from and in fluids) from different types of replaced rocks such as zebra-like (or non-zebra) replacing limestones and dolomitized internal sediments were distinguished.

Hydrothermal precipitates have a diagnostic symmetrical structure (Fig. 4.31A&B) and a very low level of silicate impurities (Al 2 O 3 typically less than 0.05 wt %). CC-I, CC-II, WC and TC are precipitates, while TC may also formed as a replacement product of unstable Fe-dolomite (Fig.

B A

4.28). All the dolomite precipitates are sub-idiomorphic (anhedral/nonplanar) and have curved crystal shapes (saddle). In some cases the full compositional range i.e. from CCD-Ia to CCD-II (Fig. 4.26) is seen in one single zoned crystal. Internal (central) porosity is free or plugged by WC and/or TC phases. Replacive dolomites are best identified by their mosaic textures and/or by their higher content in silicate impurities (Fig. 4.31). The replacive (dark) bands of zebras typically have higher contents of Al 2 O 3 (0.1-0.3 %) than those of the corresponding (void filling) white bands. Dolomite sands (also termed as int. sed.) have the highest content of non-carbonate impurities (Al 2 O 3 up to 1.5%). Since these impurities are essentially of clayey origin (Fig. 4.31), hence it is interpreted that these particular rocks (former clay-rich sediments) accumulated in ponds of the prehydrothermal cave system and were later converted to dolostone together with the surrounding limestones.

Dolomite crystal sizes of replaced rocks increase as their FeO content (and δ 18 O) decreases: replaced limestones lacking zebra structure have the smallest grain size (tens of microns) and rocks reworked by CCD-II fluids the highest (millimetres). In the absence of later deformation, the matrix porosity of replaced rocks varies inversely with the abundance of silicate impurities. For instance, porosity is very low in the dolomitized internal sediments (DS), where the non-carbonate material (clays and pyrite) concentrates in the cavities left between the growing dolomite crystals. suggesting that the fluids flowed through the limestone and were abundant enough to shift their oxygen signatures in the surrounding areas (Fig. 4.33). δ 13 C of hydrothermal precipitates cluster in a narrow range (+2 to 0‰ V-PDB) which is slightly, but consistently lower than its limestone counterpart (+3 to +1.5‰ V-PDB). This may indicate that some external carbon was brought by the fluids and/or δ 13 C -temperature fractionation produced the calcite and dolomite precipitates (Emrich et al., 1970). Limestone δ 13 C signatures cannot be distinguished from primitive values and those of marine cements as reported in Rosales & Pérez-Garcia (2010). It is noteworthy that carbonates in the Pb-Ba vein have the same δ 13 C as host limestone, suggesting an early genesis by δ 13 C buffered fluids and later δ 18 O shifting by dolomitizing fluids.

Fluid inclusion analyses

Fluid inclusions (FIs) are microscopic pockets of liquid and/or gas trapped within crystals.

They provide three basic types of information, which include nature of fluid, estimate of the temperature at which the fluid incorporated in the host mineral and estimates of fluid density [START_REF] Emery | Inorganic Geochemistry: Applications to Petroleum Geology[END_REF]. Petroleum explorationists are generally interested in temperature and fluid composition as it helps in determining 1) temperature, age and duration of mineral cement growth, 2) temperature and timing of episodes of fluid migration (including water, oil and gas), and

3) temperature of fracture healing [START_REF] Burruss | Hydrocarbon fluid inclusions in studies of sedimentary diagenesis[END_REF][START_REF] Pagel | Application of Micro-FT-IR Spectroscopy to individual hydrocarbon fluid inclusion analyses[END_REF][START_REF] Mclimans | The application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs[END_REF]. Fluid inclusions are classified as primary as well as secondary. Primary fluid inclusions are small droplets of the mother solution, which may be trapped in cavities during crystal growth. On the other hand, secondary fluid inclusions are those trapped in the crystals in a later stage from crack-healing mechanism. Two double-polished sections (each from zebra dolomite and late saddle dolomite)

were prepared (for methodology, see chapter 3). Fluid inclusion petrography was carried out to perform microthermometry (measurement of the temperatures of phase changes in inclusions as The estimation of salinity was done according to Bodnar's equation [START_REF] Bodnar | Revised equation and table for determining the freezing point depression of H 2 O-NaCl solutions[END_REF]. The salinity of fluid inclusions in the selected massive, nonplanar (CCD-I) dolomite has a broad range from 11.7 to 21.0 eq. wt. % NaCl (Fig. 4.39B). The mode value for these fluid inclusions is 16.3±4.2 eq. wt. % NaCl. Salinity of the massive dolomite shows no considerable variation with the change in homogenization temperature (T H ).

Zebra Dolomite (ZD):

The homogenization temperatures (T H ) for the fluid inclusions of zebra-like dolomite cement phase (ZD) dolomite range from 131 to 196ºC (average T H = 174.1±16.4ºC), most values lying between 140 and 180°C (Fig. 4.39A).

Melting temperature (T M ) for zebra-like (ZD) dolomite varies between -21 to -2ºC. The estimation of salinity was done according to Bodnar's equation [START_REF] Bodnar | Revised equation and table for determining the freezing point depression of H 2 O-NaCl solutions[END_REF]. The salinity of fluid inclusions in the selected zebra-like (ZD) dolomite has a broad range from 4.5 to 21.3 eq. wt % NaCl (Fig. 4.39B). The mode value (major occurrence) of salinity is 15.2±4.6 eq. wt. % NaCl as only few T M were below -10ºC, most are between -20 and -15ºC. The parent fluid isotope chemistry was determined using Land (1985) Helium porosity and relative permeability analyses were carried out on selected plugs collected from various studied sections/sites in the Ranero area. These selected plugs consisted of various dolomite phases, hence exhibited different porosity and permeability values (Appendix-V).

Various alteration products of dolomite phases were also analysed. Forty-nine samples were selected for petrophysical studies (porosity, permeability) in the three selected sites (Pozalagua quarry, fault section & vein section).

Pozalagua quarry site: Nonplanar dolomite contains considerably low porosity/permeability values, which ranges from 1 to 2.5% (porosity) and 0.1 to 0.4mD (permeability), although dissolution may enhance the porosity values considerably as observed in Fig. 4.41A. Zebra dolomite show relatively high porosity (2.1 to 11%) but low permeability values (0.1 to 0.3mD).

Relatively high porosity values might be due to replacive phase in the zebra dolomite (Fig. 4.41B).

Breccia or cataclastic dolomite contains porosity values ranging from 1.6 to 3.8% and permeability values up to 0.2mD (Fig. 4.41C). In the Pozalagua quarry site, the porosity/permeability analysis does not give any systematic variation due to random sampling although dolomite facies variations indicate change in porosity/permeability values (see appendix-V).

Ranero fault section: In the Ranero fault section, porosity/permeability values for nonplanar dolomite vary from 0.5 to 7.3% and 0.1 to 1.6mD respectively (see appendix-IV). Nonplanar CCD-I dolomite showed high porosity (more than 7%) and permeability (1 to 2mD) values, which is due to dissolution porosity as also observed in the above discussed Pozalagua quarry (Fig. 4.41A). It is observed that the porosity/permeability values greatly differ from one side of the section to the other side. In the eastern part of the studied section (near the fault plane), porosity/permeability values are relatively higher as compared to the western part of the section where these values are much lower (see appendix-V). Petrographic studies show that fine to medium crystalline nonplanar dolomite in the eastern part exhibits relatively high porosity values (3 to 7%) as compared to very coarsely crystalline dolomite in the western part of the studied section (less than 3%). Zebra dolomite show relatively high porosity (up to 4%) and permeability (up to 1.5mD), which is due to the intercrystalline pore spaces in the replacive dolomite phase as cement dolomite phase contain negligible porosity (Fig. 4.41B). Planar dolomite (CCD-I) contains high porosity but low permeability values, which range from 4.2 to 6.0% and 0.3 to 0.7mD respectively (Shah et al., 2010). High porosity values are due to intercrystalline porosity in these planar dolomites.

Cataclastic deformation resulted in the increase in the porosity but show no effect on the permeability, which is evident by high porosity values (up to 6%) and low permeability values (0.3mD). Various calcite phases (WC and TC) are responsible for occluding the considerable pore spaces resulted from cataclastic deformation/brecciation (Fig. 4.41D). Ranero front section: Most of the dolomite phases observed in the Ranero front section are occluded by late stage calcite (TC; Fig. 4.43A-C). The process of dedolomitization may enhance or reduce the pore spaces (Smosna, 1984;[START_REF] Purser | Carbonate-siliciclastic transitions in an arid climate: Holocene sedimentation on the Egyptian coast of the Red sea[END_REF]. Although, the dedolomitization commonly observed in the studied section resulted in destruction of porosity and permeability (Fig. 4.43A).

Cataclastic deformation/brecciation might enhanced the porosity and permeability of medium to coarse crystalline dolomite (CCD-I) and coarse to very coarse crystalline dolomite (CCD-II).

Although, pore-filling calcite cement (WC) filled the intercrystalline spaces (Fig. 4.43C). Coarse to very coarse crystalline, pore-filling dolomite (CCD-II) showed negligible porosity (Fig. 4.43D). sections/sites also helped in understanding the mechanism of dolomite and calcite formation (Table 4.1).

Three main stages of diagenetic events were observed in the study area, which include: (i) pre-dolomite calcitization, (ii) dolomitization stage, and (iii) post-dolomite calcitization (Fig. Fault and fracture reactivation marked the beginning of dolomitization, where Fe-rich dolomite consists of core (CCD-Ia) and zoned along crystal borders (CCD-Ib) formed in the initial stage (Fig. 4.44). Coarse crystalline, saddle, non-ferroan dolomite (CCD-II) marks the ending of dolomitizing event, whereas pyrite crystals were oriented along the borders of the CCD-II dolomite crystals. Two phases of replacive dolomite i.e., zebra dolomite (ZD) and dolomite sands (DS), formed in the beginning of dolomitization due to selective replacement (Fig. 4.44). Zebra dolomite may result from mimic replacement of coral fragments (cf. Nielsen et al., 1998), while various workers believed in its tectonic origin [START_REF] Iriarte | Zebra-dolomite, tectonic deformation and hydrothermal fluid-flow: lessons learned from Asón valley hydrothermal dolomites (northern Spain)[END_REF][START_REF] López-Horgue | An example of the tectonic origin of zebra dolomites: the San Martín beach outcrop (Santoña, North Spain)[END_REF]Appendix-II). Zebra dolomite occurs as patches in CCD-I and CCD-II, hence indicating its formation prior to CCD-I. After the dolomitization event, cataclastic deformation resulted in the brecciation of CCD-

II, where open spaces between dolomite clasts were filled by white calcite (WC). Transparent calcite (TC) of meteoric origin also occludes the pore spaces (Fig. 4.44). Selective dedolomitization was restricted to rimmed dolomite (CCD-Ib), where Fe-rich phase was readily effected by late stage calcite (TC).

Synopsis

Following important findings are reported on the basis of the detailed investigations (discussed in previous sections) in the Ranero area, which include:

• Linear, fracture-filled dolomite bodies support the idea that the dolomitising fluids migrated and spread through the sedimentary pile along discontinuities and strictly indicate tectonic control on the dolomite distribution (Fig. 4.7;[START_REF] Garcia-Mondéjar | Plate reconstruction of the Bay of Biscay[END_REF]López-Hogue et al, 2005).

•

The sharp limestone-dolomite contacts mostly cross-cutting stratification and sedimentary structures suggest a late origin for the dolomites (Fig. • CCD-II dolomite consisted of interlocking anhedral crystals, which underwent aggradational neomorphism demonstrating the evolution into planar dolomite crystals as was described by Nielsen et al. (1994) and Vandeginste et al. (2005).

•

Previous workers revealed that zebra dolomite formed due to shear stresses mainly in two different structural directions: along fracture shear-corridors [START_REF] López-Horgue | An example of the tectonic origin of zebra dolomites: the San Martín beach outcrop (Santoña, North Spain)[END_REF] and flexural-slip bands nearly parallel to bedding [START_REF] Iriarte | Zebra-dolomite, tectonic deformation and hydrothermal fluid-flow: lessons learned from Asón valley hydrothermal dolomites (northern Spain)[END_REF], but it is believed that zebralike, banded dolomite (ZD) and pockets of layered dolomite interpreted as dolomitized internal sediments (DS), resulted from the replacement of host limestone.

•

Coarse crystalline, white colored calcite (WC) postdates dolomitisation and observed as veinand pore-fillings in brecciated dolomite.

•

Pore-and vein-filling, non-luminescent calcite (TC) showing depleted δ 18 O and δ 13 C values respectively, which is similar to calcite formed near to meteoric recharge (Choquette & James, 1988;Niemann & Read, 1988;Meyers, 1991;Reeder, 1991).

•

Pb-Ba mineralization associated with the initial phase of dolomitisation CCD-I (Fig. . Various dolomite and calcite phases exhibit higher Sr 87 /Sr 86 ratios compared to the original marine signatures may indicate interaction of the dolomitising fluids with radiogenic lithologies during burial conditions (Fig. 4.37).

•

Fluid inclusions analyses show high homogenization temperatures (120 -200°C) and salinities (12 -21 eq. wt% NaCl) of the primary inclusions (Fig. 4.39). Calculated δ 18 O values of the parent fluid following Land's (1985) dolomite-water fractionation equation (cf. Adams et al., 2000), show that estimated water δ 18 O values range between +2.0 and +4.0‰ V-SMOW, indicating some 18 O depletion relative to normal seawater (Fig. 4.40;Land, 1983).

•

Porosity and permeability studies revealed that post-dolomite alteration may enhance and/or reduce the pore spaces in the dolomite. Brecciation and cataclastic deformation generate open spaces but late stage calcitization may occlude these pore spaces (Figs. 4.41C&D;4.43A&C).

Dissolution in CCD-I also resulted in the enhancement of porosity and permeability (Figs.

4.41A&B).

EL-MORO AND EL-MAZO AREAS

In this section, the contrasting features (field characteristics, petrography and geochemistry) of the limestone host, fault-and/or fracture related dolomite bodies in El-Moro and El-Mazo areas with respect to those exposed in the vicinity of Ranero (cf. Field observations: At outcrop, weathered, dark beige colored dolomite occur along a sharp contact with the off-white colored host limestone (Fig. 4.48A). Various dolomite and calcite phases are documented, which helped in the construction of comprehensive paragenetic sequence (Swennen et al., in press). A white colored, coarse to very coarse crystalline calcite (WC) observed in contact with dolomite, displays fault-related features on the weathered surfaces such as fault striations and confirms its syntectonic origin (Aranburu et al., 2002;Fig. 4.48 B).

EL-MAZO

EL-MORO EL-MORO VALLEEY

MO-I MO-II MO-III

A B

A B

only destroyed by white calcite (WC) but non-luminescent calcite (TC), likely of meteoric origin (see later), also occluded these pore spaces (Fig. 4.49E&F).

In the MO-III section, the exposed faulted surface shows fault striations in the white calcite (WC). Host limestone is mostly composed of wackstone to packstone and grainstone, with large bivalves. Void-filling calcite (CC-I) is mostly restricted to the host limestone and not documented in any of the dolomite phases, hence pre-dates dolomitisation (Fig. In this part, several dolomite bodies lie between the El-Moro western area and the El-Moro valley (see Fig. 4.45). Isolated limestone lenses can also be observed in one of the studied section (Fig. 4.51 A&B). In these studied sections, Pb-Zn mineralization was commonly observed. This appears to be a considerably mineralized zone in the study area as abandoned mines are found there (Fig. 4.51 A&B). The dolomite bodies observed in the valley between El-Moro and El-Mazo showed similar features as those that were discussed before. Various transects across dolomite bodies were carried out to understand the possible changes in dolomite phases in this lower stratigraphic level as compared to Ranero area.

Field observations:

The grey colored host limestone and the dark beige colored dolomite body exhibits a sharp contact, while dolomite is intensely fractured as compared to nearby limestone host rock (Fig. It is rarely observed that twinned calcite (CC-II) partially replaced by dolomite cement (Fig.

4.55A

). Brecciation usually observed in the dolomite as well as in the host limestone, which generally indicates the occurrence of fault and/or subsidence zone. The hydrothermal breccias known as collapse breccias result from the dissolution of underlying carbonate beds and are interpreted as hypogenic or hydrothermal karst (Kyle, 1981;Sass-Gustkiewicz et al., 1982;Leach and Sangster, 1993). In the studied section, brecciated dolomite consisted of clasts of dolomite particles ranging in size from few mm to cm (Fig. In order to explain their depleted δ 18 O values, precipitation of related dolomites out of hot fluids may be invoked (e.g. Land, 1983). As mentioned above, the δ 13 C values lie within the known values of seawater for Early Cretaceous rocks. Accordingly, all the dolomite and calcite phases were formed isotopically in equilibrium with Early Cretaceous seawater (with respect to δ 13 C) or the system was rock-buffered during their formation. PDB) and δ 13 C (-6.2‰ V-PDB) values, invoking its meteoric origin (Shah et al., 2010).

Fig. 4.57. Dolomite and calcite phases in El-Mazo area. (A) Wackstone to packstone containing dolomite (yellow arrow) and calcite (white arrow) veins. (B) CCD-I dolomite containing stylolites (arrow), as these stylolites are mostly confined to initial phase of calcite and dolomite. (C&D) In the coarse crystalline, twinned calcite (CC-II), CCD-I dolomite pre-date CCD-II dolomite. (E) CL photomicrograph showing intercrystalline spaces in CCD-I dolomite filled by dull luminescent calcite (WC). (F) Selective dedolomitisation of CCD-I dolomite by late calcite (TC).

CC-II

CCD

Fig. 4.61. Oxygen-and carbon-isotopic analyses of calcite and dolomite phases as well as dolomite host rocks

in El-Moro valley, the analyzed dolomite and calcite phases exhibits depleted δ 18 O and δ 13 C values.

El-Mazo area:

In El-Mazo area, limestone host rocks show depletion in their δ 18 O values (-14.7 to -13.0‰ V-PDB) with respect to the original Albian marine signatures (Veizer et al., 1999). The initial dolomite phase (CCD-I) exhibits linear trend for depleted δ 18 O (-16.5 to -14.6‰ V-PDB) and Besides host limestone, the above described dolomite and calcite phases show high 87 Sr/ 86 Sr ratios, hence does not fit the Sr-curve with respect to time (Shah et al., in press). However, the corresponding burial curve of López-Horgue et al., (2010), confirms the late Cretaceous origin of these dolomite and calcite phases. • High 87 Sr/ 86 Sr ratios indicate interaction of dolomitising fluids with the radiogenic lithologies.

• Zn-mineralization mostly observed in the western and central part of the El-Moro area, while eastern El-Moro and El-Mazo areas are devoid of Zn-mineralization. Such mineralizations are observed in the Fe-rich CCD-Ia dolomite and are particularly prone to dedolomitization (Shah et al., submitted).

• Comparing the paragenetic sequences of El-Moro/El-Mazo areas with the Ranero area shows that the same sequence of hydrothermal events (i.e. CCI and II, CCD-Ia, Ib, CCD-II and WC) and the same telogenetic stage (TC) occurred in all the studied areas. Nevertheless, some subtle differences do exist:

• isotope signatures ( 18 O, 13 C) are slightly shifted from one area to the other ;

• primary Zn mineralisation (MVT type) is absent from the Ranero area, and only present in some of the dolostone veins of the El-Moro and El-Mazo blocks.

These subtle spatial variations in fluid chemistry, temperature and/or metal content suggest that the circulating fluids were not uniformly sourced. What appears as a regional dolomisation event is seemingly the result of relatively small (hydraulically independent) fluid circulation pulses that share the same general driving mechanism and temperature conditions, but not exactly the same sources or pathways.

Chapter: 5

INTERPRETATIONS AND DISCUSSIONS

The present chapter deals with the interpretation of the data collected from the two studied sites (i.e., Ranero and El-Moro/El-Mazo). The chapter includes the discussions on field observations, diagenetic evolution and establishment of a comprehensive paragenetic sequence, chemistry and origin of the dolomitising fluids, which lead to multiphase dolomitisation model.

Besides this, dolomite distribution and variations in the both the studied sites are taken into account.

The last section of the chapter consisted of the reservoir characteristics of various dolomite phases.

The NW-trending Pozalagua fault and other fractures, related to early Cretaceous (early Albian) rifting, appear to have been (re)activated through sinistral strike-slip motion, followed by hydrothermal activity during late Albian to Turonian times (Thiébaut et al., 1988;Aranburu et al., 1994;Schärer et al., 1999;Lopéz-Horgue et al., 2010;Appendix-II), or during the tectonic inversion of the basin in late Cretaceous-Paleogene times. The fact that the dolomite bodies are associated to faults indicates a tectonic control on the dolomite distribution (e.g. [START_REF] Garcia-Mondéjar | Plate reconstruction of the Bay of Biscay[END_REF][START_REF] Lopéz-Horgue | Fault -Related Hydrothermal Dolomite Bodies in Early Cretaceous Platform Carbonates Karrantza Area (North Spain): Outcrop Analogue for Dolomite Reservoir Characterization: 10 eme Congrès Française du Sedimentologie[END_REF]& 2010;Gasparrini et al., 2006;Shah et al., 2010;Appendix-II).

Various dolomite phases are believed to have formed due to the circulation of Mg-rich dolomitising fluids along faults/fractures, hence invoking multiple pulses of these fluids (Appendix-II).

FIELD OBSERVATIONS

The presence of linear, fault and fracture-filled dolomite bodies supports the idea that the dolomitising fluids migrated and spread through the sedimentary pile along these vertical discontinuities (Figs. 4.7;4.46 & 4.47). Dolomite bodies show different geometries in the Ranero area (Appendix-I), which include linear, fracture filled, fault constrained and irregular fronts. The El-Moro and El Mazo areas mostly consisted of fracture-and fault constrained dolomite bodies.

The Ranero dolomitic front (its margins away from the major fault) is irregular, tongue-like (fronts), suggesting that the porosity/permeability and mineralogy of the precursor limestone were important factors in the distribution of dolomite bodies (Figs. 4.1 & 4.12;[START_REF] Murray | Cause and control of dolomite distribution by rock selectivity[END_REF][START_REF] Bullen | Dolomite selectivity and mimic replacement[END_REF]. Physical characteristics of the host limestone rocks could partly control the dolomite distribution (e.g. Nader et al., 2007). In other terms, permeability determines fluid flow, and particle size determines the surface area available for fluid-rock interaction. Chemical characteristics such as the solubility of carbonate minerals may have played a significant role as well.

Detailed investigations resulted in a comprehensive paragenetic sequence established on the basis of excellent exposures of dolomite and calcite phases in the Pozalagua quarry (Fig.

DIAGENETIC EVOLUTION AND PARAGENETIC SEQUENCE

The present study involved a larger set of data including field observations, petrographic studies, as well as various types of geochemical analyses allowing the elaboration of a detailed paragenetic sequence of the various dolomite and calcite phases and some more information about their spatial distribution (Shah et al., in press). Petrographic studies helped in distinguishing various calcite phases, whereas homogeneous behavior (saddle) of various dolomite phases hindered to group various dolomite phases according to the classification scheme of [START_REF] Sibley | Classification of dolomite rock textures[END_REF] In such scenario, geochemical analyses helped in the classification of various dolomite phases (Fig. . Such calcites (CC-I & CC-II) often confined to faulted zones and exhibited relatively less depleted δ 18 O values (-12 to -14‰ V-PDB). These characteristic features show resemblance with the hydrothermal calcites of the Albian Jorrios area, hence these calcites have syntectonic origin (Aranburu et al., 2002). Zn-Pb deposits, situated NW of the study area (Velasco et al., 2003 andSymons et al., 2009).

Sphalerite-Galena associated dolomite phases in the Réocin area resulted in precipitation of Fe-rich dolomite in internal sediments and in open spaces (sulphide deposition). This resembles with the dolomite sands (DS) in the study area (e.g. Ranero quarry). Since internal sediments, such as frequently reported in MVT deposits [START_REF] Kendal | Ore deposits and sedimentary features, Jefferson City Mine, Tennessee[END_REF], need a large network of void space to form, and based on field observation and paragenesis, it is suggested that void-forming processes in the present case are preliminary rather than a consequence of HTD forming processes.

Various workers described the development of zebra dolomite as controlled by sedimentary facies (e.g., Beales & Hardy, 1980;[START_REF] Martin | Facies control of strata bound ore deposits in carbonate rocks. The F-(Pb-Zn) deposits in Alpine Triassic of the Alpujarrides, southern Spain[END_REF]Tompkin et al., 1994), while others described its cross-cutting relationship with sedimentary structures (Boni et al., 2000;Swennen et al., 2003;Vandeginste et al., 2005;Gasparrini et al., 2006). The studied zebra dolomite most likely resulted from the replacement of host limestone (Figs. 4.4D,4.10E,4.50E;Shah et al.,in press).

The second episode of dolomitisation (CCD-II) exhibits local-scale vein-filling dolomites, which showed replacement of pre-existing dolomite (CCD-I; as discussed above). In contrary to CCD-I, non-ferroan dolomite (CCD-II) does not alter the host limestone substantially. Non-ferroan dolomites were formed at relatively high temperature as indicated from fluid inclusion studies (Shah, 2008;Lopéz-Horgue et al., 2010). CCD-II dolomite consisted of interlocking anhedral crystals, which underwent aggradational neomorphism demonstrating the evolution into planar dolomite crystals as was described by Nielsen et al. (1994) and Vandeginste et al. (2005) (Fig.

4.5D

). Fault reactivation resulted in brecciation of non-ferroan dolomite, creating voids that were later on filled by white calcite (WC). Calcitized, non-luminescent part of CCD-I show less depleted δ 18 O and depleted δ 13 C values, likely formed near meteoric recharge (Choquette & James, 1988;Niemann & Read, 1988;Meyers, 1991;Reeder, 1991;Nader et al., 2008).

Furthermore, the two dolomitisation episodes and the associated hydrothermal events (early and late calcite formation) are believed to have occurred during the early to late Albian and Cenomanian age (Figs. 4.54B, 4.57B;López-Horgue et al., 2010, Appendix-II). Atleast two generations of bed-parallel stylolites pre-and post-dated dolomite episodes, where burial events are mostly restricted to early to late Albian and Eocene age. In order to assign the probable age of various calcite and dolomite phases, pre-dolomite calcitization (1) resembles syntectonic hydrothermal calcite of the Jorrios area, which is assigned as mid Albian age (Aranburu et al., 2002). Initial phase of dolomitisation ( 2 In conclusion, the study area mainly features two distinct phases of hydrothermal dolomitisation and two minor phases of hydrothermal calcite deposition along fluid pathways controlled by paleo-and hypogene karstification, fracturing and brecciation. Perhaps the most remarkable aspect of this case is that the first dolomitizing phase is a ferroan one (CCD-I), while the second is non-ferroan (CCD-II), both being precipitated at relatively high temperature as suggested by the very negative δ 18 O values (as low as -19‰ VPDB ; Figs. 4.32-4.35 and 4.59-4.62) and by fluid inclusion homogenization temperatures (120 -200°C;Shah et al., 2010;López-Horgue et al., 2010). This sequence is less commonly observed in HTDs (Davies and Smith, 2006) or MVT deposits (Leach et al., 2005), as the dolomites are usually Fe-rich during the whole dolomitisation.

Besides, the early ferroan phase appears to have the highest regional extent (pervasive dolomite)as it is found and documented at several sites in the study area and its surroundings -while the later non-ferroan one seems to occur as vein-fillings. In the El-Moro area, the same two dolomite stages are reported, where the first (ferroan) stage is associated with some Zn-Pb sulfides (Shah et al., in press). consistent with multiphase dolomitization and dolomite recrystallization (Nielsen et al., 1994).

CHEMISTRY OF DOLOMITIZING FLUIDS

According to Veizer et al., (1999), oxygen and carbon isotopic signatures of the Early Cretaceous marine limestone ranges from -3 to +1‰ δ 18 O and from 0 to +4‰ δ 13 C, while the studied limestone and dolomite phases indicate a clear shift from the Early Cretaceous marine limestone isotope signatures -with the exception of early marine calcite cements which show close resemblance with it . The limestones close to the dolomites also show depleted δ 18 O values, implying recrystallization during dolomitization. Depleted δ 13 C values may be interpreted as resulting from interference of late telogenic calcite phases . The reported δ 13 C values of such dolomites are not far from the original marine signature of the host rocks (i.e. early Cretaceous), which possibly also can be explained by the slight temperature fractionation of 0.03‰ per degree Celsius (Emrich et al., 1970). However CCD-II dolomite in the El-Moro fault sections showed slightly depleted δ 13 C values, which can possibly be explained by contamination with calcite (TC) as no organic matter is observed in the analysed samples (Figs. 4.53C & 4.59;Emrich et al., 1970).

Different sources supply various amount of Sr, which resulted in broad range of 87 Sr/ 86 Sr ratios of seawater. According to [START_REF] Elderfield | Strontium isotope stratigraphy[END_REF], two main sources of Sr responsible for the 87 Sr/ 86 Sr variation in seawater. These include: (i) The hydrothermal alteration of basalts near mid-ocean ridge, which gives low isotope ratio of Sr (0.702), (ii) The exposure of Rb-rich continental rocks results in high isotope ratio of Sr (~ 0.718). Various workers contributed in the establishment of Sr-curves, which illustrate the 87 Sr/ 86 Sr ratios of seawater of different age [START_REF] Burke | Variation of seawater 87 Sr/ 86 Sr throughout Phanerozoic time[END_REF][START_REF] Denison | Construction of the Mississippian, Pennsylvanian and Permian seawater 87 Sr/ 86 Sr curve[END_REF][START_REF] Smalley | Seawater Sr isotope variations through time: a procedure for constructing a reference curve to date and correlate marine sedimentary rocks[END_REF], Veizer et al. 1999).

The analyzed limestone exhibits 87 Sr/ 86 Sr signatures lie within the range of the primary marine lower to upper Albian sequence (Fig. 4.37;McArthur et al., 2001). This indicates that the host limestone originated from marine water and any subsequent recrystallisation process took place either in a closed system with respect to Sr or with water of similar Sr isotope composition (e.g. [START_REF] Banner | Water-rock interaction history of regionally extensive dolomites of the Burlington-Keokuk Formation (Mississippian): isotopic evidence[END_REF][START_REF] Banner | Application of the trace element and isotope geochemistry of strontium to studies of carbonate diagenesis[END_REF]. The 87 Sr/ 86 Sr ratios for CCD-I and CCD-II are mostly higher than those of lower to upper Albian seawater, which excludes the possibility of direct precipitation of the dolomites from it (Figs. 4.37 & 4.63). In order to use the Sr-curve of [START_REF] Smalley | Seawater Sr isotope variations through time: a procedure for constructing a reference curve to date and correlate marine sedimentary rocks[END_REF],

the Sr isotope composition of the dolomites (CCD-I & CCD-II) and calcites (CC-I, CC-II &WC) exhibit higher 87 Sr/ 86 Sr ratios than those of seawater of most geological times (Shah et al., in press).

Therefore, a radiogenic nature for the dolomitising fluids can be inferred. Detrital and igneous silicate minerals with high Rb/Sr ratios can be the potential source of radiogenic Sr [START_REF] Perry | The effects of diagenesis on the redistribution of strontium isotopes in shales[END_REF]. The decay of 87 Rb to 87 Sr produces elevated 87 Sr/ 86 Sr ratios in these minerals.

Albitisation or dissolution of alkali feldspar, dissolution of mica and conversion of smectite to illite may result in the release of radiogenic Sr (Stueber et al. 1987, Chaudhuri and[START_REF] Chaudhuri | Strontium isotopic composition and potassium and rubidium contents of formation waters in sedimentary basins: clues to the origin of the solutes[END_REF]. Linear correlation between TiO 2 and Al 2 O 3 in their crossplot and high concentration of TiO 2 in the CCD-II dolomite indicate their relationship with rift-related alkaline igneous rocks as documented in the Mesozoic-early Cenozoic Newfoundland rifted margin deposits in the northwestern Atlantic (Robertson, 2007). The 87 Sr/ 86 Sr ratios of dolomite and calcite phases are higher than those of the host limestones, whereas the Sr-curve also verifies higher Sr signatures of dolomite and calcite phases than seawater 87 Sr/ 86 Sr ratios of most geological times (Shah et al., in press). Therefore, dolomitising fluids may have interacted with radiogenic lithologies (sandstones and shales) during late Albian intense tectonic activity, confirming the results of Bustillo et al. (1992). The other possibility may be that these fluids transferred from a deeper Permo-Triassic siliciclastics aquifer during the late Cretaceous-Eocene inversion of the basin [START_REF] Gómez | Inversion tectonics of the northern margin of the Basque Cantabrian Basin[END_REF]. As explained earlier, the estimated salinity of the primary inclusions of these dolomite facies are up to three to four time greater than seawater (12 -21 eq. wt. % NaCl; Shah et al., 2010), which eliminates meteoric water as possible explanation for depleted δ 18 O values and temperature increase is the likely cause for the depleted δ 18 O values as argumented by the high T H values (Shah et al., 2010). Calculated δ 18 O values of the parent fluid following Land's (1985) dolomite-water fractionation equation (cf. Adams et al., 2000), show that estimated water δ 18 O values range between +2.0 and +4.0‰ Vienna standard mean ocean water (V-SMOW) (Fig. 4.40). These δ 18 O fluid of CCD-I and ZD dolomite are typical of influxes of basinal brines (Goldstein and Reynold, 1994). Integration of fluid inclusion data with isotope and geochemical analyses show that these dolomites formed at temperatures higher than the ambient temperature, hence hydrothermal in origin and exhibits resemblance with St. George Group of Western, New foundland (Conliffe et al., 2010).

In order to understand the present scenario related to MVT bearing fluids, most CCD-I related fluids should be acidic and Mg-rich, capable to replace limestone pervasively (Appendix-III). Moreover, they should not be H 2 S-rich in order to allow the transport of reduced Fe and Mn. In dolomitizing fluids is reminiscent of that advocated for Australian Proterozoic cedex deposits (Cooke et al. 2000) between oxidized and reduced brines, although the inferred pH characteristics may be quite different.

ORIGIN OF DOLOMITIZING FLUIDS

The distinct nature of the two major dolomite phases (CCD-I and CCD-II) resulted from fluids of different origin. This is evidenced from their physico-chemical characteristics, as described above. Accordingly, some information could be inferred regarding the origin of the various dolomitizing fluids.

CCD-I dolomitizing fluids

Mg-rich fluids likely originated as sulphate-dominated marine-related waters (compactional waters or marine waters mixed with ancient -stored -aquifer brines; Appendix-III). In order to increase their acidity, such fluids need to be heated -being driven towards a hot zone or mixed with hot fluids, and undergo localized sulphate reduction (TSR) with their own content of local reductant source (organic matter, oil or gas). The fact that the fluids became acidic is crucial for pervasive dolomitisation, because Mg-rich fluids which gained acidity are prone to couple limestone dissolution and precipitation of dolomite. It should be noticed that, whatever the ultimate origin of the fluids (either cold or hot), the sulfate (and Mg) and the reducing agent are supposed to meet in a hot siliciclastic host. This may apply to compactional fluids, as they can be expelled towards the platform edge area at a moment when a temperature anomaly occurs due to differential subsidence and faulting linked to crustal stretching processes (Fig. 4.46) (García-Mondéjar et al., 2004b;López-Horgue et al., 2010). Note also that the compactional fluid drive provides a simple explanation for pressure build ups and related pulses of overpressure relaxation (expressed by dilatational jointing and brecciation) as observed for CCD-I.

CCD-II dolomitizing fluids

The origin of the fluids that precipitated the non-ferroan dolomites (CCD-II) is seemingly different, or at least their history involved different steps. If these fluids gained the needed H 2 S from TSR, they must have been buffered to lose their capacity to react with calcite before invading the Ranero Fault system (Appendix-III). The iron poor carbonate platform limestones may have buffered the fluid acidity. To follow this path, the fluids should pass through a TSR prone, hot zone that is most probably located within the interior platform. The ultimate origin of the sulphate is less constraining, as the corresponding fluids are not necessarily Mg-rich and evaporitic sulphate (Hanor, 1994) can be invoked as well. In this scenario, the Pondra Diapir, which is at the intersection of the Ramales and Cabuérniga Faults (Lopez-Horgue et al., 2010) and underlies the Ranero area, could have acted both as a source of sulphate and as the core of a thermal anomaly owing to the salt conductivity (Fig. 5.3). Similar diapirism and associated structural effects has been recorded in the coeval hydrothermaly dolomitised reservoirs in Aquitaine (France; Canérot et al., 2005). Accordingly, convective flow adjacent to salt diapir and subsequent TSR within a limestone host may provide the right conditions to generate CCD-II dolomitizing fluids. It is important to emphasise that the resulting fluids loose very soon their capacity to react with calcite, hence their effects may be difficult to detect in the platform carbonates. Conversely, the dolomitizing fluids reacted with any Fe-bearing lithology (including Fe-dolomite) to precipitate pyrite.

5.5-MULTIPHASE DOLOMITIZATION MODEL

On the basis of the above discussions, two episodes of dolomitization resulted in the observed ferroan dolomite (CCD-I) and non-ferroan dolomite (CCD-II), respectively. The origin of the hypogene karstification before Fe-rich dolomitization is unknown, but one possibility could be "cooling of formation waters" (Giles and de Boer, 1989). Its impact is particularly significant in (iii) In the El-Moro area, host limestone shows higher δ 13 C values as compared to those observed in the Ranero area.

Dedolomitisation is frequently found in all studied sites. This has been associated with telogenetic processes involving meteoric diagenesis. Finally, it is worth stressing again that Ranero area exhibits a larger volume of dolomites, mainly associated to the Pozalagua fault. While an earlier phase of dolomitisation (Fe-rich, assumed to originate from compactional fluid flow) has been documented and interpreted as pervasively affecting the Ramales Platform, the later phase of dolomitisation (Fe-poor, associated to a thermal anomaly) appears to mainly occur as vein-fillings in the study area.

RESERVOIR CHARACTERIZATION

Dolomitization may generate, preserve or destroy porosity depending on the textures of the replaced carbonates, rate and composition of fluids and duration of the process [START_REF] Lucia | Porosity evolution through hypersaline reflux dolomitization[END_REF]. Dissolution during dolomitization and precipitation of dolomite cement are considered responsible for positive or negative effects on porosity development, respectively. In the analyzed dolomite samples, dissolution/precipitation decreased the porosity, while cataclastic deformation present in some samples increased the porosity (Appendix-V). Porosity and permeability analyses indicate that majority of the dolomite phases contain considerably low porosity and permeability values due to over-dolomitization and calcite cementation (Shah et al., 2008). Dissolution followed by precipitation mostly occluded the porosity in the analyzed dolomite facies (Shah et al., 2008).Initial phase of dolomitisation (CCD-I) exhibited wide range of porosity (1.6 to 7.0%) and permeability values (0.3 to 1.23mD), while average porosity of zebra dolomite (ZD) and dolomite sand (DS) ranges up to 3.7%. It is in general consensus that dedolomitization usually have negative effect on porosity generation, but present studies indicate that selective dedolomitization in CCD-I resulted in the enhancement of porosity (6.0 to 6.6%) but relatively less permeability values (0.12 to 0.22mD; Appendix-V).

The porosity and permeability values of CCD-II dolomite varies from 1.6 to 3.8% and 0.16 to 0.31mD respectively (Appendix-V). It is also observed that CCD-II dolomite consisted of considerably high porosity (8.28 to 11.6%) and permeability values (0.9 to 1.64mD), which is related to the post-dolomite brecciation (Appendix-V). So, post-diagenetic alterations resulted in enhancement of the reservoir characteristics of the CCD-II dolomite phase.

INTRODUCTION

Hy dro ther mal do lo mite seems to oc cur more ex ten sively than pre vi ously thought [START_REF] Mountjoy | Multiphase fracture and fault-controlled burial dolomitization, Upper Devonian Wabamun Group, Alberta[END_REF][START_REF] Knipe | Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: An introduction[END_REF]Berger and Davies, 1999;Moore, 2001;Cantrell et al., 2004;[START_REF] Lavoie | Hydrothermal dolomitization in the Lower Silurian Sayabec Formation in northern Gaspé-Matapédia (Québec): Constraints on timing of porosity and regional significance for hydrocarbon reservoirs[END_REF]Nader and Swennen, 2004;Davies and Smith, 2006]. Hy dro thermal dolomites are mostly strata de struc tive (but stratiform in some cases), cut ting across host lime stone and form ing broad belts along ma jor re gional faults [START_REF] Wil | -Do lo mi ti za tion front geo me try, fluid flow pat terns and the ori gin of mas sive do lo mite: the Trias sic La te mar buil dup, nor thern Ita ly[END_REF]Nader et al., 2004]. Since po rous do lo mite is prob a bly hydro ther mal in or i gin in many oil [Ghawar, Saudi Ara bia; Cantrell et al., 2004] and gas res er voirs [North field, Arabian Gulf; Sudrie et al., 2006], un der stand ing this par tic u lar dolomitization pro cess is of ma jor eco nomic con cern.

Var i ous mod els (frac tures and faults, vol ca nism and salt diapir as so ci ated) have been pro posed for hy dro ther mal dolo mite for ma tion by dif fer ent work ers [START_REF] Charef | Pb-Zn mineralization associated with diapirism: fluid inclusion and stable isotope (H, C, O) evidence for the origin and evolution of the fluids at Fedj-El-Adoum, Tounisia[END_REF]Cervato, 1990;[START_REF] Duggan | Fault controlled dolomitization at Swan Hills Simonette oil field (Devonian), deep basin west-central Alberta[END_REF]Nader et al., 2004;[START_REF] Al-Aasm | The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry[END_REF]Davies and Smith, 2006]. In ad di tion to this, [START_REF] Smith | Hy dro ther mal al te ra tion of car bo nate re ser voirs: How com mon is it?[END_REF] pro posed that hy dro ther mal dolomitization must in volve some sort of ep i sodic con vection. These ther mal con vec tion flow mod els have also been in voked by [START_REF] Machel | General constraints on extensive pervasive dolomitizationand their application to the Devonian carbonates of western Canada[END_REF] and Gasparrini et al. [2006]. Ther mal con vec tion may ac count for more ef ficient dolomitization than other mech a nisms be cause the Mg-rich flu ids can be re cy cled many times through the precur sor car bon ates [START_REF] Wil | Spatial pat terns of dia ge ne sis du ring geo ther mal cir cu la tion in carbo nate plat forms[END_REF]. This pa per ad dresses the petrographic char ac ter is tics of frac ture-re lated dolomites in Up per Cre ta ceous car bon ate rocks of the Cantabrian Moun tains as well as their geochem i cal at trib utes and re sults of fluid in clu sions. Hence, a con cep tual model ex plain ing the ob served fea tures of dolomitization is pro posed and some in sights are given to its im pli ca tion on res er voir prop er ties.

LOCATION AND TECTONIC SETTING OF THE STUDY AREA

The study area is lo cated near the Ranero vil lage in Karrantza val ley (north west ern Spain), at the bor der of the Basque coun try and the Prov ince of Cantabria (fig. 1). This area is part of the Basque-Cantabrian ba sin (BCB), which lies be tween the Pyr e nees and the Cantabrian moun tains in the north of Spain. The Cre ta ceous sed i men tary evo lu tion of the re gion can be re lated to the late tec tonic re la tion ship be tween the Eu ro pean and Ibe rian plates, and closely linked to the open ing of the North At lan tic Ocean and the Bay of Biscay [Malod and Mauffret, 1990;Olivet, 1996]. Pre vi ous work ers used paleomagnetic sig na tures to de lin eate the bound ary be tween Ibe rian and Eu ro pean plates, which likely cor re sponds to the fault zone of the Biscay synclinorium [START_REF] Vandenberg | New paleomagnetic data from the Iberian peninsula[END_REF][START_REF] Schott | Paleomagnetism of the lower Cretaceous red beds from northern Spain, evidence for a multistage acquisition of magnitization[END_REF]Rat, 1988;Gar cia-Mondéjar et al., 1996]. On the ba sis of sur face and subsurface data, BCB wit nessed var i ous ep isodes of rift ing in the early Cre ta ceous and an other rift ing stage took place in late Cre ta ceous age [Lamolda et al., 1983;Meschede, 1985;Cabanis and Le Fur-Balquet, 1990;Castanares et al., 2001]. The BCB un der went mul ti di rectional stretch ing (NNE-SSW and then NW-SE) dur ing early Cre ta ceous rift ing [Montadert et al., 1979;Grimaud et al., 1982;Malod and Mauffret, 1990;Olivet, 1996].

The study area (Ranero) con tains NW-SE, E-W, N-S, and NE-SW trending faults, which are in ter preted as re lated to the extensional his tory of the study area (fig. 1). Ma jor structures in clude NW-SE ori ented (Güenes and Ranero faults), N-S ori ented (Ramales fault), E-W ori ented (Arredondo and Hornijo faults) and other small scale NE-SW di rected faults and fault splays (fig. 2). The Güenes fault con tains oblique-slip and horse tail splay fea tures and formed dur ing Early-Mid Albian [Aranburu et al., 1994], while the Ranero fault (left lat eral strike slip) is be lieved to be the splay of the Güenes fault, which con tains do lo mite bod ies along its ex ten sion (fig. 4B) [Gar cia-Mondéjar et al., 1996] as well as along mi nor faults and horse-tail splays. So, these NW-SE ori ented faults are re lated to early Cre ta ceous rift ing in the BCB [Grimaud et al., 1982;Boillot and Malod, 1988;Olivet, 1996]. N-S faults (e.g., Ramales fault) are base ment-re lated listric faults [Gar cia-Mondéjar and Pujalte, 1975]. The E-W ori ented Arredondo and Hornijo faults (Early-Mid Albian) are deep seated and are pres ent along the car bon ate plat form mar gins, which post-date NW-SE ori ented faults and fractures [Gar cia-Mondejar, 1985].

The study area (Karrantza val ley) is part of the Ramales plat form, which con tains Aptian-Albian car bon ate build ups. At the foot of these reefal and back reef car bon ate build ups, slope and basinal de pos its also oc cur (fig. 1A-B). The short dis tance be tween the plat form car bon ates and the basinal de pos its sug gests the for ma tion of an intra-plat form trough rather than a deep ba sin, which is also shown in the paleogeographic map of the Early-Mid dle Albian age of Gar cia-Mondéjar [1996] (fig. 1A-B).

METHODS

Do lo mite bod ies were de lin eated by means of ae rial pho tographs, and later on checked dur ing field work. 110 rock samples were col lected from the do lo mite bod ies and host lime stone in such a way that dif fer ent do lo mite fa cies are rep re sented across the main Ranero fault, the Ranero vein (do lo mite body east of the main Ranero fault), the do lo mite front (ir reg u lar do lo mite tongues on the west ern side of Ranero fault) and Pozalagua quarry (fig. 3). Petrographic obser va tions in cluded con ven tional (Nikon ECLIPSE LV 100 POL) and cathodoluminescence mi cros copy (Cathodyne OPEA; op er at ing con di tions were 12 to 17 kV gun po tential, 350 to 600 µA beam cur rent, 0.05 Torr vac uum) of thin sec tions. For ferroan/non ferroan-do lo mite and cal cite differ en ti a tion, thin sec tions were stained with aliz a rin Red S and po tas sium ferri cyanide [START_REF] Son | Car bo nate iden ti fi ca tion and ge ne sis as re vea led by stai ning[END_REF]. Im age anal y sis has been per formed by means of JMicrovision soft ware. XRD anal y ses [to de ter mine bulk min er al ogy, stoichiometry and crys tal or der ing of the dif fer ent do lo mite phases) of the twenty-seven se lected sam ples were car ried out us ing PANalytical X'Pert PRO XRD diffractometer (Cu-K␣ ra dia tion ~ 45 kV, 40mA). The scan speed was set at 0.2° min -1 and sam pling in ter val at 0.001° per step. The do lomite stoichiometry mol% CaCO 3 was de ter mined by ap plying Lumsden's equa tion [1979] to the mea sured d[104] spac ing (M = 333.3 × d-spac ing -911.99).

Ninety four sta ble iso tope (␦ 18 O and ␦ 13 C) anal y ses of dif fer ent do lo mite types, cal cite ce ments and host lime stone was car ried out in the Laboratoire de Biominéralisation et Paléoenvironnement; Université Pi erre et Ma rie Cu rie-Paris VI and Departement de Géologie, Université Jean Monnet, Saint-Etienne (ta ble. I). All sta ble iso tope val ues are re ported in per mil (‰) rel a tive to Vi enna Pee Dee Belem nite (V-PDB). Do lo mite iso to pic com po si tion val ues are cor rected by frac tion ation fac tors given by Rosenbaum and Sheppard [1986]. Microthermometry was per formed on two dou ble-pol ished sec tions (each from ze bra do lo mite and late sad dle do lo mite) us ing a Linkam THMSG 600 heat ing cool ing stage. Twenty-five do lo mite crys tals con tain ing primary, two-phase pri mary in clu sions were an a lyzed.

Sev enty sam ples (4 cm in length and 2.2 cm in di am e ter) were se lected for petrophysical anal y ses (po ros ity, per meabil ity; ta ble. II). For po ros ity de ter mi na tion, micromeritics GeoPyc TM 1360 and micromeritics AccuPyc 1330 were used in the Res er voir Char ac ter iza tion De part ment of IFP. For per me abil ity anal y sis, the stan dard tech nique of vacuum gen er a tion us ing Boyle's Law was used.

FIELD OBSERVATIONS

Based on weath er ing col ors, do lo mite bod ies can clearly be dif fer en ti ated from host lime stone even in the ae rial pho tographs of the study area (fig. 3). Do lo mite is yel low ish-brown to dark grey in color and dis plays crum bly weath er ing, whereas lime stone is light grey col ored and de vel ops a karren karst (fig. 4A). Fault-con trolled as well as ir reg u lar do lo mite bod ies (fronts) are in sharp con tact with the host lime stone.

Field stud ies have been fo cused on three spe cific do lomite bod ies close and/or on the Ranero fault (fig. Be sides Ranero fault re lated do lo mite bod ies, a linear/elon gated do lo mite body oc curs in the east ern part of the Ranero fault (fig. 3) and is in di cated as: Ranero vein (frac ture filled, lin ear/elon gated do lo mite body; fig. 4D).

In the above men tioned do lo mite bod ies, it oc curs as mas sive and ze bra do lo mite. Mas sive do lo mite con sists of milky white to light pink col ored, me dium to coarse crystalline sad dle do lo mite (fig. 4E) and light to dark grey col ored, me dium crys tal line sug ary do lo mite (fig. 4F). Ze bra do lomite con sists of al ter nat ing bands of dark grey col ored replacive do lo mite phase and off-white col ored ce ment phase (fig. 5A).

Fault-re lated do lo mite bod ies are gen er ally ori ented N-S, NW-SE and NE-SW. These do lo mite bod ies show vari a tion in their fa cies dis tri bu tion across the fault. In the Pozalagua quarry site, var i ous do lo mite phases (dark to light grey, brown to yel low ish, pink ish and milky white to light pink) are ob served, which could re late to mul ti ple in flux of the dolomitizing flu ids [Swennen et al., 2010]. More over, do lomite color is in de pend ent from the com po si tion and/or color of the host li thol ogy. Iso lated blocks con sist ing of ze bra dolo mite oc cur in the pre vi ous do lo mite and in di cate an early for ma tion as com pared to other do lo mite types (fig. 5B). Lo cally, dolomites in the Pozalagua quarry con tain brecciated lime stone clasts in do lo mite ce ment (fig. 5C).

In the Ranero fault up-slope site, var i ous do lo mite facies were sam pled along with host lime stone (fig. 3). Besides these ma jor struc tural fea tures, do lo mite is also as so ci ated with mi nor faults and/or frac tures (fig. 4B). Horse tail splays con tain ing do lo mite were also ob served, which in di cate the strike-slip na ture of the Ranero fault (fig. 5D) [Har ding, 1974]. In fault-con trolled bod ies, massive do lo mite fa cies are dom i nant and ex hibit a milky white ap pear ance, curved crys tal faces in ter locked with each other and neg li gi ble inter-crys tal line po ros ity (fig. 4E). Be sides mas sive do lo mite, ze bra do lo mite also oc curs in this stud ied sec tion (fig. 5A).

The do lo mite dis tri bu tion across the fault/frac ture is gen er ally de pend ent upon the na ture of the host rock and dolomitizing flu ids (i.e., rel a tively high po rous and/or perme able rocks per mit dolomitizing flu ids to cir cu late, while rate of flow de ter mines the ex tent of dolomitization as well). Ir reg u lar-shaped, fin ger like do lo mite bod ies (Ranero fronts) in trud ing into the host lime stone, oc cur in the western part of the Ranero fault near the Pozalagua Quarry (fig. 4C). Var i ous do lo mite fa cies are ob served in the Ranero front sec tion. Dom i nant fa cies in clude dirty grey col ored, sug ary do lo mite that con tains con sid er able intercrystalline pore spaces (fig. 4F).

Frac ture filled, lin ear do lo mite body (Ranero vein) trending NW-SE, is cut by al most E-W ori ented right-lateral strike-slip fault (fig. 4D). Sam pling was done along an east-west sec tion across the do lo mite body and the host lime stone. In the Ranero vein sec tion, cal cite veins oc cur in both pre cur sor lime stones as well as dolostones and gen erally have the same re gional trend as that of the faults. In the host lime stone, early cal cite veins have their cen tral part filled by or ange col oured do lo mite (fig. 5E). Mac ro scopic ob ser va tions in di cate that these do lo mite filled cal cite veins are partly brecciated and cross cut by late stage cal cite veinlets (fig. 5F).

PETROGRAPHY

Mi cro scopic ex am i na tion of the col lected sam ples (limestone and do lo mite fa cies) from Pozalagua quarry (on the main Ranero fault), NE-SW ori ented Ranero fault and vein sec tions and N-S ori ented Ranero front sec tion was done (fig. 3). Var i ous do lo mite fa cies were dis tin guished on the ba sis of the shape of the crys tal bound ary (pla nar and nonplanar) and crys tal size dis tri bu tion (unimodal and polymodal) us ing the clas si fi ca tion of [START_REF] Sibley | Classification of dolomite rock textures[END_REF]. Mas sive dolomites com posed of pla nar (sugaric) or nonplanar (sad dle) do lo mite, while ze bra do lo mite mostly com posed of al ter nat ing bands of unimodal, nonplanar crys tals. Due to the ab sence of con crete clas si fi ca tion on size range of do lo mite, these are termed as coarse, me dium and/or fine crys tal line do lo mite on the ba sis of rel a tive abun dance of var i ous sizes.

Pozalagua quarry

Lime stone ranges from wackestone to packstone with partially ce mented fos sils and fos sil frag ments [START_REF] Ham | Clas si fi ca tion of car bo nate rocks ac cor ding to depo si tio nal tex ture[END_REF] (fig. 6A-B). These fos sils in clude biomolds, tab u lar cor als, de bris of rudists and forams.

Mas sive do lo mite mostly con sisted of pla nar (sugaric), rhombic, subhedral to euhedral me dium crys tal line do lomite (fig. 6C-D). Inter-crys tal line pore spaces are filled with cal cite and lo cally also with py rite (see fig. 6C). Cathodoluminescence (CL) ex am i na tion high lights the rhombic shape of these pla nar do lo mite crys tals with lo cally well-de vel oped intercrystalline po ros ity (fig. 6D). Be sides pla nar do lo mite, nonplanar, coarse-crys tal line do lo mite shows undulose ex tinc tion (fig. 6E), which is typ i cal of nonplanar (sad dle) do lo mite [Radke and Mathis, 1980]. Nonplanar do lo mite ce ment dis plays pri mary crys tal growth zon ing un der CL (fig. 7A).

Ze bra do lo mite ex hib its al ter nat ing bands of fine-to-medium crys tal line and coarse crys tal line dolomites (fig. 6F). Fine to me dium crys tal line do lo mite shows straight ex tinc tion while coarse crys tal line ce ment do lo mite shows undulose extinc tion. In the cross-po lar ized light, aggradational neomorphism (crys tal over-dimensioned growth) is ob served.

Ranero fault section

Petrographic stud ies show host lime stone, cal cite ce ments and dif fer ent do lo mite fa cies along with their al ter ation prod ucts. Tex tur ally, lime stone (about 35% of the whole sec tion; fig. 9) ranges from wackestone to packstone and con tains fos sils and fos sil frag ments, which in clude tab ulate cor als and foraminifera. Host lime stone con tains veins filled with cleav age twinned cal cite and do lo mite ce ments.

Mas sive (pla nar) dolomites (about 5% in the sec tion; fig. 9) are subhedral to euhedral me dium crys tal line dolomites, rang ing in size be tween 200-500 µm. These pla nar dolomites con tained con sid er able intercrystalline pore spaces, which is of ten filled by cal cite. Coarse crystal line (300 to 700 µm), polymodal, nonplanar do lo mite (about 50% of the sec tion) of ten oc curs ad ja cent to the pla nar do lo mite and ex hib its an in ter lock ing pat tern. Under CL, nonplanar do lo mite ce ment shows dif fer ent zonations of dull to bright red colours with red rims. In the Ranero fault sec tion, the size of these nonplanar do lomite crys tals in creased from east to west as very coarsely crys tal line dolomites were ob served at the west ern extrem ity.

Ze bra and/or ze bra-like dolomites (about 5% of the section) are com posed of coarse crys tal line do lo mite ce ment (400 to 700 µm) al ter nat ing with fine crys tal line do lo mite ma trix (20 to 100 µm). Coarse-crys tal line do lo mite has an undulose ex tinc tion typ i cal of sad dle do lo mite, while fine crys tal line do lo mite ex hib its straight ex tinc tion. Intercrystalline pore spaces in var i ous do lo mite fa cies are commonly filled by cal cite, but some do lo mite veins post-dat ing the cal cite veins ex ist as well (fig. 7B). Be sides do lo mite

Ranero front section

An ir reg u larly dis trib uted tongue-shaped do lo mite front on the west ern side of the main Ranero fault was stud ied (fig. 3). Ma trix lime stone (about 21% of the sec tion; fig. 9) con tains cal cite veins, which are not ob served in the do lomite. Be sides ma trix lime stone, mas sive (pla nar and nonplanar) do lo mite and their cataclastic ag gre gates as a result of brecciation are also ob served. In con trast to the other stud ied cases, this sec tion con tains rel a tively more pla nar do lo mite. Pla nar do lo mite (about 44% of the sec tion; fig. 9) crys tals are subhedral to euhedral and range in size from 30 to 200 µm. These pla nar dolomites are sur rounded by late stage cal cite ce ment. Nonplanar do lo mite (23% of the section; fig. 9) crys tal faces are subhedral to anhedral and crystal size ranges from 50 to 400 µm. Some of the do lo mite ce ments show pla nar ap pear ance and straight ex tinc tion in cross-po lar ized light and ex hibit dull and bright red CL-patterns, which may in di cate dif fer ent gen er a tions of do lo mite growth (fig. 8 A-B). Pore-fill ing cal cite ce ment (8% of the sec tion) is also ob served.

Diagenetic al ter ations in clude cataclastic de for ma tion, which re sulted in the for ma tion of bro ken crys tals of var ious sizes ce mented by coarse crys tal line cal cite (fig. 8C). Cataclastic do lo mite (4% of the sec tion) is ob served in the north east ern ex trem ity of the sec tion. An gu lar rock fragments are ob served in cer tain zones, prob a bly due to small scale frac ture and fault pass ing through the do lo mite front.

Ranero vein section

Lime stone (about 38% of the sec tion; fig. 9) con tains uniserial ben thic foraminifera, gas tro pods, pel lets and intraclasts with con sid er able amounts of sec ond ary po ros ity, which might be due to sur face weath er ing (fig. 13D). Gener ally, the po ros ity is de stroyed by cal cite ce ment fill ing. Frac ture-filled cal cite in the host lime stone shows in crease in con cen tra tion to wards the do lo mite body.

Me dium crys tal line, polymodal, nonplanar, mas sive dolo mite (about 39% of the sec tion; fig. 9) shows in ter lock ing pat terns, char ac ter is tic undulose ex tinc tion and ex hib its dull to light red colours with bright red rim un der CL view ing. Nonplanar do lo mite in creases in crys tal size from east to west part in the stud ied sec tion as very coarsely crys tal line (> 1 mm) nonplanar do lo mite is ob served in the ex treme west of the stud ied sec tion. Ze bra and/or ze bra-like do lomite (about 16% of the sec tion; fig. 9) are com posed of a coarse crys tal line do lo mite ce ment (300 to 500 µm) al ternat ing with a fine crys tal line do lo mite ma trix (50 to 100 µm) Diagenetic al ter ations in clude a recrystallization (dis solu tion/pre cip i ta tion) phe nom e non typ i cal of nonplanar dolo mite, where dis so lu tion in cer tain do lo mite crys tals (dark grey col ored) is fol lowed by pre cip i ta tion of other do lo mite crys tals (of white col ored; fig. 8D). This pro cess par tially or com pletely de stroys the intercrystalline po ros ity, as well as dis so lu tion po ros ity. Pore-fill ing cal cite ce ment (7% of the sec tion) is also ob served.

GEOCHEMISTRY Oxygen and carbon isotopes

In the Pozalagua quarry, dif fer ent do lo mite fa cies show a wide range of ␦ 18 O de pleted val ues. These in clude mas sive (nonplanar) do lo mite, which ex hib its ␦ 18 O val ues from -17.0 to -12.0‰ and ␦ 13 C val ues from -0.7 to +1.0‰. Sugaric (pla nar) do lo mite shows wide ranges of de pleted val ues in ␦ 18 O (-13.8 to -9.7‰) and ␦ 13 C (-2.7 to -0.7‰; fig. 10). Ze bra and/or ze bra-like do lo mite shows val ues rang ing from -18.0 to -13.0‰ for ␦ 18 O and from -0.7 to +1.5‰ for ␦ 13 C (fig. 10). Cataclastic do lo mite shows ␦ 18 O val ues from -16.7 to -14.0‰ and ␦ 13 C be tween -1.6 and +1.1‰. The Ranero front sec tion con tains two do lo mite facies, which show highly de pleted ␦ 18 O. Nonplanar do lo mite var ies from -18.3 to -17.5‰ with re spect to ␦ 18 O, while ␦ 13 C val ues range from +0.4 to +1.15‰ (fig. 10). Ze bra dolo mite shows a nar row range be tween -18.2 to -18.1‰ for ␦ 18 O and +1.1 for ␦ 13 C. Late cal cite ce ment shows val ues from -10.1 to -6.1‰ for ␦ 18 O and -5.6 to -3.1‰ for ␦ 13 C (fig. 10).

In the Ranero vein sec tion, early cal cite ce ment shows val ues of -4.2‰ for ␦ 18 O and +1.8‰ for ␦ 13 C, which are close to the orig i nal ma rine sig na tures of Early Cre ta ceous car bon ates (fig. 10). ␦ 18 O val ues of ma trix lime stone range from -8.0 to -7.0‰ and ␦ 13 C val ues from +2.0 to +2.5‰. Nonplanar do lo mite val ues vary from -16.7 to -11.7‰ for ␦ 18 O and +0.8 to +1.8‰ for ␦ 13 C, while pla nar do lo mite shows a clus ter as ␦ 18 O val ues range from -14.2 to -13.0‰ and ␦ 13 C val ues vary from +1.2 to +1.3‰ (fig. 10). Early cal cite ce ment shows highly de pleted ␦ 18 O val ues (-18.1‰).

Dolomite stoichiometry

Do lo mite stoichiometry was as sessed by means of XRD (see meth od ol ogy). All ana lysed rep re sen ta tive bulk do lomite sam ples from dif fer ent sec tions show nearly stoichiometric do lo mite, rang ing from 50.1 to 51.3 mol% CaCO 3 .

Fluid inclusions analyses

An a lyzed fluid in clu sions from ze bra do lo mite and mas sive, nonplanar do lo mite are two-phase, pri mary/pseudosecondary inclusions as most of these are iso lated and lo cated along the bor der of the crys tals. The crys tals dis play uni form cloud i ness due to the pres ence of small fluid in clu sions. The size of the in ves ti gated in clu sions is vari able (up to 5 µm) and their shape is ir reg u lar.

Ho mog e ni za tion tem per a tures (T H ) for the fluid in clusions of ze bra do lo mite range from 131 to 196ºC (av er age T H = 167.1±16.4ºC), most val ues ly ing be tween 140 and 170 o C (fig. 11). For late sad dle do lo mite, the T H var ies from 125 to 185ºC (av er age tem per a ture range = 158.9±13.6ºC; fig. 11).

Many phase changes at low tem per a ture (i.e. melt ing of salt hy drates) could not be iden ti fied and in most fluid inclu sions only the melt ing tem per a tures of ice (T M ), of ten cor re spond ing to the fi nal melt ing tem per a tures (T M fi nal), were mea sured. Melting tem per a ture (T M ) for ze bra do lomite var ies be tween -21 to -2ºC, while it ranges from -18 to -8ºC for mas sive, nonplanar do lo mite. The es ti ma tion of sa lin ity was done ac cord ing to Bodnar's equa tion [START_REF] Bodnar | Revised equation and table for determining the freezing point depression of H 2 O-NaCl solutions[END_REF]. The sa lin ity of fluid in clu sions in the se lected ze bra do lo mite has a broad range from 4.5 to 21.3 eq. wt% NaCl (fig. 12). The mode value (ma jor oc cur rence) of sa lin ity is 15.2±4.6 eq. wt.% NaCl as only few T M were be low -10ºC, most are be tween -20 and -15ºC. The sa lin ity of fluid inclu sions in mas sive, nonplanar do lo mite has a broad range from 11.7 to 21.0 eq. wt.% NaCl (fig. 12). The mode value for these fluid in clu sions is 16.3±4.2 eq. wt.% NaCl. Sa linity of the mas sive do lo mite shows no con sid er able vari a tion with the change in the ho mog e ni za tion tem per a ture (T H ).

In or der to de ter mine the chem is try of the par ent flu ids us ing Land [1983] crossplot, ␦ 18 O val ues (-18.5 to -11.5‰ VPDB) and ho mog e ni za tion tem per a ture (125-195 o C) of mas sive (nonplanar) and ze bra dolomites are plot ted. The re sult ing ␦ 18 O val ues rang ing from -2.5 to +6.5‰ VSMOW (fig. 13).

POROSITY AND PERMEABILITY ANALYSIS

Se lected sam ples from dif fer ent sites were cho sen for petrophysical stud ies to as sess any petrophysical vari a tions as a func tion of do lo mite tex tures (ta ble II).

In the Pozalagua quarry site, nonplanar do lo mite is char ac ter ized by low po ros ity and per me abil ity val ues respec tively (1 to 2.5% and less than 0.5 mD). Ze bra do lo mite shows rel a tively higher po ros ity (2.1 to 11%) but sim i lar per me abil ity val ues. Rel a tively high po ros ity val ues might be due to the ma trix phase in the ze bra do lo mite (fig. 14A). Cataclastic do lo mite con tains po ros ity val ues rang ing from 1.6 to 3.8% and per me abil ity val ues up to 0.2 mD.

In the Ranero fault sec tion, po ros ity/per me abil ity values for nonplanar do lo mite range up to 7.3% and 1.6 mD re spec tively (ta ble II). The po ros ity/per me abil ity val ues differ sig nif i cantly (up to 5%) from one side of the sec tion to the other side, in agree ment with ob vi ous dif fer ences in textures (fine to me dium crys tal line nonplanar do lo mite show con sid er able pore spaces in the east ern part as com pared to very coarsely crys tal line, in ter locked and over-ce mented sad dle do lo mite with neg li gi ble po ros ity in the west ern part of the sec tion). Ze bra do lo mite shows higher po ros ity (up to 4%) and per me abil ity (up to 1.5 mD), which is due to the intercrystalline pore spaces in the ma trix do lo mite phase as the ce ment do lo mite phase ex hib its neg li gi ble po ros ity. Planar do lo mite ex hib its high po ros ity but low per me abil ity val ues, which range up to 6.0% and 0.7 mD re spec tively. High po ros ity val ues are due to intercrystalline po ros ity in these pla nar dolomites (fig. 14B-C).

Cataclastic de for ma tion re sulted in an in creased po rosity (up to 6%, if not oc cluded by late cal cite ce ment) without in creas ing the per me abil ity (0.3 mD). The nonplanar and pla nar do lo mite in the Ranero front sec tion shows almost same val ues of po ros ity (2-7%) and per me abil ity (0.1-0.3 mD). Cataclastic do lo mite ex hib its com par a tively lower po ros ity (up to 4%) and per me abil ity (0.1 mD) val ues (ta ble II).

In the Ranero Vein sec tion, lime stone ex hib its rel a tively high dissolutional po ros ity in some places (fig. 14D). Nonplanar do lo mite shows low po ros ity (1 to 4%) and perme abil ity (0.1 to 1 mD) val ues through out the sec tion. Planar do lo mite shows intercrystalline po ros ity rang ing up to 3.5% and per me abil ity up to 0.5 mD. Cataclastic do lo mite ex hib its slightly higher po ros ity val ues (up to 4%), which is due to the break age of pre-ex ist ing sad dle do lo mite.

DISCUSSION

The study area un der went three rift ing phases: 1) Early Trias sic rift ing re sulted in the for ma tion of Cantabrian graben; 2) Late Ju ras sic rift ing caused the de po si tion of Cre ta ceous suc ces sions and the open ing of Bay of Biscay and 3) Early Cre ta ceous rift ing re sulted in NNE-SSW stretch ing nor mal to the axes of the main struc tural trend [Rat, 1959;Pujalte, 1977;Gar cia-Mondejar, 1989]. These rift phases cre ated or re ac ti vated ma jor faults and frac tures in NW-SE, E-W and NE-SW di rec tions. Two pe ri ods of fault-con trolled re gional sub si dence (Mid dle Tri as sic to Mid dle Ju ras sic and Late Cre ta ceous) re sulted in thick sed i men tary suc ces sions of up per Ju ras sic -lower Cre ta ceous age [Rat, 1959[Rat, , 1988;;[START_REF] Voort | Zum Flysch Problem in den West Pyrenean[END_REF]Feuillée and Rat, 1971;Gar cia-Mondejar, 1989;Rosales, 1995]. These sed i men tary suc ces sions comprise up per Ju ras sic -Barremian con ti nen tal clastics, lower Aptian -up per Albian plat form rudist lime stone, basinal marls and mudstone, and up per Albian -lower Cenomanian flu vial siliciclastics to turbidites [Gar cia-Mondejar, 1989]. In the study area, Aptian-Albian mas sive and micritic limestone with orbitolinas, cor als, oys ter-like chondrodonta and rudist de bris oc cur (Ramales For ma tion), con form ably over lies the Rio Yera For ma tion, while the up per con tact with the Valmaseda For ma tion is un con form able. Tran sitional ma rine shales and sand stones (lower Hauterivian to up per Barremian) of the Villaro For ma tion are pres ent in the intraplatform de pres sion [Gib bons and Moreno, 2002].

The Ranero fault is re lated to early Cre ta ceous rift ing (Early Albian) [Aranburu et al., 1994] and ap pears to have been re ac ti vated through sinistral strike-slip mo tion, followed by an ear lier phase of meta mor phic and hy dro ther mal ac tiv ity dur ing Early to Mid-Albian times [Thiébaut et al., 1988;Schärer et al., 1999]. The pres ence of lin ear (frac ture filled) do lo mite bod ies sup port the idea that the dolomitising flu ids mi grated and spread through the sed imen tary pile along these dis con ti nu ities (fig. 4D). Do lo mite bod ies show dif fer ent ge om e tries nearby the Ranero fault, which in clude ir reg u lar (fronts), lin ear (frac ture filled) and fault con strained.

On the Ranero front (mar gin, away from ma jor fault) irreg u lar, tongue-like but partly con form able do lo mite bod ies (fronts) sug gest that the po ros ity/per me abil ity and the primary min er al ogy of the pre cur sor lime stone were im por tant fac tors in the dis tri bu tion of do lo mite bod ies (figs. 4C -14D) [Murray and Lu cia, 1967;[START_REF] Bullen | Dolomite selectivity and mimic replacement[END_REF]. Phys i cal char ac ter is tics of the host lime stone could partly con trol dolo mite dis tri bu tion [e.g. Nader et al., 2007]. In other terms, per me abil ity de ter mines fluid flow, and par ti cle size de termines the sur face area avail able for fluid-rock in ter ac tion. Chem i cal char ac ter is tics such as the sol u bil ity of car bon ate min er als, may have played a sig nif i cant role as well. On the con trary, fault con strained do lo mite bod ies (cor ri dor) strictly in di cate tec tonic con trol on do lo mite dis tri bu tion (fig. 4B) [Gar cia-Mondejar, 1996;Lopez-Hogue et al., 2005].

The sharp lime stone-do lo mite con tacts mostly cross-cutting strat i fi ca tion and sed i men tary struc tures sug gest a late or i gin for the dolomites (fig. 4A). In the Pozalagua quarry (on the main Ranero fault), var i ous gen er a tions of do lo mite fa cies in di cate mul ti ple pulses of the dolomitising flu ids (fig. 5B) [Swennen et al., 2010]. Ze bra do lo mite ex isted as bro ken clasts in the nonplanar do lo mite, in di cat ing its rel ative early for ma tion with re spect to other do lo mite phases.

Mas sive and ze bra do lo mite mostly con sisted of pla nar and nonplanar crys tals [START_REF] Gregg | Epigenetic dolomitization and the origin of xenotopic dolomite texture[END_REF]. Pla nar dolo mite rep re sents subhedral to anhedral sub-rhombic do lomite crys tals, rang ing in size from 200 to 700µm and ex hibit straight ex tinc tion. Nonplanar do lo mite con tains subhedral to euhedral crys tals, show ing undulose ex tinc tion (typ i cal of sad dle do lo mite) and size ranges from 100 to 700 µm (fig. 6E). Dull and bright red col oured zon ing in nonplanar do lo mite might re late to ep i sodic stages of dolomitization of the host rock. Pla nar and nonplanar do lomite were also af fected by al ter ation (cataclastic de for mation and recrystallization; figs. 8C-D). The de vel op ment of ze bra do lo mite has long been con sid ered as con trolled by sed i men tary fa cies [e.g., Beales and Hardy, 1980;Mar tin et al., 1987;Tompkin et al., 1994], but later work ers re ported that ze bra dolomites cross-cut sed i men tary struc tures [Boni et al., 2000;Swennen et al., 2003;Vandeginste et al., 2005;Gasparrini et al., 2006]. In the study area, ze bra struc tures are of ten un con form ably ori ented rel a tive to the bed ding of the host lime stone, which may ex clude the pos si bil ity of facies-con trolled for ma tion of ze bra dolomites (fig. 5B). Polymodal, nonplanar do lo mite con sisted of in ter lock ing anhedral crys tals, which un der went aggradational neomorphism dem on strat ing the evo lu tion into pla nar do lo mite crys tals as was de scribed by Niel sen et al. [1994] and Vandeginste et al. [2005] (fig. 7A).

Replacive do lo mite and void-fill ing do lo mite ce ment were rec og nized. Replacive do lo mite orig i nated by the replace ment of pre cur sor lime stone and do lo mite, while void-fill ing dolomitization con sisted in the pre cip i ta tion of sparry do lo mite, which filled cav i ties and frac tures cre ated dur ing the dolomitization pro cess (figs. 8 A-B). Replacive and void-fill ing do lo mite phases have sim i lar geo chem i cal sig na tures (fig. 10). This sug gests rather uni form physicochem i cal con di tions dur ing their for ma tion. It is as sumed that a con tin u ous dolomitization pro cess evolved from a replacive stage to wards a void-fill ing stage in a nearly isochemical sys tem [Gasparrini, 2003].

Two cal cite ce ment gen er a tions (early and late) have been iden ti fied in the stud ied sam ples. Mi cro scopically, early cal cite ce ment shows a brown or ange CL-pat tern (fig. 7C). The sec ond type of cal cite is non-lu mi nes cent (fig. 7D), which is sim i lar to cal cite formed near to me teoric re charge [Choquette and James, 1988;Niemann and Read, 1988;Meyers, 1991;Reeder, 1991].

On the ba sis of rel a tive abun dance of do lo mite fa cies in dif fer ent mea sured sec tions, it is ob served that pla nar do lomite shows high con cen tra tions in those parts of the do lomite bod ies (Ranero front sec tion), where the in flux of dolomitizing flu ids is as sumed to be mod er ate (in va sion into the host lime stone; fig. 9). In con trast, nonplanar (cement dom i nated) and ze bra do lo mite formed mostly along ma jor faults where fluid in flux might have been high (Ranero fault and Ranero vein sec tions).

The paragenetic se quence starts with the de vel op ment of faults and frac tures in the host lime stone, which were first filled by early cal cite ce ment (fig. 14 and15). Later on, an ep i sode of shear ing pre cedes dolomitization. This dolomitization event is also re corded in early cal cite, where do lo mite filled the cen tral part of some cal cite veins (fig. 5E,F). Dif fer ent do lo mite fa cies are rec og nized, which in clude pla nar, nonplanar and ze bra do lo mite (figs. 6C-F). These do lo mite fa cies un der went al ter ations, which in clude neomorphism, fill ing and in the end cataclastic de for ma tion (fig. 8C-D). Late stage cal cite ce ment fill ing in the open spaces (frac ture filled or intercrystalline) ce mented the dolo mite (fig. 7D). Be sides this, mi nor amounts of sul fides (py rite) are also as so ci ated with these dolomites (fig. 15).

The sta ble iso tope anal y ses re veal a broad range of ␦ 18 O values mainly be tween -18.5 and -11.5 (fig. 10). The broad range of ␦ 18 O val ues is con sis tent with multiphase dolomitization and do lo mite recrystallization [START_REF] Niel | Mul tiple-step re crys tal liza tion wi thin mas sive an cient do lo mite units: an example from the Di nan tian of Bel gium[END_REF]. Ac cord ing to Veizer et al. [1999], ox y gen and car bon iso to pic sig na tures of the Early Cre ta ceous ma rine car bon ate ranges from -3 to +1‰ ␦ 18 O and from 0 to +4‰ ␦ 13 C, while stud ied lime stone and do lo mite phases in di cate a clear shift from the Early Cre ta ceous ma rine car bon ate iso tope sig na tures but early ma rine cal cite shows close resem blance with it (fig. 10). The re ported ␦ 13 C val ues of such dolomites are not far from the orig i nal ma rine sig nature of the host rocks (i.e. early Cre ta ceous), thus the carbon iso to pic com po si tion of the dolomitizing flu ids may have been buf fered by the host rock. The lime stones close to the dolomites also show de pleted ␦ 18 O val ues, im ply ing recrystallization dur ing dolomitization (fig. 10). Other depleted ␦ 13 C val ues may be in ter preted as re sult ing from late telogenic cal cite phases (fig. 10). All the ob served fa cies show de vi a tion to wards neg a tive ox y gen-iso tope sig na tures, which may ei ther be due to in crease in tem per a ture or mixing of fresh wa ter. As stated above, sa lin ity of the pri mary in clu sions is three to four time greater than sea wa ter, which elim i nates fresh wa ter as a source of neg a tive ␦ 18 O val ues. So, in creased tem per a ture is the likely source of de pleted ␦ 18 O val ues. Fluid in clu sions anal y ses show high ho mog eni za tion tem per a tures (120-200 o C) and sa lini ties (12 -21 eq. wt% NaCl) of the pri mary in clu sions (figs. 11 and 12). This rules out the in va sion of me te oric flu ids as the driv ing mech a nism in the dolomitization sce nario. Cal cu lated ␦ 18 O val ues of the par ent fluid fol low ing Land's [1985] do lo mite-wa ter frac tion ation equa tion [cf. Adams et al., 2000], show that es ti mated wa ter ␦ 18 O val ues range be tween -2.5 and +6.5‰ V-SMOW, in di cat ing some 18 O deple tion rel a tive to nor mal sea wa ter (fig. 13) [Land, 1983].

Dolomitization may gen er ate, pre serve or de stroy poros ity de pend ing on the tex tures of the re placed car bon ates, rate and com po si tion of flu ids and du ra tion of the pro cess [Lu cia and [START_REF] Shah | Po ro si ty evo lu tion through hy per sa line re flux do lo mi ti za tion[END_REF]. Dis so lu tion dur ing dolomitization and pre cip i ta tion of do lo mite ce ment are con sid ered re sponsi ble for pos i tive or neg a tive ef fects on po ros ity de vel opment, re spec tively. In the an a lyzed do lo mite sam ples, dis so lu tion/pre cip i ta tion de creased the po ros ity (fig. 8D), while cataclastic de for ma tion pres ent in some sam ples increased the po ros ity (fig. 8C). Pla nar and ze bra dolomites show intercrystalline po ros ity be tween 3 to 5% (figs. 14A-C).

Pos si ble sources of dolomitizing flu ids can be dewatering of 7-8 km thick basinal sed i ments in the Bilbao trough due to rapid sub si dence and up ward move ment of these dolomitizing flu ids through faults and frac tures [Deming, 1992]. The Bilbao-Villaro Fault zone was sup posed to pro vide path ways to dolomitize Aptian-Albian car bon ates. Other sources may in clude mag matic wa ters from the base ment rocks and subsurface salt diapirs (fig. 16). in the early Cre ta ceous ba sin-to-plat form car bon ates in Cantabria (north ern Spain) re sulted in the fol low ing con clu sions.

CONCLUSIONS

-Field work helped in as sess ing the ge om e try and dimen sions of the do lo mite bod ies and their re la tion ship with the Ranero Fault.

-Petrographic stud ies ev i denced three ma jor do lo mite facies: ze bra, pla nar to sucrosic, and nonplanar (in ter lock ing). More over, tex tural stud ies helped in iden ti fy ing three dif fer ent do lo mite al ter ation types (i.e. cataclastic de for ma tion, recrystallization -and cal cite ce men ta tion), which oc curred dur ing the multiphase hy dro ther mal dolomitization.

-The rel a tive abun dance (%) of dif fer ent do lo mite facies in di cates the dif fer en tial dis tri bu tion in dif fer ent places (de pend ent upon the in ten sity of the dolomitizing flu ids).

-Highly de pleted ␦ 18 O val ues (-18.5‰ V-PDB) and the high T H range (up to 200ºC) of fluid in clu sions in di cate a hot and deep source of dolomitizing flu ids, in agree ment with the upwelling of these flu ids along ma jor faults (Güenes fault and Bilbao-Villaro Fault zone).

-Geo chem i cal stud ies (O and C sta ble iso topes) show a broad range of ␦ 18 O from -18 to -11‰ V-PDB, and con firm the multiphase or i gin of dolomitising flu ids, while ␦ 13 C val ues (-0.25 to +2.5) are not far from the orig i nal ma rine sig na ture of the host rock, thus car bon iso to pic com po si tions of the dolomitizing flu ids may have been buf fered with the host rock.

-Po ros ity/per me abil ity data rep re sents the ef fect of differ ent do lo mite fa cies on the po ros ity/per me abil ity val ues. Be sides this, some do lo mite al ter ation prod ucts show increase in po ros ity (cataclastic do lo mite).

Ackno wledg ments. -This con tri bu tion is part of the PhD pro ject, par tial ly fun ded by Pe tro bras and IFP. The au thors would like to thank Lau rent Emma nuel (UPMC, Pa ris) and Chris tophe Re nac (Geo logie, Uni ver si té Jean Mon net Saint-Etienne) for stable iso tope ana ly ses. Po ro si ty/per mea bili ty ana ly ses by Sa mir Be kri and Jean Gue lard (IFP) and XRD ana ly ses by Eric Ko hler (IFP), fol lo wed by fruit ful dis cus sions that are hig hly ap pre ciated. Thanks are also due to Fla vien Wau cher (IFP) for thin-sec tions pre para tion and Her man Nijs (K.U. Leu ven) for wa fers pre pa ra tion. We grea tly ap pre ciate the cri ti cal re view done by Chris tian Beck (Uni ver si ty of Savoie) and one ano ny mous re vie wer, which im pro ved the fi nal ver sion of the ma nus cript. The first au thor be ne fits from a CIFRE (ANRT) fun ding.

Bull

INTRODUCTION

Pervasive dolomitisation has been linked with various processes in diverse geological settings (Warren, 2000;Machel, 2004). Presently, various models have been proposed by a large number of workers (Adams & Rhodes, 1960;[START_REF] Badiozamani | The dorag dolomitization model -application to the middle Ordovician of Wisconsin[END_REF][START_REF] Machel | General constraints on extensive pervasive dolomitizationand their application to the Devonian carbonates of western Canada[END_REF]Cervato, 1990;[START_REF] Braithwaite | The geometry and petrogenesis of dolomite hydrocarbon reservoirs[END_REF], Nader et al., 2004, 2007 The present study concerns momentous dolomite exposures in early Albian (Cretaceous) platform carbonates in Northwest Spain. It aims at deciphering the mechanism and extent of dolomitisation and their relationship to the regional tectonic scenario, and to determine the nature and origin of the dolomitising fluids. Such aspects were not substantially discussed yet. For this purpose, petrographic and geochemical studies were carried out in two sites (Ranero and El-Moro, north western Spain). Hence, additional understanding of the exposed dolomites in the study area and their dolomitising fluids is presented in this paper.

LOCATION AND GEOLOGICAL SETTINGS

The study area is part of the Basque Cantabrian basin (BCB), which hosts the only onshore Ayoluengo oil field discovered in north-western Spain [START_REF] Lo | Petroleum geology of the onshore Cantabrian basin[END_REF]. The study area is bounded by Basque and Asturian massifs in the east and west, while the Bay of Biscay and Tertiary Ebro/Duero basins mark the northern and southern boundaries respectively (Fig. 1A). The studied sites, Ranero and El-Moro areas are located at the border of Basque country and province of Cantabria (NW Spain), near the town of Ramales (Fig. 1B).

Tectonic evolution:

In the BCB, two periods of fault-controlled regional subsidence (from middle Triassic to middle Jurassic and early to late Cretaceous) occurred (Rat, 1959;Pujalte, 1977;[START_REF] Garcia-Mondéjar | Strike-slip subsidence of the Basque-Cantabrian basin of northern Spain and its relationship to Aptian-Albian opening of Bay of Biscay[END_REF]Olivet, 1996;Lopéz-Horgue et al., 2010). Besides regional subsidence, three major tectonic events are reported in the BCB: (i) Permo-Triassic rifting stage, (ii) Late Jurassic-Early Cretaceous rifting and opening of Bay of Biscay and (iii) Eocene-Oligocene Pyrenean orogeny. The BCB formed by the Late Jurassic tectonic extension between the European and Iberian plates, which resulted in the opening of the Bay of Biscay and caused the deposition of a thick Cretaceous sedimentary sequence (Boillot and Malod, 1988;Malod and Mauffret, 1990;Olivet, 1996). Later on, the Iberian plate rotated back

Lithostratigraphy:

In the study area, the Aptian carbonates are mostly shallow marine, while early to mid-Albian carbonates change from shallow marine to reefal facies and show deltaic conditions (sandstones and lutites) in the upper most part (Fig. 2; Rosales, 1995). Four sequences bounded by unconformities occur in the Albian stage, which include early to late Albian platform to slope carbonates (basinward equivalent to marls), carbonate breccia and siliciclastic deposits (Figs. Towards the south, basinal marls, shales and siltstones of Río Calera unit onlap these shallow marine carbonates (Sopeña and Ranero units), unconformably overlain by shallow marine siliciclastics of La Escrita unit (Fig. 3). Laterally, the Río Calera and La Escrita units can be correlated with Ranero and These two karst systems show distinct characteristic features, which helped in their recognition [START_REF] Bosák | The evolution of karst and caves in the Konĕprusy region (Bohemion karst, Czech Republic), Part-II Hydrothermal Paleokarst[END_REF]Aranburu et al., 2002;Swennen et al., in press).

METHODS

Aerial photographs helped in delineating brown to dark-grey colored dolomite bodies in the light grey colored host limestone (Fig. 4). Systematic sampling was carried out across the dolomite bodies. Each sample represented certain dolomite facies and/or host limestone in the Ranero and El-Moro areas (Fig. 4). Rock slabs and thin sections were stained with Alizarin Red S and potassium ferricyanide (Dickson, 1966) to differentiate ferroan/non-ferroan dolomite and calcite. Petrographic studies were carried out using conventional (Nikon ECLIPSE LV 100 POL) and cathodoluminescence microscopy (Cathodyne OPEA; operating conditions were 12 to 17kV gun potential, 350 to 600 µA beam current, 0.05 Torr vacuum) of 260 thin sections. 54 selected samples were analysed (to determine bulk mineralogy, stoichiometry and crystal ordering of the different dolomite phases) using a PANalytical X'Pert PRO X-ray diffractometer (Cu-Kα radiation ~ 45kV, 40mA). The scan speed was set at 0.2°θ min -1 and sampling interval at 0.001°θ per step. The dolomite stoichiometry was determined by applying Lumsden's equation (1979) to the measured d104 spacing (M = 333.3 × d-spacing -911.99) and expressed as mol% CaCO3.

Geochemical analyses of the selective rock phases and whole rock samples were obtained by means of X-ray fluorescence (XRF) and inductively-coupled plasma optical emission spectrometry (ICP-OES) depending on the amount of material available from micro-drillings and/or plugs. In total 250 samples were analysed by ICP-OES, and 128 samples by XRF in Ecole des Mines, Saint Etienne. XRF analysis was performed with a SRS3400 spectrometer, using glass discs/pressed pellets for major/trace elements, respectively. ICP-OES analysis is performed on a JI Activa sequential device using acid solutions prepared by HF digestion. Both analytical routines are calibrated against geostandards.

Coupling these techniques is effective in overcoming the main drawback of each one, i.e. sensitivity for minor and trace elements by XRF (below 0.1% and 10 ppm) and reproducibility by ICP-OES (5%). Fifteen Sr isotope analyses of the selected dolomite samples were performed at the Scottish Universities Environmental Research Centre in Glasgow. These analyses are used to reveal radiogenic influence that may have changed the original Sr isotope signature of the carbonates. Carbonate samples were leached in 1M ammonium acetate prior to acid digestion. Calcite was digested in 1M acetic acid, and dolomite in 6M HCl. Sr was separated in 2.5M HCl using Bio-Rad AG50W X8 200-400 mesh cation exchange resin. Total procedure blank for Sr samples prepared using this method is < 200pg. In preparation for mass spectrometry, Sr samples were loaded onto single Ta filaments with 1N phosphoric acid. Sr samples were analysed on a VG Sector 54 -30 multiple collector mass spectrometer.

A 88 Sr intensity of 1V (1×10 -11 A) ± 10% was maintained and the 87 Sr/ 86 Sr ratio was corrected for mass fractionation using 87 Sr/ 86 Sr = 0.1194 and an exponential law. The VG Sector 54-30 mass spectrometer was operated in the peak-jumping mode with data collected as 15 blocks of 10 ratios. For this instrument NIST SRM987 gave 0.710260 ± 11 (1 SD,n=17) during the course of this study. The representative analytical data are given in Table-I.

RESULTS

Field observations:

The Ranero and El-Moro/El-Mazo study areas are separated by the Karrantza valley (Fig. 4). In both areas, dolomite bodies can easily be differentiated by their dark grey color as compared to offwhite host limestone (Fig. 5A). In the eastern sub-area (Ranero), different outcrops were studied namely a dolomite occurrence in the Pozalagua quarry, called "quarry" (Fig. 5B), a 15-20m thick dolomite body along the Ranero fault (sometimes also called Pozalagua fault) called "fault" (Fig. 5C), inter-fingered dolomite body in the limestone called "front", a road side cataclastic limestone cemented by dolomite (called "breccia") and a >20m thick vein dolomite called "vein"(Fig. 5D). In the western sub-area (El-Moro), a 30m thick dolomite body was studied at three different locations (MO-I to MO-III) to understand the vertical variations in the same dolomite body (Fig. 6A), exposing fault-related features (striations) along with white colored calcite (MO-III section, Fig. 6B

Diagenetic (micro)facies:

The present study only focuses on dolomitisation events in the host limestone, since the early limestone diagenesis has been described in detail by Lopéz-Horgue et al.

(2009 & 2010) and Rosales

& Pérez-Garcia (2010). Various calcite and dolomite phases were distinguished on the basis of excellent exposures and petrographic studies. These include: cavity-filling calcite cement (CC-I and CC-II); medium to coarse crystalline dolomite (CCD-Ia and CCD-Ib); coarse crystalline saddle dolomite (CCD-II); white calcite cement (WC) and transparent calcite (TC). Bed parallel and an oblique generation of stylolites were observed in host limestone. The oblique stylolite system was also seen in the calcite and dolomite phases. CC-II calcites record various episodes of fracture activation, while brecciation of late stage dolomite (CCD-II) is also reported before the emplacement of white calcite cement (WC). Further brief description of each calcite and dolomite phase is given below.

Cavity-filling calcite cements (CC-I & CC-II):

In the study area, cavity-filling, bladed calcite cement (CC-I) developed along the borders of the cavities of the host limestone and the crystals are oriented towards the centre of the cavity, while coarse crystalline calcite (CC-II) filled the remaining cavity except the central part, which may be filled

Medium to coarse crystalline dolomite (CCD-Ia & CCD-Ib):

In the breccia zone, fault reactivation resulted in brecciating the limestone into clasts, with medium to coarse crystalline dolomite (CCD-I) surrounded these clasts while open spaces are filled by white calcite (Fig. 7C). These medium to coarse crystalline dolomites (CCD-I) mostly consist of alternating bands of various colors (brown, grey and white) and Fe-rich layer bordering the walls of the vein and open cavities (Fig. 7D). Microscopically, they appear as medium to coarse crystalline, nonplanar interlocking dolomite crystals. The CCD-I dolomites occur in almost all the studied sections and post-date cavity filling, coarse crystalline calcite (CC-I; Fig. 7E). They are further sub-divided into Fe-rich, dark colored, dark orange (in CL) rimmed saddle dolomite (CCD-Ia) and grey colored, dull luminescent saddle dolomite (CCD-Ib), which terminate in interstitial pores (Figs. 8D-E). Selective dedolomitisation of the Fe-rich part of the coarse crystalline dolomite (CCD-Ia) is observed. These pore spaces are filled by very coarse to coarse crystalline, pore filling dolomite (CCD-II), which also replaces CCD-I, locally. Pyrite (now often oxidized) occur in the pores and along the fractures and in the stylolites present in CCD-I (Fig. 7F).

Coarse crystalline saddle dolomite (CCD-II):

Milky white to light pink colored coarse crystalline saddle dolomite (CCD-II), usually plugs the cavities in CC-II and cross-cut host limestone and CCD-I (Figs. 7A&D), sometimes replacing CCD-I. On the basis of cross-cutting relationship, CCD-I pre-dates CCD-II, hence formed during a first dolomitisation stage (Fig. 7D). It is also observed that CCD-II post-date all the dolomite phases in the quarry site (Fig. 7D). The termination of dolomite event is marked by the deposition of pyrite along the borders of CCD-II (Fig. 8A). Microscopic observation revealed that such late stage dolomitisation consist of coarse to very coarse crystalline nonplanar and dull luminescent saddle dolomite (CCD-II).

Such dolomite mostly occurs as vein-and/or fracture filling and does not alter the host limestone, but can replace CCD-I dolomite (Fig. 8B). Such dolomite phase was best exposed in the Pozalagua quarry site.

Coarse crystalline, pore-filling white calcite cement (WC):

After the dolomitisation event, further cataclastic deformation (brecciation) resulted locally in the breakdown of dolomite into clasts, shortly after filling of open spaces by coarse crystalline, pore and vein-filling white calcite (WC; Fig. 8A). Petrographic studies show distinct crystal twinning behavior of these coarse crystalline calcite, indicating exposure to tectonic stresses (Swennen et al., in press). CL studies of these pore-filling, white calcite (WC) revealed dull-luminescence and formed after the dolomitisation stage (usually surrounds broken dolomite fragments). White calcite (WC) is widespread in all the studied sites (Fig. 8C).

Medium to coarse crystalline, transparent calcite (TC):

Transparent to dirty white calcite (TC) usually occur as latest pore-and vein-filling phase.

Microscopically, medium to coarse crystalline, pore-filling transparent calcite (TC) exhibits nonluminescence. Such calcite is quite common and mostly responsible for reduction/destruction in porosity as it occludes open spaces in dolomite (Fig. 8D). Besides this, dedolomitisation of coarse crystalline dolomite (CCD-I) is mostly associated with this calcite.

Replacive dolomites (ZD & DS):

Beside the above stated dolomite cements, dolomite also occurred as a replacement product of the host limestone in zebra and in pockets of layered, pink sucrosic rocks interpreted as dolomitized internal sediments (DS) of a cave system (Figs. 9A&C). Zebra dolomites (ZD) mostly consist of interlayered planar to nonplanar, fine to medium-crystalline dolomite matrix and nonplanar, coarse crystalline dolomite cement phases, giving zebra-like texture (Fig. 9B). Zebra dolomites mostly occur next to faults and fractures adjacent to the fault, quarry, breccia and vein sections but they were not observed in the front section in the Ranero area. In the El-Moro area, zebra dolomite is not as common as observed in the Ranero area and was only identified in MO-I and MO-II sections. Dolomite sand (DS) consists of medium to coarse crystalline, nonplanar dolomite, clays and pyrite (Fig. 6F). These rocks display a laminated texture at the hand specimen scale and invariably contain much more silicate impurities that the other dolomites (up to 2 % Al2O3; Table-I and Lόpez-Horgue et al., in press). Silicates (illite, chlorites) are grouped with pyrite in the residual space between dolomite crystals. This lithotype is best exposed in the quarry site as paleo-cavity filling dolomites and more difficult to identify in the other places.

MVT-type mineralization:

MVT-type mineralization (Galena-Barite and Sphalerite-Galena) was also observed near the studied sites. Galena-Barite mineralization is observed in one single vein from the Ranero area, within a marly carbonate host (slope facies). Sphalerite-Galena mineralization is absent in the Ranero area, but present by places in El Moro area; it is always hosted in CCD-I dolomite bodies. Primary sphaleritegalena mineralization is rarely preserved, but it seems to predate or to be coeval with CCD-I dolomite; secondary mineralisation including smithsonite (bright blue colored in CL; Fig. 9D) and Pb-rich calcites is more frequently observed in El Moro area, but it clearly postdates dolomite.

Stoichiometry and Geochemical attributes:

In order to know the mineralogical and chemical characteristics of the identified dolomite and calcite phases, X-ray diffraction studies as well as geochemistry of major and trace elements were carried out. Dedolomitization, as an example of diagenetic processes, is also favored by nonstoichiometric dolomites (Dorobek et al., 1993;Nader et al., 2008). For this purpose, initially Xray diffractometry was used to determine the stoichiometry of the selected dolomite phases. All the dolomite samples analysed exhibit sharp diffraction peaks. The d104 spacing is quite constant and ranges between 2.8863 and 2.8912Å. These d104 spacing values correspond to a Ca content between 50.1 and 51.7 mol%, hence exhibited stoichiometric behaviour (Lumsden, 1979).

Major and trace elements:

Various dolomite facies are grouped on the basis of their major and trace element contents. FeO contents in various dolomite phases helped in categorizing them into ferroan (>0.2%) and non-ferroan (<0.2%; Figs. 10A&B). Fe-rich dolomite mostly coincide with the initial phase of pervasive, medium to coarse crystalline saddle dolomite (CCD-I), which is further sub-divided into CCD-Ia (Fe-rimmed; ~ 1% Fe) and CCD-Ib (band-filling; ~ 0.5% Fe). The FeO-contents in coarse crystalline, vein-and fracturefilled, non-ferroan dolomite (CCD-II) ranges from 0.2% to 0 (Figs. 10A&B). The crossplot δ 18 O Vs FeO shows contrast between Fe-rich dolomite (CCD-Ia & CCD-Ib) and non-ferroan dolomite (CCD-II). In the Ranero vein section, Fe-rich dolomite (CCD-Ia and CCD-Ib) is abundant, while non-ferroan dolomite is rare. On the other hand, both the Fe-rich and non-ferroan dolomites are reported in all the other studied sites (plateau, fault, front, quarry and breccia; Fig. 10A). Dedolomitisation almost selectively affects the ferroan rich dolomite in the Ranero front section. Galena-Barite vein is associated with the non-dolomitised limestone near the Pozalagua quarry.

In the El-Moro area, pervasive, ferroan dolomite and vein-filling, non-ferroan dolomite occur in all the studied sections (Fig. 10B). However Fe-rich, medium to coarse crystalline dolomite (CCD-I) largely dominates in the western part (Moro I to III and Moro IX-X sections). In the central and eastern part (Moro IV-V, Moro VII-VIII and El-Mazo), both the ferroan and non-ferroan dolomite phases are present. Galena-Sphalerite and the secondary Zn-Pb mineralisation are mostly observed in the central part of the El-Moro area within ferroan dolomite bodies.

The Fe-and Mn-contents are proportional to each other in the studied dolomites (Ranero and El-Moro areas), hence Fe-rich dolomite (CCD-I) shows high Mn-contents as compared to non ferroan dolomite (CCD-II; Figs. 10C&D). Besides, dolomites containing substantial amounts of Zn shows high Mn-contents and is ferroan (Fig. 10F). In the Ranero area, ferroan dolomite exhibited negligible Zn mineralization, while in the El-Moro area show high Zn-contents are reported from the western (MO I-II-III & MO IX-X) and central parts (MO IV-V), while the eastern part (MO VII-VIII & El Mazo) appears to be less affected by Zn mineralization (Figs. 10E&F). Zn-rich dolomite samples are also Fe-rich and are particularly prone to dedolomitization.

Stable isotopes:

In the studied sites, various dolomite facies show broad range of depleted δ 18 O values (-18.0 to -10.0‰ V-PDB), while their δ 13 C values (0.0 to +2.0‰ V-PDB ) are close to the range of reported carbonates precipitating from early Albian seawater i.e., 0.0 to +4.0‰ V-PDB (Veizer et al., 1999).

However compared with the analysed limestones from our study area, which exhibit values of +3.0 It is noteworthy that dedolomitised facies show less depleted δ 18 O values and highly depleted δ 13 C values. Dedolomitised samples represent intimate mixtures between dolomite and calcite. In these samples, δ 13 C depletion increases with calcite abundance, generating a mixing line whose depleted endmember is isotopically similar to transparent calcite (TC, Fig. 11A). This strongly suggests that the dedolomitization process is coeval with transparent calcite deposition and involves surface-derived fluids contaminated by soil-CO2. In the El-Moro area, Sphalerite-Galena associated dolomites show less depleted δ 18 O (-13.99 to -3.11‰ V-PDB) and δ 13 C values (-5.58 to -0.58‰ V-PDB), which corresponds to its association with dedolomitised rim in the Fe-rich dolomite as stated in the previous section (Fig. 11B).

Strontium isotopes:

The Sr 87 /Sr 86 versus δ 18 O cross plot (Fig. 12A) shows that Sr 87 /Sr 86 ratio and δ 18 O values of the host limestone corresponds to 0.70741 and -4.45‰ V-PDB respectively, which lies within range of the Sr 87 /Sr 86 signatures (ca. 0.70731 to 0.70745) of the original marine early to late Albian carbonates (McArthur et al., 2001). The Sr 87 /Sr 86 values of pore-filling early calcite (CC-I and CC-II) ranges from 0.70844 to 0.70852, while early stage, Fe-rich dolomite (CCD-I) exhibits Sr 87 /Sr 86 values from 0.70827 to 0.70847. In contrast, the Sr 87 /Sr 86 values of late stage non-ferroan dolomite (CCD-II) ranges from 0.70813 to 0.70826, while late stage white calcite (WC) shows Sr 87 /Sr 86 values in the range of 0.70877 and 0.70881. The above stated data indicate that most of the various dolomite and calcite phases are clustered and exhibits higher Sr 87 /Sr 86 ratios compared to the original Sr-isotope marine signature.. In addition, the presence of oblique stylolites in these dolomite phases invoke their formation prior to latest deformation during burial. Thus the relatively high Sr 87 /Sr 86 ratios of the various investigated dolomites may indicate interaction of the dolomitising fluids with the radiogenic lithologies (Fig. 12B) during burial conditions prior to the formation of tectonic stylolites.

DISCUSSIONS

The NW-SE trending Pozalagua fault and other fractures, related to early Cretaceous (early Albian) rifting, appear to have been activated through sinistral strike-slip motion, followed by

Hydrothermal diagenesis and dolomite formation:

Although a generalized paragenetic sequence was established in part of the study area on the basis of field observations, petrographic studies and stable isotope analyses (Shah et al., 2010), the present study involved a larger set of data including geochemical analyses allowing the elaboration of a detailed paragenetic sequence of the various dolomite and calcite phases and some more information about their spatial distribution (Fig. 13). Non-ferroan dolomite were formed at relatively high temperature as indicated from fluid inclusion studies (Shah, 2008

Mechanisms of dolomitisation:

The Basque trough is an irregular graben-like feature developed adjacent to the Ramales platform (study area), where more than 8500m thick shales, sandstones and marls accumulated during 11A&B). The highly depleted δ 18 O values may either be due to increase in temperature or/and 18 Odepleted fluids. The slight shift in δ 13 C of dolomites with respect to the host limestone can be explained by the slight temperature fractionation of 0.03‰ per degree Celsius (Emrich et al., 1970). The estimated salinity of the primary inclusions of these dolomite facies are three to four time greater than seawater (12 -21 eq. wt. % NaCl; Shah et al., 2010). This piece of information together with the observed presence of sulphate phases (Bustillo et al., 1992) Sr isotope analyses indicate that the calcite and dolomite phases contain radiogenic signatures, which is evident by the clear shift from the marine early Cretaceous signatures (Fig. 12A). Most of the dolomite phases possess a signature that varies from 0.70820 -0.70850, which conclude that dolomitising fluids may have interacted with radiogenic lithologies (sandstones and shales) during late Albian intense tectonic activity, confirming the results of Bustillo et al. (1992) (Fig. 12B).

Dolomite distribution and variations:

Dolomite bodies are widely observed in the Ranero area, where pervasive dolomitisation extended more than 1km along the Pozalagua fault and as much as 500m wide in the north-western part of Ramales platform. Such extensive distribution of dolomite bodies in the Ramales area is believed to be due to the prior development of paleo-karsts as observed in the Pozalagua quarry. In contrast to this, dolomite bodies in El-Moro area are strictly confined to faults and fractures that developed at the platform edge to basin transition, and exhibits little vertical and lateral extension. Besides the variation in size of dolomite bodies in the Ranero and El-Moro, other remarkable contrasting features are:

(i) Relatively broad range of δ 18 O values in the Ranero area as compared to El-Moro area. (ii) Galena-Barite mineralization observed in the Ranero area, while Sphalerite-Galena mineralization is restricted to some parts of the El-Moro areas: (iii) in the El-Moro area, host limestone shows higher δ 13 C values as compared to Ranero area. Dedolomitisation is frequently found in both the studied sites, hence telogenetic processes can possibly can explain their formation. Finally, it is worth stressing again that Ranero area exhibits a larger volume of dolomites, mainly associated to the Pozalagua fault. While an earlier phase of dolomitisation (Fe-rich, originated due to compactional fluid flow) has been documented in this paper and interpreted as pervasively affecting the Ramales Platform, the later phase of dolomitisation (Fe-poor, associated to a thermal anomaly) appears to mainly affect the Ranero fault area.

CONCLUSIONS

Field observations of the hydrothermal dolomites in the early Cretaceous basin-to-platform carbonates (Karrantza valley, NW Spain) including the development of a paragenetic sequence based on crosscutting relationships, petrography, geochemical studies and isotope analyses resulted in the following conclusions:

• Hydrothermal processes include (in paragenetic order) calcite precipitation (CC-I & CC-II), followed by two distinct dolomite facies (ferroan and non-ferroan dolomite), and post-dolomite calcite (WC) precipitation. Late stage calcite (TC) mostly occluded the pore spaces and is of telogenetic origin. Zebra dolomite (ZD) and dolomite sands (DS) occurred as partially replacive facies of host limestone. Two episodes of mineralisation were observed in the Ranero (Galena-Barite) and El-Moro areas (Sphalerite-Galena).

• Isotope geochemistry (O/C stable isotopes and Sr isotopes) revealed that early calcite precipitation • The 87 Sr/ 86 Sr ratios of dolomite and calcite phases are higher than those of the host limestones, whereas dolomitising fluids may have interacted with radiogenic lithologies (sandstones and shales) during late Albian intense tectonic activity. • Replacive dolomites (ZD & DS) indicate relatively high porosity and permeability as compared to dolomite precipitates. Beside this, late diagenetic alterations (brecciation, dissolution and meteoric calcite related dedolomitization) also show positive effects on the enhancement of porosity of various dolomite phases.

• Proposed multiphase diagenetic model indicate initial phase of dolomitising fluids resulted from burial compaction, as they can be expelled towards the platform edge area at a moment when a temperature anomaly occurs due to differential subsidence and faulting linked to crustal stretching processes. Second phase of dolomitising fluids resulted from convective flow above a salt diapir and subsequent TSR within a host limestone.

Further studies are needed to better understand the genesis of these hydrothermal dolomites, which include the dating of Pb-Zn mineralization and to model the basin using software of Temis-3D type, which will permit to better control of the burial curve and paleo-temperature for the elevated points (horsts) and depressions (Grabens), hence will contribute about the timing of the petroleum system and to compare/recall various episodes of dolomitization. It is also important to know why there is no hydrocarbon in the reservoir neither in the form of accumulations nor any traces of migration (fluid inclusions etc.).

In addition, the distribution and lateral variations within the hydrothermal dolomites can be modelled to understand the rock-fluid interaction. For this purpose, the above stated studies should be incorporated to construct a 3D reactive geochemical transport model capable of simulating the formation of hydrothermal dolomites using COORES TM (IFP) and ARXIM (ENSMSE-IFP) softwares.

• In order to determine the subsurface extension of dolomite body in the study area, gravity and magnetic survey should be planned, which proved effective results in other parts of the world (e.g., [START_REF] Hinks | Evaluation of the effectivness of using gravity and magnetic data to define 3-D seismic survey areas for fault-related hydrothermal dolomite reservoir identification[END_REF].

INTRODUCTION

Dolomite was first reported more than 200 years ago, by a French scientist Déodat de Dolomieu, who noticed slight acid reaction with calcareous rocks and curved crystal faces (saddle dolomite; Dolomieu, 1791a). Many workers contributed in the understanding of processes involved in dolomite formation [START_REF] Braithwaite | Dolomites, a review of origins, geometry and textures[END_REF][START_REF] Machel | Golden dolomite, Barbados: Origin from modified seawater[END_REF][START_REF] Wright | An organogenic origin for widespread dolomite in the Cambrian Eilean Dubh Formation, northwestern Scotland[END_REF][START_REF] Braithwaite | The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland[END_REF]Adams et al., 2000;Boni et al., 2000;Warren, 2000;[START_REF] Duggan | Fault controlled dolomitization at Swan Hills Simonette oil field (Devonian), deep basin west-central Alberta[END_REF][START_REF] Machel | Hydrothermal dolomite-a product of poor definition and imagination[END_REF]Swennen et al., 2003;Cantrell et al., 2004;Machel, 2004;Nader and Swennen, 2004;[START_REF] Al-Aasm | The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry[END_REF]Davies and Smith, 2006;Gasparrini et al., 2006 and others). In fact, dolomites can form in many ways and almost everywhere (Wilson et al., 1990;Swennen et al., 2003;Vandeginste et al., 2005;Smith & Davies., 2006;[START_REF] Nader | Petrographic and geochemical study of Jurassic dolostones from Lebanon: Evidence for superimposed diagenetic events[END_REF]Nader et al., & 2007)). The origin of dolomite has not been disclosed yet, since it is still difficult to synthesize dolomites at near surface environmental conditions. Dolomite is a highly variable mineral whose molecular structure, stoichiometry and trace element composition express different conditions of formation and evolution [START_REF] Purser | Dolomites-A volume in honour of Dolomieu[END_REF]. Recrystallization process also partially or completely destroys the genetic characteristics of early dolomite (Nielsen et al., 1994). The physico-chemical conditions that determine dolomite nucleation and subsequent growth in a particular environment are still often unknown.

The geochemistry of the dolomites also remains problematic due to neomorphic nature of the dolomite crystals, difficulty of intra-crystalline micro-sampling, and interference of clay content.

In order to investigate these problems, workers seem to favour stepping back to observe the broader picture provided by fieldwork (e.g. mapping of dolomite outcrops) before studying in detail by doing microscopic investigations. Field studies have characterized the link between brittle deformation and/or dolomite recrystallization during fracturing [START_REF] Tarasewicz | Carbonate dilation breccias: Examples from the damage zone to the Dent Fault[END_REF], highlighting the intimate relationship between multiple phases of fracturing, fluid flow pattern and dolomitization (Wilson et al., 1990;[START_REF] Mountjoy | Multiphase fracture and fault-controlled burial dolomitization, Upper Devonian Wabamun Group, Alberta[END_REF][START_REF] Duggan | Fault controlled dolomitization at Swan Hills Simonette oil field (Devonian), deep basin west-central Alberta[END_REF]. Fluid flow is important for mineral diagenesis in carbonate aquifers as there exists a general consensus that permeability and fluid flow is the key for pervasive dolomitization [START_REF] Machel | Effects of groundwater flow on mineral diagenesis, with emphasis on carbonate equifers[END_REF]. In nature, dolomitizing fluids are common but circulation of these fluids under special and stable conditions for a certain time is required. Thus, the mass balance calculation remains an important tool for checking the plausibility of any proposed model of dolomitization.

Hydrothermal dolomitization occurs when Mg-rich, hot, chemically active fluids (usually originating from deeper strata) circulate along faults and fractures and invades the limestone rocks. These fluids, called hydrothermal as they have higher temperature than the host-rock, alter the composition of the carbonate host rocks and induce dolomitization by replacing Ca by Mg within the calcite crystal lattices. The tendency to produce coarser crystals prevails, hence resulting considerable intercrystalline porosity. Yet, in many cases over-dolomitization may also occur, whereby the created intercrystalline porosity is destroyed by dolomite cement upon further dolomite precipitation.

The growing global interest on understanding the processes that control hydrothermal dolomitization increases as the resultant rocks are potential oil reservoirs and / or proven very useful (Smith & Davies, 2006). However, the mechanisms of this type of transformation and diagenetic (s) influence (s) on the porosity and permeability of reservoir rocks are not well known and highly debated (Machel & Lonne, 2002). Same dolomite phases show diverse nature of porosity and permeability from one site to another. Besides this, previously considered homogeneous hydrothermal dolomite reservoirs, when intercepted by the boreholes showed complex heterogeneities.

CARBONATE DIAGENESIS

According to [START_REF] Bathurst | Carbonate sediments and their diagenesis[END_REF] "Carbonate rocks are as much the products of diagenesis as they are of primary deposition". Diagenesis refers to any chemical/biological and/or physical process that alters the pre-existing carbonates after sediment deposition. Due to changes in environmental conditions and/or migration of extrinsic fluids into the rock-mass, drastic dissolution/precipitation and mineralogical changes may occur. These are termed 'diagenetic processes' and they include infestation, compaction, cementation, recrystallization and replacement [START_REF] Parker | Quantitative diagenesis: Recent developments and applications to reservoir geology[END_REF].

The main diagenetic environments include marine, meteoric and burial or subsurface (Fig. 1.1); each of which has specific characteristics concerning diagenetic processes -e.g. dissolution, cementation, replacement -and the produced diagenetic phases -e.g. solutionporosity, cement, dolomite. The marine realm comprises a stagnant zone and an active zone.

While the former is characterized by minor cementation (rather micritization), the latter includes pervasive cementation -e.g. isopachous fibrous aragonite -chiefly due to more water circulation.

The meteoric (fresh water) realm is divided into (upper) vadose and phreatic environments [START_REF] Tucker | Sedimentary petrology[END_REF]Warren, 2000). The former includes a zone of precipitation where minor meniscus, pendent and spelean cementation occur. The fresh water phreatic environment is characterised by three distinct zones (i.e. solution, precipitation and stagnant), whose limits are function of the aquifer's water-table. Moldic and vuggy porosities are the result of intense dissolution by undersaturated waters in the solution zone, while little cementation is recorded in the stagnant zone, which is probably due to the absence of water circulation. This is contrasted to active water circulation and rapid cementation within the precipitated zone, usually leading to porosity destruction. Equant calcite cement (completely replacing aragonite and occluding pores) characterizes this zone. If burial conditions were initiated, the special patterns of drusy mosaic, syntaxial overgrowth cements are expected to form in marine settings. The burial (subsurface) realm is mainly characterized by compaction and pressure solution, which are lithology dependent. Sparry calcite cement (relatively coarsely-sized) usually characterizes subsurface diagenesis. In addition, mineral replacement (e.g. dolomitization, silicification -which could also occur during early diagenesis -as well as clay chemical reactions (e.g. illite/smectite) often occur within the burial realm.

Other diagenetic realms include special marine-related environments (e.g. marine vadose, sabkha and mixing-zone). Sabkhas are "low-lying salt encrusted surfaces sometimes adjacent to perennial/ephemeral bodies of brine. Recently, themes related to the microbial effects on diagenesis, have attracted the attention of many workers [START_REF] Riding | Microbial Sediments[END_REF]. Microbes (bacteria, small algae, fungi and protozoans) may produce acids that alter/dissolve pre-existing minerals, or set chemical environments that favour (induce and protect) mineral precipitation. In other words, these abundant organisms, present in the various diagenetic realms, are capable of generating, modifying and sustaining sediments.

Diagenesis is one of the major factors that influence porosity/permeability distribution within carbonate rocks hosting aquifers and hydrocarbon reservoirs. More than 50% of hydrocarbon occurrences are known to be in such carbonate rocks. Therefore, assessing their "diagenetic susceptibility" (Wilson, 1975) is an important task for reservoir geologists. This has been mainly achieved by the sole description of diagenetic products and their association to special diagenetic realms -with distinct physico-chemical conditions (see above). Subsequently, "quantitative diagenesis" [START_REF] Parker | Quantitative diagenesis: Recent developments and applications to reservoir geology[END_REF] emerged as an approach to quantify processes and responses (e.g. geochemical mass-balances, thermal evolution) from micro to basinal scales. Then, "diagenetic modelling" as a 'magic tool' appeared to provide predictions and explanations of diagenetic processes [START_REF] Boudreau | Diagenetic models and their implementation[END_REF]. For instance, forward modelling may result in substantial information about the porosity/permeability heterogeneous evolution in a certain reservoir. [START_REF] Nader | Petrographic and geochemical study of the Kesrouane Formation (Jurassic), Mount Lebanon: Implications on dolomitization and petroleum geology[END_REF]. [START_REF] Sibley | Classification of dolomite rock textures[END_REF].

By means of petrographic analysis, a comprehensive classification of recognizable allochems, matrix and void filling can be achieved. Allochems and pre-existing cements may be unreplaced, patially replaced, replaced mimically, or replaced nonmimically. Allochems may be as well dissolved, leaving empty molds. Matrix can be unreplaced, patially replaced or replaced by a unimodal or polymodal dolomite type.

Unimodal size distributions generally indicate a single nucleation event on a unimodal substrate. Polymodal sizes can be formed by multiple nucleation events on a unimodal or polymodal substrate or differential nucleation on an originally polymodal substrate. Planar crystal boundaries develop when crystals undergo faceted growth, and nonplanar boundaries develop when crystals undergo nonfaceted growth. Nonplanar boundaries are characteristic of growth at elevated temperature and/or high supersaturation. Both planar and non-planar dolomite form as cement, replacement of CaCO 3 , or neomorphism of a precursor dolomite [START_REF] Sibley | Classification of dolomite rock textures[END_REF]. Crystal boundary shape is generally controlled by growth kinetics.

Nonplanar texture consists of closely packed anhedral crystals with mostly curved, lobate, serrated, or otherwise irregular intercrystalline boundaries. Preserved crystal-face junctions are rare and crystals often have undulatory extinction in crossed polarized light. Planar textures are subdivided as euhedral (e) or subhedral (s). In planar-e (euhedral) texture, the dolomites chiefly consist of rhombic crystals supporting each other and forming intercrystalline open spaces (alternatively filled by another mineral). This is referred to as sucrosic texture. In planar-s (subhedral) texture, most dolomite crystals are subhedral to anhedral with straight, compromise boundaries and many crystal-face junctions. Such dolomite rock contains low porosity and/or low intercrystalline matrix [START_REF] Sibley | Classification of dolomite rock textures[END_REF].

Porosity development in dolomite

Porosity evolution and reservoir characteristics vary greatly from one dolomite type to another, depending up on the original sediment fabric, the prevailed mechanism of dolomitization, and the extent to which early formed dolomites were further modified by postdolomitization diagenetic processes (e.g., recrystallization, cementation, karstification, fracturing and burial corrosion; [START_REF] Weyl | Porosity through dolomitization: Conservation of mass requirements[END_REF][START_REF] Sun | Dolomite reservoirs: Porosity evolution and reservoir characteristics[END_REF][START_REF] Cantrell | Genesis and characterization of dolomite, Arab-D reservoir, Ghawar field[END_REF]. Porosity and permeability depend on the intensity of crystal nucleation, e.g. the number of crystals per unit volume and their size (Fig. 1.3). Many dolomites which have replaced tidal-flat mud have a high crystalline density which, if has not destroyed porosity, results in low permeability. The evolution of intercrystalline, moldic and vuggy porosity due to the process of dolomitization is typical of most dolostone reservoirs; yet the porosity in the dolostones is not solely due to postdolomitization leaching [START_REF] Murray | Origin of porosity in carbonate rocks[END_REF][START_REF] Lucia | Diagenesis of a crinoidal sediment[END_REF]. Generally, dolomitization is believed to take place concomitantly with calcite or aragonite dissolution, hence the excess solution over dolomite growth during the late stage of the dolomitizing process is viewed as the most likely cause for dolomite porosity (Sun, 1992). Practically, there are three possible ways of porosity evolution (enhancement/destruction), which depends up on the precise composition of the dolomitizing fluids [START_REF] Purser | Dolomites-A volume in honour of Dolomieu[END_REF]. These include:

1) If fluids are such that dissolution of the precursor limestone equals precipitation of the dolomite, then there is no change in the porosity, although porosity may be rearranged and permeability increased. This balance is highly improbable because the process is an open system involving an external source, at least for Mg [START_REF] Weyl | Porosity through dolomitization: Conservation of mass requirements[END_REF].

2) If the rates of dissolution are exceeded by the rates of dolomite precipitation, notably when all material is derived from an external source, clearly any pre-existing porosity diminishes as the dolomite becomes cemented (over dolomitization).

3) If the volume of the precursor carbonate dissolved exceeds the volume of dolomite precipitated, and the rock does not compact enough to account for this volume change, porosity will increase.

Microporosity is evident by examining the dolomitized peloids and bioclasts under the Scanning Electron Microscope (SEM). Nevertheless, the possibility that this porosity was created before dolomitization during the inversion of metastable carbonate into calcite admittedly cannot be denied, although the absence of an intermediate calcite phase in many cases militates against this eventuality. The situation concerning permeability is less complex than that of porosity. Dolomitization frequently increases the size of component particles, particularly where the process affects micritic limestones. Thus, a porous but relatively impermeable lime mudstone may be transformed in to a porous and permeable dolomite. [START_REF] Murray | Origin of porosity in carbonate rocks[END_REF] observed that there is a slight decrease in porosity up to approximately 50% dolomite. As the dolomite contents increases above 50%, the porosity increases rapidly to values approximating 30% at 80-90% dolomite.

Dolomitization models

Various workers proposed different dolomitization models (Land, 1985;[START_REF] Machel | Chemistry and environments of dolomitization: a reappraisal[END_REF]Morrow, 1990a;[START_REF] Tucker | Carbonate sedimentology[END_REF][START_REF] Braithwaite | Dolomites, a review of origins, geometry and textures[END_REF], which exhibit many diagenetic environments and involving fluids with a wide range of chemical composition (e.g. sea water, microbial, sabkha, reflux, mixing zone, burial and hydrothermal (Adams and Rhodes, 1960;[START_REF] Folk | Mg/Ca ratio and salinity: Two controls over crystallization of dolomite[END_REF][START_REF] Machel | Golden dolomite, Barbados: Origin from modified seawater[END_REF][START_REF] Muchez | Dolomitization caused by water circulation near the mixingzone: An example from the Lower Viséan of the Campine Basin (northern Belgium)[END_REF][START_REF] Vasconcelos | Microbial mediation of modern dolomite precipitation and diagenesis under anoxic conditions (Lagoa Vermelha, Rio de Janeiro, Brazil)[END_REF][START_REF] Wright | An organogenic origin for widespread dolomite in the Cambrian Eilean Dubh Formation, northwestern Scotland[END_REF]Machel, 2004) (Fig. 1.4). On the basis of mode of formation, these models can be subdivided into three groups:

1) Evaporative and seepage-reflux models explain the formation of massive dolomite by circulation of hypersaline brines (Fig. 1.4A,B). Dolomites may form by direct precipitation in evaporitic environments like Sabkhas (McKenzie, 1981) and coastal evaporitic lakes (Von der [START_REF] Der Borch | Geological significance of the Coorong dolomites[END_REF]. The seepage-reflux model (Fig. 1.4B) requires the percolation and descent of concentrated seawater from coastal lagoons or Sabkhas into the underlying carbonates (Adams and Rhodes, 1960). The downward fluid flow motion would be driven by the density contrast between the heavy, concentrated seawater and the lighter groundwater.

2) Mixing-zone and seawater models are based on the assumption that highly concentrated fluids are not necessarily required for dolomitization and that normal or even dilute seawater may produce dolomite as well. In the mixing-zone model (Fig. 1.4C) hyposaline solutions originate from the mixing of seawater and dilute groundwater (Hanshaw et al., 1971). The Mg/Ca ratio decreases relative to pure marine water but it can be kept high enough to remain suitable for dolomitization. The seawater models (Fig. 1.4D) assume normal marine water, or seawater slightly modified by water-rock interaction, as the most likely dolomitising fluids (Land, 1985;Morrow, 1990b). These fluids may circulate in host rocks according to a variety of mechanisms.

Hence, various hydrologic systems have been proposed, including seawater thermal convection or Kohout model.

3) Burial dolomitization models are based on the evidence that under moderate to deep burial conditions, the kinetic requirements for dolomite formation are more easily satisfied than at surface [START_REF] Choquette | Geologic nomenclature and classification of porosity in sedimentary carbonates[END_REF]. The increasing temperature with depth makes the burial environment suitable for dolomitization (on both kinetic and thermodynamic levels), since it reduces the proportion of hydrated magnesium and increases dolomitization rates. Four main types of burial models are distinguished on the basis of hydrologic drives of the fluid flow (Morrow, 1998):

• Compaction flow (Fig. 1.4E),
• topography-driven flow (Fig. 1.4F),

• tectonically-driven flow (Fig. 1.4G), and

• and thermal convection flow (Fig. 1.4H).

Compaction-flow (Fig. 1.4E) is induced by the compaction of sediments under burial and consequent pore water squeezing [START_REF] Illing | Deposition and diagenesis of some Upper Paleozoic carbonate sediments in western Canada: New York[END_REF]. The topography-driven flow model (Fig. 1.4F) may take place in uplifted thrust belts exposed to meteoric recharge. Gravity-driven meteoric water is pumped through the basin in front of the thrust belt and during circulation it may pick up enough Mg to become a potential dolomitising fluid (Morrow, 1998). Tectonically-driven flow (Fig. 1.4G) is initiated by tectonic loading and compression during the development of orogenic thrust belts and causes the expulsion of metamorphic and basinal fluids towards the basin margins. The thermal convection of fluids can be driven by heat gradient in the crust [START_REF] Wilson | Spatial patterns of diagenesis during geothermal circulation in carbonate plateforms[END_REF]. In many cases a heat source, such as a magmatic intrusion, is invoked to generate convection cells (Coniglio et al., 1994;[START_REF] Wendte | High temperature saline (thermoflux) dolomitization of Devonian Swan Hills platform and bank carbonates, Wild River area, west-central Alberta[END_REF]. The genesis of high temperature dolomites, commonly called "Hydrothermal dolomites", is frequently linked to the thermal convection model (Fig. 1.4H). [START_REF] Machel | Hydrothermal dolomite-a product of poor definition and imagination[END_REF] described hydrothermal dolomites (HTD) as formed at higher temperatures compared to the surrounding rocks at the time of dolomitisation, regardless of the absolute temperature of origin or the chemical nature of the dolomitizing fluids. Various workers extensively discussed hydrothermal dolomite formation [START_REF] Braithwaite | The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland[END_REF]Warren., 2000;[START_REF] Davies | Thermoboric dolomitization: Transient pressure driven processes and the role of boiling-effervescence in fabric/reservoir development[END_REF][START_REF] Wilson | Spatial patterns of diagenesis during geothermal circulation in carbonate plateforms[END_REF]Machel, 2004;Davies and Smith, 2006). Recent integrated studies suggest that hydrothermal dolomite occurs extensively than previously thought [START_REF] Knipe | Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: An introduction[END_REF]Berger and Davies, 1999;Moore, 2001;[START_REF] Cantrell | Genesis and characterization of dolomite, Arab-D reservoir, Ghawar field[END_REF][START_REF] Lavoie | Hydrothermal dolomitization in the Lower Silurian Sayabec Formation in northern Gaspé-Matapédia (Québec): Constraints on timing of porosity and regional significance for hydrocarbon reservoirs[END_REF]Nader and Swennen, 2004;[START_REF] Lavoie | Hydrothermal dolomitization in the Lower Ordovician Romaine Fm of the Anticosti Basin: Significance for hydrocarbon exploration[END_REF]Davies, 2006).

FRACTURE-RELATED HYDROTHERMAL DOLOMITE

Hydrothermal dolomite is strata destructive, prevailing throughout the host limestone and forms broad belts along major regional faults (Wilson et al., 1990;Nader et al., 2004). These dolomites range from minor saddle dolomite in and around faults and fractures to pervasively dolomitized fronts. A good percentage of porous dolomite in oil and gas reservoirs is probably hydrothermal in origin, which makes better understanding of the related dolomitization processes of great economic interest.

Hydrothermal dolomites are commonly white to grey coloured, anhedral to subhedral and medium to coarse crystalline (crystal size from 150 to 2000 µm) [START_REF] Sibley | Classification of dolomite rock textures[END_REF][START_REF] Gregg | Dolomitization of the Wausortian Limestone (Lower Carboniferous) in the Irish Midlands[END_REF][START_REF] Chen | Multistage hydrothermal dolomites in the Middle Devonian (Givetian) Carbonates from the Guilin area, South China[END_REF][START_REF] Lonnee | Pervasive dolomitization with subsequent hydrothermal alteration in the Clarke Lake gas field, Middle Devonian Slave Point Formation, British Columbia, Canada[END_REF]. Porosity varies from 5 to 20% in different hydrothermal dolomite facies [START_REF] Lucia | Carbonate reservoir characterization[END_REF]Nader et al., 2004). Saddle dolomite cement occludes fractures and vugs. Hydrothermal dolomites usually have depleted δ 18 O values (-11.0 to -4.0‰ VPDB) and contain two-phase aqueous fluid inclusions that have relatively high salinities and homogenization temperatures higher than 50°C [START_REF] Braithwaite | The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland[END_REF][START_REF] Swennen | Fluid circulation in the Ionian fold and thrust belt (Albania): implications for hydrocarbon prospectivity[END_REF][START_REF] Wright | Fluid migration and rock interactions during dolomitization of the Irish Midlands and Dublin basin[END_REF][START_REF] Gregg | Dolomitization of the Wausortian Limestone (Lower Carboniferous) in the Irish Midlands[END_REF][START_REF] Machel | Hydrothermal dolomite-a product of poor definition and imagination[END_REF][START_REF] Nagy | Early dolomitization and fluid migration through the Lower Carboniferous carbonate platform in the SE Irish Midlands: Implications for reservoir attributes[END_REF]Gasparrini et al., 2006). The Sr 87 /Sr 86 isotope ratios are usually radiogenic, which indicates that the dolomitising fluid is allochthonous and passed through siliciclastic sediments or basement rocks (Schrijver et al., 1996). Many of these dolomites have high concentrations of Fe and Mn and, therefore, display dull red luminescence when examined under cathodoluminescence [START_REF] Allan | Dolomite reservoirs-Geochemical techniques for evaluating origin and distribution: AAPG continuing education course note series[END_REF].

Hydrothermal dolomites are of considerable interest because (1) they may be sites of hydrocarbon accumulation or mineralization (Warren, 2000;[START_REF] Smith | Structurally controlled hydrothermal alteration of carbonate reservoirs: Introduction[END_REF], and ( 2) their origins are commonly controversial or poorly understood (Machel, 2004).

Geometry of the dolomitized bodies

The factors required for a hydrothermal dolomitization process to occur and to produce an HTD body with a specific geometric pattern include: (1) a proper tectonic setting for the circulating dolomitizing fluids, ( 2) an effective net of conduits for the dolomitizing fluids to flow within the host rock, (3) a conspicuous source of Mg to supply and maintain the high Mg content of both fluid and dolomite phases, and ( 4) a source of heat to facilitate the dolomitization from a thermodynamic point of view (and to explain the very high temperatures inferred from fluid inclusions analyses for such dolomites and associated calcites (Gasparrini et al., 2003).

The vertical and lateral extent of the hydrothermal dolomitization depends on several factors, such as porosity/permeability and composition of the host rock, pressure, temperature and composition of the hydrothermal fluid, the efficiency of the fluid recharge into the fault system, the effectiveness of the seal, and the spacing and types of faults. In some cases, these hydrothermal dolomites extend from 45 to more than 200 km and appear to be regional in their trend; otherwise they are restricted to the close-vicinity of the faults, along which fluid flow occurred (Nader et al., 2004). Gasparrini et al. (2003) demonstrated that hydrothermal dolomitization occurred in the Paleozoic carbonates of the Cantrabrian mountains, when hot Mg-rich brines flow laterally into permeable carbonates that are typically less than 1 km from the surface. This may also give an idea about the vertical size of HTD reservoirs. The local volume of the produced HTD body as well as the dolomite texture, fabric, pore type and pore volume are controlled mainly by the facies of the original limestone host. Porosity and permeability of the host at the time of dolomite emplacement strongly influence the size of the dolomite body and its lateral distribution away from the fault conduits [START_REF] Sun | Dolomite reservoirs: Porosity evolution and reservoir characteristics[END_REF]Nader et al., 2007). Dilational breccias, zebra fabric, arrays of shear micro-fractures (rimmed micro-fractures) and related fabrics may be formed preferentially proximal to periodically-active faults, which act as fault proximity indicators (Davies, 2004).

Chemistry of the Dolomitizing Fluids

Salt brines play an important role in the process of hydrothermal dolomitization. [START_REF] Machel | Coastal mixing zone dolomite, farward modelling and massive dolomitization of platform-margin carbonates-Discussion[END_REF] demonstrated that approximately 30m 3 of saline brine at 100˚C are required to make 1m 3 of dolomite from a limestone with 40% porosity. Fluid inclusion analyses show that void-filling saddle dolomite is precipitated from brines with salinities that are as much as two to nine times more saline than that of modern sea water (Al-Aasm et al., 1995). Fluid inclusion analyses, mainly from Ordovician hydrothermal dolomite of Anticosti Island indicates MgCl 2 -CaCl 2 -NaCl brine composition [START_REF] Lavoie | Hydrothermal dolomitization in the Lower Ordovician Romaine Fm of the Anticosti Basin: Significance for hydrocarbon exploration[END_REF]. These characteristics argue against simple sea water or slightly modified sea water fluid and support a modified post evaporite residual brine source (Morrow et al., 2001). Salinity generally increases with depth to near halite saturation in sedimentary basin. Any fluids flowing up faults from deeper sources should have higher salinity (and temperature) than those in the shallower host formation.

Extensive anhydrite and halite evaporite deposits may satisfy the volumetrics of post evaporative brine source for large scale dolomitization [START_REF] Shields | Mass balance and fluid flow constraints on regional-scale dolomitization, Late Devonian, Western Canada sedimentary basin[END_REF]. The source of Mg for Lower and Middle Ordovician-hosted hydrothermal dolomite (including Trenton-Black River unit) is also conjectural. Few Cambrian or Ordovician evaporites in these basins exist, leaving open the possibility of brine down flow from overlying Silurian evaporites as a possible source (Smith, 2007).

Hydrothermal dolomites typically have relatively light δ 18 O values (-12 to -20‰ PDB), radiogenic 87 Sr/ 86 Sr values relative to sea water for the time of formation deposition, fluid inclusion homogenization temperatures greater than 75˚C and fluid inclusion salinities higher than sea water (>3.5 wt.%). Oxygen isotope values depend on the composition of the fluid.

Hydrothermal dolomite form from subsurface brines, which commonly have δ 18 O values between 0 and +10‰ V-SMOW. If the water is closer to 0 +10‰, dolomite that forms at temperatures near 100˚C may have δ 18 O values closer to 0 or even positive values. Thus many dolomites reflexively interpreted as reflux or mixing zone due to their isotopic signature may in fact be hydrothermal in origin (Smith, 2007).

Significance of faults and fractures

Faults and fractures play an important role in the formation of hydrothermal dolomites as they provide pathways for the dolomitizing fluids to alter the composition of host carbonate rock.

Various workers [START_REF] Gale | Predicting and characterizing fractures in dolostone reservoirs: using the link between diagenesis and fracturing[END_REF]Davies andSmith, 2006 and[START_REF] Smith | Hy dro ther mal al te ra tion of car bo nate re ser voirs: How com mon is it?[END_REF]Davies, 2006) described different aspects of fluid flow and geo-mechanics related to faults and fractures. In structurally controlled (faults and fractures) hydrothermal processes, the system is episodically very dynamic, with abrupt changes in applied stress, pore-fluid pressure and the rate of fluid flow (Fig. 1.5).

Structurally controlled hydrothermal fluid movement is favoured by specific structural settings: 1) Extensional faults, 2) Wrench faults, and 3) Extensional/Wrench faults.

(1) Extensional faults: Here dolomitization is preferentially occurring on the hanging wall (downthrown) side of a fault, whether purely extensional or transtensional. Several mechanisms contribute to this preference, which include buoyancy (thermal density) drive into the hanging wall [START_REF] Phillips | Hydraulic fracturing and mineralization[END_REF], pressure-driven preferential flow to the upper hanging wall during fault-tip propagation (Knipe, 1993), damage zone preference [START_REF] Knipe | Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: An introduction[END_REF], and increased fracturing in the upper hanging wall [START_REF] Steen | Predicting the distribution of small faults in hydrocarbon reservoirs by combining outcrop, seismic and well data[END_REF].

(2) Wrench faults: Hydrothermal dolomite reservoirs show a strong correlation with extensional and particularly strike-slip (wrench) faults (Berger and Davies, 1999). Davies and Smith (2006) described several characteristics of wrench faults, which favour hydrothermal fluid flow, mineralization and dolomitization, and the occurrence of dolomite in vertical pipes.

(3) Intersections of extensional and/or wrench faults, including transform faults: The relative contribution of mainly extensional versus mainly wrench faults in localizing hydrothermal fluid flow and dolomitization is usually influenced by the position within the sedimentary basin, the orientation of extensional and transtensional stresses, the type and orientation of reactivated basement structures and other factors (Davies and Smith, 2006). Thrust faults usually do not appear to be favourable sites for hydrothermal mineralization and dolomitization. Various models have been proposed by different workers, for the formation of hydrothermal dolomites by different workers [START_REF] Al-Aasm | The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry[END_REF]Davies and Smith, 2006;Nader et al., 2004;Cervato, 1990 and[START_REF] Charef | Pb-Zn mineralization associated with diapirism: fluid inclusion and stable isotope (H, C, O) evidence for the origin and evolution of the fluids at Fedj-El-Adoum, Tounisia[END_REF][START_REF] Charef | Pb-Zn mineralization associated with diapirism: fluid inclusion and stable isotope (H, C, O) evidence for the origin and evolution of the fluids at Fedj-El-Adoum, Tounisia[END_REF]. Fracture-controlled hydrothermal dolomites are formed along major faults, through which the fluids can easily pass upon fault-movements and alter the composition of the carbonate rocks (see fig. Besides fracture-related dolomite bodies, presence of magmatic/volcanic rocks in the vicinity of the HTD bodies, may represent an important heat flow activity for dolomitization process. In case of hydrothermal dolomites associated with the heat flow activity, the size of dolomitization depends up on the extent of magmatic/volcanic activity and the heat propagation, which will be best exported via fractures and faults. Nader et al. (2004) has illustrated that mixing of hypersaline to mesosaline evaporated sea waters with waters originated from dissolution of the underlying Late Triassic evaporites and sea water, heated up by the Jurassic volcanism and circulated along faults and fractures through convection cells caused the formation of hydrothermal dolostones in Central Lebanon. Some hydrothermal dolomites were also associated to salt diapirism (e.g. [START_REF] Al-Aasm | The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry[END_REF]. [START_REF] Charef | Pb-Zn mineralization associated with diapirism: fluid inclusion and stable isotope (H, C, O) evidence for the origin and evolution of the fluids at Fedj-El-Adoum, Tounisia[END_REF] attributed Pb-Zn mineralization in northern Tunisia to hydrothermal fluids associated with Triassic diapirs that intruded the Cretaceous limestones. [START_REF] Al-Aasm | The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry[END_REF] observed that dolomites are in sharp contact with the host rock or scattered in the diapir itself. The related dolomitization events, therefore resulted from the expulsion of formation water from sedimentary rocks in the inter-diapiric basin during diapirism and prevailing tectonic activity. The presence of the diapir is believed to have played an important role in producing a localized abnormal heat flow gradient as the diapiric salt is a heatconductor. In addition, due to the tectonic activity (faulting) associated with diapirism, fluids that have circulated along the edge of the diapir are believed to have reacted with the salt and gained more dolomitizing potential (such as additional amounts of Mg 2+ and higher salinity). Diapirrelated dolomitization usually occur away from the abnormally hot sites -e.g. on the top of the diapir-structures, where the fluids are chemically aggressive and become enriched in Mg 2+ .

Introduction

Dolomites remain one of the most enigmatic lithologies in the sedimentary record, and it commonly is difficult or impossible to unravel their precise origin. Many different dolomitisation models have been proposed over several decades (see reviews in Warren, 2000;Machel, 2004). Dolomites that reflect the circulation of hot fluids have received particular attention since they may form good hydrocarbon reservoirs. Such dolomites commonly are fault-related and, as a consequence, there is a marked structural control on the architecture of the dolomite bodies. However, similar coarse crystalline dolomites may also form important stratabound bodies [START_REF] Sharp | Stratigraphic architecture and Fracture Controlled Dolomitisation of the Upper Khami and Bangestan Groups (Cretaceous), Zagros Mountains, Iran -An outcrop case study. In: Mesozoic and Cenozoic carbonate systems of the Mediterranean and the Middle Eaststratigraphic and diagenetic reference models[END_REF]. Detailed petrography, geochemical and microthermometric investigations provide evidence of the involvement of hot fluids in the precipitation of these coarse crystalline dolomites. Yet, it is commonly difficult to determine whether fluids were hydrothermal or thermobaric in origin (see discussion in Davies & Smith, 2006).

A particular difficulty relates to the timing of the dolomitisation event(s). Based on the paragenetic sequence it may be possible to deduce a relative timing, but an absolute timing can only be achieved if radiogenic mineral phases formed coevally with the dolomites. In most cases the timing is deduced by indirect evidence. The driving mechanism(s) of the dolomitising fluids provide an additional challenge. A variety of hydrodynamic mechanisms has been proposed (Machel, 2004), but it is commonly only by inference that a dolomite can be linked to a specific driving mechanism. A number of recent papers have reported on earthquake-induced fluid flow [START_REF] Noir | Fluid flow triggered migration of events in the 1989 Dobi earthquake sequence of Central Afar[END_REF][START_REF] Miller | Aftershocks driven by a high-pressure CO2 at depth[END_REF][START_REF] Chiarabba | Pore-pressure migration along a normal-fault system resolved by time-repeated seismic tomography[END_REF] and it is likely that some dolomite occurrences relate to such earthquakeinduced circulation. However, it is difficult to prove this relationship, in part because outcrop conditions commonly hamper good field observations. The aim of this paper is to describe the sedimentary setting and diagenetic evolution of fault-related dolomites in the Pozalagua Quarry (Ranero, Cantabrian Mountains). A detailed paragenetic sequence can be constructed, based on cross-cutting relationships and successive overgrowth structures, and a mechanism of multiple diagenetic phases can be proposed. Coarse crystalline dolomites are exceptionally well-exposed in the quarry due to its recent rehabilitation and transformation into an amphitheatre. Multi-decametre scale cut faces on the quarry walls allow detailed investigation of the complex diagenetic history of dolomite emplacement. The cut faces are traversed by major faults, related to the Pozalagua Fault system (Figs 1A,1B and 2B), along which metre-scale displacements can be inferred locally.

Interpretations at the end of each descriptive section (illustrated by field photographs) highlight the key issues of timing and relationship to tectonic events. The mechanisms acting to expel fluids will be addressed in the Discussion section. However, the recrystallised nature of some dolomite generations sometimes requires reference to diagenetic products that paragenetically post-date those described.

Data on petrography, geochemistry (trace elements and C, O and Sr-isotope analysis) together with fluid inclusion microthermometry of the dolomites in the area are provided by Shah et al. (2010) and López-Horgue et al. (2010).

Geographical and geological setting

The Pozalagua Quarry (López-Horgue et al., 2000) lies between Bilbao and Santander, on the border of the Basque Country and Cantabria in northern Spain (Fig. 2A). Following the Hercynian orogenic cycle, Permian and Triassic deposition took place in a series of intracontinental rift basins (Rat, 1988) that formed as a consequence of transtensional movements along dominantly north-west to south-east faults superimposed on Hercynian structural trends (García-Mondéjar et al., 1996). The basins were filled by terrigeneous and evaporitic sedimentary sequences [START_REF] Curnelle | Evolution structuro-sédimentaire du Trias et de l'Infra-Lias d'Aquitaine[END_REF] [START_REF] Yilmaz | Tectonic evolution and paleogeography of Europe. In: Peri-Tethys Memoir 2: Structure and Prospects of Alpine Basins and Forelands[END_REF].

The lithostratigraphical succession of the Cretaceous rocks in the Basque-Cantabrian Basin (BCB) has been summarized by Martín-Chivelet et al. (2002) and López-Horgue et al. (2010). The Albian period in particular witnessed several major pulses of accelerated subsidence separated by intervals of tectonic quiescence (Fig. 3;[START_REF] Garcia-Mondéjar | Pulsating subsidence during a rift episode: Stratigraphic and tectonic consequences (Aptian-Albian, northern Spain)[END_REF]. The Late Albian tectonic activity was correlated mainly with left-lateral north-west to south-east transtension punctuated by transpression in the BCB [START_REF] Agirrezabala | A coarse-grained turbidite system with morphotectonic control (Middle Albian, Ondarroa, northern Iberia)[END_REF]Aranburu et al., 1994;López-Horgue et al., 2000;[START_REF] Agirrezabala | Syntectonic deposits and punctuated limb rotation in an Albian submarine transpressional fold (Mutriku village, Basque-Cantabrian basin, northern Spain)[END_REF][START_REF] Iriarte | La Depresión Intermedia entre Leitza y Elizondo (Pirineo Occidental): Estratigrafía y relaciones tectónica-sedimentación durante el Cretácico[END_REF], and is attributed to a rapid acceleration in the south-easterly drift of Iberia. Combined with the global sea-level rise [START_REF] Immenhauser | Late Aptian to Late Albian sea-level fluctuations constrained by geochemical and biological evidence (Nahr Umr Fm, Oman)[END_REF], the Albian marine transgression established a connection between the opening of the Bay of Biscay with the Neo-Tethys Ocean that allowed Tethyan currents to reach the BCB. Reef environments developed on shallowwater carbonate platforms like the Ramalas block, that formed palaeohighs during at least the middle Cretaceous; these formed the so-called Urgonian and Supra-Urgonian facies (Martín-Chivelet et al., 2002). In basinal areas of the BCB a thick prism of sediments, up to 7 km, accumulated during the Aptian-Albian [START_REF] Cámara | The Basque Cantabrian Basin' Mesozoic tectono-sedimentary evolution[END_REF]. During this period, extensive volcanism occurred in both the BCB and the Pyrenean domain [START_REF] Cabanis | Le magmatisme Crétacé des Pyrénées -Apport de la géochimie des éléments en traces -Conséquences chronologiques et géodynamiques[END_REF].

A number of dolomite bodies, including both fault-related and stratabound deposits have been recognized in the Ramalas area (the Ranero, El Mazo, El Moro, Bueras and Matienzo bodies; Figs 2B and4), hosted in Aptian-Albian limestones (Fig. 3; in the Ranero and Sopeña limestones in particular).

As can be seen in Figure 4 the dolomite body develops around the major faults. This is also the case for the dolomite body in the slope deposits of the Pozalagua fault, however in the platform setting the latter fault borders the dolomite body. Thus faulting predates dolomitisation. The limestones in the Pozalagua Quarry reflect deposition during the Early and Late Albian on a slope bordering a platform margin that can be followed laterally for several kilometres. The margin is well-exposed in a crosssection near the city of Ramalas (Fig. 5). Aerial and satellite photographs show that the slope carbonates are cut by a number of traverse faults, including the Pozalagua Fault. Most of these faults commonly die out in both the basinal deposits and the platform carbonates, but it is along these faults that the dolomite bodies, up to 50 m wide and 2 km long, are developed (Fig. 5). The Pozalagua Fault is one of the exceptions since this fault can be followed over at least 3 km (Fig. 1A). In the Pozalagua Quarry several satellite faults to the major fault (Fig. 1B), henceforth called the Pozalagua Fault system, can be seen. In the platform setting, the Pozalagua Fault borders a major dolomite body, at least 700 x 600 m wide. In the slope setting the dolomite body is less than 100 m wide, and develops around the fault system. It is the latter that is exposed in the quarry. Estimated sinistral displacement along the Pozalagua Fault is about 500 m (Dewit et al., in review). As documented by [START_REF] Agirrezabala | Syntectonic deposits and punctuated limb rotation in an Albian submarine transpressional fold (Mutriku village, Basque-Cantabrian basin, northern Spain)[END_REF], and also argued by Aranburu et al. (2002) the Basque -Cantabrian Basin was severally tectonised during the Late Albian. It therefore is not unlikely that the Pozalagua fault also was formed in this time period.

Pozalagua Quarry: The Limestone Host rock

Limestone lithology

The dark grey limestones in the Pozalagua Quarry are predominantly recrystallised bioclastic to intraclastic wackestones to mudstones (Fig. 6A), although coarser-grained bioclastic packstones to grainstones and interbeds of conglomeratic floatstone occur locally (Fig. 6B). The clasts in the conglomeratic units are rounded to elongated grey bioclastic packstone to grainstone with diameters ranging from 1 mm to 15 cm and are surrounded by mudstone or calcite cement (Fig. 6B andC). The clast margins are often indistinct and there appears to be a transition between the interior of the clast and the mudstone matrix. Bioclasts are typically broken, but locally include large solitary and colonial corals, bivalves (some rudist fragments up to 15 cm), and a bioclast hash (fragments 3 mm diameter).

Bedding is only vaguely defined by the alignment and sorting of the clasts and the presence of elongated cemented cavities. A dip of ca 40 to 50°S (Fig. 6B) is inferred that contrasts with the otherwise sub-horizontal shallow marine platform carbonates to the north. Major clinoforms have been identified along the Karrantza valley section that cuts the platform edge in a setting corresponding to that of the Pozalagua Quarry. Elongated sheet-like cracks (5 to 40 cm long) are lined by up to four generations of radiaxial calcite cements (Fig. 6C). In some places, these are overlain by a geopetal sediment before crystallisation of white equant calcite cement (Fig. 6C). Locally, these cements are cut by, and therefore pre-date, stylolites. Numerous semi-continuous bedding-parallel stylolites are spaced at decimetre intervals but are deflected around clasts. A few tectonic stylolites, oriented perpendicular to bedding are also present. Veins that pre-date stylolitisation are common; these crosscut the limestone (Fig. 6A andC) and are filled principally by milky white calcite cement. However, other veins cross-cut, and thus post-date, stylolitisation.

The massive bioclastic wackestones to mudstones, with reworked limestone clasts and bioclasts are interpreted as platform margin deposits. The dip of the bedding at 40 to 50° is related to the depositional slope of these deposits. Platform shedding took place along the slope, with down-slope transport explaining the detached and sometimes rounded fragments/clasts. The transitional margin between clasts and mudstone matrix is interpreted as the result of slope-failure with partial disintegration of the slope sediments, that became enclosed by micrite, the increased portion of which reflects a deeper marine setting. Debris-flows with metre-sized clasts are present locally. The interpretation of the platform edge accords with the palaeogeographic maps of García-Mondéjar et al. (2005). Intergranular pores between some fragments were lined by multiple generations of radiaxial calcites that are interpreted as of marine phreatic origin (see Moore, 2001). This interpretation is supported by the geopetal sediment that locally covers these cements. Similar calcite cements also occur lining sheet-like cracks, interpreted to relate to downslope sediment transport, accentuating the inclination of the strata. Later milky-white calcite cement is tentatively interpreted as of meteoric phreatic origin, pre-dating fracturing and stylolitisation. This interpretation accords with the presence of palaeokarst, related to intra-Albian unconformities (López-Horgue et al., 2000& 2010;García-Mondéjar et al., 2005).

Palaeokarst development and filling (PK) in the host limestone

Near-vertical irregular pipes are present in the limestones in all quarry walls (varying from several centimetres to 2 m in diameter). These pipes typically cross-cut the inclined bedding and commonly are filled with angular fragments (Fig. 6D). Centimetre-size clasts are elongated and polymict and locally include reworked fragments of recrystallised microspar and radiaxial calcite (Fig. 6E); some are stained red. There are no individual bioclasts. The matrix between the fragments may be black or red, but is clay-rich and commonly laminated, locally forming geopetal floors. Some pipes are almost entirely filled by a red-stained matrix or by black sub-millimetre laminae of clay and organic-rich limestone. Where present, stylolites formed preferentially at the contact between the pipe filling and the host limestone and locally around the fragments within the pipes. Interpenetrating relationships are seen between adjacent fragments. No cements have been observed in the pipes.

The pipes form a widely spaced (10 to 20 m) network of conduits interpreted as palaeokarst; this is tentatively regarded as intra-Cretaceous and may have formed during one of the late Albian-Turonian periods of emergence (López-Horgue et al., 2010). The angular fragments (locally with reworked radiaxial cement) probably reflect a stage of rock fragmentation. The material resembles rock rubble formed in immature soils (for example, lithosols) that accumulated in the pipes after transport. The red staining implies oxidation and soil related alteration. This interpretation is in line with the presence of clayey matrix and laminated fill that probably formed by dissolution of the limestones, leaving a claydominated insoluble residue. The fact that geopetal filling has been recognised also supports the palaeokarst interpretation. The pipe fillings pre-date stylolitisation, and some burial compaction has occurred between adjacent fragments.

Cavity development in host limestone (CA)

Centimetre to metre-sized cavities occur within the host limestone (Fig. 6F) of the central quarry wall and some seem to have formed close to the palaeokarst (PK) conduits. The contacts with the host limestone are sharp and the cavities commonly are sub-rounded or irregular. Similar outlines characterise the centimetre to decimetre-size clasts that occur in some larger cavities (Fig. 6F). Clasts, of similar composition to their host rock, commonly occur at the bottom of the cavities and seem to 'float' in the two-dimensional cut-faces (Fig. 6F). Relatively large fragments that have been detached along stylolite contacts are present in some cavities and a few of these can be placed in position in the present-day roofs of the cavities, i.e. the outline along one side of the fragments fits with the stylolite border at the top of the cavity (Fig. 6F). Some clasts contain stylolites that are restricted to them (Fig. 7A).

The irregular sub-rounded shapes and sharp contacts with the host rock suggest that the cavities formed as a result of dissolution; they can best be explained as enlarged vugs and small caves. Also the infill at the bottom of these cavities, that consists of dominantly monomict corroded fragments, is the result of dissolution. However, the similarity between the lithology of the clasts and the host rock, and the absence of fine-grained sediment fill, suggests that the clasts are of local origin. Unlike the PK pipes, these cavities were not connected to the surface where fine-grained material was probably present. When they formed, stylolites were already present in the host rock, as shown by their restriction to some fragments. Thus, the limestones had been buried to several hundreds of metres (see [START_REF] Dunnington | Stylolites development post-date rock induration[END_REF][START_REF] Lind | Stylolites in Chalk from Leg 130, Ontong Java Plateau[END_REF] before cavity development began. This makes meteoric karst development less likely, and is in line with the absence of any fine-grained sedimentary fill, unless a deep karst system comparable to the Floridan aquifer system [START_REF] Back | Comparison of chemical hydrogeology of the carbonate Peninsulas of Florida and Yucatan[END_REF] developed.

Alternative possibilities relate to hydrothermal karstification (cf [START_REF] Giles | Origin and significance of redistributional secondary porosity[END_REF][START_REF] Nielsen | Columnar calcites at the boundary between Upper Tournaisian dolomites and limestones (Belgium): multiple origins for apparently similar features[END_REF] or mixing corrosion (cf Esteban & Taberner, 2003).

Coarse crystalline calcite cementation (CC1 to 4)

The cavities described above (CA) are typically cemented by one to four generations of a coarse (commonly centimetre size) crystalline calcite cement (CC1 to CC4) (Figs 6F, 7A and 8A). First a white to white grey calcite up to 1 cm thick with blocky to bladed elongated crystals (CC1) lining the CA-cavity walls and/or surrounding fragments in the cavities developed, followed by white, 1 to 2 cm calcite crystals, typically containing impure grey to black inclusions (CC2). These are overgrown by white calcite with a beige-reddish tint consisting of centimetre-sized crystals (CC3) and centimetresized white calcite crystals (CC4), filling the major part of the remaining cavity. A white-beige coarse crystalline dolomite may occur as the final phase occluding any porosity remaining in the central part of the cavity (Fig. 6F). The last two calcite cement phases (CC3 and CC4) also fill enlarged fractures and veins in some large cavities (CA). CC3-cemented fractures locally cross-cut CC1 and CC2 (Fig. 6F). The surface of the CC2 cement is irregular, and the crystal rim varies in thickness, indicating dissolution before CC3 cementation. The 'roof collapse fragments' in the cavities are partly surrounded by CC1 and CC2. However, only CC3 is present adjacent to stylolites. CC1 to CC4 locally cut calcite-cemented fractures, but are themselves cross-cut by additional veins and fractures.

Stylolites do not cross-cut any of the CC1 to CC4 cements, but the outlines of cavity walls are commonly accentuated by stylolite formation. A microscopic feature common to CC1 to CC4 is the presence of cleavage twins (Fig. 8A).

The fact that these coarse crystalline calcite cements line entire cavities and surround fragments, and the absence of geopetal fillings, makes a vadose origin unlikely but supports generation during burial.

Additional features include the enclosed host rock fragments with intra-fragmental stylolites, and fractures that pre-date and post-date the cavity fillings. At least one fracturing event took place between CC2 and CC3. The fragments of host limestone (with stylolites) that are covered on one side by CC1 and CC2 and apparently partially float in CC3-cement, can be best explained by roof detachment, taking place after CC2-cementation but before CC3-cementation. Stylolites may have acted as weaker surfaces along which detachment took place. Thus, it is likely that some tectonic activity affected the area, in order to create fractures. The enlarged nature of the pre-CC3-filled fractures and cavities points to a renewed stage of dissolution. The overall characteristics of the cavities and their cement fills resemble those of the columnar calcite cements described by [START_REF] Nielsen | Columnar calcites at the boundary between Upper Tournaisian dolomites and limestones (Belgium): multiple origins for apparently similar features[END_REF] and interpreted as hydrothermal fillings. However, no fluid inclusion data are presently available that might refine the origin of these cements. The existence of cleavage twins support that the calcites have been affected by tectonic stress.

Pozalagua Quarry: Limestone -coarse crystalline dolomite relationship Dolomite has developed around secondary faults in the Pozalagua Quarry, and particularly those associated with the Pozalagua Fault system cutting the slope carbonates (Fig. 1A). The contacts between the limestone and the coarse crystalline dolomite commonly are sharp and accentuated by stylolites, with irregular sub-rounded or lobate outlines (Fig. 7B). The dolomite at the contact (whether or not it is stylolitic) is stained brown locally over about 10 cm. Dolomite formation did not follow layering, or the inclination of sedimentary structures, stylolites or calcite cemented fractures. Successive dolomitisation pulses (described below) invaded the host rocks, without any apparent lithological control, and dolomite development is particularly complex adjacent to the Pozalagua Fault. Whether the palaeokarst pipes and dissolution cavities described acted as fluid conduits is difficult to infer, but this is likely, as some cavities cemented by CC1 to CC4 have been occluded by coarse crystalline dolomite. In contrast to the limestones where stylolites are common, in most dolomites stylolites are rare. Thus, stylolitisation pre-dates dolomitisation, that partly or totally obscured stylolites originally present in the limestones. However faint outlines of relict stylolites are present in zebra dolomites (described below) and as will be described below some dolomites are crosscut by stylolites, implying that there was more than one episode of stylolite development.

Pozalagua Quarry: Dolomites

The dolomitised intervals include a complex mixture of dolomite lithotypes. These can be grouped into three categories: (i) replacive dolomite; (ii) partially replacive dolomite; and (iii) dolomite cement.

Replacive Dolomite

Early replacive laminated dolomites (LD)

Dark-grey to red-brown metre-sized fragments of finely laminated dolomite are common in the northern wall of the quarry. These fragments display a jig-saw puzzle relationship (Fig. 7C; mosaic or crackle breccia according to [START_REF] Morrow | Descriptive field classification of sedimentary and diagenetic breccia fabrics in carbonate rocks[END_REF], with an apparent continuity of laminae between adjacent blocks, implying only minor displacements between them. The spaces between fragments are filled by blue-grey or/and a white crystalline dolomite (see below). Laminae in the fragments are generally of constant thickness but locally show gradual changes in thickness (Fig. 7D). In a few cases soft sediment deformation structures are present. No evidence of cross-bedding or features indicating algal lamination have been found. Isolated centimetre to millimetre-sized rounded and angular rock fragments with well-defined boundaries are present both within laminae that are locally disturbed and within thicker more homogeneous intervals; these are partly replaced by brown-grey to white, medium to coarse crystalline dolomite. A few laminated intervals include aligned gastropod fragments and fossil hash. Millimetre granules of Fe-oxy/hydroxide phases are present in darker intervals. No (former) cement has been recognised. Locally the blocks contain stylolites parallel to the lamination. These blocks are interpreted as brecciated cave pond sediments (cf [START_REF] Kos | Stratigraphy, sedimentary development and palaeoenvironmental context of a naturally accumulated pitfall cave deposit from southeastern Australia[END_REF][START_REF] Auler | Cyclic sedimentation in Brazilian caves: Mechanisms and palaeoenvironmental significance[END_REF] that incorporated small fragments of rock and broken calcite crystals, some of which had been rounded during transport. The dark colour of the host sediment reflects an organic matter/clay-rich composition, which is consistent with the presence of pyrite now transformed to Fe-oxy/hydroxide.

Stylolites cross-cut these lithologies and karst formation and cave pond sediment accumulation therefore preceded stylolite development. Whether dolomitisation of these lithologies occurred before or after stylolite formation is unclear. Karst development is tentatively placed as time-equivalent with the (PK) karst pipe formation described above. However, in contrast with the karst pipes that are filled with rock fragments and a fine-grained matrix, the cave pond sediments dominantly consisted of finegrained sediments (with few small rock fragments). It is, however, possible that the cave pond deposits reflect a separate karst-forming event, as a number of quasi-contemporary emergence periods have been recognised (García-Mondéjar et al., 2005;López-Horgue et al., 2010), but the general similarities in lithologies support a common origin.

Replacive coarse crystalline laminated dolomite (RCCD)

Large surfaces (up to 3 by 4 m) of all quarry walls, but especially those on the southern margin (Fig. 9A), close to some of the exposed faults, consist of laminated planar-S to planar-E dolomite (Fig. 8B).

Individual crystals can be up to 3 mm in diameter, with a regular 'saddle' outline. In some areas the distribution of these dolomites implies the filling of huge cavities; elsewhere they form irregular patches within disrupted breccia blocks. Locally the coarse dolomite forms 'triangular' patches. The lamination reflects the alternation of fine and coarser millimetre-thick parallel crystalline layers that vary in thickness (Fig. 9B), generating a wavy pattern, and wrapping around irregularities. No crosslamination has been observed. The lamination locally is obscured partly by recrystallisation (see below). Some of the laminae develop in smaller cavities and show a geopetal arrangement. These dolomites locally show some intercrystalline porosity, which, based on thin-section image analysis, is in the order of 4 to 7%. Some of the intercrystalline spaces are filled by authigenic clays (Fig. 8B).

There is a divergence of <20° between laminae in the dolomite and the dip recorded in the slope limestones. Bedding-parallel stylolites cross-cut the RCCD and, where it occurs in large blocks, the stylolites are restricted to these blocks.

The parallel lamination, geopetal arrangement and cavity filling character of these deposits point towards transport and sedimentation in open spaces. These features are, however, incompatible with primary deposition in a platform to slope setting. By analogy with the replacive laminated dolomites (LD), these laminated patches can best be interpreted as replacing laminated fine to coarse-grained cave floor deposits; they resemble the 'dark matrix floating saddle' (DMFS) fabric of [START_REF] Davies | Hydrothermal (thermobaric) reservoir facies. Proprietary report[END_REF]. It might be argued that the dolomite reflects direct precipitation from fluids that circulated within caves at depth, or that it represents reworked dolomite crystals. However, the fact that no transport-related features, such as eroded crystal edges have been recognised makes these interpretations less likely. All scenarios have in common that the "dolomite" or its precursor accumulated in large caves.

Partially Replacive Dolomite

Partially replacive banded dolomite: Zebra dolomite (ZD)

Dark grey and pinkish dolomites with typical zebra banding, consisting of dark medium crystalline 'a' bands (non-planar dolomite) symmetrically bounded by white to beige coarse crystalline 'b' bands (planar-s dolomite), are very common in the quarry. The contacts between the zebra bands commonly are irregular. Symmetrical 'abba' or 'abccbabccba' banding, where 'c' corresponds to a second coarse crystalline beige to pinkish dolomite or a calcite cement, locally display millimetre to centimetre-scale displacements of bands, as described by Nielsen et al. (1998;Fig. 9C). The dark-grey zebra dolomites, in which the bands are approximately 1 to 10 mm thick, are comparable to the classical zebra dolomites described by Nielsen et al. (1998), Davies (2004), Vandeginste et al. (2005) and others.

Typical shear banding, and an increase in band inclination from bed parallel to about 30° (i.e. 'ladder zebra' of [START_REF] Davies | Hydrothermal (thermobaric) reservoir facies. Proprietary report[END_REF] are common. Porosity is locally developed in the central part of the bands. The pinkish zebra dolomite typically forms centimetre-thick bands of dark-grey to black fine to mediumcrystalline (sub-millimetre) non-planar dolomite 'a', alternating with bladed centimetre-thick milky planar-s 'b' dolomite, with a characteristic pinkish-brown (millimetre) planar-s 'c'-rim. The latter dolomite is followed locally by coarse crystalline beige dolomite and pyrite, i.e. CCD2 described below. Close to the 'c' layers, the typical symmetrical banding is less clearly developed, due to the assimilation of the 'b' crystal phases by the later coarse beige dolomite. Thus, the main contrast between the dark-grey and the pinkish zebra dolomite, apart from the colour, relates to the thickness of the zebra bands, although local band displacements and increasing band inclination are less common in the pinkish dolomites. Shah et al. (2010) reported homogenisation temperatures (Th) values for primary fluid inclusions in saddle dolomite crystals of the "b" bands varying between 130 to 195ºC, with most values plotting between 140 to 170ºC. In both zebraic lithologies there are transitions to laminated dolomite (LD). These are of similar composition to the dark grey non-planar fine crystalline 'a' dolomite. Gradually the bands thicken and may become inclined, but generally zebra structures run sub-parallel to the assumed original (sedimentary?) lamination. Relict outlines of stylolites occur locally along one side parallel to the 'a' banding.

The Pozalagua zebra dolomites are interpreted as the result of the expulsion of hot fluids within finegrained laminated and/or stylolitised precursor lithologies. It seems that such lithologies were prone to develop zebraic banding as a result of the differential permeability along the layering, prone to preferential dissolution -reprecipitation. However, the 'b' dolomite seems to split up the laminae, thus explaining the volumetric expansion seen where there is a transition from laminated to zebraic dolomite. This may reflect the injection of fluids under suprahydrostatic conditions, as described by Nielsen et al. (1998) and Vandeginste et al. (2005) with a total expansion (based on visual estimation) of the 'b' bands in the order of 25 to 30%. This is, however, less than the total volume of white coloured 'b' bands and only corresponds to the transparent (non-milky) and zoned cathodoluminescent part of the 'b' bands. Following Vandeginste et al. (2005), the milky and non-luminescent part of the 'b' coarse crystalline dolomite, adjacent to the 'a' bands, is considered to result from aggrading neomorphism rather than cementation. This reflects the reaction front of the injected fluids, partially recrystallising the laminated fine to medium crystalline 'a' dolomites. The disrupted nature of the banding is also interpreted in terms of the injection of suprahydrostatic fluids, with fracturing, shearing and zebra-band tilting occurring during dolomitisation. The two types of zebra dolomites, i.e. the dark grey and pink, may reflect two generations of development, but might also reflect the contrasting responses of the original host rock lithologies.

Dolomite Cement

Open fill dolomite type 1: Coarse crystalline white vein dolomite fragments (CCD1)

White coarse crystalline dolomite (CCD1) occurs as isolated elongated fragments (10 to 15 cm by 30 to 100 cm) but also encrust zebra dolomite (Fig. 10A andB) or black finely laminated (LD) dolomite fragments, the latter especially occur in the northern part of the quarry. Commonly, euhedral centimetre-sized saddle crystals grow perpendicular to their irregular contact accentuated with the substrate surface that characteristically has a brownish ferroan stain. However, locally the contact is vague and marked by a gradual textural transition. Some central parts of vein fragments display intercrystalline porosity (about 2%). In the outcrop there are parallel rows of elongated CCD1 fragments with their crystal terminations facing each other (Fig. 10A andB). Minute (<0.05mm) pyrite crystals occur locally between CCD1 phases. The contacts with CCD1 fragments, and the overlying blue-grey dolomite or coarse crystalline dolomite 2 (BGD or CCD2, respectively, described below), are irregular and corroded.

The fragments of CCD1 dolomite with opposing crystal terminations can best be explained as remnants of partially cemented fracture linings. The irregular nature of the fracture walls suggests that dissolution occurred after fracturing but before cementation by CCD1. Corroded CCD1 crystal surfaces attest to a period of dissolution post-dating cementation. The gradual contacts with fracture walls suggest local recrystallisation and substrate assimilation but the sharp borders of recrystallised fragments of the substrate indicate that this occurred before refracturing. The coarse crystalline character and the saddle-like form of the dolomite within the fractures support a high temperature origin (Radke & Mathis, 1980;[START_REF] Al-Aasm | Multiple fluid flow events and the formation of saddle dolomite: case studies from the Middle Devonian of the Western Canada Sedimentary Basin[END_REF], but no fluid inclusion data are available.

Open fill (and partially replacive) dolomite type 2: Grey to beige grey massive fine crystalline dolomite (MFD)

Locally, grey to beige-grey uniform fine-crystalline and generally non-planar (ferroan) dolomite (MFD), rarely with a reddish hue, fills discontinuous, vertical fractures up to 20 cm wide in northern quarry faces. In part this dolomite seems to be replacive (Fig. 10A) because similar crystals also invade their substrate adjacent to the fractures. In general the fractures are irregular and fracture walls do not necessarily fit together. Although they cross-cut earlier dolomite generations, their relationship to the CCD1 is uncertain, as locally there is a gradual transition between MFD and CCD1 (Fig. 10A).

The nature of this dolomite is not clear. It is later in the paragenesis than the zebra dolomites as it fills fractures cross-cutting them. A transitional relationship and co-occurrence with the CCD1 suggests that MFD formed time-equivalent to the open fracture CCD1 cement. However, it is not always clear whether MFD is a fracture fill or replacive.

Open fill dolomite type 3: Geopetal infill (GF)

A dark fine-crystalline laminated dolomite fill (Fig. 11A) locally occurs above metre-sized dolomite clasts and blocks, and particularly locally overlying CCD1 in the central quarry wall. This geopetal relationship indicates settling through the pore space relative to the present gravity field. Thicker accumulations are present in depressions and laminae thin in areas where the fill covers crystals projecting above the substrate. A brown (ferroan) dolomite rim is nearly always present at contacts with the CCD1 beneath the fill.

Although these deposits are volumetrically of minor importance (<0.01%), they illustrate the fact that sediment infiltration occurred in an open cavity system, and their distribution indicates that the blocks have not moved significantly since the sediment was deposited. The laminated nature of the deposits reflects differences in sediment transport, supporting the existence of an open fracture and/or cavity network.

Open fill dolomite type 4: Blue-grey zoned dolomite (BGD)

A thick (up to 40 cm) blue-grey fibrous (ferroan) dolomite (BGD) cement is present in spaces between large (up to 2 by 3 m) brecciated fragments (Fig. 11A andB) in the northern and central quarry faces.

Crystals are prominently zoned with a characteristic brown, now calcitised (Fig. 8C andD), rim marking the base of each zone grading upwards or outwards into blue and finally white dolomite. The crystals are fibrous, 1 to 10 mm long, non-planar, and subhedral with a sweeping extinction (Fig. 8C).

The contact with the brecciated fragment substrate is commonly smoothly undulating. Porosity remaining between the fragments after cementation by the BGD has been filled by CCD2 dolomite (see below; Fig. 11A andB). The BGD cements are particularly well-developed close to some of the exposed faults. These cements surround four different types of fragments: (i) laminated dark palaeokarst fill (LD); (ii) dark grey and pink zebra dolomites (ZD) (Fig. 11A); (iii) CCD1 vein fragments; and (iv) fragments entirely or partially replaced by CCD2 dolomite (see below). Some of the larger fragments possess a jigsaw puzzle relationship comparable to the mosaic or crackle breccia described by [START_REF] Morrow | Descriptive field classification of sedimentary and diagenetic breccia fabrics in carbonate rocks[END_REF]. This fabric indicates that they were fractured with only a minor displacement before the emplacement of the BGD cementation. However, many fragments are moderately rounded and a number appear to lack matrix support and to 'float' in the two-dimensional face of the quarry; they are completely surrounded by the BGD phase. This 'floating' appearance is common where rounded coarse crystalline dolomite and dolomitised limestone fragments, up to 10 cm in size (Fig. 11C), are cemented by BGD. The brown rims accentuate the apparently floating relationship of the fragments that locally are bound together by this brown cement. No geopetal fill has been recognised, either between the fragments or overlying the BGD cements. Similar brown fibrous crystals are also present locally lining some fractures and along stylolites in the zebra dolomites. The fracture fillings resemble the brown calcitized dolomite developed adjacent to MFD (Fig. 10A).

The proximity of the cemented breccias to faults might imply a tectonic origin. However, fault and fracture walls and breccia fragments show evidence of partial dissolution or corrosion, and smaller fragments have become sub-rounded. This effect indicates that the brecciation more probably reflects dissolution related to fluid flow along the faults and fractures. Cementation by the brown (ferroan) dolomite marks the beginning of the BGD development. The distribution of the BGD cement implies the existence of large open spaces between blocks before BGD-cementation began. These observations raise the question whether these features reflect karst processes or not. In this interpretation the BGD might represent dolomitised fibrous speleothems, explaining the unusual fibrous crystal morphology. However, the absence of sediment overlying the BGD supports the idea that the breccias and cement developed in a system isolated from near-surface infiltration. This might be because the fault was not connected to the surface (possibly due to cementation) or because the processes of formation occurred at a certain depth. The zoned nature of the BGD might reflect dolomitisation in pulses or an evolution of the fluid chemistry with time. However, the BGD cements did not fill all of the open space as additional diagenetic phases are present in the centres of partly cemented voids. The fibrous BGD resembles the acicular dolomite described by Eichhubl and Boles (2000a) from the Miocene Monterey Formation. Although cementation filled the spaces between the breccia fragments, the apparently floating appearance, particularly of the smaller clasts, possibly implies that these were kept in suspension. Given the size of some of the blocks this could only be possible by accepting enormous fluid discharges; these may resemble the fluid discharges reported from hydrothermal dolomite occurrences (see Davies, 2004 and references therein;Eichhubl & Boles, 2000b). However, in this scenario one also has to accept that crystallisation must have taken place almost instantaneously; this has not yet been reported from experiments. Rapid crystallisation may, however, explain the fibrous nature of the cements.

Open fill dolomite type 5: Elongated relict crystals (ERC) with or without dolomite

Relics of elongated crystals (ERC) (up to 12 cm long: Fig. 11D andE), are found locally within voids in all parts of the quarry that were already lined by blue-grey dolomite cement (BGD) (Fig. 10). The relic crystals now consist of brown replacive dolomite and commonly form rosette-like clusters (Fig. 11D andE) that seem to develop preferentially upwards, overlying the BGD. Similar rosettes also occur in sub-vertical fractures. Locally relict crystals form sub-parallel groups. In general the ERC crystals are embedded in coarse crystalline white to yellow dolomite (CCD2, discussed below). They are surrounded by laminated replacive coarse crystalline dolomite, similar to the RCCD described above, but laminated RCCD phases also cover them locally (Fig. 11D). These crystals are less obvious where they are embedded in CCD2 dolomite due to their partial assimilation and recrystallisation.

The origin of these crystals is not known but they must have developed in open spaces; their general morphology suggests that they might have been either calcite or aragonite and some resemble aragonite botroyoids described from caves [START_REF] Hill | Cave minerals of the World[END_REF]. The local sub-parallel arrangement probably relates to the accumulation of broken crystals deposited at the bottom of cavities. The relict crystals subsequently were covered by younger laminated replacive coarse crystalline dolomite. This indicates either that they formed simultaneously with RCCD, or that there were two periods of deposition of laminated sediments (that were later dolomitised), giving rise to similar textures. Elongated relic crystals clearly pre-date the coarse crystalline dolomite-2 (CCD2) in which they are assimilated and recrystallised.

Dolomite cement and/or late replacive dolomites

Pale-yellow coarse crystalline saddle dolomite with pyrite (CCD2) and curve-shaped dolomite (CSD) Milky to pale-yellow homogeneous coarse crystalline (millimetre to centimetre) dolomite (CCD2) locally forms large areas (several square metres) of the dolomite body, close to faults in the southern and northern part of the quarry (Figs 11A and12A) and fills irregular fractures cross-cutting the surrounding dolomites and host limestones (Fig. 12A). The fractures are either solution enlarged, or the CCD2 reflects recrystallisation of the host carbonates along the margins, as few fracture walls fit together. Where vuggy porosity is present in the CCD2 mass, saddle dolomite crystals are covered by dodecahedral crystals of pyrite up to 2 mm in diameter. Similar pyrite crystals are also present in decimetre-long streaks within the CCD2, and at the contacts between the CCD2 and later calcite cements. Where the dolomite is overlain by calcite, it commonly consists of broken and corroded pieces (Fig. 11F). In bulk it is typically intensely jointed, with up to 10 fractures per metre (measured along a horizontal transect) with a dominance of sub-vertical joints (Fig. 12A). Commonly joints are brown stained due to near-surface alteration. Although most appear closed, samples break preferentially along them.

Metre-sized rock fragments are present in the CCD2, with faint relics of the structures of some of the previous dolomite generations (Fig. 12A). The outlines of these fragments are not always well defined due the partial replacement or assimilation by CCD2. The dominant relict rock in the fragments is 'laminated replacive coarse crystalline dolomite (RCCD)', characterised by the parallel arrangement of the relic laminae (Figs 9A and 12A). This dolomite seems to be only moderately affected by the CCD2, whereas other lithologies adjacent to the 'laminated dolomite (RCCD)' have been completely converted to CCD2-type dolomite. Other relics are of zebra dolomite, in which only the fine crystalline 'a' bands are still recognisable whereas the coarser 'b' bands are converted to CCD2. The relict banding in the assimilated fragments is normally horizontal, but in one example it is nearly vertical. Smaller rock fragments that are nearly completely assimilated, apparently 'float' in the CCD2, with neighbouring areas sometimes dispersed metres from each other. Locally well-developed inclined stylolites cross-cut the CCD2 dolomite but a few are oriented perpendicular to bedding (Fig. 12B). Some centimetre-sized elongate irregular 'curve-shaped' pale-yellow dolomite crystals (CSD) are present in the 'laminated replacive coarse crystalline dolomite (RCCD)' (Fig. 12C). These developed here symmetrically along impure fine-crystalline streaks that probably correspond to former stylolites.

The long axes of these crystals commonly are perpendicular to the lamination of the RCCD but at contacts between the coarse crystalline dolomite and the RCCD they form curvilinear semi-spherical or rosette-like aggregates. The 'curve-shaped' outline in two dimensions (Fig. 12C) may relate to the saddle like nature of these crystals, but as these crystals never develop in open cavities the crystal shape is difficult to constrain. Commonly the 'curve-shaped' crystals are composite, and grade into massive coarse crystalline dolomite CCD2 (Fig. 12C). Within the latter, remnant laminae, oriented parallel to the 'laminated replacive coarse crystalline dolomite' can be followed for more than a metre.

Bedding-parallel and locally also perpendicular stylolites cross-cut the RCCD, the 'curve-shaped' dolomite and CCD2, outlining the contacts between the different dolomite types.

From the description above, it is clear that the CCD2 locally appears either as a cement or as a replacement product. Homogenisation temperatures (T h ) of primary fluid inclusions of these coarse saddle crystals vary between 125 to 185ºC (Shah et al., 2010) and thus indicate the involvement of hot fluids. The association with pyrite suggests that some sulphidic fluids circulated in the system.

The dolomitizing fluids responsible for the CCD2 invaded the host carbonates along faults and fractures forming part of the Pozalagua Fault system. These fissures were enlarged partially by dissolution or breccia fragment displacement. The presence of rounded, detached and partly assimilated rock fragments also points to the combined effects of dissolution, cementation and replacement. The assimilative process is nicely represented by the faint outlines of fragments of recrystallised zebra dolomite 'floating' in CCD2. For large as well as smaller (decimetre-sized) fragments, it is difficult to assess its shape in two-dimensional quarry faces. The larger fragments most probably originally formed as a kind of rubble accumulation, such as is created by roof collapse in caves. This explains why most elongated fragments are still to some extent oriented parallel to each other. In this scenario the fragments were in fact touching in three-dimensions and open pores were subsequently widened during dissolution. The assimilation of fragments, especially of smaller ones, probably also contributed to the creation of an apparently floating relationship. An alternative explanation for the fragments to be 'floating' would imply the involvement of very high fluid velocities, to render fragments 'buoyant', and an extremely rapid crystallisation to 'freeze' them in their floating position (see Discussion below). Smaller scale recrystallisation is reflected by the 'curveshaped' dolomite, and can be inferred from the continuous nature of relic dolomite laminae adjacent to CSD. This recrystallisation is interpreted as coeval with the emplacement of the CCD2, as the CSD displays many features in common with and apparently grades into the CCD2. The faint relict laminae in CCD2 suggest that it is locally of replacive origin. Horizontal stylolites formed after the development of the CCD2 and reflect additional burial. Also some tectonic stylolites were generated locally.

Late stage calcite cementation

White calcite filling of fractures in CCD2 dolomite (WC)

Milky-white coarse (>1 cm) crystalline calcite (WC) generally with non-luminescence to dull-brown luminescence fills fractures and cavities but predominantly occurs as a passive fill between brecciated CCD2 fragments. The latter fragments accumulated in the lower parts of cavities prior to cementation.

Although it is ubiquitous in the quarry, it typically forms <1% of surfaces. This geopetal fill is parallel to that in earlier fill phases and also to the dominant banding of the zebra dolomites. The cement is not cross-cut by joints, that are abundant in the CCD2, and nowhere is cut by stylolites. Crystals include cleavage twins (Fig. 8E).

The stable isotope signature with δ 18 O PDB varying around -16‰ (Shah et al., 2010), together with the coarse crystalline characteristics suggest that this calcite formed from hot fluids. As it is not crosscut by fractures or joints, it probably post-dates the last important tectonic phase. However, the CCD2 commonly is brecciated, particularly close to former large cavities and vugs, thus a deformation pulse preceded WC cementation. The presence of cleavage twins may, however, indicate that the latter crystals were subjected to tectonic stress after crystallisation. López-Horgue et al. (2010) report on one high temperature calcite (T h = 127.7°C) from Pozalagua, with mean salinities of 9.6 wt% NaCl.

Translucent calcite infill in fractured CCD2 dolomite (TC)

Translucent coarse crystalline (>1 cm) calcite (TC) fills fractures and cavities and forms the passive fill of fractured coarse crystalline dolomite CCD2 (Fig. 11F). It is broadly comparable to the WC but less common, and nowhere do the two occur together. Like the WC, the translucent calcite (TC) is not cross-cut by joints or stylolites. However, unlike WC, the TC crystals are zoned predominantly with a yellow luminescence (CL) and do not show cleavage twinning (Fig. 8F). Stable isotope analyses indicate depleted δ 18 O PDB, varying between -3 to -9‰ and δ 13 C PDB between -2 to -9‰ (Shah et al., 2011) supporting a meteoric origin with involvement of soil derived CO 2 . However, as yet no salinity data from fluid inclusions are available to support this interpretation.

Late stage calcite cementation: Sub-Recent speleothems

Sub-Recent speleothems have developed along some fractures and faults; these consist of multiple concentric crusts of brown to honey coloured transparent fibrous calcite, similar to that described by [START_REF] Frisia | Calcite fabrics, growth mechanisms, and environments of formation in speleothems from the Italian Alps and southwestern Ireland[END_REF]. δ 18 O and δ 13 C PDB vary around -5‰ and -8‰ respectively and thus fall within the field of TC stable isotopic signatures. These features reflect the development of the telogenetic regime following the most recent uplift of the study area and represent the last phase of the diagenetic history.

Paragenesis

The carbonates in the Pozalagua Quarry reveal a complex paragenesis of diagenetic products, reflecting a contrasting series of fluid pulses expelled along the Pozalagua Fault system. A large number of diagenetic stages have been recognised (Fig. 13), although the story is incomplete since this study focussed on the diagenetic features adjacent to the fault related dolomite body. It does not incorporate the different fracturing events and their cementation history in the slope and platform limestones.

The features described here can be grouped into seven major stages (Fig. 14), namely:

Stage 1: This stage includes the deposition of slope sediments, and early marine cementation in the conglomeratic lithologies. Subsequently subaerial exposure was reflected in near surface (eogenetic) karst processes. Dissolution pipes (PK) formed and were then filled with limestone rubble and clay/organic-rich carbonate mud. The laminated dolomite (LD) probably reflects early cave pond sedimentation and the coarse crystalline geopetally organized replacive RCCD dolomite is interpreted to reflect cave floor sedimentation. These karst products probably reflect one of the Late Albian sealevel variations described by López-Horgue et al. (2000, 2010) and García-Mondéjar et al. (2005).

They may relate to the Late Albian sandstone fill in karst pipes described by Aranburu et al. (2002), the end Cenomanian emergence (Fig. 3) or the fall in sea level at the Cenomanian-Turonian boundary.

Equant calcite cement probably formed during this stage and it is likely that the limestones became recrystallised as their depleted stable oxygen isotopic signature (ca -6 to -10‰ PDB) implies (Shah et al., 2010).

Stage 2:

The presence of karst cavities and the probable development of the Pozalagua Fault system may have facilitated the subsequent development of hydrothermal karst. A cycle of fracturing, dissolution, corrosion and cementation (phases C1 to C2 and subsequently C3 to C4) has been recognised. This sequence of events also characterises the emplacement of the dolomites. The calcites are similar to those described by Aranburu et al. (2002).

Stage 3:

The development of the zebra dolomites reflects a similar cycle, probably coupled with the expulsion of suprahydrostatic dolomitising fluids (see Nielsen et al., 1998). From this stage, the Pozalagua Fault system clearly acted as a major feeder system for hot fluids (based on T h values of fluid inclusions), because all of the dolomite types described are grouped along the Pozalagua Fault. Following reactivation, the fault became filled with a breccia including fragments of host rock, zebra dolomite and coarse crystalline dolomite (CCD1). Locally fragments were covered by geopetal sediment. The later banded blue-grey dolomite cement (BGD) and elongated relict crystals (ERC) testify to the continuing existence of this open fault system. The massive fine-crystalline dolomite (MFD) probably formed at the same time as the coarse crystalline dolomite 1 (CCD1) as the two are always found together and locally some gradation is observed between them. The zones within the BGD may reflect the cyclic expulsion of fluids, but an alternative explanation is that the BGD replaced speleothems and this explains why it consists of fibrous crystals. The coarse crystalline replacive dolomite, covering the elongated relict crystals testifies to a renewed deposition in caves of sediment that was later replaced by dolomite. An alternative explanation requires only one stage of RCCD development, post-dating crystallisation of the ERS, but in this scenario huge cavities formed either before or during crystallisation of the ERS. These were filled with laminated sediments that later recrystallised to RCCD.

Stage 5: This stage again reflects a phase of reactivation of the Pozalagua Fault system. This phase was followed by the development of coarse crystalline dolomite 2 (CCD2). The apparent lack of grain support of decimetre to metre-sized blocks of host rock fragments, 'floating' in CCD2, probably reflects severe dissolution of clast and fragment margins but an alternative explanation involving extreme fluid fluxes along the Pozalagua Fault is discussed below. The replacive coarse crystalline dolomite (RCCD) and 'curve-shaped' dolomite (CSD) probably also formed at this stage, in which the CSD, based on its very irregular outline and larger crystal size, reflects a more advanced stage of recrystallisation. Bedding-parallel stylolites (BPS) probably developed at several times in the area, but two major stages can be differentiated. The first represents the period before hydrothermal karst formation (before Stage 2) as indicated by roof collapse fragments in dissolution cavities that contain stylolites or were detached along stylolites. Relict stylolites have been identified in zebra dolomites, and appear to exert a control on their development. The second period of bedding-parallel stylolite development postdates the formation of the CCD2 that is clearly cross-cut by stylolites that do not affect later calcite cements. A few tectonic stylolites (oriented perpendicular to bedding) have also been recognised within the CCD2, implying that all of the diagenetic stages, including Stage 5, formed before the onset of compressional tectonics, i.e. before the Eocene Alpine compression.

It is difficult to calculate meaningful estimates of the volumes of the various diagenetic features in the Pozalagua Quarry in part because not all of the quarry walls can be inspected in detail. Recently Kurz et al. (2011) used hyperspectral analysis as a new quantitative tool. Based on field photographs and hyperspectral analysis, it is clear that the dominant dolomite phases are the zebra dolomite (ZD) and the CCD2 each estimated at 35%, followed by replacive coarse crystalline dolomite (RCCD) estimated at 15% and banded blue-grey dolomite cement (BGD) estimated at 8%. All other diagenetic phases are subordinate at <2%. However, major variations in dominant phases occur locally.

Discussion

Timing of dolomitisation

No absolute dating is available and therefore the timing of dolomite formation only can be constrained However, the presence of geopetal sediments overlying Stage 3 diagenetic products (overlying CCD1) and of laminated sediment phases overlying ERC (now RCCD) indicates that there might have been uplift of the area between Stages 2 to 3. This can be explained by the tectonic instability that characterises the area during the late Albian-Cenomanian. However, the possibility of infiltration of sediments to depths of several hundred metres cannot be excluded, and highlights the presence of cavities along the Pozalagua Fault system.

The presence of tectonic stylolites supports a minimum age that is constrained by the onset of compression related to the Pyrenean orogeny. Layer-parallel shortening on stylolitic planes normally records pre-folding deformation. As shown by [START_REF] Railsback | Tectonic stylolites in the 'undeformed' Cumberland Plateau of southern Tennessee[END_REF] tectonic stylolites typically form in flat-lying strata in front of fold and thrust belts, a feature also discussed by [START_REF] Engelder | Fossil distortion and décollement tectonics of the Appalachian Plateau[END_REF] relative to gently folded rocks in the foreland of the fold and thrust belt of New York.

The fact that the WC, but not the TC, is characterized by cleavage twins supports the view that it was subject to tectonic stress and therefore formed in the burial realm, and further evidence is provided by the depleted stable oxygen signatures of these calcites. The absence of cross-cutting joints can be explained to some extent by differences in the rheology of the dolomite and calcite, but their absence in the WC might indicate that these calcites formed after major tectonic deformation. This interpretation leads to the conclusion that Stages 2 to 6, formed between the upper Albian and the Eocene. Aranburu et al. (2002) described synsedimentary faults of the Albian carbonate platform margin near Jorrios, approximately 7 km north-east of the Pozalagua Quarry. These authors illustrated a 20 m deep and 1 km wide synsedimentary trough (halfgraben), formed along the Valnero-Ruahermosa fault system. The fill consists of mudstones, quartz-arenites and arkoses and the occurrence of sandstone layers intercalated between hydrothermal calcite cements in fault related cavities, indicated that faulting occurred early during the Late Albian dispar/appenninica zone (Aranburu et al., 2002).

Late Albian tectonism and magmatism in the Basque-Cantabrian Basin

Faulting and diagenesis were related to local extension in a large-scale strike-slip regime. Similarly, [START_REF] Agirrezabala | Syntectonic deposits and punctuated limb rotation in an Albian submarine transpressional fold (Mutriku village, Basque-Cantabrian basin, northern Spain)[END_REF][START_REF] Agirrezabala | Errata. Syntectonic deposits and punctuated limb rotation in an Albian submarine transpressional fold (Mutriku village, Basque-Cantabrian basin, northern Spain)[END_REF] reported similar active tectonism (two major and two minor shortlived pulses) in the Aitzeta structure (35 km east of the Pozalagua Quarry). These authors interpreted the major pulses as coinciding with the lower and upper limits of the Late Albian auritus subzone.

These results accord with Albian tectonic pulses described by García-Mondéjar et al. (2005). López-Horgue et al. (2009) have described a number of sections in Albian platform and basin sediments in the Karrantza Valley, and in the Trucíos and Balmaseda regions to the west of Bilbao. These authors identified upper Albian strata resting unconformably on basinal carbonates and marls of late early Albian age. This hiatus, representing the middle Albian and possibly also part of the upper Albian, probably also relates to regional tectonic activity. [START_REF] Agirrezabala | Mid-Cretaceous hydrothermal vents and authigenic carbonates in a transform margin, Basque-Cantabrian Basin (western Pyrenees): a multidisciplinary study[END_REF] described authigenic carbonates from the Basque-Cantabrian basin, north-east of Bilbao, that can be linked to hydrothermal vents related to synsedimentary transpressive activity of the Mutriku fault and the growth of the adjacent Aitzeta fold during the Late Albian auritus subzone. These observations all lead to the conclusion that the Basque-Cantabrian Basin was tectonically very active in the Late Albian.

Both magmatism and metamorphism occurred in the basin during the Late Albian. [START_REF] Badillo | Las facies supraurgonianas entre la Avanzada y el Puente de Rontegui (Bizkaia) son de edad Albiense Superior[END_REF] described submarine volcanism 28 km east of Jorrios, near Bilbao in the central part of the basin. [START_REF] Cabanis | Le magmatisme Crétacé des Pyrénées -Apport de la géochimie des éléments en traces -Conséquences chronologiques et géodynamiques[END_REF], [START_REF] Carracedo | Estructura orgnanización de las colades volcánica submarines: relación entre colades tabulares y lavs almohadilladas Cretácicas en la cordillera Vasco-Cantabrica (País Vasco)[END_REF] and Castanares et al. (2001) reported extensive volcanism in the Basque-Cantabrian Basin and also in the Pyrenean domain.

Martínez [START_REF] Torres | El Manto de los Mármoles (Pirineo occidental): Geología Estructural y Evolución Geodinámica[END_REF] reported coeval low pressure and high-temperature metamorphism at the plate boundary in the eastern part of the basin. In the Cameros Basin, 50 km south of the Basque-Cantabrian Basin, metamorphism of age equivalent strata has been reported along a major basement fault [START_REF] Mas | Evolución tectonosedimentaria de una cuenca extensional intraplaca: la cuenca finijurásica-eocretácica de Los Cameros (La Rioja-Soria)[END_REF][START_REF] Guimerá | Basin inversion[END_REF]. Thus, it is likely that hydrothermal fluids were circulating in the Basque-Cantabrian Basin during the Late Albian.

Thermobaric dolomitisation and fluid expulsion mechanism

The features described testify to the cyclic expulsion of vast amounts of potentially dolomitising fluids following faulting and/or reactivation of the Pozalagua Fault system. As pore-pressures increased, the effective normal stress across the fault decreased, whereas the shear stress, transmitted only by the rock framework, was unaffected. When the shear stress finally exceeded the normal stress across the fault plane, the fault failed, resulting in abrupt pressure transients. Due to the low permeability of the already cemented (and stylolitised) slope mudstones and wackestones, the pressure transients could not 'bleed off'. Thus fluids were injected into the host rock along an array of shear microfractures parallel to the main fault and were particularly prominent in fine-grained lithologies, where zebra dolomite formed.

Hydrofracturing [START_REF] Phillips | Hydraulic fracturing and mineralization[END_REF] and dilatational brecciation of the host rock (CCD1, BGD and ERD) possibly were the result of 'instantaneous' pressure differences between the low permeability host rock and the fluids circulating along the fault system. 'Floating clast' breccias, typically suspended in saddle dolomite, have been reported from many ore deposits (see [START_REF] Sibson | Faulting and fluid flow. In: Fluids in tectonically active regimes of the continental crust[END_REF]. The carbonates were probably not deeply buried when dolomitised. López-Horgue et al. (2010) suggest 600 to 900 m, but this possibly was less, because geopetal infilling becomes less likely with increasing depth. The dolomites are thought to have been formed by hydrothermal fluids at shallow burial depths with salinities of 10 to 24 eq. wt. % NaCl with reported T h values from primary fluid inclusions varying between 140 to 170ºC (Shah et al., 2010). However, López-Horgue et al. (2010) report values of 75 to 240°C and up to 22 wt. % NaCl. These characteristics indicate thermobaric dolomitisation as defined by [START_REF] Davies | Hydrothermal (thermobaric) reservoir facies. Proprietary report[END_REF], and endorsed by López-Horgue et al. (2010). The dolomite emplacement was related to shear stress generating abrupt pressure transients that resulted in hydrofracturing along faults.

Fracturing was commonly followed by dissolution and/or corrosion and by cementation. Two systems can be differentiated: (i) fluid flow after fault rupture and large-scale brecciation of the immediately adjacent host rock, with subsequent fault occlusion due to cementation that may have been accompanied by an increase in effective stress; and (ii) fluid flow in an open fault with cyclic cementation taking place without major fracturing of the adjacent host rocks. Notwithstanding the near-ideal outcrop only a small part of the fault system is revealed and differentiation of the two fluid systems may only reflect local conditions. The first system is represented by the creation of the CC1 to CC4, the zebra dolomites, and the coarse crystalline dolomites (CCD2). The second system is characterised by the development of veins of coarse crystalline dolomite (CCD1), blue-grey dolomite (BGD) and the development of elongated relict crystals (ERC). Nielsen et al. (1998) and Vandeginste et al. (2005) argued that in order to form zebra dolomites fluids must be suprahydrostatic. If fragments in the breccias really are 'floating' then pressures must have been extremely high. A fluid system comparable to that of the San Andreas system, reported by Eichhubl and Boles (2000a, b), where flow rates of a minimum of 10 -2 m/second were calculated might be invoked.

Alternative fluid flow systems can explain some observations. 'Squeegee'-type fluid expulsion during compression [START_REF] Machel | Low-flux, tectonically-induced squeegee fluid flow ("hot flash") into the Rocky Mountain Foreland Basin[END_REF] is sometimes invoked to explain large-scale fluid flow from the deep burial realm. This mechanism was invoked by [START_REF] Roure | Incidence of tectonics and natural fluid transfers on reservoir evolution in foreland Foldand-Thrust Belts, Oil & Gas Science and Technology[END_REF] (Morrow, 1998). However, at present the origin of the dolomitising fluids is unclear and circulation of Mg-bearing fluids reflecting Late Albian metamorphism and magmatism cannot be excluded.

The above observations suggest a mechanism of fluid forcing during fault failure, described in the literature as fault valve activity [START_REF] Ramsay | The crack-seal mechanism of rock deformation[END_REF][START_REF] Sibson | Implications of fault valve behaviour for rupture nucleation and recurrence[END_REF][START_REF] Sibson | An episode of fault-valve behaviour during compressional inversion? -The[END_REF][START_REF] Byerlee | Model for episodic flow of high pressure water in fault zones before earthquakes[END_REF][START_REF] Hickman | Introduction to special section: Mechanical involvement of fluids in faulting[END_REF][START_REF] Petit | Crack-seal', slip: a new fault valve mechanism?[END_REF]. The fracture and dilation of adjacent veins is interpreted to have been controlled by repeated fluctuations in fluid pressure associated with cyclic, deformation-induced, changes in fault permeability during fault valve behaviour. This is a cyclic process in which fluids trapped in overpressured 'compartments' are released intermittently through a ruptured fault when the pore pressure is raised enough to weaken the fault under stress. Rupture results in the creation of a damage zone with fracturing of the bordering host rock locally filling the fault. As a result of suprahydrostatic fluid expulsion the pore fluid pressure within the ruptured zone will fall. The subsequent effective stress increase, accompanying fault cementation, will promote fault sealing that will lead, in turn, to a renewed accumulation of overpressure and a decrease of fault strength, inducing a new episode of rupture and fluid expulsion. This likely happened over a rather important time interval. Such cyclicity is reflected in the varied diagenetic products of the Pozalagua Quarry. This process has been applied to examples worldwide [START_REF] Sibson | Fluid flow accompanying faulting: field evidence and models[END_REF][START_REF] Sibson | Implications of fault valve behaviour for rupture nucleation and recurrence[END_REF][START_REF] Cox | Faulting processes at high fluid pressures: an example of fault valve behavior from the Wattle Gully Fault, Victoria, Australia[END_REF] and may help to explain expulsion of hot fluids accompanying seismic events during shallow burial [START_REF] Sibson | An episode of fault-valve behaviour during compressional inversion? -The[END_REF].

As noted, Stage 4 diagenesis (CCD1, BGD and ERS) relates to a situation in which the Pozalagua Fault system remained (partially) open. The diagenetic products that gradually filled the fault indicate a cyclic fluid expulsion. It can be assumed that flow was moderate in what was effectively a leaking system. The cyclic nature of the precipitates may reflect post-seismic fluid pressure wave generating aftershocks, as reported from the 1997 Umbria-Marche earthquake [START_REF] Miller | Aftershocks driven by a high-pressure CO2 at depth[END_REF]. Variations in the CO 2 released at the surface have been related to these aftershocks [START_REF] Caracausi | Long-term geochemical monitoring and extensive/compressive phenomena: case study of the Umbria Region (Central Apennines, Italy)[END_REF].

The succession of dissolution/corrosion followed by precipitation (cementation/replacement) reflects the evolution of the fluid in the expulsion systems induced, from carbonate undersaturated to oversaturated fluids. The degree of under or oversaturation of fluids with respect to carbonates depends on many factors, including pH, partial pressure of CO 2 (pCO2), temperature, and concentrations of carbonate and other ions dissolved in the waters. It is likely that cooling will occur during the ascent of hot fluids. Cooling is commonly cited as a possible cause of carbonate dissolution (the so-called 'hydrothermal karst effect'; [START_REF] Giles | Origin and significance of redistributional secondary porosity[END_REF][START_REF] Giles | Diagenesis: A quantitative Perspective[END_REF], due to the retrograde solubility of calcite relative to decreasing temperature. During fluid ascent the total (over)pressure decreases, and consequently also pCO 2 will decrease and such changes may occur instantaneously.

Fluids with high pCO 2 are undersaturated and tend to dissolve carbonates rather than precipitate, thus a sudden drop in CO 2 might explain cementation/replacement. As Davies (2004) noted, this process might be driven by 'boiling' of the source fluid, and will be most efficient as a precipitation mechanism at depths of less than 500 m. It is tempting to use such a mechanism to explain the apparent 'floating fragments and blocks' in these cements and the aggressive nature of the fluid is easily explained in this way. [START_REF] Bonini | Structural controls on a carbon dioxide-driven mud volcano field in the Northern Apennines (Pieve Santo Stefano, Italy): Relations with pre-existing steep discontinuities and seismicity[END_REF], in an attempt to explain dissolution phenomena in a mud volcano field in the Northern Apennines (Italy), suggested that variations in pCO 2 might be expected during the fault-failure cycle, following the modifications induced by fault failure. This suggestion introduces a serious complexity to the process, especially when other parameters controlling carbonate dissolution and/or precipitation are taken into account.

Porosity and permeability

The distribution of the dolomite body in the slope sediments is clearly controlled by the Pozalagua Fault system and is restricted to ca 100 m width. However, in contemporary platform wackestones to grainstones the dolomite extends several hundred metres. In the Pozalagua Quarry, present-day porosity is confined mainly to zebra dolomite, the coarse replacive laminated dolomite and the CCD2, where some vuggy porosity remains. Limited intercrystalline porosity is present in the matrix dolomites close to the boundary with the limestones. However, at large-scale with each fluid pulse more porosity was lost by dolomite cementation. An additional pore-destructive phase relates to calcite cementation after joint development in the dolomite (CCD2). However joints are virtually absent in the limestones; this reflects the different mechanical behaviour of both lithologies. an impressive network of cavities, as was also deduced from hyperspectral analysis of the quarry walls (Kurz et al., 2011). Layered and laminated sediments (now replaced by coarse crystalline dolomite and brecciated) have been interpreted as cave pond and floor deposits. Together, these created a heterogeneity in the subsurface, possibly controlling to some extent the development of the Pozalagua Fault. The diagenetic features of Stages 3 to 5 reflect the expulsion of fluids upwards through the fault system, possibly relating to cyclic earthquake events. The CO 2 -rich hot aggressive fluids were responsible for local dissolution as they cooled. However, fluids finally became oversaturated causing cementation. The main factor inducing relatively rapid oversaturation was probably a decrease in pCO 2 pressure. It is not clear whether the formation of the white calcite forms part of the history of expulsion of hot fluids, but their depleted stable isotopic signature suggests that this may be so.

Scenario for fluid evolution along the Pozalagua Fault system in the Pozalagua Quarry

However, the translucent calcite testifies to the onset of a telogenetic regime.

Conclusions

The Pozalagua Quarry exposes a unique succession of diagenetic products providing evidence of the repeated expulsion of hot fluids along the Pozalagua Fault. The host rocks are limestones of Albian age in which sedimentary structures imply deposition on a slope inclined at 40 to 50°. Equant calcite cements are of phreatic origin and near-surface karst cavities reflect fluctuations in sea-level.

Comparison with other areas suggests that these formed in the Late Albian. Later diagenetic products reflect the episodic expulsion of hot fluids along the Pozalagua Fault system. At each stage of fracturing, the fluids expelled resulted in dissolution of carbonates followed by pervasive cementation.

Seven stages of diagenetic history can be recognised (Fig. 14):

Stage 1: Sedimentation was followed by the deposition of several generations of fibrous calcite cement in a marine phreatic environment. The distribution of these cements indicates the depositional dip of the bedding. This phase of activity was followed by a period of meteoric karst formation. Three types of near-surface karst fillings, that may have developed contemporaneously, have been recognised in karst pipes up to metre diameters: (i) oligomict limestone rubble with angular fragments in an organic and clay-rich mud to wackestone matrix; (ii) finely laminated organic and clay-rich dolomudstones to dolowackestones (LD); and (iii) laminated coarse crystalline replacive dolomite (RCCD). All are interpreted as cave filling products. Differences in crystal shapes in the dolomites are interpreted as reflecting differences in the grain-size of the parent sediments.

Stage 2: Cavity development was followed by cementation by two generations of coarse crystalline calcite (CC1 and CC2). Renewed movement on fractures, and further dissolution were followed by growth of coarse calcite (CC3 and CC4). The presence of stylolites in fragments within the fill and of local fragment detachments along bedding-parallel stylolites, indicates that these processes followed burial. Stage 5: Coarse saddle dolomite (CCD2), in which crystals are regularly covered with minute crystals of pyrite, is one of the most pervasive phases but locally can be interpreted as either cement or replacing earlier dolomite generations including both coarse replacive laminated dolomite and zebra dolomite. It is intensely jointed, and around former cavities it is often brecciated. However, centimetre to metre-size relics of host rock fragments apparently 'float' within the dolomite. This might reflect extensive recrystallisation of fragments, but such an interpretation would imply that up to 80% of the fragments had been assimilated. Bedding-parallel and perpendicular stylolites, testifying to tectonic compaction linked to the Pyrenean compression, are present in this dolomite. Albian tectonic activity with earthquake-induced fluid expulsion, as this is reported to have been a tectonically active period in the area (López-Horgue et al., 2010).

The Pozalagua Quarry is a unique geological site where contrasting generations of calcite and dolomite are related to the tectonically induced release of fluids. These characteristics invite geoscientists to take initiatives to classify this site as a 'geosite' of high scientific value. Robador [START_REF] Moreno | Mapa Geológico de Cantabria[END_REF].

Introduction

The Ranero area, and specifically the Pozalagua Quarry (in the vicinity of the Ranero village, NW Spain), expose unique fault-related high temperature dolomite (HTD) features. The walls of the Pozalagua Quarry (Fig. 1) provide a 'mega thin-section'-view whereby different petrographic aspects can be studied macroscopically. This fact has attracted several research groups to the Ranero area and its vicinity (e.g. López-Horgue et al., 2010;Shah et al., 2010;Swennen et al., in press;Kurz et al., 2011). Interest in hydrothermal dolomites is also based, at least, on two major facts: i) Recent integrated studies suggest that hydrothermal dolomite exists in many forms and are likely to be far more common than previously thought (Berger and Davies, 1999;Cantrell et al., 2004;Nader et al., 2004;Davies and Smith., 2006;Nader et al., 2007;López-Horgue et al., 2010;[START_REF] Ronchi | Multistage dolomitization and distribution of dolomitized bodies in Early Jurassic carbonate platforms (Southern Alps, Italy)[END_REF]Conliffe et al., 2010); and ii) some of the known oil and gas carbonate reservoirs consists of porous dolomites that are believed to have been affected by hydrothermal fluids -whether genetically or diagenetically (e.g. Ghawar, Saudi Arabia; Cantrell et al., 2004;North field, Arabian Gulf;Sudrie et al., 2006).

In the Ranero area the occurrence of good outcrops of large HTD bodies allows a detailed multidisciplinary study of an outcrop analogue of this type of hydrocarbon reservoir rocks. In the Aptian and Albian rock units of the Ramales Carbonate Platform several dolomite bodies related to faults and fractures originated in a time of intense synsedimentary tectonic activity during the mid-Cretaceous (López-Horgue et al., 2010).

The dolomites in the study area can be considered one of the best outcrop analogues of HTD that can serve to better understand the controlling factors on hydrothermal dolomitisation, the morphology of dolomite lithosomes and porosity/permeability variations (e.g., [START_REF] López-Horgue | Fault-related hydrothermal dolomite bodies in early Cretaceous platform carbonates, Karrantza area (North Spain): outcrop analogs for dolomite reservoir characterization[END_REF]& 2010;[START_REF] Caline | Fault-related hydrothermal dolomites of Cretaceous platform carbonatesoutcropping in the Karrantza area (North Spain): lessons learned for a better characterisation of subsurface dolomite reservoirs[END_REF]Sudrie et al., 2006;[START_REF] Schröder | Characterization of fault-related dolomites bodies from outcrop analogs: application to carbonate reservoirs[END_REF][START_REF] Dewit | Geomerty, distribution and characteristics of hydrothermal dolomite (HTD) bodies hosted by an Aptian-Albian carbonate platform, Basque-Cantabrian Basin, northern Spain[END_REF]& 2010), which are all matters of prime interest in oil and mineral resources exploration and production.

The aim of this paper is to present the sedimentary and diagenetic aspects of the Ranero dolomites by compiling results from different groups (mentioned above) that have been working in this area for several years. First, a review on the geological settings including the stratigraphic and structural factors, which are believed to have played important roles in the resulting dolomitisation, is provided. Then, results of detailed petrographic and geochemical analyses are used in order to characterize the different diagenetic phases, before constructing a generalized paragenetic sequence. Some ideas related to the dolomitizing fluids and mechanisms for their circulation and subsequent diagenetic impact are inferred. Finally, the petrophysical properties of these dolomites are presented.

Geological setting

The studied area, near the village of Ranero, is located in the provinces Biscay and Cantabria in northern Spain, at the western margin of the now inverted Basque-Cantabrian Basin (BCB). Hydrothermal dolomites are common in the BCB and typically crop out along main faults. In the area of Ranero and its surroundings, HTD are hosted in Early Albian limestones and, to a lesser extent, in Late Albian and Aptian limestones.

The Basque Cantabrian Basin (BCB)

The geodynamical evolution of the BCB is directly linked to extensional tectonics related to the opening of the North Atlantic Ocean and the displacement of the Iberian plate with respect to the European plate (Boillot and Malod, 1988;[START_REF] Vergés | Peri-Tethys Memoir 6: Peri-Tethyan Rift/Wrench Basins and Passive Margins[END_REF] leading to the opening of the Bay of Biscay (Triassic-Early Cretaceous).

Rotation of Iberia led to geodynamical changes in the BCB with alternation of rifting and strike-slip regimes (e. g. [START_REF] Vergés | Peri-Tethys Memoir 6: Peri-Tethyan Rift/Wrench Basins and Passive Margins[END_REF]. The BCB originated upon the onset of the Permian-Triassic boundary in which rifting subsidence led to the development of thick continental successions in the margins. Jurassic times provided a relative quiescence stage with a less active subsidence and development of marine carbonate ramps with minor thickness changes. At the end of the Jurassic and earliest Cretaceous a main rifting phase began with a continental rift fill that was followed by the development of marine successions on faulted blocks during Aptian and Albian. The highest subsidence in the BCB is related to cortical extension trending NE-SW and NW-SE with the development of transtensive faults during the Aptian and Albian (e. g., García-Mondéjar et al., 1996, 2004b). The Ranero area is characterised by E-W trending extensional faults that acted as sinistral shear faults mainly during mid Cretaceous (Fig. 2 Fault that connects the former ones (e.g. [START_REF] López-Horgue | El Aptiense-Albiense de Karrantza-Lanestona (Bizkaia y Cantabria)[END_REF]. These faults had a strike-slip motion at least during the Aptian and Albian when shallow marine carbonate sedimentation took place on footwall highs. The carbonate platform sedimentation changed abruptly towards deeper marine siliciclastic sediments on hanging walls, which formed troughs. Accordingly, the area between the Cabuérniga and Bilbao Faults was a large-scale structural high that controlled the development of the Ramales Carbonate Platform (e. g., García-Mondéjar et al., 2004a) (Figs. 2, 3). This platform extended around 60 km southwesterly from the platform margin that follows the trend of the main strike-slip faults and of minor faults trending NNE-SSW (Fig. 2), from which there was a facies change to deeper marine siliciclastic successions to the east (Figs. 3,4).

The Ramales and related Faults are the main faults in the study area, to which dolomitisation is associated; they cut across the platform margin and interior in the Ranero overstep between the Ruahermosa and Cabuérniga Faults (Fig. 5). Diapirism of Triassic evaporites is also related to the activity along these main faults.

Stratigraphy of the HTD host

The Ramales Platform is the largest carbonate platform that developed in the BCB, it hosts several HTD bodies such as the Ranero Body. Along the NS trending Ramales Fault the Asón River incised a considerable sedimentary succession. In total more than 3,000m of Triassic to Turonian strata are now exposed -1,100m of this succession correspond to the Aptian-Albian host limestones (López-Horgue et al., 2010). Aptian successions are totally eroded to the east of the Ramales Fault, in the Ranero area, where an angular unconformity separates Valanginian sandstones and the Early Albian limestones (López-Horgue et al., 2010). Aptian-Albian limestones of the Ramales Carbonate Platform, show four sedimentary stages separated by regional unconformities [START_REF] López-Horgue | El Aptiense-Albiense de Karrantza-Lanestona (Bizkaia y Cantabria)[END_REF]López-Horgue et al., 2009a;Fig. 4): 1) Aptian ramp, 2) earliest Albian distally steeped ramps, 3) late Early Albian to earliest Late Albian rimmed platform with steep clinoforms transitional to resedimented deposits and deep marine siliciclastics, and 4) late Albian calcarenitic ramp with a micritic-mound belt facing shallow marine siliciclastics.

Angular unconformities between stages 1-2 and 3-4 are related to subaerial exposures and testify of the synsedimentary fault activity in the area (López-Horgue et al., 2010).

The unconformity between stages 2 and 3 is an erosive surface probably related to a tectonic-subsidence change in the area that conditioned the transition from ramp to rimmed platform and the inception of the deepening of the basin easterly adjacent to the carbonate platform (e. g., García-Mondéjar et al., 2005). A drowning event affected the Ramales Platform at the middle Late Albian leading to the termination of the platform and the initiation of a shallow marine muddy sedimentation [START_REF] López-Horgue | El Aptiense-Albiense de Karrantza-Lanestona (Bizkaia y Cantabria)[END_REF].

Methods

Aerial photographs helped in delineating dolomite bodies, which were later groundmapped in the field. Sampling was carried out in the host limestone as well as across the dolomite bodies. Rock slabs and thin sections were stained with Alizarin Red S and potassium ferricyanide to differentiate ferroan from non-ferroan dolomite and calcite (Dickson, 1966). Petrographic studies of 260 thin sections were carried out using conventional (Nikon ECLIPSE LV 100 POL) and cathodoluminescence microscopy (Cathodyne OPEA; operating conditions were 12 to 17kV gun potential, 350 to 600 µA beam current, 0.05 Torr vacuum).

In the Ranero HTD Body, 270 plug samples were collected in sections perpendicular and parallel to the Pozalagua Fault as well as randomly. Some 120 plugs were selected for standard helium porosity and Klinkenberg permeability measurements. Part of this material was analysed systematically by ICP-AES for major/trace elements and stable isotopes.

Stable isotope analyses (δ 18 O and δ 13 C) of 275 selected samples of different dolomite types, calcite cements and the host limestone was carried out in the Department of Geology, University of Erlangen, Germany and Département Géologie, Jean Monnet Université, Saint Etienne. All stable isotope values are reported in per mil (‰) relative to the Vienna Pee Dee Belemnite (V-PDB). The dolomite isotopic composition values are corrected by fractionation factors given by Rosenbaum & Sheppard (1986). Fifteen Sr isotope analyses of the selected dolomite samples were performed in the Scottish Universities Environmental Research Centre (SUERC) in Glasgow. The Ranero area is the eastern structural block of the hydrothermal dolomitisation system that shows characteristics of an overstep between the E-W trending Cabuérniga and Ruahermosa Faults (Fig. 5). Important structures of this overstep are NW-SE trending extensional faults and fractures, of which the main fault is the dolomitized Pozalagua Fault. The Pozalagua Fault dolomite facies (and textures) display a complex polyphase dolomitisation history (several phases of dolomites are observed in the Pozalagua Quarry, cf. Fig. 1). Besides, their characteristic geometries (irregular, stratadiscordant, fronts dying out away of the major fault; cf. Nader et al., 2004;Nader et al., 2007) may suggest that the fault was a hydrothermal fluid-conduit.

Analytical results

Field observations

A large dolomite body expands laterally -nearly parallel to the bedding -along the Pozalagua Fault (trending NW-SE); its width increases upwards considerably in the upslope platform rocks. The dolomite body is up to 2 km wide in the north-western part of the Ranero plateau (platform), and has a minimum thickness of ca. 500 m along the Pozalagua Fault (slope) (refer to Shah et al., this volume). Detailed mapping permits the identification of different fracture-related dolomite bodies, ranging from millimetrewide dolomite-filled joints and decimetre-size pockets, to kilometre-scale large bodies. Such large dolomite bodies (Fig. 6A) are often associated with calcite dyke-like features (in the lower end of the dolomite body featured in Fig. 6A), cross-cutting basinsediments (calciturbidites) (Fig. 6B). The dolomite/limestone contacts are easily observed in the field due to the colour contrast (beige/brown for dolomite; light grey for limestone), besides they seem to be parallel to S 1 joint set in the limestone (Fig. 6C).

The structural elements associated to the dolomites have been observed during fieldwork, such as joints and pores arranged along S1 planes (Fig. 6D). All fractures in the Ranero area cut across the Albian host limestone stratification at right angles extending from fore reef to reef margin and inner platform facies and show shearkinematic indicators (Figs. 6E &F). The offset of the platform margin along the Pozalagua Fault indicates a left-lateral movement [START_REF] Dewit | Geomerty, distribution and characteristics of hydrothermal dolomite (HTD) bodies hosted by an Aptian-Albian carbonate platform, Basque-Cantabrian Basin, northern Spain[END_REF].

Since the dolomite body extends from distal slope to reef margin and inner platform carbonates the fracture system that controls the HTD occurrence is predominantly independent of the limestone facies. The dolomite bodies in the Ramales Platform developed along main fault-zones (e.g. Pozalagua Fault and Ramales Fault) and expand laterally in their upper part forming large almost tabular bodies nearly parallel to bedding. Dolomite body boundaries follow joint planes (Fig. 6C) or show gradual rapid change to the host limestone. In the Pozalagua Fault zone dolomitisation is fabric destructive. Several dolomitisation phases can be distinguished according to a complex arrangement of replacement and cementation features that have different fabrics, i.e. including hydrofracturation, breccias and dolomite cements (preferentially) occurring along fractures enhanced by dissolution.

Away from the fault zone, the dolomites show some primary sedimentary structures; e.g. preserved bioclasts. In both fault zones and areas away from the fault-zones, decimetric-scale zebra dolomites are present, predominantly brecciated and irregular in fault-zones and subparallel to stratification away from fault zones. The origin of zebra dolomite is related to shear stresses mainly in two different structural directions: along fracture shear-corridors [START_REF] López-Horgue | An example of the tectonic origin of zebra dolomites: the San Martín beach outcrop (Santoña, North Spain)[END_REF] and flexural-slip bands nearly parallel to bedding [START_REF] Iriarte | Zebra-dolomite, tectonic deformation and hydrothermal fluid-flow: lessons learned from Asón valley hydrothermal dolomites (northern Spain)[END_REF]. Besides, some zebra dolomite clasts look very similar to fragments of corals and may have been formed by mimic replacement of the latters (cf. Nielsen et al., 1998).

Petrography and geochemistry

The excellent exposures in the Pozalagua Quarry provide a survey of the main lithology types and invaluable geometrical relationships between successive stages of brecciation and calcite/dolomite precipitation and/or replacement. The present petrographic and geochemical study covers typical members of the hydrothermal sequence described by Swennen et al. (in press) in the Pozalagua Quarry together with samples collected in a systematic way along multiple sections across the main dolomite body and another vein body, one kilometre eastward (cf. Fig. 6A). This hydrothermal sequence is part of the complete diagenetic sequence proposed for the Albian host limestone and its hydrothermal dolomites of the Asón Valley area described in López-Horgue et al.

(2010).

Petrographic attributes

This section is not intended to present the full details of petrographic analyses, but to only describe the sequence of diagenetic events that are significant to the objectives of this study. For additional data on the petrographic characteristics of these dolomites the readers are referred to Shah et al. (this volume) and López-Horgue et al. (2010). The Albian limestones, which are exposed in the study area, display a complex diagenetic history at regional scale (López-Horgue et al., 2010;Rosales & Perez-Garcia, 2010). • coarse crystalline calcite is found as symmetrical fracture-or cavity-linings (Fig. 7A), in two substages: 1) a centimetre-scale palisade with a prominent chevron growth zoning (CC-I), 2) coarse crystalline calcite up to several centimetres displaying neither apparent zoning nor preferred orientation (CC-II).

• ferroan dolomite cements (CCD-I) display a characteristic banding (sub-stages) with alternating layers of variable colour (white, brown, grey) and Fe contents that line large cavities (Pozalagua Quarry) or vein walls (Figs. 7B,C). These are composed of two substages: an early one (CCD-Ia), which includes a centimetre-scale rim of brown (Fe-rich) saddle dolomite -usually preferentially calcitised (see below), and a later grey to beige saddle dolomite cement with moderate Fe content (CCD-Ib). CCD-Ia is present as a cement in a dense network of veins in the Ranero limestone and as symmetrical linings of fractures and breccias (Fig. 7B), while CCD-Ib is seen, predominantly, as a precipitate in the largest cavities only (Fig. 7C).

• non-ferroan dolomite cements (CCD-II) are composed of coarse white saddle crystals, often lacking systematic orientation, but plugging cavities lined by CCD-Ib, or in independent decimetre-scale veins cutting massive CCD-I and/or limestones (Fig. 7D).

• pyrite deposition followed by white coarse calcite (WC) that is precipitated in the central void spaces of CCD-I or CCD-II (Fig. 7E), and as decimetre veins cutting across.

At this stage, it is worth noting that dolomite is also present as a replacement product of limestone linked to CCD-I (ferroan, Fig. 7B), as a separate cement phase in zebraswhich are also invaded by CCD-II (non ferroan, Fig. 7D) -, and in pockets of layered, pink sucrosic rocks interpreted as dolomitized internal sediments of the prehydrothermal cave system (Fig 7F). The fact that bed-parallel stylolites pre-and postdate dolomites suggests that dolomitisation occurred during the Late Albian regional tectonic activity (Swennen et al., in press).

The sequence of cements -listed above -may be found filling up the same structures or, alternatively, as cross-cutting veins, thus suggesting that the fluids followed new pathways at each stage while still reusing the previous ones. A formerly mined vein containing coarse white calcite, galena, and barite within ferroan dolomite (described in [START_REF] Herrero | Las mineralizaciones de Zn, Pb, F en el sectoroccidental de Vizcaya: Mineralogía, geoquímica y metalogenia[END_REF]) is found cutting across the slope carbonate next to the Pozalagua Quarry.

Besides, the deposition of clear, honey-colour calcite (TC), not included in the sequence of hydrothermal phases (listed above), is considered to represent the latest diagenesis cementation event, and is found in the form of as pore-fillings and dedolomitisation (calcitization and oxidation) of the most unstable dolomites (mainly CCD-Ia).

Geochemical attributes

As previously reported in López-Horgue et al. ( 2010 values, probably suggesting that the fluids flowed through the limestones -downflow of the limestone-dolomite front -and were abundant enough to shift their oxygen signatures over a relatively large magnitude. δ 13 C of hydrothermal precipitates cluster in a narrow range (0 to +2‰) which is slightly, but consistently lower than its limestone counterpart (+1.5 to +3‰). This may indicate that some external carbon was brought by the fluids to produce the calcite and dolomite precipitates. Another likely explanation relates to the weak temperature fractionation effect on δ 13 C (i.e. 0.03 per °C; Emrich et al., 1970). Limestone δ 13 C signatures cannot be distinguished from original values and those of marine cements as reported in Rosales & Perez-Garcia (2010).

Dedolomitisation involves calcite showing low δ 13 C values coupled with relatively heavy δ 18 O values, invoking a telogenetic origin (TC, Fig. 8A). This calcite cement phase (TC; honey-colour, see above) marks the end-member of partially calcitized dolomites (dedolomites) along a δ 13 C-depletion, δ 18 O-increasing trend (Fig. 8A).

The Fe and Mn contents of hydrothermal dolomites show clusters that correlate well with their δ 18 O values (Figs. 8B,C). For CCD-Ia and CCD-Ib ferroan dolomites, FeO contents cluster around 1-1.5% and 0.5-0.7%, respectively. CCD-II dolomites have very low FeO contents (<0.2%). Altogether, the more Fe-rich dolomites (CCD-Ia) have the less depleted oxygen isotope ratios, and the Fe-poor dolomites (CCD-II) the most depleted oxygen isotopes ratios. It shoud be noticed, however, that the contents of FeO and MnO in Figures 8B andC represent averaged values obtained from microdrillings of plugs.

Microprobe analyses of CDD-I dolomites (Fig. 8D) reveal a wider range of Fe contents and some (limited) departure from stoichiometry. Some CCD-Ia dolomites contain up to 1.7% FeCO 3 (Fe-rims) and 55% molal CaCO 3 , but these compositions are unstable in late (oxidizing) fluids, so they are rarely preserved and frequently converted to calcite (TC) and Fe-Mn hydroxides during telogenetic alteration (e.g. dedolomitisation).

The carbon and oxygen isotope ratios of replacive dolomites are similar to those of hydrothermal precipitates, so they can be linked to stages CCD-Ia, Ib or CCD-II on the basis of decreasing δ 18 O values and decreasing Fe content. However, the Fe content of replacive dolomites may be substantially larger than that of the present-day Fe content of their exclusive carbonate fraction; this simply confirms that their mineralogy includes pyrite and/or silicates in addition to dolomite, and that the corresponding rocks have a multi-stage history.

Back-scatter SEM and Major/Trace Element Composition

Hydrothermal precipitates (or cements) have a diagnostic symmetrical structure (Fig. 9A) and a very low level of silicate impurities (Al 2 O 3 typically less than 0.05 wt %; Fig. 9B). CC-I, CC-II and WC are such precipitates, while TC mostly appears to have been formed, later on, both as a replacement product of unstable Fe-dolomite and as cement in pores (in a telogenetic realm). All dolomite cements are subidiomorphic (anhedral/nonplanar) and have curved crystal shapes (saddle) (Fig. 9C &D). In some cases the full compositional range (CCD-Ia to CCD-II) is seen in one single zoned crystal. Internal (central) porosity is free or plugged by WC and/or TC phases.

Replacive dolomites are best identified by their mosaic textures and/or by their higher content in silicate impurities. The replacive (dark) bands of zebras typically have a higher Al 2 O 3 content (0.1-0.3 %) (Fig. 9B) than those of the corresponding (void filling) white bands (<0.1%). Dolomites with a layered macroscopic structure (Fig. 7F) have the highest content of non-carbonate impurities (Al 2 O 3 up to 1.5%). Since these impurities are essentially of clayey origin (see also Shah et al., this volume), we interpret these particular rocks as former clay-bearing sediments that accumulated in ponds of the pre-hydrothermal cave system and were later converted to dolomite together with the surrounding limestones. Dolomite crystal sizes of replaced rocks increase as their FeO content (and δ 18 O) decreases. Replaced limestones lacking zebra texture have the smallest grain size (tens of microns) and rocks reworked by CDD-II fluids the highest (millimetres). All replacive dolomites, however, have curved crystal shapes and are subidiomorphic (subto anhedral). Interestingly, the non-carbonate paragenesis varies with the hydrothermal stage, with illite +/-kaolinite at stage CCD-I (cf. Fig. 9B) and Mg-chlorite at stage CCD-II (cf. Figs. 9C &D); quartz is typically absent.

Petrophysical analyses

The host rock, which is a tight limestone, is characterised by very low porosity (< 0.5%) and permeability values (0.01 mD). HTD are characterized by a much wider range of porosity and permeability values. Porosity values range from 1.8 to 12.1% and the average is 5.7%. Permeability values vary between 0.01 and 17.42 mD and have an average of 1.1 mD. It can thus be concluded that the dolomitisation had a positive effect on the reservoir properties of the altered host rock. Both porosity (Fig. 10) and permeability (Fig. 11) values in the Pozalagua (Ranero) HTD Body, show clusters of high and low values.

The investigated HTD can be divided in three classes based on their texture and different pore types (Fig. 12). First, the dark grey matrix dolomite (fine crystalline dolomite) is characterised by subhedral small dolomite crystals and small rounded pores with a diameter less than 3 µm (Figs. 12A,B). CCD-I & II cements (irrespective of Fecontent) are represented by coarse crystalline pink to white dolomite crystals, generally anhedral with sweeping extinction. They are characterised by bladed crystals with saddle morphology. Pores are intercrystalline to vuggy (Figs. 12C,D). Zebra dolomites are from a textural point of view built up by alternating layers of matrix dolomite and cement dolomite in an ABBA arrangement (Vandeginste et al., 2005). Pores are generally elongated and occur between two layers of cement dolomite (Figs. 12E,F).

Matrix dolomites have porosity values ranging from 5% to 11.8% with an average of 6.8%. Permeabillity values occur in a broad range and are between 0.03 mD and 17.4 mD and the average permeability is 2.3 mD. Cement dolomites have porosities ranging between 1.9% and 11.7%, with an average of 5.8%. Permeability values are between 0.01 mD and 10.3 mD, with an average of 1 mD. Zebra dolomites are the dolomite type that occurs most frequently and it is characterised by porosity values between 1.8% and 12.1% with an average porosity of 5.5%. Permeability values are between 0.01 mD and 16.8 mD, the average is 1 mD.

Discussion

The Ranero HTD case features mainly two distinct phases of hydrothermal dolomitisation and two minor phases of hydrothermal calcite deposition along fluid pathways controlled by palaeo-and hypogene karstification, fracturing and brecciation.

Perhaps the most remarkable aspect of this case is that the first dolomitizing phase is a ferroan one (CCD-I), while the second is non-ferroan (CCD-II), both being precipitated at relatively high temperature as suggested by the very negative δ 18 O values (down to -19‰ VPDB ) and by fluid inclusion homogenization temperatures (López-Horgue et al., 2010). This sequence is less commonly observed in HTDs (Davies and Smith, 2006) or MVT deposits (Leach et al., 2005), as the dolomites are usually Fe-rich during the whole dolomitisation. Besides, the early ferroan phase at Ranero appears to have the highest regional extent -as it is found and documented at several sites in the vicinitywhile the later non-ferroan one seems to be more abundant in the vicinity of the Pozalagua Fault. A few km away from Ranero, where the same two dolomite stages are reported, the first (ferroan) stage is associated with some Zn-Pb sulfides (Shah et al., this volume).

Enlarging the picture to the Basque-Cantabrian Basin (BCB) and its ore geology, the Ranero case can be viewed as a high temperature, Fe-poor end-member within a large variety of carbonate-hosted Fe-Zn-Pb deposits: the opposite end-member is represented by the relatively lower temperature -and very Fe-rich-La Troya deposit [START_REF] Velasco | Mississipi Valley-type, sedex, and iron deposits in lower Cretaceous rocks of the Basque-Cantabrian basin[END_REF], and intermediate members include typical MVT deposits such as Reocín (Velasco et al. 2003) and perhaps Itxaspe [START_REF] Piqué | In situ thermochemical sulfate reduction during ore formation at the Itxaspe Zn-(Pb) MVT occurrence (Basque-Cantabrian basin, Northern Spain)[END_REF]. Note that in this picture the Bilbao Fe-carbonate ores (e. g., [START_REF] Simon | Estudio isotopic y de inclusions fluidas en depósitos de calcita y dolomita del sector oeste del Anticinal de Bilbao y su relacíon con las mineralizaciones de Fe-Zn-Pb[END_REF], which are both Fe-rich and record rather high fluid inclusion temperatures, are set apart because they are hosted in shallow marine limestones. Considering the overall similarity of Ranero's dolomites with HTDs and HTD hosted MVT deposits, their genesis raises essentially the same questions which are briefly discussed hereafter, i.e. ( 1) how did the fluids migrate and why were they focused along the platform edge and ( 2) what chemical composition is characteristic of the dolomitizing fluids, and why did they react with the host carbonates? However, several differences compared to the "archetypal" HTD's sequence as proposed by Davies and Smith (2006) may question some aspects of the currently accepted models and suggest some new genetic schemes.

Geometry, fluid pathways and fluid drives

An important aspect of the Ranero case, which fits only superficially the "archetypal" HTD is the association with palaeo-and hypogene karstification. Here, it must be noted that this type of karstification differs from the early meteoric karst features that were previously described by López-Horgue et al. (2010) and Kurz et al. (2011). The early phase of dolomite precipitation clearly post-dates this hypogene dissolution phases and earlier calcite fillings (CC-I and CC-II) that precipitated at relatively high temperatures.

The volume of dolomite is significant in the Pozalagua Quarry, and this is likely due to the large development of pre-hydrothermal fracture and dissolution-enhanced voids.

Since internal sediments, such as frequently reported in MVT deposits [START_REF] Kendal | Ore deposits and sedimentary features, Jefferson City Mine, Tennessee[END_REF], need a large network of void space to form, we suggest that void-forming processes in the present case are preliminary rather than a consequence of HTD forming processes.

From a structural point of view, pre-hydrothermal dissolution is seemingly controlled by surface proximity (and unconformities) and the development of vertical strike-slip faults. Anchoring vertical structures on these weak zones, and perhaps on deeper structures, is believed to generate and to maintain potential fluid pathways breaching the edge of the platform carbonates (cf. Fig. 4b), hence connecting the basinal shales with deep-seated horizons (and potentially aquifers) (López-Horgue et al., 2010). Although this is not the only possibility, we suggest that this particular geometry enables the Ranero Fault (and its nearby faults) to represent realistic escape pathways, both for fluids stored in deep aquifers (and potentially below the platform as well) and for fluids released by compaction of the basinal shales. Moreover, such a hydraulic connectivity may ultimately result in pressure buildups (driven by shale compaction) along the whole pathway until the carbonate undergoes dilational fracturating and the top seal is breached.

The Ramales Platform carbonates were indeed adjacent to a basin that has been the depocenter of some 7,000m of sediments (mostly siliciclastics; Fig. 4b) which have been relatively rapidly deposited during the Albian (López-Horgue et al., 2010). During burial, compaction dewatering processes must have driven a large quantity of marinederived waters along the few possible escape routes. Alternatively, fluids may have been moving in response to gravity (salinity) gradients from the platform side or as a consequence of heat anomalies (convection) inside the platform or along its edge.

Potential sources of heat anomalies (temperature gradients) are quite numerous, including: i) the Keuper diapiric deformation (e.g. Canérot et al., 2005), ii) the differential subsidence along the platform border, and ii) the strike-slip movements themselves, ultimately related to crustal thinning (López-Horgue et al., 2010).

Altogether, the fluid drives are not well constrained in the Ranero case, but the capacity of the system to focus fluid flow along pathways transverse to the edge of the platform remains the most remarkable aspect. Furthermore, the two dolomitisation episodes and the associated hydrothermal events are believed to have occurred during the Late Albian, as they are pre-and post-dated by bed-parallel stylolites (Swennen et al., in press). [START_REF] Lopez-Horgue M | Fault-re la ted hy dro ther mal do lo mite bo dies in Ear ly Cre ta ceous plat form carbo na tes Kar rant za area (North Spain): Out crop ana logue for dolo mite re ser voir cha rac te ri za tion. -10 ème Con grès Fran çais de Sé di men to logie[END_REF] proposed a latest Albian-Turonian age for the hydrothermal dolomitisation in the studied area constrained by stratigraphical, structural and burial analyses.

Fluid chemistry and reaction drives

The very first episode (Fe-rich) CDD-Ia developed an extended stockwork of veinlets over the whole Ranero Body. Albeit this distribution is reminiscent of hydraulic (dilational) fraturating and overpressure, it does not imply large fluid fluxes. Besides, much of the following CCD-Ib dolomites actually replace limestone. The coeval mass transfer requires much larger fluid fluxes and sustained fluid undersaturation with respect to calcite. Interestingly, the replacement of early hydrothermal calcite (CC-II) by CCD-Ib dolomite is well exposed in the satellite body (also called vein-body). The newly formed dolomites have a particular texture and form a palisade of plumose, decimetre scale crystals. The mere fact that CC-II calcites are very coarse, hence they offer very low reactive surface to dolomitizing fluids, explains simply why their dolomitisation is very difficult, so it appears in the field as a relict calcite dyke (cf. Fig. 6B) engulfed in CCD-Ib dolomite.

The CCD-II veins are, usually, nearly straight and small (centimetre to decimetre scale) when hosted in the limestone (Fig. 7A), while they expand to the metre-scale and develop irregular limits when entering the CDD-I dolomite body in the Pozalagua Quarry. Therefore, they do not seem to pervasively replace limestone in the Pozalagua Quarry, but rather replace previous CCD-I dolomites (including the zebras). Another (chemical) argument for such a replacement is that some dolomites have mineral compositions characteristic of a second stage (Fe-poor) and highly depleted δ 18 O values (CCD-II) while the bulk rock Fe content is typical of stage CCD-I: the excess Fe is hosted in (oxidized) pyrite and it is interpreted as inherited from a CCD-I dolomite being converted to CCD-II (+ pyrite).

From a geochemical viewpoint, these features suggest that most CCD-I related fluids should be acidic and Mg-rich, promoting limestone replacement (Fig. 13). Moreover, they should not be H 2 S-rich in order to allow the transport of reduced Fe and Mn. These are frequently advocated properties of MVT ore fluids. On the contrary, the genesis of non-ferroan CCD-II dolomites does not require the fluids to be acidic (as they do not dissolve calcite) or particularly Mg-rich (as they mostly replace previous Fe-dolomite).

CCD-II related fluids are obviously Fe poor. Given that this second stage ends with some pyrite deposition, a likely possibility is that the corresponding fluids were rich in reduced sulphur (H 2 S, HS -) and thus almost unable to transport Fe. We emphasize that highly reduced sulphur content could invoke the reaction of CCD-II fluids with all Fe-bearing minerals (including Fe dolomite and silicates) to produce Fe-poor dolomite, Mg-chlorite and pyrite. The suggested chemical contrast between early (ferroan) and late (non-ferroan) dolomitizing fluids is reminiscent of that advocated for Australian Proterozoic sedex deposits (Cooke et al. 2000) between oxidized (MVT-like) and reduced brines, although the inferred pH characteristics may be quite different. This chemical contrast and the inferred high fluid temperatures give permissive evidence for a somewhat new genetic scenario.

CCD-I Dolomitizing Fluids

Mg-rich fluids (CCD-I) likely originated as sulphate-dominated marine waters. This fits with compactional waters or marine waters mixed with ancient (stored) aquifer brines.

In order to increase their acidity, such fluids need to be heated -being driven towards a hot zone or mixed with hot fluids -(Fig. 13), and undergo localized sulphate reduction (TSR) with their own content of local reductant source (organic matter, oil or gas). The fact that the fluids became acidic is crucial for pervasive dolomitisation, because Mgrich fluids which gained acidity are prone to coupled limestone dissolution and precipitation of dolomite. It should be noticed that, whatever the ultimate origin of the fluids (either cold or hot), the sulfate (and Mg) and the reducing agent are supposed to meet in a hot siliciclastic host. This may apply to compactional fluids, as they can be expelled towards the platform edge area at a moment when a temperature anomaly occurs due to differencial subsidence and faulting linked to crustal stretching processes (García-Mondéjar et al., 2004b;López-Horgue et al., 2010). Note also that the compactional fluid drive provides a simple explanation for pressure buildups and related pulses of overpressure relaxation (expressed by dilational jointing and brecciation) as observed for CCD-I.

CCD-II Dolomitizing Fluids

The origin of the fluids that precipitated the non-ferroan dolomites (CCD-II) is seemingly different, or at least their history involved different steps. If these fluids gained the needed H 2 S from TSR, they must have been buffered to lose their capacity to react with calcite before invading the Ranero Fault system (Fig. 13). The iron poor carbonate platform limestones may have buffered the fluid acidity. To follow this path, the fluids should pass through a TSR prone, hot zone that is most probably located within the interior platform. The ultimate origin of the sulphate is less constraining, as the corresponding fluids are not necessarily Mg-rich and evaporitic sulphate (Hanor, 1994) can be invoked as well. In this scenario, the Pondra Diapir, which is at the intersection of the Ramales and Cabuérniga Faults (Fig. 5) and underlies the Ranero area, could have acted both as a source of sulphate and as the core of a thermal anomaly owing to the salt conductivity. Similar diapirism and associated structural effects has been recorded in the coeval hydrothermaly dolomitised reservoirs in Aquitaine (France; Canérot et al., 2005). We thus suggest that convective flow above a salt diapir and subsequent TSR within a limestone host may provide the right conditions to generate CCD-II fluids. If this model is correct, it is important to emphasise that the resulting fluids loose very soon their capacity to react with calcite, hence their effects may be difficult to detect in the platform carbonates. Conversely, they should react with any Febearing lithology (including Fe-dolomite) to precipitate pyrite. The implication is that a rock record of these fluids should be searched for along the contacts between platform carbonates and the sourrounding siliciclastics, under the form of pyritization halos around the veins emerging from the carbonates.

Conclusions

Regional stratigraphic and structural factors prevailing through the Albian, resulted in the development of a deep basin with thick sedimentary pile (troughs in the Basque-Cantabrian Basin, BCB) adjacent to a carbonate platform (the Ramales Platform), which was undergoing local folding, faulting and deformation due to diapirism.

Pre-hydrothermal and hypogene karstification along faults generated fluid pathways across the platform margin. This karstificatoin was succeeded by the precipitation of hydrothermal calcite, various stages of dolomitisation, hydraulic fracturing, brecciation, limestone replacement and a late stage of calcite precipitation. Dolomitisation at Ranero features two main stages of hot (150-200°C) fluid migration, that caused increasingly 18 O depleted dolomites (from -10.5 to -18.7‰ V-PDB), with decreasing Fe contents and different authigenic mineral associations (illite and kaolinite versus Mg-chlorite; Shah et al., this volume). While these characteristics point towards substantial changes in the chemistry of the successive fluid pulses, the system evolved from producing, regionally distributed HTD bodies dominated by zebras and limestone replacement, towards narrower and more local dolomite veins reworking the previous ones, with little apparent replacement of the host limestones. Although the regional-scale mechanism of HTD (seemingly related to compactional fluids) may explain enhanced reservoir properties during dolomitisation with respect to the original limestone, the second, non-ferroan dolomite phase seems to destroy the preexisting porosity. In addition, successive deformation phases generate heterogeneities within the HTD reservoirs.

Fig. 1 . 2 .

 12 Fig. 1.2. Aerial photograph showing the location of the sampled sections in the Ranero, El-Moro and El-Mazo areas.

Fig. 2 . 2 .

 22 Fig. 2.2. Extensional basin development by simple shear couple of sinistral strike-slip (left) and dextral strike- slip (right), movement along the principle Bilbao and Ventaniella transform faults.

  2.3B). The BCB consisted of sediments and volcanics ranging from Paleozoic to Cretaceous in age, which will be discussed comprehensively in the proceeding section. Permo-Triassic siliciclastics are well exposed at the base of the stratigraphic section in the western part of the basin. The study area is located in the central part of the Basque-Cantabrian basin (BCB) and comprises E-W trending mountain ridges containing Aptian-Albian limestones and dolomites in the north-western (Ranero) and western (El-Moro and El-Mazo) sides of the Karrantza valley (north-western Spain), at the border between the Basque country and the Province of Cantabria (Fig. 2.3A).

Fig. 2 . 3 .

 23 Fig. 2.3. (A) Stratigraphic map of the study area, indicating the distribution of Aptian-Albian-Cenomanian rocks (modified from Lopez-Horgue et al., 2009). (B) Tectonostratigraphic map of the Basque-Cantabrian basin, showing the location of the study area (modified from Gibbsons & Moreno, 2002) .

Fig. 2 . 4 .

 24 Fig. 2.4. Structural map of the Basque-Cantabrian basin, showing the location of Ranero left lateral strike-slip fault and adjoining Ramales fault in the study area (modified from Garcia Mondéjar, 1996).

Fig. 2 . 5 .

 25 Fig. 2.5. Early to late Aptian depositional evolution stage, where siliciclastic influx seized and was progressively replaced by carbonates in the platforms and slopes of the Basque Cantabrian basin.

Fig. 2 . 6 .

 26 Fig. 2.6. In the late Aptian period, carbonate build-ups developed significantly developed in the platform region, while basinal sediments can be observed in the southern part of the BCB.

Fig. 2 . 7 .

 27 Fig. 2.7. Early Albian period shows a lateral increase of basinal deposits due to the deepening of the Bilbao intraplatform basin resulting from intense tectonic activity.

Fig. 2 . 8 .

 28 Fig. 2.8. Lateral facies variation in the Basque-Cantabrian basin, where abrupt changes in rock facies from

Fig. 2 . 9 .

 29 Fig. 2.9. Stratigraphic column representing the Aptian-Albian succession, where fault-related dolomites along with mineralization restricted to early Albian carbonates (indicated by red colored bracket).

  4.2). Sampling of host limestone and various dolomite and calcite phases were carried out in the uphill side and across the Ranero fault, in the so called Ranero fault section (Fig. 4.1). Irregular, lobe-shaped dolomite bodies in the carbonate slope deposits situated in the western side of the Pozalagua quarry, named as Ranero front (Fig. 4.1). Such dolomite bodies show lateral extension in the host limestone, where sampling was carried out in the N-S direction (i.e., across the lobate-shaped dolomite body; Fig. 4.1). Another N-S trending linear dolomite body (Ranero vein) outcrops about 1km to the east of Ranero fault (Fig. 4.1). This dolomite body is about 2km in length and about 30m wide. The Ranero breccia site exposes brecciated carbonates, surrounded by dolomite cement along the road and is located between Ranero vein and Pozalagua quarry (Fig. 4.1). The brecciated zone is about 100m wide and about 15m high from the road.

Fig. 4 . 1 .

 41 Fig. 4.1. Aerial photograph showing the various studied sections/sites in the Ranero area. NW-SE trending Ranero fault is shown by red line. Note that Ranero village is in the eastern part of the study area.

Fig. 4 .

 4 Fig. 4.4E) and blocky white (likely meteoric) calcite (TC; Fig. 4.4F).

(Fig. 4 .

 4 Fig. 4.4B). Isolated patches of zebra-like dolomite (ZD) occur as well in various dolomite phases (Fig. 4.4D).The termination of dolomitisation in Pozalagua quarry is marked by the presence of disseminated pyrite along the borders of late stage, yellowish colored, coarse crystalline dolomite (CCD-II), followed by the infilling of white calcite (WC; Fig.4.4E). In some cases, late stage transparent calcite (TC) occluded the remaining pore spaces in CCD-II, where pyrite exhibited the same distribution as evident with the white calcite (Fig.4.4F).

Fig. 4 . 2 .

 42 Fig. 4.2. Panoramic view of the Pozalagua quarry site in the Ranero area. The site exposed on the Ranero fault and exhibited excellent exposures of various dolomite and calcite facies.

Fig. 4 . 3 .CFig. 4 . 4 .

 4344 Fig. 4.3. Cavity filling calcite (A) hydrothermal karst filling by calcite, showing various banded calcite types, while late stage cavity infilling of yellowish dolomite (CCD-II). (B) Photograph showing zoomed image of the part of A, where various bands of calcite indicates distinct appearance. (C&D) Cross-cutting relationship of various dolomite cements (CCD-I & CCD-II) with the karst-filling calcite in the host limestone.

  4.5B&C). Fine to medium crystalline dark grey to black colored dolomite shows straight extinction while coarse crystalline white to yellow colored cement dolomite (CCD-II) shows undulose extinction. It is observed that fine to medium crystalline, planar to nonplanar dolomite exhibits considerable intercrystalline pore spaces as compared to adjacent medium to coarse crystalline, nonplanar dolomite (Fig. 4.5C). Oxidized Fe-crystals (previously pyrite) occurred in the intercrystalline pore spaces and along the stylolites (postdate dolomitization) of medium to coarse crystalline dolomite (Fig. 4.5C). Post-dolomite vein-filling calcite (WC) is usually observed in such dolomites (Fig. 4.5B). Aggradational neomorphism (crystal's over-dimensioned growth) is also observed in the medium to coarse crystalline dolomite (CCD-II), which indicated crystal's overdimensioned growth (Fig. 4.5D). Post-dolomite tectonic activity resulted in the brecciation of CCD-I dolomite, while open spaces are occluded by late stage zoned, WC calcite (Fig. 5.4E). The tectonic activity was immediately followed by calcite precipitation, which is evident by floating of dolostone clasts in zoned, WC calcite (Fig. 5.4E). Partial dedolomitisation resulted from reddish colored stained calcite (TC), selectively replaced medium to coarse crystalline dolomite (CCD-I).

(

  ~300m), medium to coarse crystalline dolomite (CCD-I) contained disseminated grains of galena and barite. The radiating crystals typical of barite is associated with CCD-I dolomite (Fig. 4.6 A&B). Replacive dolomite (CCD-II) represented higher contents in silicate impurities, where noncarbonate material (clays and pyrite) concentrated in the pore spaces (Fig. 4.6C&D).

Fig. 4 . 5 .

 45 Fig. 4.5. Photomicrographs showing various dolomite and calcite phases from Pozalagua quarry. (A) Host limestone (LS) in contact with coarse crystalline calcite (CC-I), note that the arrow indicating partially dolomitized limestone. (B) Zebra dolomite (ZD) showing coarse crystalline dolomite cement (C) in contact with fine to medium crystalline matrix (M), note that late stage, calcite vein (WC) cut across the zebra dolomite. (C) Medium to coarse crystalline dolomite (CCD-I), while pyrite is restricted to intercrystalline pore spaces and stylolites. (D) Aggradational neomorphism observed in the medium to coarse crystalline dolomite (CCD-I). P= pore space (E) Brecciated dolomite (CCD-I), while the pore spaces and fracture-filled with banded calcite (TC). (F) Selective dissolution porosity development in the medium to coarse crystalline dolomite (CCD-I), which later on occluded by calcite (TC).

  Fig. 4.6. Photomicrographs showing various dolomite, barite and silicates near Pozalagua quarry. (A&B) PPL and CL photomicrographs showing lath-like Barite in the calcite. (C&D) CPL and CL photomicrographs showing coarse crystalline dolomite (CCD-II), while pore spaces are filled by silicate minerals.

Fig. 4 . 7 .

 47 Fig. 4.7. Panoramic view of the Ranero fault (dashed line), showing the location of the Pozalagua quarry site and Ranero fault section (A-B).

Fig. 4 . 8 .

 48 Fig. 4.8. Photograph showing the measured and sampled Ranero fault section as shown by measuring tape. Note date the colour contrast between dolomite and limestone.

Fig. 4 .

 4 Fig. 4.9. (A&B) Photograph showing the contact between off white host limestone and dirty brown dolomite in (A) and weathered color dark grey to light brown dolomite in (B).

Fig. 4 .Fig. 4 .

 44 Fig. 4.10. Photomicrographs showing various dolomite and calcite phases in Ranero fault section (A) .The host limestone in contact with coarse crystalline calcite (CC-I), note that the cavity-filling calcite containing pyrite.(B) Banded calcite (CC-I) showing zonation of various kinds. (C) Medium to coarse crystalline dolomite (CCD-I), where hexagonal shaped pyrite crystals can be observed.(D) CL photomicrograph showing light orange colored calcite (WC) in the pore spaces of dark colored dolomite (CCD-I). (E) Zebra dolomite (ZD) showing considerably high intercrystalline porosity (Blue) in matrix dolomite, while coarse crystalline dolomite (cement) exhibited negligible pore spaces. (F) Partial dedolomitization and pore-filling by late calcite (TC).

Fig. 4 .

 4 Fig. 4.12. Panoramic view of the study area, showing the position of the Ranero front section (A-B). Note that the dolomite (Dol.) show inter-fingering in the host limestone (LS).

Fig. 4 .

 4 Fig. 4.13. Photograph showing the location of the sampled Ranero front section as shown by measuring tape. Note that the Pozalagua quarry site is in the background (upper left corner).

Fig. 4 .Fig. 4 .Fig. 4 .Fig. 4 .

 4444 Fig. 4.14. Photomicrographs showing various dolomite and calcite phases in the Ranero front section. (A) Limestone containing fracture-filled dolomite, note that late stage stylolite cross-cuts dolomite (see arrow), hence formed after dolomitization. (B) Partial dedolomitization of coarse crystalline dolomite (CCD-II). (C&D) CPL and CL photomicrographs showing aggradational neomorphism, while selective dedolomitization (arrow) usually observed as one band. (E&F) The pore spaces in CCD-I are usually filled by CCD-II, while remaining intercrystalline porosity is occluded by calcite (WC).

Fig. 4 .

 4 Fig. 4.18. Field characteristics in the Ranero vein section. (A) Photographs showing contact between off-white limestone and brown to dark brown colored dolomite. (B) Calcite vein (CC-I) in the host limestone. Inset shows the infilling of dolomite (CCD-I) in the central part.

Fig. 4 .

 4 Fig. 4.19. (A) Dolomite veins in the host limestone, cross-cut and displaced by late stage calcite veinlets. (B) Enechelon type fracture filled dolomite in the host limestone.

Fig. 4 .

 4 Fig. 4.20. Sketch showing the section (A-B), where various dolomite and calcite phases are observed in the studied Ranero vein area.

Fig. 4 .Fig. 4 . 22 .Fig. 4 .

 44224 Fig. 4.21. Various dolomite and calcite phases as well as host limestone in the dolomite vein section. (A) Limestone in contact with coarse crystalline calcite (CC-I), where partial dolomitization (see arrow) is also observed. (B) Partially dolomitized limestone (see arrow), note the significant dissolution porosity (blue). (C) Host limestone surrounded by early, coarse crystalline calcite (CC-I). (D) Undulose extinction of planar to nonplanar, medium to coarse crystalline dolomite (CCD-I). (E) Coarse crystalline calcite (CC-I) in contact with host limestone, while medium to coarse crystalline dolomite (CCD-I) observed in the centre as clasts and late stage calcite (TC) cut across the calcite and dolomite phases. (F) Zoom in view of the figure (E), where late stage calcite (TC) cut all the phases.

Field observations :Fig. 4 .

 observations4 Fig. 4.24. Field observation in the Ranero road side breccia site. (A) Fracture-filling calcite veins cross-cutting each other, CCD-II vein is bedding parallel and resulted from hydrofracturing. (B) Coarse crystalline calcite dyke (CC-II) in dolomite. (C) Brecciated limestone clasts surrounded by dark colored dolomite cement. (D) Zebra dolomite (ZD) clast, showing alternating bands of dark grey colored (matrix) dolomite and white colored (cement) dolomite. (E) Dolomite cement along the border of limestone clast. Note that the dolomite cement containing coarse crystalline saddle dolomite CCD-I. (F) Infilling of milky white colored calcite in between the open spaces of CCD-I dolomite cement.

  crystalline, planar to nonplanar dolomite (CCD-Ia) display dark to dull red colored luminescence, while their crystal borders are characterized by a bright red colored luminescence of CCD-Ib dolomite cement (Fig. 4.25D). The intercrystalline pore spaces are filled by dull orange luminescent calcite (WC; Fig. 4.25D). Besides the occurrence of CCD-II in conjunction with CCD-I, the former (CCD-II) shows bright red luminescence and exhibits almost negligible open spaces in between the dolomite crystals. The pore spaces if present are mostly occluded by late-stage, bright orange colored calcite cement (WC) (Fig. 4.25E). The interaction of red-stained colored, non-luminescent calcite (TC) resulted in selective dedolomitization of various dolomite phases. Mostly, medium to coarse crystalline (CCD-I) readily dedolomitized as observed in Fig. 4.25F. The dark rimmed ferroan dolomite of CCD-I exhibits dedolomitization in first phase, followed by the rest of dolomite crystals (Fig. 4.25F).

Fig. 4 .

 4 Fig. 4.25. Photomicrographs showing various dolomite and calcite phases in the Ranero breccia site. (A&B) CPL and CL photomicrograph showing contact between host limestone and medium to coarse crystalline dolomite (CCD-I), note that Ca-rich dolomite phase in between. (C) Clasts of host limestone in the dolomite (stained thin-section). (D) CL showing intercrystalline pore spaces in the medium to coarse crystalline dolomite (CCD-I) filled by orange colored calcite (WC). (E) Pore-filling calcite (WC) in coarse crystalline dolomite (CCD-II). (F) Partial dedolomitization restricted to rimmed CCD-I dolomite and its central part.

  4.26A&B) and/or among various dolomite phases and calcite cements. In order to know the variation within dolomite crystal, a transect (A-B) is made from the core to border in the zoned dolomite cement (CCD-I) to observe the variation in its Fe content (Fig. 4.26C). It is evident that the zoned dolomite consists of light grey colored core, while the outer growth zones posses slightly light grey and dark grey colors (Figs. 4.26A&B). The light grey colored core of the zoned dolomite (CCD-Ia), possesses a high Fe-concentration (1.5 to 2.0 wt. %), while the zoned light grey band (CCD-Ib) contains lower Fe-contents (0.4 to 0.6 wt. %) as grey colored band show negligible Fe-contents (0.1 to 0.3 wt. %; Fig.4.26C). It is observed that there exists a sharp decrease in Feconcentration from core to the outer-growth zones in the dolomite (CCD-I), whereas outer growth zones show resemblance to CCD-II. White calcite inclusions in the core as well as in the slightly grey colored outer zone are also evident (Fig. 4.26A&B).

Fig. 4 .

 4 Fig. 4.26. SEM results of zoned dolomite (CCD-I) from Ranero fault section. (A) Transect a-b across zoned dolomite from core to border, (B) Alternating bands of light grey and dark grey colored zones, (C) Diagram showing the distribution of Fe-concentration from core to outer zones.

Fig. 4 .Fig. 4 .

 44 Fig. 4. 27. (A) Vein-filled dolomite (CCD-II) in CC-I and CC-II calcite from Ranero vein section. (B) Mgconcentration in host limestone, calcite phases and vein-filling dolomite CC-II.

Fig. 4 .

 4 Fig. 4. 29. Back Scattered Electron microscope (BSE) photomicrographs showing various dolomite and silicate phases.(A) In the Ranero vein section, Illite occurrences in between the growing crystals of CCD-I dolomite (arrow), as shown by their corresponding spectra. (B) Mg-Chlorite observed in the open cavities of dolomite sand (DS), can be observed by the spectra given in front of Fig. B, where as the white border along open spaces resulted from the excess of charge.

Fig. 4 .

 4 Fig. 4. 30. Major and trace element relationship with δ 18 O values in the various studied sections/sites of Ranero area. (A) FeO Vs δ 18 O values indicating high FeO values in CCD-I as compared to CCD-II. (B) MnO Vs δ 18 O values as high Mn-contents mostly associated with CCD-II.

Fig. 4 .

 4 Fig. 4.31. Major and trace elements occurrences in host limestone and various dolomite and calcite phases. (A) FeO Vs Al 2 O 3 (in %) sketch showing distribution of various dolomite and calcite phases in the Ranero front section.

Fig. 4 .

 4 Fig. 4. 32. O-and C-isotope composition of various dolomite and calcite phases in the Pozalagua quarry site. Note that the Ba-containing carbonates show variation in their δ 18 O values while transparent calcite (TC) shows depleted δ 13 C values.

Fig. 4 .

 4 Fig. 4. 33. Stable isotope composition of host limestone, dolomite and calcite phases in the Ranero fault section. Note that the host limestone shows depleted δ 18 O values as dolomite and calcite phases, while transparent calcite (TC) exhibited δ 13 C values.

Fig. 4 .

 4 Fig. 4.34. In the Ranero front section, the host limestone (LS) shows progressive depletion in δ 18 O values. The coarse crystalline dolomite ( CCD-II) shows highly depleted δ 18 O values as compared to other dolomite and calcite phases. Note that the dedolomitized phase (DEDOL) indicates depletion in δ 13 C values.

Fig. 4 .

 4 Fig. 4. 35. O-and C-isotope composition in the Ranero vein section, showing broad range of depletion in δ 18 O values of host limestone and medium to coarse crystalline dolomite (CCD-I), while late-stage vein-filling calcite exhibited highly depleted δ 18 O values. Transparent calcite (TC) shows depleted δ 18 O and δ 13 C values.

Fig. 4 .

 4 Fig. 4.36. Stable isotope composition in the Ranero breccia site. The host limestone shows depleted δ 18 O values,

  they are heated and cooled on a microscopic stage) and determine salinity of the fluid inclusions entrapped in host mineral. Microthermometry provides information regarding the melting temperature (T M ), which tells us about the fluid chemistry while homogenization temperature (temperature at which inclusion becomes single phase on heating; T H ) provides minimum temperature at which the inclusion was trapped.a) MICROTHERMOMETRYAnalyzed fluid inclusions from massive, nonplanar dolomite (CCD-I; Fig.4.38A) and zebralike dolomite cement (ZD; Fig.4.38B) are two-phase, primary/pseudo-secondary inclusions as most of these are isolated and located along the border of the crystals. The crystals display uniform cloudiness due to the presence of small fluid inclusions. The size of the investigated inclusions is variable (3 to 5µm) and their shape is irregular.

Fig. 4 .

 4 Fig. 4.38. Two-phase, primary fluid inclusions. (A) red circle indicating primary fluid inclusion in medium to coarse crystalline dolomite (CCD-I). (B) arrow indicating fluid inclusion in zebra dolomite (ZD).

Fig. 4 .

 4 Fig. 4.39. Microthermometric studies of the selected samples (A) Histogram showing distribution of homogenization temperature with respect to number of readings from zebra and nonplanar dolomite samples from the Pozalagua quarry. (B) Salintiy Vs Homogenization temperature cross-plot in zebra and nonplanar dolomite.

Fig. 4 .

 4 Fig. 4.40. Parent fluid chemistry determined by using Land's equation. Note that δ 18 O values are plotted against homogenization temperature (T H ).

Fig. 4 .

 4 Fig. 4. 41. Photomicrographs showing various dolomite and calcite phases. (A) Dissolution porosity resulted in the enhancement of pore spaces considerably in medium to coarse crystalline dolomite (CCD-I). (B) Pore spaces (blue) are more clealy visible in matrix dolomite phase as compared to cement dolomite phase of zebra dolomite (ZD). (C&D) Brecciated dolomite occluded by calcite cement (red).

Fig. 4 .

 4 Fig. 4. 42. Photomicrographs showing host limestone and dolomite phases in the Ranero vein section. (A) Limestone containing considerable dissolution porosity. (B) Partially dolomitized limestone relatively high porosity as compared to limestone not affected by dolomitization in the upper left portion. (C) Intercrystalline porosity in planar to nonplanar, medium to coarse crystalline dolomite (CCD-I). (D) Almost negligible pore spaces in the coarse crystalline, nonplanar dolomite (CCD-II).

Fig. 4 .

 4 Fig. 4. 43. Photomicrographs exhibiting various dolomite and calcite phases in the Ranero front section. (A)

Fig. 4 .

 4 Fig. 4.44. Proposed paragenetic sequence observed in the Ranero studied sites. Note that the red lines indicate events occurred during late diagenesis in the Albian carbonates.

  4.18A). In the Pozalagua quarry (on the main Ranero fault), various generations of dolomite facies indicate multiple pulses of the dolomitising fluids (Figs. 4.3 & 4.4; Appendix-II). • Hydrothermal process started from the emplacement of less depleted, pore-and karst-filling calcite (CC-I & CC-II), which predates dolomitisation. Relict calcite dykes of CC-II observed in CCD-I dolomite as coarse crystalline calcite (CC-II) offer very low reactive surface to dolomitizing fluids, explaining the difficulty in dolomitisation of this particular rock. • Initial stage of dolomitisation (CCD-I) is characterized by Fe-rich, relatively less depleted (in δ 18 O) replacive phase, further subdivided into CCD-Ia (dull red luminescent core) and CCD-Ib (bright and dull red luminescent zonations). Such dolomite phase resulted from the pervasive dolomitisation of host limestone. CDD-I dolomite reveals a wider range of Fe-contents (Appendix-III) and some (limited) departure from stoichiometry. Some CCD-Ia dolomites contain up to 1.7% FeCO 3 (Fe-rims) and 55% molal CaCO 3 , but these compositions are unstable in late (oxidizing) fluids, so they are rarely preserved and frequently dedolomitized (cf. Fig. 4.28) during telogenetic alteration. • Late stage dolomitisation consisted of Fe-poor, highly depleted (in δ 18 O), partially replacive dolomite phase (CCD-II). Such dolomite phase does not seem to replace limestone, but rather replace CCD-I dolomite. Such observations are supported by following arguments: (i) CCD-II veins are nearly straight and small (centimetre to decimetre scale) in the limestone (Fig. 4.3C), while they expand to the metre scale and develop irregular limits when entering the dolostone body. (ii) Some dolostones have dolomite compositions characteristic of a late stage (Fe-poor) and highly depleted δ 18 O values while the bulk Fe-contents is typical of stage CCD-I. This excess Fe is hosted in pyrite (cf. Fig.4.4E & F) and interpreted as inherited from a CCD-I dolostone being converted to CCD-II (+ pyrite) by Fe-poor fluids.

  section 4.1) are discussed. El-Moro and El-Mazo areas are located in the western part of the Karrantza valley (near the town of Ramales); and they are separated by a small valley (Fig. 4.45). El-Moro area is further subdivided into western and central parts on the basis of the location of studied sections. At outcrop, dark grey colored dolomite can easily be distinguished from off-white host limestone (Fig. 4.46). The dark grey colored dolomite usually observed as vein-and fracture-filled (Fig. 4.46A-C) or irregularly distributed in the limestone host rock (Fig. 4.46D). In total, seven transects were achieved across different dolomite bodies in El-Moro area. These have been named as MO-I, MO-II, MO-III, MO-IV, MO-V, MO-VI, MO-VII, MO-VIIa, MO-VIII, MO-IX and MO-X, three sections were sampled in the El-Moro valley (MO-VII, MO-VIIa and MO-VIII), while four sections were sampled across dolomite bodies in El-Mazo area (MA-I to MA-IV ; Fig. 4.1; Chapter-4). Various dolomite and calcite phases were observed as well as sulphide mineralization in the host limestone. These include: medium to coarse crystalline dolomite (CCD-I), coarse to very coarse crystalline, nonplanar dolomite (CCD-II), zebra-like dolomite (ZD), dolomite sand (DS), cavity-filling, medium crystalline rimmed calcite (CC-Ia & b), coarse crystalline, pore-filling calcite (CC-II), white calcite (WC) and telogenetic calcite (TC). Pb-Zn mineralization is mostly evident in the central part of El-Moro area, where disseminated minerals are associated with medium to coarse crystalline dolomite.

Fig. 4 .

 4 Fig. 4.45. Panoramic view El-Moro and El-Mazo areas with the valley in between.

Fig. 4 .

 4 Fig. 4.46. Dark grey colored dolomite bodies in the El-Moro (A&B) and El-Mazo (C&D) areas surrounded by offwhite colored host limestone.

Fig. 4 .

 4 Fig. 4.47. Dolomite body along the El-Moro fault (red dashed line) in the western part of the El-Moro area. (A) Studied El-Moro fault sections MO-I, MO-II and MO-III. (B) Close up view of the MO-III studied section, inset shows fault striations in calcite (weathered surface), while red line indicates the probable extension of the fault.

Fig. 4 .

 4 Fig. 4.48. Field observations in the western El-Moro area. (A) Dolomite-limestone contact where dolomite shows dull grey appearance, while limestone exhibits dirty grey color. (B) White colored calcite vein in the dolomite body oriented along the fault.

  4.50 A&B). CCD-I dolomite is further subdivided into CCD-Ia (core, dull red luminescent) and CCD-Ib (zoned, bright red luminescent), where CCD-Ib consisted of dark colored rim formed due to selective dedolomitisation (cf. chapter 4; Fig. 4.50 C&D). Brecciated and zebra-like dolomites are mostly restricted to the fault zone (around fault striations and grooves), while saddle dolomite (CCD-II) exists throughout the section. Zebra dolomite mostly consisted of alternating bands of medium crystalline dolomite matrix and coarse crystalline, saddle type (undulose extinction) dolomite cement (Fig. 4.50E). The matrix phase of the zebra dolomite contained considerable porosity, while cement phase exhibited negligible pore spaces. Pyrite mostly restricted to fractures and pore spaces, hence indicating its formation at later stages (Fig. 4.50F). White colored, vein-filled calcite (WC) is observed at the contact of pre-existing limestone and saddle dolomite (CCD-II).

Fig. 4 .Fig. 4 .

 44 Fig. 4.49. Illustrations of various calcite and dolomite phases in El-Moro fault sections (MO-I, II & III). (A&B) PPL & CL photomicrograph showing late stage white calcite (WC) pre-date coarse grained, twinned calcite (CC-II). (C) CL showing detailed view of the CCD-I, where dull luminescent core (CCD-Ia) can be distinguished from bright luminescent zonations (CCD-Ib), while pore spaces are filled by dull luminescent calcite (WC). (D) Grey colored dolomite (CCD-I) showing dark colored rims along the crystal borders (arrow), with white colored, coarse crystalline dolomite occurring in the centre. Locally, pore spaces are filled by reddish stained color calcite. (E&F) PPL and CL photomicrographs showing destruction of intercrystalline pore spaces by meteoric calcite (TC) in CCD-I.

Field observations :

 observations The studied sections mostly consisted of light to dark grey colored dolomite, while pore spaces contained coarse crystalline, curved crystals (saddle) dolomite oriented towards the center of pores (Fig.4.51C). Vein-filling transparent to white calcite usually occurred in the light grey dolomite (Fig.4.51D). Isolated pyrite grains are also observed in the calcite vein, where pyrite mostly restricted to the calcite-dolomite boundary (Fig.4.51D). Pb-Zn mineralization is quite evident, where as disseminated pyrite crystals are engulfed in the light grey colored dolomite.Botryoidal sphalerite is disseminated in light grey dolomite, while galena crystals are also observed (Fig.4.51E&F). The mineralized dolomite consisted of lenses and patches of these pyrites. In one of these studied sections, fault striations indicate the presence of a fault zone along the dolomite body.

Fig. 4 .

 4 Fig. 4.51. Field observations in the central part of El-Moro area. (A&B) Dolomite corridors showing the location of sampled sections. (C) Coarse crystalline, pore-filling dolomite showing curved crystal faces (arrow). (D) White to transparent colored calcite vein in the brownish grey colored dolomite. (E) Botryoidal sphalerite associated with initial phase of dolomite CCD-I. (F) Galena particles disseminated in the dolomite.

Fig. 4 .

 4 Fig. 4.52. Illustrations of various calcite and dolomite phases in the central part of El-Moro area. (A&B) Veinfilling, zoned dolomite (CCD-II) in the bright luminescent dolomite matrix (CCD-I). (C) Aggradational crystal growth showing alternating zonations of white and dull orangr colored bands. (D) Partial dissolution of dolomite vein observed in late calcite. (E) Vein-filling, dull luminescent calcite (WC) in the dull orange luminescent dolomite (CCD-I). (F) Botryoidal sphalerite (smithsonite) associated with CCD-I dolomite.

  4.53A). In the host limestone, vein-filling calcite cements (CC-I & CC-II) formerly described as pore-and/or karst-fillings, predate dolomitisation as observed by cross-cutting relationship between dark grey colored dolomite vein (CCD-I) and dark orange colored vein-filling calcite (CC-I; Fig. 4.53B). In Figure 4.53C, a white colored dolomite vein (CCD-II) post-dates offwhite dolomite (CCD-I), what is in line with previous observations (cf. chapter 4). It is also noted that CCD-I filled bed parallel stylolites in the host limestone, while late stage dolomitisation (CCD-II) does not show any evidence of stylolitisation (Fig. 4.53C). It is also evident that dissolution resulted in enhancement of pore spaces in CCD-II, which are later on filled by reddish colored (stained) calcite (Fig. 4.53C). In contrast to CCD-II, dissolution features are not observed in CCD-I dolomite in contact with calcite (WC) and host limestone (Figs. 4.53C&D). Petrography: Calcite cementation (pre-dolomite) resulted in pore-, karst-and vein-fillings, where lense-like calcite (CC-Ia) oriented along the border of the open spaces, while twinned, irregularly oriented calcite (CC-Ib) occurred towards the centre (Fig. 4.54A). The presence of stylolites in the twinned, coarse crystalline calcite (CC-II) indicates its development after hydrothermal event (Fig. 4.54B). The initial phase of dolomitisation (CCD-I) mostly consisted CCD-Ia and CCD-Ib phases, where CCD-Ib readily dedolomitized or dissolved out, resulted in the generation of pore spaces, if not occluded by late stage calcite (WC) (Fig. 4.54C&D). Selective dissolution may also be observed in dull red luminescent dolomite (CCD-I), resulted in the creation of pore spaces (Fig. 4.54E&F).

Fig. 4 .

 4 Fig. 4.53. Field characteristics of dolomite and calcite phases in the El-Moro valley sections. (A) Dull beige colored dolomite in sharp contact with dark grey colored limestone. (B) Cross-cutting relationship of vein-filling dolomite (CCD-I) with calcite (CC-I) in the host limestone. (C) CCD-I dolomite pre-date white colored CCD-II dolomite, note that the stylolites (white arrow) are confined to host limestone and CCD-I. (D) In the host limestone (LS), dark grey colored WC calcite vein (white arrow) post-date brownish grey colored CCD-II dolomite (black arrow) vein.

  4.55B). In the pore spaces of medium crystalline, dull luminescent dolomite (CCD-I), rimmed, bright blue luminescent smithsonite (secondary mineralization) is observed, indicating its post-dolomite formation (Fig.4.55C). In the present study, the process of dedolomitization in CCD-I usually commenced from the crystal boundaries and destroy the whole crystal, where late stage, meteoric calcite (see later) mostly responsible for such process (Fig.4.55D). Besides dedolomitization, CCD-I dolomite exhibited selective formerly calcitized zone (cf. section 4.1.6), which may considerably enhance the reservoir characteristics (approximately 10 to 15% porosity) of these dolomites (Fig.4.55E&F).

Fig. 4 .Fig. 4 .

 44 Fig. 4.54. Illustration of various calcite and dolomite phases from El-Moro valley sections. (A) Pore-filling, predolomite calcite phase consisting of lensoidal crystals (CC-Ia) and irregularly crystal growth (CC-Ib) in contact with host limestone. (B) Coarse crystalline, twinned calcite (CC-II) containing stylolites. (C&D) PPL and CL photomicrograph showing CCD-I dolomite crystal containing dull luminescent core (Ia), and zoned, bright luminescent borders (Ib). (E&F) PPL and CL photomicrograph showing selective dissolution (dark rims in dolomite crystals), which results in increase in pore spaces.

Fig. 4 .

 4 Fig. 4.56. Field and plug observations from El-Mazo areas. (A) Dark grey colored, vegetated dolomite body in the whitish colored host limestone. (B) Coarse crystalline calcite (WC) containing clasts of brownish grey colored dolomite, while in contact with host limestone. (C&D) Sampled plugs showing CCD-I pre-dating CCD-II dolomite (arrow) phase in the host limestone.

Fig. 4 .

 4 Fig. 4.58. Petrographic characteristics of dolomite and calcite phases in El-Mazo area. (A) CCD-I dolomite containing pyrite grains (arrow) in the intercrystalline openings. (B) Coarse crystalline dolomite (CCD-II) exhibiting undulose extinction, typical of saddle dolomite. (C&D) PPL and CPL photomicrograph showing intercrystalline porefilling of red colored stained calcite (TC) in CCD-I dolomite. (E&F) PPL and CL photomicrograph showing intercrystalline as well as dissolution enhanced porosity (arrow) in CCD-I dolomite.

Fig. 4 .

 4 Fig. 4.59. Oxygen and carbon isotopic analyses of various dolomite and calcite phases as well as host limestone rock.

Fig. 4 .

 4 Fig. 4.60. Oxygen-and carbon-isotopic analyses of calcite and dolomite phases as well as dolomite host rocks in the central part of the El-Moro area. It is noteworthy to see the trend of dedolomitized part of CCD-I and ORE, which most likely relates to meteoric calcite.

δ

  13 C values (0.0 to +1.8 V-PDB; Fig. 4.62). The CCD-II dolomite exhibits δ 18 O values ranging from -19.5 to -17.5‰ V-PDB, while δ 13 C values vary from 0.0 to +1.4‰ V-PDB (Fig. 4.62). It is important to note the opposite trend in their δ 18 O and δ 13 C values of the two dolomite phases (Fig. 4.62). White calcite (WC) exhibits δ 18 O values ranging between -16.5 and -16.7‰ V-PDB, falling in between the δ 18 O values of the two dolomite phases. The dedolomitized part of the CCD-I dolomite indicates depleted δ 18 O (-13.0 to -11.0‰ V-PDB) and δ 13 C (-2.6 to -1.0‰ V-PDB) values, confirming that dedolomitisation could be associated with telogenic calcite (TC; Fig. 4.62).

Fig. 4 .

 4 Fig. 4.62. Oxygen-and carbon-isotopic analyses of calcite and dolomite phases as well as dolomite host rocksin El-Mazo area. Note that the opposite linear trends of two dolomite phases.

Fig. 4 .

 4 Fig. 4.63. 87 Sr/ 86 Sr Vs δ 18 O crossplot showing clear shift from original Albian marine signatures. Note that white calcite showing high 87 Sr/ 86 Sr-ratios as compared to various dolomite and calcite phases.

Fig. 4 .

 4 Fig. 4.64. Proposed paragenetic sequence observed in the El-Moro and El-Mazo areas. Note that the red lines indicate events occurred during late diagenesis in the Albian carbonates.

4 . 2 ;

 42 Appendix-II). In the host limestone, infilling of paleokarsts by CC-I & CC-II calcite predates dolomitisation (Fig. 4.3). First episode (Fe-rich) CDD-Ia developed an extended stockwork of veinlets in the study area. Albeit this distribution is reminiscent of hydraulic (dilatational) fracturing and overpressure, it does not imply large fluid fluxes. Besides, much of the following CCD-Ib dolomites actually replace limestone (Fig. 4.3B). The coeval mass transfer requires larger fluid fluxes and sustained fluid undersaturation with respect to calcite. It is noteworthy that replacement of early hydrothermal calcite (CC-II) by CCD-Ib dolomite is well exposed in the Ranero vein (inset of Fig. 4.18B). The newly formed dolomites have a particular texture and form a palisade of plumose, decimetre scale crystals. Because CC-II calcites are very coarse, hence they offer very low reactive surface to dolomitizing fluids. This explains simply why their dolomitisation is very difficult, and because they appear in the field as a relict calcite dyke engulfed in CCD-Ib dolomite (cf. Fig. 4.18B).The CCD-II veins are, usually, nearly straight and small (centimetre to decimetre scale) when hosted in the limestone, while they expand to metre-scale and develop irregular limits within the CDD-I dolomite body in the Pozalagua Quarry(Figs. 4.4A&B). Therefore, they do not seem to pervasively replace limestone in the Pozalagua Quarry, but rather replace previous CCD-I dolomites (including zebra dolomites). Post-dolomite calcite (WC and TC) occurred as vein-and pore-fillings in CCD-I and CCD-II dolomites (Fig.4.4E&F).

4 .

 4 30 & 4.31). Calcite cement phases (CC-I and CC-II; cf. Fig. 4.3) filled paleo-and hypogene karstification in contrast to the early meteoric karst features that were previously documented by López-Horgue et al. (2010) and Kurz et al. (2011). Cavity-filling calcite (CC-I & CC-II) represented an initial stage of hydrothermal activity prior to dolomitisation and showed depleted δ 18 O values compared to original marine signatures of Albian limestones (

  Bedding parallel stylolites postdate cavity-filling calcite phases (CC-I & CC-II) Early phase of dolomite clearly post-dates hypogene dissolution and earlier calcite fillings (CC-I and CC-II; Figs. 4.3C&D). It is believed that the large development of fracturing and hydrothermal dissolution before dolomitisation enhanced the formation of voids resulting in significant volume for dolomitisation especially in the Pozalagua quarry and its surroundings as compared to other studied sites.The first episode of dolomitisation (CCD-I) appears to have resulted from the influx of Ferich dolomitising fluids along reactivated faults/fractures, which regionally replaced the host limestone and calcite (CC-II) in particular(Figs. 4.17, 4.18A, 4.50A&B). The process of replacement is evidenced by irregular (interfinguring) contacts between limestone host rocks and dolomite, which were observed in the study area(Fig. 4.19C). Fe-rich dolomite (CCD-I) seems to contain Sphalerite-Galena mineralization. Similar observations have been reported from the Réocin

  ) accompanied by replacive phases (3) resulted during early to late Albian age(Fig. 4.46). Late Albian-Turonian age has been assigned for the late phase of hydrothermal dolomite (4) and post-dolomite calcite (5) in the studied area constrained by arguments resulting from stratigraphical, structural and burial analyses(López-Horgue et al., 2010).Late stage telogenic calcite (6) formed in the near surface conditions and very late in the geologic age.On the basis of the burial curve ofLópez-Horgue et al., 2010 (Fig. 5.2), two hypotheses regarding the origin of dolomitisation fluids can be proposed, depending on whether dolomitization occurred: (i) during the Albian-Turonian, at a time when the basin was still impacted by extension and normal faults being still acting as conduits for deeper hydrothermal fluids, which were in thermal disequilibrium with the host rock (Appendix-II). In this case, the hot fluids migrated laterally and vertically from the adjacent early Albian basinal sediments. or (ii) during the Eocene, at the time of maximum burial along with remobilization of basinal fluids due to positive inversion and reactivation/re-opening of former normal faults as a result of Pyrenean tectonics. In this case, the fluids were in thermal equilibrium with the host rock. However, because the mineralizing fluids have exotic chemistry, they could have migrated from below the salt, i.e. from Permo-Triassic siliciclastics aquifer by vertical migration.

Fig. 5 . 1 .

 51 Fig. 5.1. Paragenetic sequence representing the spatial distribution of various dolomite and calcite phases.

Fig. 5 . 2 .

 52 Fig. 5.2. Burial history of in the various sedimentary units cropping out in the study area. Notice that hydrothermal dolomitisation is restricted to units 15-20. I have plotted here the various dolomite phases and their probable time of formation (modified from Lopez-Horgue et al., 2010).

  Dolomite and calcite phases in the studied area show a broad range of depleted δ 18 O values, while δ 13 C values indicate a slight shift from analysed nearby host limestone (Appendix-III). In El-Moro area, relatively less dispersion in terms of δ 18 O values and similarly depleted δ 13 C values are observed (Appendix-III). In both the studied areas, ferroan dolomite (CCD-I) shows less depleted δ 18 O values (-16 to -11‰ V-PDB; cf. Sections 4.1.4b & 4.2.2a), whereas nonferroan dolomite exhibited high depleted δ 18 O values (-19 to -15‰ V-PDB) The broad range of δ 18 O values is

Fluid

  inclusions analyses show high homogenization temperatures (120 -200°C) and salinities (12 -21 eq. wt% NaCl; Shah et al., 2010) of primary inclusions (Figs. 4.39A&B), which rules out the invasion of meteoric fluids as the driving mechanism in the dolomitization scenario.The broad range of estimated salinity values may indicate the presence and variable mixing of multiple dolomitising fluids as observed in MVT-type mineralization(Leach et al., 2005). The highly depleted δ 18 O values may either be due to increase in temperature or/and 18 O-depleted fluids.

  contrast to CCD-I, the formation of CCD-II dolomites does not require acidic fluids (as they do not considerably replace calcite) or particularly Mg-rich (as they mostly replace CCD-I dolomite).CCD-II related fluids are obviously Fe poor. Given that this second stage ends with some pyrite deposition as observed in the Pozalagua quarry, a likely possibility is that the corresponding fluids were rich in reduced sulphur (H 2 S, HS -) and thus almost unable to transport Fe (Fig.4.4E). It is obvious that highly reduced sulphur content could trigger the reaction of CCD-II fluids with all Febearing minerals (including Fe dolomite and silicates), resulting in Fe-poor dolomite and pyrite (Fig.4.4E). The suggested chemical contrast between early (ferroan) and late (non-ferroan)

  providing voids and permeability network that could have facilitated the flow of the early stage dolomitisation fluids. Initially, Fe-rich dolomitizing fluids may have liberated from the adjacent basinal deposits and resulted in precipitation of. For the second episode of dolomitization, the circulating fluids exhibited very high temperature as evidenced by the T h values (140 to 200°C) of the fluid inclusions (explaining also the highly depleted δ 18 O). In the study area, the circulation of such high temperature fluids along faults/fractures which could be associated with flexuring in the Aptian-Albian limestone due to the presence of diapiric structures in the area(López-Horgue et al., 2010; Fig. 5.3), succeeded in the formation of CCD-II. It can be speculated that such dolomitizing fluids may be related to different sources, such as igneous activity and convective flow induced by the high temperature magmatic activity due to their high TiO 2 ratios(Robertson, 2007; Shah et al., 2010; Appendix-II). Still two contrasted scenario can be considered: either hot dolomitising fluids circulated during Albian-Turonian time, thus migrating laterally and vertically from deeper and warmer Albian basinal sequences, or during the Late Cretaceous to Paleogene Pyrenean orogeny, exotic fluids coming from nearby underlying Permo-Triassic siliciclastics aquifers. The same questioning is actually debated in many other inverted basins, i.e. in the Roer Valley basin in Netherlands, where thermal modelling rather favors the remobilization of basinal fluids during inversion episodes, rather that during early episodes of rifting and associated volcanism (Luijendijk, 2011a,b). The Basque trough is an irregular graben-like feature developed adjacent to the Ramales platform (study area), where more than 8500m thick shales, sandstones and marls accumulated during upper Valanginian-late Cenomanian (Gibbons & Moreno, 2002). During burial, compactional dewatering may have resulted in hydrodynamic fluid flow along the NW-SE and NE-SW trending faults existing adjacent to the basin-platform margins (cf. Vicente-Bravo & Robles,1995). According toBustillo et al. (1992), the dolomitising fluids originated in the NE of the basin from the mudrocks situated in the deeper part of the basin, where trapped sea water may have provided the Mg-rich fluids for dolomitisation. These hot, compactional fluids (120-200°C; according toShah, 2008 and López-Horgue et al., (2010) pervasively dolomitised the host limestone (Fig.4.46). During the burial of the sedimentary basin and later hydrodynamic fluid flow, permeable carbonate platform limestones and faults/fractures control the extent of dolomitisation (e.g.Qing and Mountjoy, 1989). Such pre-requisites as faults/fractures and paleo-karst are present in the study area (as discussed above). The presence of linear (fracture-controlled) dolomite bodies supports the idea that the dolomitising fluids migrated and spread through the sedimentary pile along such discontinuities(Fig. 4.46; Shah et al., 2010). Alternatively, fluids may have been moving in response to gravity (salinity) gradients from the platform side or as a consequence of heat anomalies (convection) inside the platform or along its edge. Potential sources of heat anomalies (temperature gradients) including: i) the Keuper diapiric deformation (e.g.Canérot et al., 2005), and ii) the differential subsidence along the platform border. Altogether, the fluid drives are not well constrained in the study area, but the capacity of the system to focus fluid flow along pathways transverse to the edge of the platform remains the most remarkable aspect.

Fig. 5 . 3 .

 53 Fig. 5.3. Sketch showing compactional fluids heated up while invading the subsurface of platform resulted in CCD-I type dolomitization, while juvenile fluid circulation along the salt diaper resulted in CCD-II type of dolomitization.

  FIG. 1. -Tec to nos tra ti gra phic map of Basque-Can ta brian ba sin (BCB), rec tan gu lar box re pre sents the lo ca tion of the stu dy area where ear ly and late Cre taceous rocks are ex po sed [mo di fied from Gib bons and Mo re no, 2002]. FIG. 1. -Carte struc tu rale et stra ti gra phique du bas sin Basque-Can ta brique (BCB), la po si tion de la zone d'é tude est en cadrée où les ro ches du Cré ta cé Infé rieur et su pé rieur sont ex po sés [d'a près Gib bons and Mo re no 2002, mo difiée].

  3): Pozalagua quarry (Ranero fault, down-slope; fig. 4B); Ranero fault (up-slope; fig. 4B); Ranero front (mar gin, away from ma jor fault; fig. 4C). Bull. Soc. géol. Fr., 2010, n o 4 FAULT-RE LA TED HY DRO THER MAL DO LO MI TES IN CRE TA CEOUS CAR BO NA TES (CAN TA BRIA, NOR THERN SPAIN) TABLE I. -␦ 18 O and ␦ 13 C stable iso tope re sults of the va rious do lo mite fa cies and cal cite en coun te red in the dif fe rent do lo mite sec tions stu died in the area. Tabl. I. -Com po si tions iso to pi ques ex pri mées en ␦ 18 O et ␦ 13 C des dif férents fa ciès de do lomie et de cal cite re le vés dans les cou pes étu diées.

  FIG. 2. -Struc tu ral map of the Basque-Can ta brian ba sin, sho wing ma jor faults in the stu dy area [mo dified from Gar cia-Mon dé jar et al., 1996]. FIG. 2. -Carte struc tu rale du bas sin Basque-Can tabrique, mon trant les fail les ma jeu res du site d'é tude [d'a près Gar cia-Mon dé jar et al., 1996, mo difiée].

  FIG. 4. -Va rious geo me tric dis tri bu tion of do lo mite bo dies (A) Co lour con trast bet ween do lo mite (dark grey) and li mes tone (white), evi dent in the field. (B) Do lo mite pre sence across the main Ra ne ro fault and sur roun ding mi nor frac tu res, note that the po si tion of Po za la gua Quar ry. (C) Irre gu lar do lo mite bo dies (fronts) in va ding in the host li mes tone away from the fault. (D) Li near do lo mite body in the vein, sho wing ho ri zon tal dis pla ce ment cut by fault. (E) Inter loc ked, non pla nar do lo mite ha ving mil ky white co lour. (F) Pla nar do lo mite ex hi bits su ga ry tex ture, while mil ky white is saddle do lo mite. FIG. 4. -Illus tra tion des dif fé ren tes mor pho lo gies des corps do lo mi ti ques. (A) Le con traste de co lo ra tion entre do lomie (gris sombre) et cal caire (blanc) ap pa raît clai re ment. (B) Do lomie au tour de la faille de Ra ne ro et de frac tu res mi neu res, et po si tion de la car rière de Poz za la gua. (C) Corps do lo mi ti ques à contour lo bés (front) en ra ci nés sur la faille. (D) Corps do lo mi tique fi lo nien (veine) re je té par une frac ture ho ri zon tale. (E) Mo saïque de do lomie non planaire, blanche. (F) Do lomie pla naire (gris) à tex ture su cro sique, en vahie par la dolomie baroque (blanche).

  FIG. 5. -Dif fe rent do lo mite and cal cite fa cies in the stu dy area: (A) Ze bra do lo mite shows al ter na ting bands of dark grey re pla cive and whi tish ce ment phase. (B) Iso la ted clasts of ze bra do lo mite in dif fe rent do lo mite ce ments in the Po za la gua quar ry (bar = 500 cm). (C) Li mes tone clasts floa ting in do lomite ce ment in Po za la gua quar ry. (D) Horse-tail splays fil led with do lo mite, sho wing strike-slip faul ting in the stu dy area. (E) Cal cite vein fil led by dark grey co lo red do lo mite vein in the cen tral part. (F) Host li mes tone shows mul tiple epi so des of cal cite-fil led frac tu res and do lo mite fil ling in cal cite vein. FIG. 5. -Exem ples de fa ciès de do lomie et de cal cite. (A) Do lomie ze bra, à al ter nance de ban des gri ses (re pla ce ment) et blan ches. (B) Frag ments de dolomie ze bra iso lés dans dif fé rents ci ments do lo mi ti ques, car rière de Po za la gua (barre d'é chelle = 0,5 m). (C) Frag ments de cal caire dans un ci ment do lomi tique, car rière de Po za la gua. (D) Fais ceau de dé cro che ments à rem plis sage do lo mi tique. (E) Veine de cal cite avec rem plis sage cen tral do lo mi tique (gris). (F) Cal caire en cais sant mon trant plu sieurs épi so des de frac tu ra tion et des rem plis sa ges calcitiques et dolomitique.

  FIG. 6. -Pe tro gra phic cha rac te ris tics of li mes tone and do los tone fa cies. (A and B) Par tial ly re pla ced li mes tone by twin ned cal cite, contai ning fos sils and fos sil-frag ments, note that fos sil frag ments are also re pla ced. (C) Sub he dral to eu he dral pla nar do lo mite, in ter crys tal line spa ces are fil led by cal cite. (D) CL pho to mi cro graph sho wing pla nar do lo mite fa cies, which ex hi bit bright red boun da ries and dull red cen ter (P = pore; D = do lo mite; bar = 250 µm). (E) CPL pho to mi cro graph of non pla nar do lo mite shows un du lose ex tinc tion, ty pi cal of saddle do lo mite. (F) CPL pho to mi cro graph of ze bra do lo mite showing coarse-crys tal line ce ment phase and fine to me dium crys tal line ma trix phase. FIG. 6. -Ca rac té ris ti ques pé tro gra phi ques des fa ciès cal cai res et do lo mi ti ques. (A et B) Cal caire fos si li fère par tiel le ment rem pla cé par la spa rite. (C) Dolomie au to morphe à su bau to morphe, ci mentée par la cal cite. (D) Image en ca tho do lu mi nes cence de la do lomie pla naire : les bor du res des cris taux sont rouge vif, les coeurs très som bres (P = pore ; D = do lomie ; échelle = 250 µm). (E) Pho to mi cro graphie CPL de do lomie non pla naire montre ex tinc tion ondulée, ty pique de do lo mite en selle. (F) Pho to mi cro graphie CPL de zè bres do lo mite mon trant phase de ci ment cris taux gros siers et fins à moyens phase matrice cristalline.

  FIG. 7. -Pe tro gra phic cha rac te ris tics of do los tone fa cies and cal cite ce ments. (A) CL shows ag gra da tio nal crys tal growth in non pla nar do lo mite. (B) Stained pho to mi cro graph shows a do lo mite vein cross-cut ting (thus, post-da ting) cal cite vein let (bar = 300 µm). (C) CL pho to mi cro graph ex hi bits pore space fil led dull orange cal cite ce ment. (D) CL pho to mi cro graph sho wing open space fil ling red dish, non lu mi nes cent cal cite ce ment. FIG. 7. -Ca rac té ris ti ques pé tro gra phi ques des fa ciès de do lomie et des ci ments de cal cite. (A) Image CL mon trant la zo na tion de crois sance des cris taux dans la do lomie non pla naire. (B) La co lo ra tion montre une veine de do lo mite re cou pant des vei nu les de cal cite plus an cien nes (barre d'é chelle = 300 µm). (C) Image CL du ci ment cal ci tique in ter gra nu laire (orange terne). (D) Image CL des po res rem plis de ci ment tar dif de cal cite non lu mi nes cente.

  FIG. 8. -Pe tro gra phic cha rac te ris tics of do lo mite ce ment and dia ge ne tic al te ra tion. (A and B) CPL and CL pho to mi cro graphs sho wing zo ned do lo mite cement with pore spa ces fil led with red dish (in CPL) and dull orange (CL) cal cite. (C) PPL pho to mi cro graph ex hi bit ca ta clas tic de for ma tion, re sul ted in non pla nar do lo mite, note that open spa ces are fil led with red dish cal cite ce ment. (D) PPL pho to mi cro graph shows dis so lu tion of dark grey do lo mite and pre ci pi ta tion of white do lo mite, which des troyed se con da ry po ro si ty. FIG. 8. -Caractéristiques pétrographiques des ciments dolomitiques et de leur altération diagénétique. (A et B) Images en LP et CL montrant une dolomie zonée avec des pores remplis de calcite (orange terne en CL). (C) Image en LP montrant la déformation cataclastique dans une dolomie non planaire, cimentée par de la calcite (rouge). (D) Image en LP de la dissolution de la dolomie primaire (gris foncé) remplacée par une autre dolomie (blanc) avec destruction de la porosité.

  FIG. 9. -Do lo mite and li mes tone fa cies dis tri bu tion (in %) across three dif fe rent mea su red sec tions in the stu dy area (fault, front and vein). The per cen tage of fa cies was es ti ma ted ba sed on field and pe tro gra phic ob serva tions of the fa cies across each sec tion. FIG. 9. -Dis tri bu tion des fa ciès de do lomie et de cal caire (%) dans trois sec tions dif fé ren tes de la zone de Ra ne ro (faille, front et veine). Les pro portions de fa ciès ont été es ti més sur la base des ob ser va tions de ter rain et pétro gra phi ques dans chaque section.

  FIG. 11. -His to gram sho wing dis tri bu tion of ho mo ge ni za tion tem pe ra ture with res pect to num ber of rea dings from ze bra and non pla nar do lo mite sam ples from the Po za la gua quar ry. FIG. 11. -His to gramme mon trant la dis tri bu tion des tem pé ra ture de ho mogé néi sa tion dans les in clu sion flui des des do lomie ze bra et non pla nai res pro ve nant de la car rière de Po za la gua. FIG. 12. -Sa lin tiy vs ho mo ge ni za tion tem pe ra ture cross-plot in ze bra and non pla nar do lo mite. FIG. 12. -Dia gramme sa li ni té vs tem pé ra ture d'ho mo gé néi sa tion (Th) dans les do lo mies ze bra et non pla naire.

  FIG. 13. -Cross-plot of ␦ 18 O ver sus ho mo ge ni za tion tem pe ra ture of ze bra and non pla nar do lo mite to de ter mine the pa rent fluid che mis try [mo di fied from Land, 1983]. FIG. 13. -Dia gramme ␦ 18 O vs tem pé ra ture d'ho mo gé néi sa tion (T h ) dans les do lomie ze bra et non pla naire pour la dé ter mi na tion des flui des pa rents [d'a près Land, 1983, mo di fié].

  FIG. 14. -Po ro si ty dis tri bu tion in do lo mite and li mes tone fa cies. (A) Inter crys tal line po ro si ty in ze bra do lo mite. Note that ma trix phase of ze bra do lo mite contain much po ro si ty as com pa red to ce ment phase (2-3 %). (B and C) PPL and XPL pho to mi cro graph sho wing in ter crys tal line po ro si ty in pla nar do lomite (10-15 %). (D) XPL pho to mi cro graph sho wing dis so lu tio nal po ro si ty in host li mes tone (3-5 %). FIG. 14. -Dis tri bu tion de la po ro si té dans les di vers fa ciès de do lomie et les cal cai res. (A) Po ro si té in ter cris tal line dans la do lomie zèbre. No ter que la phase ma tri cielle des zè bras contient beau coup de po ro si té par rap port au ci ment (2-3%). (B et C) Image en LT et LP mon trant la po ro si té in ter cris tal line dans la do lomie plane (10-15%). (D) Image en LP de la po ro si té par dis so lu tion dans le cal caire hôte (3-5%).

  FIG. 16. -Li thos tra ti gra phic cross-sec tion of the BCB, sho wing stu dy area in red, dot ted rec tan gu lar box. The pos sible sour ces of do lo mi ti zing fluids are in di ca ted by va rious co lou red ar rows (yel low = deep ba si nal for ma tio nal fluids; red = Mg-rich fluids from ba se ment rocks; green = fluids from salt dia pirs) and paths for their cir cu la tion and pum ping into the Cre ta ceous car bo na tes along faults and frac tu res to form the ob ser ved do lo mite bo dies [mo di fied from Gib bons and Mo re no, 2002]. FIG. 16. -Sec tion li thos tra ti gra phique du BCB, mon trant zone d'é tude en boîte rec tan gu laire. Les flè ches ind iquent dif fé ren tes sour ces pos si bles des fluides do lo mi ti sants (flèche fine = pro fond bas sin flui des for ma trice et flui des de dia pirs de sel ; flèche épaisse = flui des ri ches en Mg is sus des ro ches du socle) et dif fé rents che mins de cir cu la tion le long de fail les et de frac tu res pour for mer les do lo mies ob ser vées dans les car bo na tes du Cré ta cé [d'après Gibbons etMoreno, 2002, modifiée].

;

  Zhao et al., 2005 and Davies & Smith, 2006). Dolomite related to faults and/or fractures indicate tectonic control on the dolomitisation process but dolomite distribution also depends on the nature of host rock. Recent integrated studies suggest that hydrothermal dolomite exists in many forms and likely to be far more common than previously thought (Berger and Davies., 1999; Moore, 2001; Cantrell et al., 2004; Nader and Swennen., 2004; Davies and Smith., 2006; Nader et al., 2009; Lopéz-Horgue et al., 2010; Ronchi et al., 2010; Conliffe et al., 2010). Besides a few cases of stratiform hydrothermal dolomites, these usually occur as fabric destructive, strata-discordant cutting across host limestone and concentrated along major faults (Wilson et al., 1990; Nader et al., 2004; Gasparrini et al., 2006; Lopéz-Horgue et al., 2010; Shah et al., 2010; Swennen et al., in press). Some of the known oil (Ghawar, Saudi Arabia; Cantrell et al., 2004) and gas (North field, Arabian Gulf; Sudrie et al., 2006) carbonate reservoirs consist of porous dolomites, which are probably partly hydrothermal in origin. It is important to understand this particular dolomitization process, which may be of major economic importance.

  northward and collided with the European plate during Campanian to Maastrichtian time(Gibbons and Moreno, 2002). During the Early Cretaceous rifting period, BCB underwent NNE-SSW direction of simple stretching perpendicular to the axes of the main NW-SE structural trend(Montadert et al., 1979; Grimaud et al., 1982; Boillot & Malod, 1988; Malod & Mauffret, 1990). Later on, this NNE-SSW direction of simple stretching changed to NW-SE direction as the simple extension was replaced by left lateral strike-slip motion along the main NW-SE faults as evidenced in the study area (Ranero and Güenes faults). This change in the direction is linked to the anticlock-wise rotation of the Iberian plate with respect to European plate and spreading in the western part of the Bay of Biscay(Montadert et al., 1979; Boillot & Malod, 1988). Trans-tensional movements along these NW-SE oriented faults produced oblique slip and pull-apart basins, where thick sediment accumulation took place.The study area and its surroundings encompass various tectonic features, which include NW-SE oriented (Güenes and Ranero faults), N-S oriented (Ramales fault), E-W oriented (Arredondo and Hornijo faults) as well as other small scale NE-SW directed faults and fault splays, indicating the extensional history (Fig.1A). In the study area, dolomite bearing, left-lateral Ranero fault is believed to be the splay of NW-SE oriented oblique-slip Güenes fault, formed during Early-Mid Albian(Garcia- Mondéjar et al., 1996; Aranburu et al., 1994). So, these NW-SE oriented faults are related to Early Cretaceous rifting in the BCB(Grimaud et al., 1982; Boillot & Malod, 1988; Olivet, 1996). The N-S oriented Ramales fault is a basement rooted listric fault (García-Mondéjar and Pujalte, 1975), while the E-W oriented Arredondo and Hornijo faults (Early-Mid Albian) post-date NW-SE oriented faults and fractures[START_REF] García-Mondéjar | Carbonate platform-basin transitions in the Soba reef area (Aptian-Albian of western Basque-Cantabrian region northern Spain). In: Sedimentation and Tectonics in the Western Basque-Cantabrian area (northern Spain) during Cretaceous and Tertiary Times[END_REF].

  2 & 3) (García-Mondéjar et al., 2005). The Aptian-Albian carbonates in the study area mostly consist of rudist limestones accumulated in places and exhibit rapid changes of lateral facies into siliciclastic sediments, while warm and wet climatic conditions are indicated by the presence of reefal faunas, lack of evaporitic deposits, common storm deposits and frequent fossil wood in deltaic facies (García-Mondéjar, 1990; Rosales & Pérez-García, 2010). The study area mostly comprises early-to late-Albian platform to slope carbonates and shallow to deep-marine siliciclastics in the basinal regime, while dolomitisation being mostly restricted to early Albian carbonates (Figs. 2 & 3) (Lopéz-Horgue et al., 2009 & 2010; Rosales & Pérez-García, 2010). Four main stratigraphic units are recognised, which include the Sopeña and Ranero in the platform region, while La Escrita (lower half of Valmaseda Formation) and Río Calera units occur in the vicinity of the deep and shallow basinal areas (Aranburu, 1998; Lopéz-Horgue, 2000; Rosales & Pérez-García, 2010). The Sopeña and Ranero units consist of shallow marine carbonates and are stratigraphically correlated with Ramales Formation in the Ramales area (Lopéz-Horgue et al., 2009).

  Sopeña units, respectively(Lopéz-Horgue et al., 2009; Rosales & Pérez-García, 2010). The short distance between the platform carbonates and the basinal deposits suggests the formation of an intraplatform trough rather than a deep basin[START_REF] Garcia-Mondéjar | Plate reconstruction of the Bay of Biscay[END_REF]. Platform to slope carbonate successions show two major carbonate depositional systems, which include early Albian aggradational steep-sloping platform and late Albian low-gradient widespread carbonate bank development separated by a regional unconformity (Fig.3; Rosales and Pérez-Garcia, 2010).During late Albian and Turoninan stage, at least 50m sea-level fall in the study area and its surroundings resulted in development of a paleokarst system (García-Mondéjar, 1990; Lopéz-Horgue et al., 2010), hence formed metre-scale cavities (due to dissolution in limestone and localized in joints) that were filled by shallow marine sandstones (García-Mondéjar, 1990). Besides the development of paleokarst system, hydrothermal karstification is also observed in the study area.

  Stable isotope analyses (δ 18 O and δ 13 C) of 275 selected samples of different dolomite types, calcite cement and host limestone were carried out in the Department of Geology, University of Erlangen, Germany and Département Géologie, Jean Monnet Université, Saint Etienne (Table. I). All stable isotope values are reported in per mil (‰) relative to Vienna Pee Dee Belemnite (V-PDB) by assigning a δ 13 C value of +1.95‰ and a δ 18 O value of -2.20‰ to NBS19. The carbonate powders were reacted with 100% phosphoric acid (density >1.9; Wachter & Hayes, 1985) at 75°C in an online carbonate preparation line (Carbo-Kiel -single sample acid bath) connected to a Finnigan Mat 252 mass-spectrometer. Dolomite isotopic composition values are corrected by fractionation factors given by Rosenbaum & Sheppard (1986). Based on replicate analysis of laboratory standards, reproducibility is better than ±0.02‰ for δ 13 C and ±0.03‰ for δ 18 O.

  ). The two next dolomite bodies (MO-IV & MO-V) occur in the central part of the El-Moro area, while a few others (MO-VII & MO-VIII) outcrop in the valley between El-Moro and El-Mazo areas (Figs. 4; 6A). Dolomite bodies studied in the western extremity of the El-Moro area include MO-IX and MO-X.(Figs. 4; 6C). Mostly, these dolomite bodies are yellowish-brown to dark grey, crumbly weather colored and restricted to faults and fractures and exhibit more than 1km linear extension. Besides, lateral distribution of these dolomite bodies are also evident (~ 500m) in some localities of the study area. Fault-related dolomite bodies are generally oriented N-S, NW-SE and NE-SW. They show variation in their textural distribution across the fault as dolomitization can range from saddle dolomite in and around faults and fractures to pervasively dolomitised margins and considerably massive dolomitised bodies (Shah et al., 2010). Dolomite veins also existed in the host limestone as their density decreases away from the main dolomite body. Besides various phases of dolomite, white to transparent calcite mostly occurs along the borders of the dolomite bodies in the study area. Excellent dolomite exposures in the Pozalagua quarry site show different diagenetic phases (dark to light grey, brown to yellowish, pinkish and milky white to light pink) and hence may confirm the repetitive expulsion of dolomitising fluids along the Ranero fault (Swennen et al., in press).

  by late stage dolomite and/or calcite (Figs. 7A). Such calcite (CC-I & CC-II) filling is restricted to host limestone. Microscopic observations of the samples collected from the Pozalagua area show bladed and coarse crystalline early calcite cement (CC-I & CC-II), which occur in contact with host limestone (Fig. 7B). The bladed calcite (CC-I), usually 300µm to a few millimetre in diameter, possesses a dull red luminescence. The CC-I crystals are elongated and pointed towards the coarse crystalline, nonluminescent calcite (CC-II; Fig. 7B). In contrast to the Pozalagua area, the early cavity-filling calcite (CC-I & CC-II) has only been observed in a few locations of the El-Moro area (MO-I, III and VII). Oblique stylolites have been observed in the cavity-filling calcites (CC-I & CC-II), hence indicating their formation prior to regional burial according to the burial curve of Lopéz-Horgue et al. (2010).

  ±1.0‰ δ 13 C, the dolomites show relatively depleted δ 13 C values, which may indicate a possible external source of carbon during dolomite precipitation (Figs. 11A&B) or a temperature dependent fractionation effect. In order to explain depleted δ 18 O values, it has been well documented that precipitation of dolomites from hot fluids leads to relatively depleted δ 18 O compositions (Land, 1983). The analysed host limestone also shows considerable depletion in their δ 18 O values (-17.10 to -4.5‰ V-PDB), which may be due to recrystallisation by hot fluids. Cavity-filling calcite cements (CC-I and CC-II) show almost the same distribution of depleted δ 18 O (-14.02 to -10.06‰ V-PDB) and δ 13 C (+0.53 to +1.99‰ V-PDB) values in Ranero and El-Moro (Figs. 11A&B). The Fe-rich coarse crystalline dolomite (CCD-I) show less depleted δ 18 O values (-16.35 to -12.05‰ V-PDB) as compared to non-ferroan dolomite (-19.25 to -16.60‰ V-PDB), indicating different temperature of dolomitising fluids or/and involvement of a different fluid (Figs. 11A&B). Vein-and pore-filling calcite (WC) shows highly depleted δ 18 O values (-20.10 to -16.05‰ V-PDB; Figs. 11A&B). In the Ranero area, carbonates associated with Galena-Barite mineralisation show similar δ 13 C values as host limestone, indicating a buffered system, but the depleted δ 18 O values indicate involvement of hot or depleted dolomitising fluids (Fig. 11A).

  hydrothermal activity during late Albian to Turonian times(Thiébaut et al., 1988; Aranburu et al., 1994; Schärer et al., 1999; Lopéz-Horgue et al., 2010; Swennen et al., in press). The fact that the dolomite bodies are associated to faults indicates a tectonic control on the dolomite distribution (Figs. 5&6; Garcia-Mondéjar, 1996; Lopéz-Horgue et al., 2005 & 2010; Gasparrini et al., 2006; Shah et al., 2010; Swennen et al., in press). Various dolomite phases are believed to have formed due to the circulation of Mg-rich dolomitising fluids along faults/fractures, hence invoking multiple pulses of these fluids (Swennen et al., in press).

  ; Lopéz-Horgue et al., 2010). Fault reactivation resulted in brecciation of non-ferroan dolomite, creating voids that were later on filled by white calcite (WC). Calcitized, non-luminescent part of CCD-I represent less depleted δ 18 O and depleted δ 13 C values (Figs. 11A&B), likely formed near meteoric recharge (Choquette & James, 1988; Niemann & Read, 1988; Meyers, 1991; Reeder, 1991). Cavity-filling calcite (CC-I & CC-II) represented an initial stage of hydrothermal activity prior to dolomitisation and showed less depleted δ 18 O values compared to original marine signatures of Albian limestones (Fig. 11). The first episode of dolomitisation (CCD-I) resulted from the influx of Fe-rich dolomitising fluids along reactivated faults/fractures, which regionally replaced the host limestone and calcite (CC-II) in particular, as was observed in the vein section. The process of replacement is evidenced by irregular (interfinguring) contacts between host limestone and dolomite. Fe-rich dolomite (CCD-I) seems to contain Sphalerite-Galena mineralization. Similar observations have been reported from the Réocin Zn-Pb deposits, situated NW of the study area (Symons et al., 2009 and Velasco et al., 2003). Sphalerite-Galena associated dolomite phases in the Réocin area resulted in precipitation of Fe-rich dolomite in internal sediments and in open spaces (sulphide deposition). This resembles with the dolomite sands (DS) in the study area. Zebra dolomite (ZD) resulted from the replacement of host limestone. The second episode of dolomitisation (CCD-II) exhibits local scale veinfilling dolomites, which showed replacement of pre-existing dolomite (CCD-I). In contrary to CCD-I, non-ferroan dolomite (CCD-II) does not alter the host limestone substantially.

3 .

 3 upper Valanginian-late Cenomanian (Gibbons & Moreno, 2002). During burial, compactional dewatering may have resulted in hydrodynamic fluid flow along the NW-SE and NE-SW trending faults existing adjacent to the basin-platform margins (Vicente-Bravo & Robles, 1995). According to Bustillo et al. (1992), the dolomitising fluids originated in the NE of the basin from the mudrocks situated in the deeper part of the basin, where trapped sea water may have provided the Mg-rich fluids for dolomitisation. These hot, compactional fluids (120-200°C; according to Shah, 2008 and Lopez-Horgue et al., 2010) pervasively dolomitised the host limestone. During the burial of sedimentary basin and later hydrodynamic fluid flow, permeable carbonate platform limestones and faults/fractures control the extent of dolomitisation (Qing and Mountjoy, 1989). Such pre-requisites as permeable carbonate platform limestones, faults/fractures and paleo-karsts are present in the study area. The presence of linear (fracture-controlled) dolomite bodies supports the idea that the dolomitising fluids migrated and spread through the sedimentary pile along such discontinuities (Shah et al., 2010). Chemistry of dolomitising fluids: Dolomite and calcite phases in the Ranero area show a broad range of depleted δ 18 O values, while δ 13 C values indicate slight shift from those of the analysed nearby host limestone. In the El-Moro area, relatively less dispersion in terms of δ 18 O values and similarly depleted δ 13 C values are observed (Figs.

  eliminate meteoric water as possible explanation for depleted δ 18 O values. Other depleted fluids cannot be excluded but temperature increase is the likely cause for the depleted δ 18 O values as argumented by the high Th values. Broad range of these salinity values may indicate the presence and variable mixing of multiple dolomitising fluids as observed in MVT-type mineralization (Leach et al., 2005). However some depleted values can also be possibly explained by contamination with calcite (TC) in the analysed samples (Figs. 11 A&B; Emrich et al., 1970); this latter cement (i.e. TC) having a relatively depleted δ 18 O signature. Two episodes of dolomitisation resulted in ferroan dolomite (CCD-I) and non-ferroan dolomite (CCD-II). The origin of the hypogene karstification before Fe-rich dolomitisation is unknown, but one possibility could be "cooling of formation waters" (Giles and de Boer, 1989). Initially, Fe-rich dolomitising fluids may have liberated from the adjacent basinal deposits and resulted in precipitation of CCD-I. For the second episode of dolomitisation, the circulating fluids exhibited very high temperature as evidenced by the Th values of the fluid inclusions (explaining also the highly depleted δ 18 O). In the Pozalagua quarry, the circulation of such high temperature fluids along faults/fractures which could be associated with flexuring in the Aptian-Albian limestone due to the presence of diapiric structures in the area (López-Horgue et al., 2010), succeeded in the formation of CCD-II. It can be speculated that such dolomitising fluids may be related to different sources, such as igneous activity and convective flow induced by the high temperature magmatic activity (Shah et al., 2010; Swennen et al., in press).

(

  CC-I & CC-II) and dolomitisation (CCD-I) show less depleted δ 18 O values, while the subsequent stage dolomite (CCD-II) and calcite (WC) exhibited highly depleted δ 18 O values, hence supporting at least two distinct sources of diagenetic fluids. δ 13 C values in the dolomites show slight depletion in line with the minor temperature related fractionation effect. Sr isotope confirms that the dolomitising fluids interacted with radiogenic lithologies (sandstones and shales). Depleted δ 18 O values (up to -20.22‰ V-PDB) and high TH values of the fluid inclusions (up to 200°C; Shah et al., 2010) indicate a hot source of dolomitising fluids. • Pervasive dolomitisation resulted from the circulation of basinal fluids, which likely evolved from the shales and clays situated in the deeper part of adjacent basin (Basque trough). NE-SW and NW-SE oriented faults and fractures provided pathways for fluids to dolomitise the early Albian carbonates.Second phase of high temperature, localized dolomitisation may be related to igneous activity and convective flow affecting mainly the Ranero area.

Fig. 1 .Fig. 2 .

 12 Fig. 1. A. Tectono-stratigraphic map of the Basque-Cantabrian basin, showing Tertiary to Paleozoic rocks and major faults. B. detailed stratigraphic succession and faults surrounding the study area (red rectangle showing Ranero, El-Moro and El-Mazo areas; modified from Gibbons, W. & Moreno, M. T. 2002 and Lopez-Horgue, M.A. et al., 2009).

Fig. 3 .

 3 Fig. 3. Stratigraphic cross-section (A-A' in Fig. 1B), showing unconformities and lateral variations from platform to basinal facies in the study area and its surroundings (modified from Rosales and Pérez-Garcia, 2010).

1 Fig. 5 .

 15 Fig. 5. Dolomite bodies in the Ranero area. (A) Color contrast between dolomite and limestone. (B) Pozalagua quarry. (C) General view of the Ranero dolomite body along the fault (dash line). (D) Dolomite vein in the host limestone, west of Pozalagua quarry.

Fig. 6 .Fig. 7 .Fig. 8 .

 678 Fig. 6. Dolomite bodies in the El-Moro area. (A) Multiple dolomite corridors (black bold arrows) in the El-Moro area, where various sections were studied and sampled. (B) Corridor along the fault in the El-Moro area with inset showing fault striations. (C) Dolomite corridor in the eastern part of El-Mazo area.

Fig. 9 .Fig. 10 .

 910 Fig. 9. Field and petrographic observations showing replacive dolomites. (A&B) Hand specimen showing interlayered dark grey and dirty white dolomite, while photomicrograph showing coarse and medium to fine crystalline dolomite exhibiting zebra texture. (C) laminated dolomitized internal sediments (DS). (D) Sphalerite mineralization observed in the ferroan dolomite (CCD-I).

Fig

  Fig. 4. Aerial 1 photograph showing the 2 location of the sampled 3 sections in the Ranero, 4 El-Moro and El-Mazo 5 areas, while inset shows 6 the geographic location 7 of the study area (red 8

Fig. 1 . 1 .

 11 Fig. 1.1. Schematic presentation of the major diagenetic realms, related processes and resulting typical rock-textures[START_REF] Nader | Petrographic and geochemical study of the Kesrouane Formation (Jurassic), Mount Lebanon: Implications on dolomitization and petroleum geology[END_REF].

Fig. 1 . 2 .

 12 Fig. 1.2. Schematic presentation of planar and nonplanar dolomite textures together with classification flow chart. All dolomites are classified as unimodal or polymodal (different crystal-sizes) and planar or nonplanar (after Sibley and Gregg, 1987).

Fig. 1 . 3 .

 13 Fig. 1.3. Porosity development with dolomitization (after Lucia, 1995).

Fig. 1 . 4 .

 14 Fig. 1.4. Simplified dolomitization models -grey areas represent dolomite bodies: A. Evaporative model; B. Seepage-reflux model; C. Mixing-zone model; D. Kohout convection model; E. Burial compaction model; F. Topographic recharge model; G. Tectonic squeeze model; H. Thermal convection model (modified from Gasparrini, 2003).

Fig. 1 . 5 .

 15 Fig. 1.5. Various fault patterns, which provide possible pathways for the circulation of hydrothermal fluids (modified fromDavies and Smith, 2006).

  1.5). Strike-slip faults are an expression of simple shear, while various components of it favour the hydrothermal fluid flow, mineralization/dolomitization and occurrence of dolomite in vertical pipes (Fig. 1.6). The fluid flow, in such contexts is episodic and associated with fluid pressure built-up and increase during times of no motion along the existing fault systems. It is believed, in a general consensus that upon excess of fluid pressures and their release as the fault is set into motion, the dolomitizing fluids produce cement (usually saddle dolomite) in a relatively short period of time, holding clasts of previous phases of dolomites and host rocks in open fractures.

Fig. 1 . 6 .

 16 Fig. 1.6. Block diagram showing the formation of hydrothermal dolomite along faults (Davies and Smith, 2006). Red arrows indicate dolomitizing fluid flow.

  , and the continental divergence culminated in the Late Jurassic. Subsequent rifting between the Iberian and European plates triggered the creation of the Bay of Biscay. During the Cretaceous, transtension across the Iberian and European margins, imposed by the counter-clockwise movement of the Iberian microcraton relative to the European plate, resulted in a sinistral shear along the Pyrenean fault zone. Transtensional shear in the Basque-Cantabrian Basin generated rifts and en-echelon pull-apart basins. The development of oceanic crust in the Bay of Biscay ceased by the early Campanian, as Iberia converged with Europe. During the Eocene, the main Pyrenean deformation period, Iberia was sutured to Europe. Finally, during the Lower Oligocene, the continuing convergence of Iberia with Europe caused the westward propagation of the Pyrenean deformation front into the Cantabrian region

Stage 4 :

 4 This stage starts with the reactivation of the Pozalagua Fault and was followed by a phase of dissolution that resulted in the development of open caves that were filled with breccias of host rock fragments. This marks the creation of an open fault system along which pulses of varied dolomitising fluids circulated. The coarse crystalline dolomite (CCD1) formed along the enlarged fault walls.

Stage 6 :

 6 Intensive jointing of the dolomite signals a new phase in which remaining and newly created cavities were cemented by coarse crystalline calcite (WC); their depleted δ 18 O-signature supports involvement of hot fluids.

Stage 7 :

 7 In contrast to the WC, Stage 7 is represented by the translucent calcite (TC); this is of meteoric origin and probably formed after uplift of the area that is reflected by speleothem development.

  in relative terms post-dating palaeokarst development during Stage 1. It is limited by two episodes of compactional stylolite development. López-Horgue et al. (2010) relate the origin of the dolomite to hydrothermal circulation in a strike-slip regime in Albian and Turonian times. These authors assume a relatively deep (at least 600 to 900 m) burial at the time of dolomitisation; this corresponds with a depth at which first generation compactional stylolites could have developed in fine-grained lithologies, before the formation of Stage 2 hydrothermal karst. The absence of any geopetal sedimentary fill in the resulting cavities supports the view that these formed in the burial realm. A second period of compactional stylolite development can be linked to the post-Turonian burial. Based on the burial curve of López-Horgue et al. (2010), the Pozalagua carbonates were buried >2000 m.

  who reported large scale fluid flow at the onset of foreland fold and thrust belt development. It is, however, not clear what specific fluid flow velocities are generated by this mechanism and the compressional setting differs from that of the extensional strike slip regime in the Pozalagua area during dolomitisation. A similar argument applies to topography driven flow. An alternative mechanism could relate to thermal convection of the dolomitising fluids

Figure 14

 14 Figure 14 illustrates the major diagenetic events of the Pozalagua Quarry. Fluid expulsion along the Pozalagua fault starts from Stage 2. Before that stage, limestones were already compacted and lithified, as shown by the development of bedding-parallel stylolites. Meteoric karst formation created

Stage 3 :Stage 4 :

 34 The development of zebra dolomites (ZD), consisting of alternating successions of medium crystalline dark grey dolomite and white to beige coarse crystalline dolomite, are interpreted in terms of expulsion of suprahydrostatic fluids along the Pozalagua Fault. Renewed fracturing along the Pozalagua Fault was followed by repeated and sometimes vigorous expulsion of hot fluids along the open fracture network generated and resulted in the deposition of coarse (centimetre) crystalline dolomite in veins and the formation of fragments of such veins (CCD1). Locally geopetal sediments overlie cements. The final fill with blue-grey dolomite (BGD) consists of (at least) three cement generations. It comprises centimetre to decimetre-size fibrous crystals, aligned normal to the substrate, and contains scattered centimetre to decimetre-sized rounded host-rock fragments that apparently 'float' in the dolomite. The dolomite is best explained by a replacement of precursor speleothems. Locally enigmatic elongated relict crystals (ERC), now composed of dolomite, are overlying the BGD dolomite; they normally form fan-like clusters radiating upwards. However, they have been extensively recrystallised and it is difficult to deduce either their original morphology or mineralogy, although calcite or aragonite are possible precursor mineralogies; their development can only be explained as reflecting crystallisation in an open cave system.

Stage 6 :

 6 White, coarse-crystalline calcite, that is neither jointed nor fractured, includes cleavage twins and is interpreted as forming from hot fluids during burial. Stage 7: Translucent calcite, lacking cleavage twins in which depleted δ 13 C signatures imply the onset of telogenetic conditions. The cyclic nature of the processes could reflect earthquake-induced expulsion of dolomitising fluids along the Pozalagua Fault. It is likely that fluid expulsion occurred already during the Late Albian, based on tectonic, hydrothermal, magmatic and metamorphic activity elsewhere in the Basque-Cantabrian Basin. 'Stage 2' cavity development and subsequent calcite cementation post-dates the first compactional stylolitisation. A second period of compactional and tectonic stylolitisation post-dates the coarse crystalline dolomites (CCD2) of 'Stage 5', and the diagenetic products described therefore formed between the Late Albian and Eocene. Many diagenetic processes may be related to Late

FiguresFigure 1 :

 1 Figures

Figure 2 :

 2 Figure 2: (A) Map showing the location of the study area between Bilbao and Santander in Northern Spain (modified after Grandia et al., 2003). (B) Detail of the study area with indication of the major faults and the location of the Pozalagua Quarry near the village of Ranero, as well as other locations where hydrothermal dolomites occur ('M' Matienzo; 'B' Beuras; 'E' El Moro & El Mazo) (map from

Figure 3 :

 3 Figure 3: The main Cretaceous succession of the Basque-Cantabrian Basin with times of tectonic pulses (TP) (modified after García-Mondéjar et al., 2005), and indications of the stratigraphic interval exposed in the Pozalagua Quarry.

Figure 4 :

 4 Figure 4: View of the area between Ramales and Ranero with exposed slope carbonates. Basinal deposits form the foreground and platform carbonates in the background. Major faults filled with brown coarse crystalline dolomite positioned in slope carbonates are indicated with arrows. Note the area of Figure 5 outlined in the left corner.

Figure 5 :

 5 Figure 5: Platform to slope section exposed near Ramales, about 10 km west of the study area. Note the reverse and high angle faults trending parallel to the slope-basin margin. Note that these do not correlate with the Pozalagua Fault that is perpendicular to the platform edge.

Figure 6 :

 6 Figure 6: Cut faces of the Pozalagua Quarry wall (east side). (A) Dark grey bioclastic to intraclastic wackestone with large fossil fragments. Most of the fragments are difficult to identify, due to corrosion and recrystallisation. A colonial coral 'C' is present in the centre of the picture. Note the stylolites 'St' and calcite cemented vein 'V'. (B) Conglomeratic limestone with centimetre rounded monomict clasts and fossil debris. Micrite dominates between the clasts but locally some fibrous 'F' and equant 'E' calcite cement is present. The dip is indicated with respect to geopetal fillings. (C) Between the sub-rounded clasts of bioclastic wackestone to mudstone two cements are present, i.e. several generations of fibrous calcite cement 'F', overlain by equant white calcite cement 'E'. A thin

Figure 7 :

 7 Figure 7: Cut faces of the Pozalagua Quarry wall (East side). (A) Detailed view of the fill in cavernous slope limestones. A mudstone fragment in the centre of the picture containing a stylolite 'St' is encased in 'CC1' and 'CC2' calcite cements. (B) Irregular, lobate contact between grey limestone 'L' and coarse crystalline dolomite. In the latter lithology separate generations of zebra 'ZD' and coarse crystalline dolomite 2 'CCD2' can be recognised. Within the latter some residual porosity (see arrows) is present. (C) Red brown millimetre-laminated dolomite fragments. Note the 'jigsaw' fit of adjacent fragments indicating only minor displacement between them. The fragments are cemented by blue grey zoned dolomite 'BGD'. (D) Detail of red brown millimetre-laminated dolomite sediment enclosing nodular fragments 'F'.

Figure 8 :

 8 Figure 8: Microphotographs of characteristic diagenetic phases (TL: transmitted light; PL: crossed polarising light). (A) Contact between recrystallised limestone (now microsparite, 'M') with relict of a stylolite 'St' and coarse crystalline calcite 1 'CC1'. Notice the presence of cleavage twins in the calcite (TL). (B) Detail of replacive coarse crystalline dolomite 'RCCD' with in the middle the presence of authigenic clays 'Cl' and Fe-oxy/hydroxides 'Fe-ox' that are relicts after pyrite (PL). (C) Contact between brown dedolomite rim (Dedol) and coarse crystalline blue grey dolomite (BGD), which clearly displays an undulose extinction (PL). (D) Detail of dedolomitised brown rim. Notice that the dedolomitisation (Dedol) is fabric selective (TL). (E) Contact between zoned coarse crystalline dolomite 2 'CCD2' and white calcite cement 'WC'. Notice the presence of cleavage twins in the calcite (PL). (F) Contact between zoned coarse crystalline dolomite 2 'CCD2' and transparent calcite cement (TC). Notice that the dolomite is corroded (see arrows) and that no cleavage twins occur in the calcite (TL).

Figure 9 :

 9 Figure 9: Cut faces of the Pozalagua Quarry wall (South side). (A) General relationship between laminated replacive coarse crystalline dolomite 'RCCD' and coarse crystalline dolomite 2 'CCD2'. Note the relict zebra dolomite 'ZD' in the lower part of the picture, and the intense fracturing of CCD2. (B) Detail of contact between laminated replacive coarse crystalline dolomite 'RCCD' and coarse crystalline dolomite 2 'CCD2' with local development of curve-shaped dolomite 'CSD' at the contact and within the laminated dolomite in the lower part of the picture. The arrow indicates the orientation of the picture. Hammer for scale. (C) Detail of zebra dolomite with typical alternations of dark grey to grey fine-crystalline 'a' bands and beige coarse crystalline 'b' bands followed by coarse crystalline beige to pinkish 'c' dolomite bands. Note the typical millimetre to centimetre displacements between the bands (some of which are indicated by arrows).

Figure 10 :

 10 Figure 10: Cut faces of the Pozalagua Quarry wall (A) with schematic drawing (B) (Northern side). A variety of dolomite phases are visible. In the centre laminated dolomite 'LD' and to the upper left recrystallised zebra dolomite 'R(ZD)' are visible with laminated replacive coarse crystalline dolomite 'RCCD'. These are cemented in the centre of the picture by coarse crystalline dolomite 1 'CCD1' overlain by blue-grey zone dolomite 'BGD' that is overgrown locally by elongated relic crystals 'ERC' and finally cemented by coarse crystalline dolomite 2 'CCD2'. Note that in the laminated dolomite 'LD' a massive fine crystalline dolomite vein 'MFD', locally transitional to coarse crystalline dolomite 1 ('CCD1', encircled area). No clear margin exists between CCD1 and MFD. A prominent brown-stained rim surrounds the fragments and is prominent at the contact with the CCD1 (white arrow) and between the MFD vein and the host rock fragment (black arrow). Notice the replacive coarse crystalline dolomite 'RCCD' in the upper part of the picture.

Figure 11 :

 11 Figure 11: Cut faces of the Pozalagua Quarry wall [eastern and northern side, respectively' (A) to (E) and (F)]. The top of this picture is indicated by the thick white arrow in (A), (D) and (E). (A) Large dolomite fragment consisting of relict replacive coarse crystalline dolomite 'RCCD' and coarse crystalline dolomite 2 'CCD2' (white areas) is surrounded by a brown-stained rim (black arrows) and overlain by coarse crystalline dolomite 1 'CCD1'. The latter has been recrystallised and is replaced by massive fine crystalline dolomite 'MFD'. Thin geopetal sediment 'GP' covers the CCD1 crystals, and is overlain by blue-grey zoned dolomite 'BGD', elongated relict crystals 'ERC' and coarse crystalline dolomite 2 'CCD2'. (B) Detail of the contact between two recrystallised zebra dolomite fragments (the fragment on the left also contains coarse replacive crystalline dolomite 'RCCD', and the white spots are 'CCD', cemented by blue-grey zoned dolomite 'BGD' (with clear brown zones) and coarse crystalline dolomite 2 'CCD2'. Note the characteristic brown rim at the contact between the host rock and fracture fill (see arrows). (C) Detail of contact between grey limestone 'L' on the right, and heavily recrystallised zebra dolomite 'ZD' to the left. The central vein is filled with blue-grey zoned dolomite 'BGD' containing rounded limestone and dolomite clasts with brown rims (black arrows),

Figure 12 :

 12 Figure 12: Cut face of the Pozalagua Quarry wall [eastern and northern side, respectively, (A) and (B) to (C)]. A. Large scale view of zebra dolomite 'ZD' to the left, cut by massive fine crystalline dolomite veins 'MFD' and coarse crystalline dolomite 2 veins 'CCD2V' passing in the right part of the picture into coarse crystalline dolomite 2 cement and replacive dolomite 'CCD2' with apparently floating relict fragments 'FF'. In the largest relic fragments some patches of replacive coarse crystalline dolomite 'RCCD' can be seen. Note the extensive jointing and fracturing of the coarse crystalline dolomite 2. (B) Detail of coarse crystalline dolomite 2, with relict zebra dolomite 'RZD' cross-cut by sub-vertical and inclined stylolites 'St'. (C) Detail of replacive coarse crystalline dolomite 'RCCD' cut by bedding-parallel stylolite 'St' with curve-shaped dolomite 'CSD' at the transition to coarse crystalline dolomite 2 'CCD2'.

Figure 13 :

 13 Figure 13: Paragenetic sequence as deduced from outcrops in the Pozalagua Quarry.

Figure 14 :

 14 Figure 14: Schematic diagram illustrating the most important diagenetic stages in the Pozalagua Quarry (for explanation see text). Abbreviations: BGD -blue-grey dolomite; CCD -coarse crystalline dolomite; RCCD -replacive coarse crystalline dolomite; E -equant cement; ERC -elongated relict crystals; F -fibrous cement; HR -host rock; LD -laminated dolomite; PK -palaeokarst; TCtransparent crystalline calcite; WC -white crystalline calcite; ZD -zebra dolomite.

  ). During Albian-Santonian times Iberia drifted southwestward along NW-SE strike-slip faults. The Late Cretaceous-Palaeogene interval is characterised by a widespread thermo-tectonic subsidence and the development of extensive marine depositional systems. Inversion of the BCB took place from late Eocene to early Oligocene times. The inverted BCB is the western branch of the Pyrenean folded chain. The study of the sedimentary successions (e. g., thickness variations, facies changes, sedimentary offsets) and preserved kinematic indicators has permitted the reconstruction of the synsedimentary fault activity. The BCB records a thick sedimentary succession, which is up to 14 km in the most subsiding areas in the middle of the Basin and dominated by Mesozoic rocks. Important synsedimentary fault activity during the Aptian and Albian led to differential subsidence. Some of the main synsedimentary faults in the BCB area are the E-W trending Cabuérniga Fault to the south of the Ranero area, the NW-SE trending Bilbao and Ruahermosa Faults to the north of the Ranero area and the N-S trending Ramales

Stage 3

 3 is divided by one of the main unconformities of the BCB associated with a hiatus comprising the Middle Albian in shallow platforms (e. g.,López-Horgue et al., 2000) and a relatively thin sedimentary record of the basal Middle Albian in the deeper troughs. Carbonate sedimentation was mainly micritic with development of carbonate microbial mounds in the reef margin and overall early diagenetic lithification[START_REF] López-Horgue | El Aptiense-Albiense de Karrantza-Lanestona (Bizkaia y Cantabria)[END_REF]. Unconformities and early synsedimentary fractures affecting limestones involve diagenetic alteration features such as dissolution, meteoric cementation and alteration of the marine cements(López-Horgue et al., 2010).

  Dolomites and Albian host limestone crop out in separate sites (e.g. Ranero, Breñas, Asón estuary; Fig. 5). In addition, in the surroundings of Matienzo (situated east of the Breñas massif) Aptian limestones host a HTD body of a considerable size. The origin of the HTD is related to the same faults and the HTD have similar paragenetic sequences (López-Horgue et al., 2010). In the Ranero area an angular unconformity separates gently dipping (10-30º to the NE) Albian carbonates from underlying Valanginian to Aptian sedimentary units. This early Albian angular unconformity corresponds to the almost complete erosion of the underlying Aptian carbonates. Where preserved in the Ranero area, these Aptian carbonates contain small patches of dolomite close to the Albian basal unconformity. A drowning unconformity separates the Albian limestones from younger Albian siliciclastics.

  Early and burial diagenetic cements (cathodoluminescence zones Z1-Z7, cf.Rosales & Perez-Garcia, 2010) are basically fabric sensitive. Diagenetic phases associated with hydrothermal fluids, are essentially fabric destructive at the grain scale and developed along NW-SE trending fracture systems. They generated both replacive dolomites and cements. Hydrothermal cements fill the remaining void space resulting from the combination of fracturing, palaeokarst development and hydrothermal enlargement of former cavities. The sequence of hydrothermal precipitates is illustrated in Figure 7; it starts with zone Z8 of Rosales & Perez-Garcia (2010) and occurs after phase 17 of López-Horgue et al. (2010), including the following phases in chronological order:

  ), successive hydrothermal cements have distinctive isotopic and chemical characteristics (Fig. 8). All these cements have low to very low δ 18 O values (with respect to the original, Albian seawater signature), suggesting precipitation from hot fluids. Besides, δ 18 O values show a decreasing trend along the sequence from CC-I & CC-II (-10 to -12‰) to CCD-I (-12 to -16‰), CCD-II (-17 to -19‰) and WC (-16 to -18‰). Host limestones show variably depleted δ 18 O

FiguresFigure 1 .

 1 FiguresFigure1.A panoramic view of the Pozalagua quarry (Ranero, NW Spain) with worldclass exposure of hydrothermal dolomites (index map for location of the Ranero study area).

Figure 2 .

 2 Figure 2. Synsedimentary structures of the Basque Cantabrian Basin (BCB) during Aptian-Albian times. No palinspastic restoration. Modified from Garcia-Mondéjar et al. (2004b).

Figure 3 .

 3 Figure 3. Paleogeographic map of the Basque Cantabrian Basin (BCB) during early Albian times. Studied area is highlighted. Modified from Garcia-Mondéjar et al. (2004b).

Figure 4 .

 4 Figure 4. a) Simplified geological map of the Basque-Cantabrian Basin. The studied area lies within a zone where main structures and faults show a strike change from NW-SE to W-E. A-A´ indicates the strike of b-the Stratigraphic cross-section shown in b. b) Stratigraphic cross-section of the Valanginian-Turonian interval in the palaeogeographical area of the Albian Ramales Carbonate Platform and its correlative subsiding basinal area to the East. The main dolomite host is the Early Albian limestone unit. No palinspastic restoration.

Figure 5 .

 5 Figure 5. Main tectonic structures from the study area showing an arrangement due to a synsedimentary strike-slip play. The thick lines (faults) and fold-axis represent main structures that controlled the dolomitisation process. The main dolomite bodies are represented in red colour. Ruahermosa and Cabuérniga faults generated an overstep on the eastern block of the Ramales fault.

Figure 6 .

 6 Figure 6. Photographs of the Ranero dolomite vein-body. A: View of the upper part of the dolomite body. B: Calcite dyke-like features in the lower end of the dolomite body, cross-cutting basin-sediments (calciturbidites). C: Dolomite/limestone boundary (parallel to S 1 joint set). D: Jointed dolomite with pores arranged along S 1 planes forming a protozebra texture. E & F: Small scale en echelon shear-joints filled with saddle dolomite, disposed in the fringe of the main dolomite body.

Figure 7 .

 7 Figure 7. Paragenetic sequence of cements, Pozalagua quarry. A: cavity filling calcites (CC-I, CC-II) cut by non ferroan dolomite (CCD-II), quarry floor; note that CCD-II does not replace the limestone. B: Fe-rich dolomite stockwork, CCD-I vertical vein and coeval zebra, quarry top level. C: large cavities filled by CCD-I precipitates in host zebras, plugged by CCD-II, NE corner. D: CCD-II (non ferroan) dolomites invading and replacing zebras, northern wall; note the older vertical CCD-I vein with its distinctive brown rim and the non-symmetrical shape of CCD-II veins, suggesting replacement. E: pyrite and white calcite (WC) cementing fractured dolomite (CCD-I, CCD-II veins), northern wall. F: layered dolomite (internal sediment) in pockets hosted in CCD-II. Scale bar is 20 cm long.

Figure 8 .

 8 Figure8. Geochemical attributes of limestones, cements and replaced rocks. Samples are classified as a function of paragenetic stage for minerals (filled symbols) or lithotype for rocks (open symbols). Colours refer to sampling locations: the Quarry stands for the stratigraphically deepest outcrops (road breccia and quarry) and main body for the upper levels (fault and plateau). A, B, C: data from microdrills or whole rocks; D: microprobe data. The FeO content of carbonate (FeO* wt%) is estimated by correcting the bulk Fe content from a silicate contribution having the same Fe/Al ratio as claystone.

Figure 9 .

 9 Figure 9. BSE images of hydrothermal precipitates and replacive dolomites. A: composite vein cutting across the limestones, road breccia. Note the symmetrical structure of vein fillings, the incipient dolomitisation of limestone, and the selectively dedolomitized Fe-rich rim. B: dark band in zebra dolomite. C & D: dolomitized internal sediments, Pozzalagua Quarry. Note the idiomorphic contour of dolomite crystals against silicates.

Figure 10 .

 10 Figure 10. Spatial distribution of helium porosity values of the Pozalagua (Ranero) HTD Body. The smallest and largest circles correspond to 1.8% and 12.1% porosity, respectively.

Figure 11 .

 11 Figure 11. Spatial distribution of Klinkenberg permeability values of the Pozalagua (Ranero) HTD Body. The smallest and largest circles correspond to 0.01D and 17.4D porosity, respectively.

Figure 12 .

 12 Figure 12. Overview of the main dolomite types (based on their texture and pore type). A: matrix dolomite, characterised by dark grey, fine crystalline dolomite. B: µCT scan showing the presence of small pores in matrix dolomites. C: Coarse crystalline cement dolomite. D: µCT scan of cement dolomite shows the relatively tight character of the dolomite type. E: Zebra dolomite consisting of alternating layers of fine crystalline, dark and coarse crystalline, light dolomite. F: µVT scan of a zebra dolomite showing the presence of aligned and closely spaced pores (~1 cm).

Figure 13 .

 13 Figure 13. Schematic representation of the dolomitisation model for the Ranero area (after López-Horgue et al., 2010) featuring conceptually the flow paths of the pervasive, ferroan (compactional) CCD-I and localized non-ferroan (diaper-associated) CCD-II dolomitizing fluids.

Figure 1 Figure 2 Figure 3

 123 Figure 1

Figure 4 Figure

 4 Figure 4

  Stable isotope composition in the Ranero breccia site. The host limestone shows depleted δ 18 O values,

	while white calcite (WC) exhibited highly depleted δ 18 O values. The dedolomitized phase indicates depleted δ 18 O and Fig. 4. 37. Sr isotopic composition of various dolomite and calcite phases. Note that the late stage calcite phase
	δ 13 C values. (WC) exhibited highly radiogenic values as compared to other phases.
	c) STRONTIUM ISOTOPE ANALYSES
	The 87 Sr/ 86 Sr Vs δ 18 O cross plot (Fig. 4.37) shows that 87 Sr/ 86 Sr ratio of the host limestone
	corresponds to 0.70741, which lies within range (0.70731 to 0.70745) of the 87 Sr/ 86 Sr signatures of
	the primary marine carbonate from lower to upper Albian sequence (McArthur et al., 2001). The
	87 Sr/ 86 Sr values of pore-filling calcite (CC-I and CC-II) range from 0.70844 to 0.70852, while
	ferroan rich dolomite (CCD-I) exhibits 87 Sr/ 86 Sr values from 0.70827 to 0.70847. In contrast, the
	87 Sr/ 86 Sr values of late stage non-ferroan dolomite (CCD-II) ranges from 0.70813 to 0.70826 (Fig.
	4.37). The above stated data indicate that various dolomite and calcite phases are tightly clustered
	and exhibit higher Sr 87 /Sr 86 values (Fig. 4.37). Thus this increase in Sr 87 /Sr 86 ratios of the dolomite
	and calcite phases with respect to that of the original seawater Sr-curve, suggest that the fluids
	interacted with the radiogenic lithologies (sandstones, shales).

Table - 4.I. Various

 - sketches showing the distribution of dolomite and calcite phases in studied parts of the Ranero area.

Fault-related hydrothermal dolomites in Cretaceous carbonates (Cantabria, northern Spain): Results of petrographic, geochemical and petrophysical studies MUMTAZ

  -RE LA TED HY DRO THER MAL DO LO MI TES IN CRE TA CEOUS CAR BO NA TES (CAN TA BRIA, NOR THERN SPAIN) M. SHAH 1 , FADI H. NADER 1 , JULIE DEWIT 2 , RUDY SWENNEN 2 and DANIEL GARCIA 3 Key-words. -Aptian-Albian, HTD, Stable iso to pes, Fluid in clu sions, He-po ro si ty, Spain.Ab stract. -The pres ent con tri bu tion doc u ments NW-SE ori ented fault and frac ture re lated dolomites in Aptian-Albian car bon ates (Karrantza area; north ern Spain). Field ob ser va tions re vealed two main do lo mite types, namely mas sive and ze bra do lo mite. Tex tur ally, these do lo mite types are mostly pla nar and nonplanar and vari ably re worked by sub se quent al ter ations, which re sulted in neomorphism and recrystallization, cataclastic de for ma tion and cal cite fill ing of dolostones. Petrographic and geo chem i cal stud ies dem on strate the su per po si tion of dif fer ent diagenetic events, which were in volved in multiphase dolomitization. Sev eral phases of hy dro ther mal cal cite ce ment pre-and post-date the dolomitisation events. Mas sive dolomites show over lap ping sta ble iso to pic ra tios rang ing from -16.9 to -8.9‰ (␦ 18 O V-PDB), and -2.6 to +3.1‰ (␦ 13 C V-PDB). Ze bra do lo mite shows more de pleted val ues of ␦ 18 O and ␦ 13 C as com pared to mas sive dolomites (␦ 18 O: -18.1 to -15.2‰V-PDB and ␦ 13 C: -8.1 to +1.6‰ V-PDB). Fluid in clu sion anal y ses show ho mog e ni za tion tem per a ture (Th) val ues from 120 to 200 o C and es ti mated sa lini ties range be tween 10 and 24 eq. wt.% NaCl. Both do lo mite types are nearly stoichiometric, with CaCO 3 val ues be tween 50 and 52 mole% . Lime stones close to the dolomites show de pleted ␦ 18 O val ues (sim i lar to those of the dolomites), im ply ing iso to pic re set ting dur ing dolomitization. Recrystallization ap pears to have de creased the bulk po ros ity val ues in the in ter lock ing nonplanar do lo -

123

SHAH M. M. et al.

FAULTmite (with neg li gi ble po ros ity), while late-stage cal cite ce ments oc clude most of the re main ing po ros ity, and make petrophysical mea sure ments dif fi cult to in ter pret. The pos si ble source of dolomitizing flu ids can be deeply bur ied Tri assic evaporitic strata in the intra-plat form ba sin, Keuper salt diapirs and/or Mg-bear ing ig ne ous rocks.

Dolomites hydrothermales

liées aux failles dans les carbonates du Crétacé (zone Cantabrique, Espagne du Nord) : caractéristiques pétrographiques, géochimiques et pétrophysiques

Mots-clés. -Aptien-Albien, HTD, Iso to pes sta bles, Inclu sions flui des, Po ro si té He, Espagne.

Ré su mé. -La pré sente con tri bu tion dé crit des do lo mies liées à des fail les et des frac tu res NW-SE dans les car bo na tes d'âge ap tien-al bien (Ka rant za, Espagne du nord). Deux ty pes prin ci paux de do lomie, mas sive et ze bra, sont ob ser vés. Ces do lo mies pré sen tent des tex tu res pla nai res ou non pla nai res, plus ou moins af fec tées par des al té ra tions su per posées, in dui sant une re cris tal li sa tion néo mor phique, une ca ta clase et un rem plis sage cal ci tique tar dif. Les don nées pé trogra phi ques et géo chi mi ques mon trent la su per po si tion de plu sieurs sta des dia gé né ti ques et une do lo mi ti sa tion mul ti phasée. Plu sieurs sta des de cé men ta tion cal ci tique pré cè dent et sui vent la for ma tion des do lo mies. Les do lo mies mas si ves ont une gamme de rap ports iso to pi ques étendue de -16.9 à -8.9‰ (d 18 O V-PDB) et de -2.6 à +3.1‰ (d 13 C V-PDB). Les do lo mies ze bra ont des com po si tions iso to pi ques re la ti ve ment plus lé gè res (d 18 O de -18.1 à -15.2‰V-PDB et d 13 C de -8.1 à +1.6‰ V-PDB). Les in clu sions flui des pré sen tent des tem pé ra tu res d'ho mo gé néi sa tion (T h ) de 120 à 200°C et des sa li ni tés entre 10 et 24 % éq. NaCl. Les deux ty pes de do lomie sont pro ches de la stoe chio -

Table I .

 I Major and trace element geochemistry, O-and C-stable isotope, Sr-isotope and stoichiometric data from the Ranero and El-Moro areas.

) TiO2 (%) Al2O3 (%) Fe2O3 (

	Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)	1.37 0.00 2.25 0.00	5.02 0.00 3.59 0.00	1.59 0.00 6.72 0.00	0.76 0.96 1.17 0.00 2.86 0.00 0.99 0.00	2.79 0.00 0.86 0.00			2.74 0.00 2.13 0.00 1.88 0.00 0.66 0.00		2.06 0.71 2.20 0.00	3.00 0.00 1.30 0.00	3.49 1.23 16.12 0.00 2.18 0.00 2.56 0.00	1.28 0.00 0.48 0.00			2.88 2.04 9.50 0.00	3.23 0.00 6.85 0.00	1.86 0.00 4.78 0.00 1.42 0.00 0.55 0.00	1.88 0.88 7.84 0.00		2.80 0.63 8.56 0.00		2.07 2.22 4.17 0.00		3.07 0.25 3.65 0.00	2.14 0.00 1.53 0.00	2.02 0.00 3240 0.00	2.32 0.90 0.90 0.00 1.14 0.00 33.70 0.00	4.39 0.00 1.95 0.00	1.78 0.35 1.09 0.00	1.34 0.00 0.75 0.00 0.00 0.00 153.1 0.00	2.09 0.00 0.92 0.00	2.25 1.15 6.67 0.00 3.09 14.22 2.12 7.00	4.00 7.38 1.47 3.60	2.40 0.91 6.48 0.00 2.34 6.60 1.80 5.60	1.96 8.00 1.58 3.60	2.00 8.59 1.46 3.80	3.12 0.00 1.38 0.00 0.68 1.52 2.01 0.80	1.83 0.34 5.84 0.00 0.46 0.91 2.41 0.00	2.65 0.00 2.39 0.00 1.27 0.87 0.70 0.00	1.84 0.15 4.36 0.00 3.06 2.68 2.60 3.30	3.27 1.78 2.21 1.80	3.10 0.85 5.69 0.00 1.68 1.03 0.84 0.90	1.42 0.59 6.02 0.00 1.82 0.81 0.81 0.00	1.30 1.10 6.07 0.00 1.68 0.93 0.70 0.00	2.53 0.00 3.90 0.00	9.67 0.68 2.80 1.30	1.33 0.00 1.77 0.00	1.46 0.00 1.24 0.00	1.07 0.00 2.68 0.00	1.09 0.68 11.32 0.00	3.55 0.00 3.62 0.00 0.80 0.45 3.02 0.00	0.31 0.15 2.30 0.00	0.90 0.25 1.93 0.00	3.60 0.00 1.51 0.00 1.43 0.00 11.26 0.00	1.49 0.40 2.50 0.00	0.94 0.00 0.51 0.00 1.35 0.49 2.26 0.00	2.80 0.00 1.80 0.00 0.78 0.45 1.14 0.00
	SiO2 (%) TiO2 (%) Al2O3 (%) Fe2O3 (%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) SiO2 (%	0.00 0.02 0.07 0.02 19.53 29.40 0.02 0.00 0.00 44.38 0.17 2.00 0.35 20.8 0.00 56.16 0.00	0.00 0.00 0.01 0.01 0.02 0.37 53.90 0.01 0.01 0.00 42.70 0.37 0.14 0.29 1.6 0.00 154.16	0.00 0.00 0.04 0.21 0.03 19.54 30.00 0.02 0.01 0.00 44.86 0.22 1.04 0.28 2.8 0.00 38.93	0.04 0.00 0.08 1.07 0.05 20.37 30.53 0.02 0.01 0.01 45.76 0.17 0.58 2.42 4.8 1.40 28.80 0.01 0.33 0.18 0.01 20.00 28.80 0.04 0.00 0.01 44.42 0.49 2.29 1.61 10.1 0.00 30.59 0.00	0.00 0.03 0.47 0.04 20.89 29.14 0.03 0.00 0.00 45.66 0.50 7.87 1.39 4.8 0.00 31.78 0.00			0.00 0.00 0.04 1.12 0.06 19.80 30.52 0.03 0.01 0.00 45.56 0.28 0.37 0.11 3.5 0.00 45.42 0.00 0.02 0.13 0.02 20.24 28.11 0.03 0.00 0.00 44.15 0.28 2.04 0.35 2.6 0.00 27.03 0.00		0.14 0.00 0.14 0.06 0.01 0.67 55.23 0.02 0.01 0.02 42.71 0.23 9.28 6.14 3.5 0.70 407.47	0.03 0.76 0.30 0.01 20.90 27.24 0.04 0.02 0.00 44.18 0.61 11.56 4.82 6.7 0.00 24.20 0.00	0.17 0.01 0.20 1.55 0.08 3.72 51.73 0.03 0.15 0.01 42.54 0.58 8.64 2.27 4.4 1.20 21.36 0.00 0.03 0.57 0.03 19.94 28.96 0.04 0.00 0.00 44.48 0.24 1.84 0.30 3.4 0.00 39.07 0.00	0.00 0.03 0.48 0.03 20.09 28.84 0.04 0.00 0.00 44.56 0.21 0.65 3.02 2.2 0.00 31.51 0.00			0.22 0.01 0.21 1.38 0.05 13.59 39.79 0.02 0.02 0.02 44.02 0.81 11.88 5.64 4.3 0.70 28.60	0.00 0.00 0.09 0.16 0.03 19.77 29.59 0.03 0.01 0.02 44.79 1.18 8.75 4.84 19.7 0.00 42.24	0.00 0.00 0.10 1.26 0.06 16.50 33.45 0.02 0.01 0.01 44.26 0.46 5.64 1.45 6.7 0.00 32.85 0.00 0.02 0.20 0.02 20.81 28.52 0.02 0.00 0.00 45.09 0.25 1.76 0.46 2.3 0.00 35.65 0.00	0.17 0.00 0.19 1.64 0.05 14.07 39.70 0.02 0.01 0.02 43.97 0.23 7.97 1.86 5.1 0.60 35.51		0.13 0.00 0.13 2.17 0.09 15.90 35.81 0.02 0.01 0.01 44.68 0.26 5.31 2.16 3.6 0.40 31.37		0.25 0.01 0.24 1.35 0.04 18.75 33.79 0.02 0.01 0.02 45.31 0.28 9.95 3.40 4.9 0.50 29.53		0.00 0.00 0.05 0.38 0.03 18.89 36.34 0.02 0.00 0.00 42.89 0.34 4.76 1.96 9.6 0.10 56.03	0.00 0.00 0.01 0.06 0.02 18.87 30.35 0.01 0.01 0.00 44.41 0.23 2.29 0.53 5.3 0.00 53.13	0.06 1.43 0.59 0.02 7.98 12.73 0.03 0.37 0.10 18.69 1.13 10.24 47.25 1529 0.00 3595 0.00	0.05 0.00 0.10 0.19 0.02 21.78 34.27 0.03 0.00 0.02 41.90 0.39 9.29 2.67 3.4 0.10 32.73 0.00 0.03 0.07 0.02 20.77 29.62 0.03 0.01 0.00 45.91 0.21 1.06 0.52 7.2 0.00 31.24 0.00	0.00 0.00 0.34 0.15 0.02 20.31 29.99 0.03 0.01 0.05 45.70 0.41 6.37 1.55 4.5 0.00 57.15	0.00 0.00 0.04 0.19 0.02 22.32 35.31 0.02 0.00 0.00 41.05 0.11 2.93 1.21 2.3 0.40 36.94	0.00 0.00 0.01 0.06 0.01 17.04 23.17 0.02 0.00 0.00 36.78 0.18 1.87 0.36 1.8 0.00 28.07 0.00 0.01 0.00 0.00 0.23 53.87 0.00 0.01 0.00 42.52 0.43 0.47 0.44 3.7 0.00 408.49 0.00	0.00 0.00 0.02 0.13 0.02 20.27 30.36 0.03 0.01 0.01 45.94 0.49 3.37 2.37 2.9 0.00 36.51	0.01 0.00 0.05 0.60 0.03 17.32 38.02 0.01 0.01 0.01 42.72 0.48 8.59 4.06 4.0 0.50 36.77 0.06 2.57 1.84 0.01 19.39 30.75 0.03 0.02 0.06 41.02 1.36 19.89 14.93 8.1 1.40 21.10 3.47	0.03 0.41 0.92 0.01 21.08 31.90 0.03 0.02 0.03 44.39 0.57 5.89 5.92 4.3 1.40 25.40 0.57	0.13 0.01 0.20 0.28 0.02 20.96 34.08 0.03 0.01 0.01 42.91 0.70 7.50 3.34 6.3 0.50 42.22 0.03 0.57 1.11 0.01 21.11 31.88 0.03 0.02 0.03 44.49 0.67 7.98 6.29 6.9 1.40 24.90 0.81	0.04 0.94 0.88 0.01 20.80 30.37 0.03 0.02 0.03 44.25 0.68 7.79 7.82 11.2 1.40 23.60 1.32	0.04 1.08 0.95 0.01 21.00 30.52 0.03 0.02 0.04 43.77 0.68 8.56 8.55 6.9 1.40 23.00 1.53	0.00 0.00 0.05 0.20 0.02 19.22 29.53 0.03 0.01 0.00 44.15 0.29 1.50 0.92 3.4 0.00 36.50 0.00 0.02 0.04 0.01 0.26 56.06 0.01 0.01 0.00 42.37 0.11 0.39 0.54 2.9 1.20 372.5 0.00	0.00 0.00 0.07 0.20 0.02 13.14 43.10 0.01 0.00 0.01 41.74 0.33 2.66 1.34 16.0 0.10 122.45 0.00 0.03 0.05 0.01 0.39 56.96 0.01 0.01 0.00 42.38 0.11 0.47 0.55 2.9 1.20 349.2 0.00	0.00 0.00 0.02 0.14 0.02 18.61 30.28 0.01 0.01 0.01 44.07 0.24 2.41 1.17 10.2 0.00 59.45 0.00 0.06 0.05 0.01 20.30 32.32 0.03 0.01 0.00 45.53 0.11 0.70 0.97 2.4 1.00 28.10 0.01	0.04 0.00 0.08 0.06 0.01 0.52 57.05 0.01 0.00 0.03 41.66 0.34 1.45 1.36 14.8 0.50 237.93 0.01 0.37 1.40 0.03 18.70 32.44 0.02 0.02 0.02 45.59 0.38 2.76 4.43 8.4 1.40 24.50 0.44	0.01 0.23 1.16 0.03 19.57 34.40 0.02 0.02 0.06 45.85 0.41 2.15 4.36 5.9 1.40 25.20 0.26	0.05 0.00 0.08 0.16 0.01 0.65 55.89 0.01 0.01 0.01 42.15 0.64 5.37 2.25 35.0 0.30 241.31 0.00 0.06 0.08 0.01 21.66 32.28 0.03 0.01 0.00 45.43 0.16 1.06 1.07 5.7 1.10 39.00 0.00	0.06 0.00 0.08 0.08 0.01 1.09 55.33 0.01 0.01 0.01 42.35 0.37 2.83 1.96 4.4 0.40 283.61 0.00 0.06 0.07 0.01 21.81 32.00 0.03 0.01 0.00 45.45 0.16 1.00 1.07 4.3 1.00 41.50 0.02	0.10 0.00 0.04 1.05 0.04 21.67 31.86 0.02 0.01 0.01 45.30 0.17 3.19 55.50 0.0 0.70 28.26 0.00 0.06 0.03 0.01 21.52 31.85 0.03 0.01 0.00 44.62 0.14 1.32 1.05 7.4 1.00 39.00 0.00	0.00 0.02 0.41 0.12 0.01 20.93 30.63 0.04 0.05 0.02 46.88 0.76 4.49 3.15 35.7 0.00 37.55	0.00 0.02 0.02 0.01 0.25 58.31 0.01 0.01 0.00 39.81 0.47 4.27 0.87 4.9 1.20 243.6 0.00	0.00 0.12 0.09 0.01 19.71 29.77 0.05 0.01 0.00 44.88 0.28 1.23 0.98 10.2 0.00 33.90 0.00	0.00 0.06 0.04 0.01 20.15 29.87 0.03 0.01 0.00 45.43 0.26 2.39 0.92 8.4 0.00 35.09 0.00	0.00 0.05 0.10 0.01 19.19 30.85 0.03 0.00 0.00 45.15 0.41 1.40 0.32 7.0 0.00 32.62 0.00	0.00 0.04 1.18 0.05 5.86 50.09 0.02 0.01 0.01 42.78 0.15 7.55 1.38 14.1 0.40 16.69 0.02	0.00 0.01 0.22 0.11 0.01 20.33 29.98 0.05 0.03 0.01 45.71 0.59 4.09 4.10 2.5 0.00 36.73 0.00 0.06 0.79 0.04 20.34 32.71 0.04 0.01 0.00 45.47 0.06 1.48 0.77 4.3 0.50 35.68 0.08	0.00 0.02 0.94 0.04 20.35 33.35 0.04 0.01 0.00 45.50 0.08 0.67 0.49 4.7 0.40 37.25 0.00	0.00 0.04 1.02 0.04 21.43 32.13 0.03 0.01 0.00 45.68 0.05 1.18 0.65 4.7 0.40 28.99 0.01	0.00 0.03 1.19 0.39 0.01 18.61 30.06 0.03 0.02 0.02 43.90 0.93 8.60 3.35 40.8 0.00 28.09 0.00 0.02 0.69 0.04 20.83 28.40 0.03 0.01 0.00 45.02 0.27 1.21 0.49 4.6 0.00 31.77 0.00	0.00 0.03 0.78 0.04 21.08 31.36 0.03 0.01 0.00 46.02 0.14 2.30 1.23 3.1 0.40 31.96 0.00	0.00 0.00 0.02 0.12 0.01 19.90 30.18 0.03 0.00 0.00 45.40 0.29 1.29 0.46 3.5 0.00 34.74 0.00 0.02 0.92 0.05 20.88 31.58 0.03 0.01 0.00 45.85 0.08 2.66 1.54 5.3 0.20 25.25 0.00	0.00 0.02 0.58 0.26 0.01 19.93 27.99 0.03 0.02 0.03 43.72 1.01 8.82 5.10 3.7 0.00 28.97 0.00 0.01 1.06 0.05 21.24 31.74 0.03 0.01 0.01 45.81 0.04 0.25 0.45 3.9 0.20 28.16 0.01
	Sr87/Sr86 stoich. Sr87/Sr86 stoich.			49.76	49.75																50.86						49.89 51.00	50.37				0.708129 50.63	0.708134 50.81																50.28					50.1
	δ18O δ18O	-14.13 -16.87	-18.62 -16.68	-15.82 -17.21	-14.47 -17.33	-14.59 -17.51	-12.69 -16.93	-8.29 -17.1	-13.23 -16.65	-13.84 -14.17	-17.10 -17.56	-10.16 -18.01	-14.82	-14.02 -15.79	-10.87 -16.59	-7.68 -15.35	-13.49	-17.28 -12.27	-12.95 -16.75	-16.98	-13.56 -17.64	-11.31 -17.45	-13.91 -8.94	-14.08 -16.61	-17.45 -13.46	-13.31	-18.84 -15.54	-11.38 -15.24	-16.36	-18.48 -16.77	-5.11	-18.59 -13.86	-18.19 -16.91	-16.32	-14.11 -17.72	-10.81	-13.69	-16.35 -17.83	-19.12 -11.61	-12.03	-18.45 -16.65	-13.18 -16.29	-11.40 -16.05		-18.22	-13.90 -18.23	-16.12 -3.69	-15.95 -8.97	-14.64 -12.07	-14.62 -16.73	-15.82 -16.16	-16.39 -8.92	-15.82 -16.19	-10.63	-10.45	-17.58 -15.45	-5.23	-16.79	-17.53
	δ13C δ13C	1.13 0.64	0.50 0.44	0.93 0.13	1.52 1.18	2.28 1.45	0.96 1.09	-2.2 1.25	1.08 1.11	1.78 -1.6	2.35 1.26	2.61 1.05	0.82	1.70 0.82	-2.17 0.16	-5.56 0.39	0.34	1.14 -0.6	0.73 1.67	1.73	1.21 1.54	-1.45 1.07	-0.55 -2.6	0.85 1.22	0.82 -0.68	-0.73	0.46 0.54	-2.40 0.97	0.42	0.47 0.69	-8.17	1.14 1.34	1.17 1.44	-0.28	-2.48 0.79	-3.16	-0.68	1.73 0.85	-0.91 1.92	1.82	1.27 2.02	2.68 0.00	2.52 0.16		1.30	1.36 1.12	0.8 2.41	0.94 2.28	1.88 2.76	1.84 0.54	1.36 -1.71	1.5 -5.03	1.82 0.72	2.77	2.72	1.64 0.78	-4.87	0.98	0.47
	Stage Stage	CCD_II	WC DS	CCD_I WC	CCD_I ZD	LS ZD	CCD_I ZD	DEDOL ZD	CCD_I CCD_II	LS DEDOL	LS CCD_II	LS DS	LS CCD_I	CC_II CCD_I	DEDOL CCD_II	TC ZD	DEDOL ZD	CCD_II DEDOL	CCD_I DS	DEDOL CCD_II	CCD_I CCD_II	DEDOL DS	DEDOL DEDOL	DEDOL CCD_II	CCD_II DEDOL	DEDOL DEDOL	CCD_II CC_I	DEDOL DS	CCD_II ZD	CCD_II ZD	CCD_II TC	CCD_II Ba	CCD_II CCD_II	CCD_I DS	DEDOL DS	DEDOL DS	DEDOL DS	CCD_I DS	CCD_II CC_I	CCD_II CC_I	CCD_II CCD_II	LS DS	LS DS	LS CCD_II	LS CCD_II	CCD_I CCD_II	ZD Ba	ZD Ba	LS Ba	LS CCD_II	ZD CCD_II	ZD TC	ZD CCD_I	LS CCD_I	LS CCD_I	DS CCD_I	TC CCD_I	CCD_II CCD_I	DS CCD_I
	Sample No. Sample No.	RQ29HB	R529C RQ30A	R529D RQ30B	R530A RQ31A	R114A RQ31B	R114B RQ33A	R114C RQ33B	R115A RQ34A	R115B RQ34B	RT66A RQ35A	RT66B RQ35B	RT67 RQ36A	RT67A RQ36B	RT67B RQ39A	RT67C RQ39B	RT68 RQ39C	RT68B RQ39D	RT69 RQ40A	RT69 RQ40B	RT70A RQ41A	RT70B RQ41B	RT70C RQ42A	RT71A RQ42B	RT71B RQ42C	RT72 RQ43A	RT72A RQ43B	RT72B RQ43C	RT73 RQ44A	RT73A RQ44B	RT74H RQ44C	RT74HA RQ45A	RT74HB RQ46A	RT75A R511A	RT75B R511B	RT76A R511C	RT76B R511D	RT76C R511E	RT999A R513A1	RT77 R513A2	RT77B R513B	RT78 R514A1	RT78A R514A2	RT79 R515A1	RT80 R515A2	R203 R515A3	RH100A R517A+	RH100B R517A	RH101A R517B	RH102A R524	RH102B R525	RH103A RC3A	RH103B RC4A	RQ24A RC5	RQ25A RC6	RQ26A RC7A	RQ26B RC7	RQ28A RC8	RQ29HA RC9
	Site Site	QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	BRECCIA QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	FRONT QUARRY	PLATEAU QUARRY	PLATEAU QUARRY	PLATEAU QUARRY	PLATEAU QUARRY	PLATEAU QUARRY	PLATEAU QUARRY	PLATEAU FAULT	PLATEAU FAULT	QUARRY FAULT	QUARRY FAULT	QUARRY FAULT	QUARRY FAULT	QUARRY FAULT	QUARRY FAULT

%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (

ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)

		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00					0.00				0.00	0.00				0.00		0.00	0.00	0.00	0.50	1.30		0.00	0.00		0.00		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
		2.19	1.06	1.12	6.15	1.69	1.38	5.23	4.30	5.85	4.71	2.98	1.52	6.63	1.43	0.67	1.33	7.39					4.39				7.27	8.54				9.87		20.76	2.60	1.53	1.83	2.25		3.72	1.47		1.34		1.28	2.65	1.25	1.96	4.56	1.66	2.33	3.24	5.85	1.67	2.52		1.57	1.09	0.87
		0.18	0.12	0.62	0.00	0.13	0.21	0.27	0.26	0.64	1.00	0.39	0.27	0.00	0.10	1.05	0.47	1.12					0.00				0.91	0.42				2.65		0.00	0.00	0.78	0.94	0.50		1.48	0.00		0.00		0.38	0.00	0.15	0.24	1.68	0.17	0.00	0.19	0.00	0.41	0.26		0.00	0.39	0.15
		0.92	1.39	2.36	0.54	0.63	1.30	1.38	1.36	1.32	1.00	0.80	1.36	1.36	1.32	1.77	1.37	1.11					0.00				0.80	0.69				0.99		0.66	0.53	0.20	0.23	0.28		1.16	0.32		0.00		0.61	0.00	0.02	0.33	1.68	0.34	0.46	0.87	1.75	0.48	0.29		0.00	0.02	-0.05
		25.44	29.64	30.78	26.87	32.22	23.00	18.53	20.05	38.16	260.02	209.08	36.16	47.11	41.45	86.18	255.77	234.70					921.38				273.20	346.13				250.09		357.95	176.44	35.40	46.90	525.30		370.75	549.44		515.32		26.10	29.74	29.23	561.12	33.70	43.95	64.23	42.75	28.24	41.57	28.21		28.06	26.00	29.95
		0.20	0.30	0.00	0.00	0.40	0.30	0.30	0.40	0.20	0.30	0.40	0.30	0.00	0.30	0.00	0.40	1.30					0.00				1.40	1.20				1.40		0.00	0.00	1.10	1.20	1.20		1.60	0.00		0.00		0.40	0.00	0.10	0.30	2.00	0.00	0.00	0.10	0.00	0.20	0.20		0.00	0.30	0.40
		4.5	4.2	5.3	4.0	3.1	4.0	4.8	5.5	23.6	7.6	2.6	13.2	21.7	18.7	10.0	13.6	0.0					3.2				0.0	0.0				0.0		2.4	4.7	3.2	5.1	3.1		1.9	1.8		6.1		2.5	3.3	3.4	3.1	2.7	2.3	9.7	3.5	2.7	2.6	3.1		7.8	2.8	3.1
		0.51	0.79	0.39	0.29	0.34	0.93	0.94	0.37	5.92	3.57	1.34	0.82	0.66	0.79	0.88	0.88	9.80					0.41				34.25	62.09				5.14		0.25	0.42	1.08	1.06	0.43		2.73	0.23		1.62		0.47	0.31	0.35	0.61	3.46	0.30	1.17	0.33	0.46	0.57	0.29		1.08	0.14	0.46
		0.84	3.54	0.58	0.23	0.51	3.30	4.53	1.50	25.44	8.32	0.88	1.36	1.29	1.39	1.89	0.51	3.56					1.12				1.49	1.82				1.90		1.00	1.04	0.43	0.32	0.19		4.19	0.79		0.00		1.70	0.13	0.18	0.99	6.39	0.41	0.59	0.31	1.75	0.64	0.59		0.09	0.20	0.28
		0.03	0.14	0.03	0.16	0.04	0.08	0.17	0.05	0.15	0.13	0.08	0.13	0.21	0.11	0.08	0.08	0.18					0.60				0.26	0.14				0.14		0.38	0.43	0.10	0.28	0.13		0.20	0.04		1.21		0.06	0.27	0.02	0.04	0.26	0.02	1.41	0.03	0.35	0.04	0.05		2.45	0.02	0.02
		45.60	45.87	45.88	44.17	46.24	45.97	44.53	45.72	45.48	42.85	41.65	43.77	43.94	43.34	42.06	40.72	37.74					41.71				38.63	39.69				40.03		40.95	42.48	45.44	45.05	41.18		42.67	41.66		44.18		44.29	44.27	45.46	40.08	45.35	45.92	47.04	45.65	45.57	45.32	45.69		47.73	45.67	45.69
		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.01	0.07	0.01	0.00	0.00	0.00	0.00	0.04	0.01	0.01					0.01				0.01	0.01				0.01		0.00	0.00	0.00	0.00	0.00		0.07	0.00		0.01		0.00	0.00	0.00	0.00	0.01	0.00	0.01	0.00	0.00	0.01	0.00		0.01	0.00	0.00
		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.01	0.01	0.01	0.00	0.01	0.00	0.00	0.00	0.02					0.01				0.01	0.01				0.02		0.01	0.01	0.01	0.01	0.01		0.05	0.00		0.02		0.01	0.01	0.00	0.00	0.06	0.00	0.01	0.00	0.01	0.01	0.00		0.01	0.00	0.00
		0.02	0.03	0.03	0.03	0.03	0.03	0.02	0.02	0.03	0.02	0.01	0.04	0.03	0.03	0.02	0.01	0.01					0.02				0.01	0.01				0.01		0.00	0.01	0.03	0.03	0.01		0.02	0.01		0.02		0.02	0.03	0.03	0.01	0.04	0.04	0.05	0.03	0.04	0.03	0.03		0.03	0.02	0.02
		31.93	31.43	32.22	28.34	31.03	32.01	38.50	34.47	34.26	56.12	57.69	35.44	30.98	35.85	37.64	58.00	60.04					52.65				59.48	57.57				57.62		51.82	53.90	32.50	33.93	57.36		53.71	54.61		56.00		32.50	28.81	31.43	58.53	32.02	32.70	32.76	32.84	29.47	32.95	31.12		31.43	31.97	31.23
		20.74	21.21	20.86	20.10	21.05	20.30	14.79	18.37	18.83	0.55	0.38	19.40	17.99	19.91	19.64	0.53	0.38					0.37				0.43	0.47				0.39		0.27	0.18	20.17	18.77	0.32		1.35	0.61		0.22		21.05	19.85	21.09	0.40	20.90	20.51	19.55	20.11	20.57	20.09	21.13		21.14	21.64	21.40
		0.05	0.04	0.03	0.04	0.04	0.05	0.05	0.06	0.04	0.01	0.01	0.01	0.01	0.01	0.02	0.01	0.01					0.01				0.01	0.01				0.01		0.01	0.01	0.04	0.04	0.01		0.02	0.01		0.01		0.04	0.06	0.06	0.01	0.04	0.05	0.09	0.08	0.02	0.04	0.06		0.08	0.06	0.07
		1.01	0.97	0.44	0.68	0.81	0.93	1.28	1.31	1.37	0.33	0.02	0.07	0.06	0.06	0.06	0.03	0.08					0.02				0.11	0.06				0.12		0.02	0.03	0.63	0.56	0.05		0.30	0.07		0.04		0.52	0.83	0.94	0.03	0.78	1.10	1.29	1.21	0.15	0.82	1.24		1.13	1.04	1.33
		0.02	0.03	0.01	0.01	0.01	0.01	0.01	0.02	0.08	0.07	0.04	0.01	0.01	0.01	0.06	0.06	0.05					0.02				0.02	0.01				0.02		0.01	0.01	0.06	0.05	0.03		0.17	0.01		0.01		0.05	0.01	0.01	0.01	0.23	0.01	0.03	0.03	0.03	0.03	0.01		0.02	0.01	0.01
		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00					0.00				0.00	0.00				0.00		0.00	0.00	0.00	0.00	0.00		0.01	0.00		0.00		0.00	0.00	0.00	0.00	0.01	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
	SiO2 (%	0.01	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.05	0.06	0.04	0.00	0.00	0.00	0.04	0.05	0.17					0.00				0.10	0.08				0.20		0.00	0.00	0.00	0.00	0.03		0.22	0.00		0.00		0.01	0.00	0.00	0.00	0.27	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
	Sr87/Sr86 stoich.							50.1		51.7			50.1	50.1										0.708516	0.708471					0.707426													0.708443														0.708473
	δ18O				-14.37			-12.28			-11.64	-14.65		-17.37		-10.28	-15.90		-12.66	-11.23	-8.13	-17.98	-11.28	-11.39	-11.47	-8.97	-7.44	-8.39	-10.06	-4.50	-4.32	-6.39	-7.68	-16.09	-13.09	-14.03	-13.62	-11.85	-11.33	-10.08	-11.11	-12.93	-11.80	-12.09		-13.28				-13.73	-13.56		-16.71		-13.09	-11.69	-14.18		-6.93
	δ13C				0.45			0.59			1.65	1.78		0.94		1.70	0.67		1.78	1.93	2.06	0.83	1.84	1.72	1.53	1.58	2.07	2.50	0.53	1.91	1.12	1.93	2.29	-0.66	1.02	1.31	1.36	1.55	1.71	1.3	1.18	1.45	1.12	1.27		1.15				0.81	1.20		0.87		1.16	1.28	1.14		-5.30
	Stage	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CC_II	LS	CCD_II	CCD_II	CCD_I	CCD_I	LS	LS	CCD_I	CC_I	LS	WC	CC_I	CC_II	CCD_I	LS	LS	LS	CC_I	LS	LS	LS	LS	WC	CC_I	CCD_I	CCD_I	CC_I	CC_II	LS	LS	CCD_I	CC_I	CC_I	CCD_I	CCD_I	CCD_I	CC_I	ZD	CCD_I	CCD_I	CCD_I	CCD_II	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	TC
	Sample No.	RC10	RC11	RC12	RC13A	RC13	RC14	RC15A	RC16	RC17	RC18A	RC19A	RC20	RC21A	RC21	RC22A	RC23A	R206	R206A	R206B	R206C	R207A	R207B	R207C	R207D	R207E	R208A	R209A	R210B	R211aA	R211aB	R211aC	R211aD	R519A	R521A	R521B	R521C	R522	RV47A	RV47B	RV48A	RV48B	RV49A	RV49B	RV50	RV51A	RV51A	RV52	RV53	RV54A	RV55A	RV55A	RV57A	RV57A	RV58A	RV58A	RV59A	RV59	RV60A
	Site	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	FAULT	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN

) TiO2 (%) Al2O3 (%) Fe2O3 (

%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (

ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)

		0.00	0.00	0.00	0.00		0.00			0.00	0.00			0.00	0.00										0.00	0.00			0.00	0.00	0.00		0.00					0.00	0.00				0.00	0.00		0.00		0.00	0.00			0.00		0.00	0.00	0.00		0.00	0.00
		2.37	0.92	1.01	1.30		1.02			1.94	2.97			4.34	1.73										8.91	2.45			2.27	6.61	0.75		1.28					3.19	98.89				1.21	1.50		18.78		4.46	5.87			6.03		10.75	5.62	5.30		4.20	4.31
		0.00	0.27	0.00	0.20		0.29			0.00	0.66			0.00	0.33										0.00	0.00			0.00	0.00	0.00		0.00					0.00	0.00				0.00	0.00		0.00		0.00	0.00			2.59		0.00	0.84	2.21		0.26	0.34
		0.00	-0.05	0.00	0.02		0.22			0.00	0.70			0.39	0.41										1.10	1.20			1.43	1.66	2.05		1.60					1.29	1.96				1.32	1.32		0.03		1.50	0.91			1.86		1.68	1.58	2.53		1.54	1.59
		33.63	27.47	24.75	24.86		43.86			343.94	256.70			39.76	39.44										36.52	45.12			30.42	39.36	38.60		38.01					31.99	34.77				47.22	47.70		503.50		40.71	40.84			244.30		36.39	221.26	37.77		95.06	88.35
		0.00	0.00	0.00	0.30		0.20			0.00	0.60			0.00	0.20										0.00	0.00			0.00	0.00	0.00		0.00					0.00	0.00				0.00	0.00		0.00		0.00	0.00			0.50		0.00	0.30	0.70		0.40	0.20
		12.3	3.2	3.7	2.8		2.5			9.5	2.2			2.8	2.7										295.8	199.1			120.8	75.0	87.8		20.6					3.4	14.5				47.8	68.4		13.7		39.2	25.4			216.6		382	98.5	514		100.1	73.0
		0.62	0.60	0.23	0.19		0.33			0.99	1.26			0.19	0.20										2.03	0.78			0.69	3.30	2.22		0.73					0.33	3.96				0.62	0.29		0.66		3.51	0.35			2.59		23.35	2.12	4.36		0.91	0.77
		0.00	0.20	0.09	0.23		0.68			0.49	1.10			0.48	0.62										2.61	0.49			2.25	3.66	3.18		2.35					2.33	4.68				0.88	1.07		0.00		5.89	0.93			3.35		2.60	2.31	5.85		1.76	1.99
		1.98	0.03	0.39	0.03		0.04			0.51	0.09			0.28	0.05										0.29	0.02			0.28	0.43	0.35		0.34					0.29	0.41				0.24	0.24		0.01		0.56	0.21			0.52		0.21	0.34	0.72		0.20	0.20
		49.07	45.83	45.61	45.96		45.65			44.23	41.06			43.85	46.16										44.24	49.57			45.86	44.92	44.27		47.83					45.19	45.81				44.22	45.25		44.53		46.35	46.00			42.35		46.42	42.64	42.72		41.16	42.24
		0.01	0.00	0.00	0.00		0.00			0.01	0.01			0.00	0.00										0.00	0.00			0.00	0.09	0.00		0.00					0.00	0.06				0.00	0.00		0.00		0.09	0.00			0.01		0.01	0.01	0.01		0.01	0.01
		0.01	0.00	0.01	0.00		0.01			0.01	0.02			0.01	0.00										0.00	0.01			0.00	0.02	0.00		0.01					0.00	0.01				0.00	0.00		0.01		0.02	0.01			0.01		0.05	0.01	0.01		0.00	0.00
		0.03	0.02	0.03	0.03		0.03			0.01	0.01			0.04	0.03										0.02	0.04			0.03	0.03	0.04		0.04					0.04	0.04				0.03	0.03		0.01		0.03	0.03			0.01		0.03	0.01	0.03		0.01	0.01
		33.02	30.69	29.75	31.06		32.30			56.00	55.23			28.70	31.37										31.33	32.14			29.90	28.57	29.38		31.52					28.92	29.30				27.81	28.67		56.36		29.20	29.71			55.49		35.63	53.01	35.98		39.66	38.47
		21.22	21.23	20.39	21.13		20.44			0.26	0.47			19.54	20.84										18.01	22.31			20.52	20.62	19.44		21.16					20.62	20.91				20.53	20.84		0.28		21.47	20.79			0.52		16.92	3.26	18.99		17.38	17.63
		0.07	0.07	0.07	0.07		0.04			0.01	0.01			0.05	0.06										0.01	0.05			0.01	0.01	0.01		0.01					0.01	0.01				0.06	0.06		0.01		0.04	0.04			0.01		0.05	0.02	0.04		0.03	0.03
		0.74	0.97	0.82	0.89		0.74			0.02	0.04			0.91	1.10										0.01	0.52			0.00	0.24	0.01		0.02					0.00	0.17				0.84	1.00		0.00		0.69	0.63			0.21		0.61	0.16	0.40		0.08	0.07
		0.02	0.01	0.01	0.01		0.03			0.02	0.06			0.01	0.01										0.03	0.05			0.04	0.39	0.03		0.03					0.04	0.39				0.01	0.02		0.01		0.10	0.03			0.30		0.39	0.10	0.22		0.03	0.03
		0.00	0.00	0.00	0.00		0.00			0.00	0.00			0.00	0.00										0.00	0.00			0.00	0.01	0.00		0.00					0.00	0.01				0.00	0.00		0.00		0.01	0.00			0.01		0.01	0.00	0.01		0.00	0.00
	SiO2 (%	0.00	0.00	0.00	0.00		0.00			0.00	0.05			0.00	0.00										0.00	0.00			0.00	0.00	0.00		0.00					0.00	0.00				0.00	0.00		0.00		0.00	0.00			0.31		0.00	0.07	0.20		0.00	0.00
	Sr87/Sr86 stoich.																								50.12				0.70815 49.98	50.26			49.6					49.94	50.17									50.01
	δ18O	-14.15		-12.81		-12.69	-15.09	-11.11	-16.73	-12.68		-11.79	-14.40	-13.83		-13.71		-6.20							-18.49	-14.54			-17.87	-18.19	-15.89		-17.93			-18.62		-18.72	-16.78			-13.03	-14.12	-14.23		-17.32	-13.17	-14.39	-14.98	-11.98	-8.12		-14.74	-13.89	-15.16
	δ13C	1.52		1.27		1.30	1.4	0.18	1.18	1.99		1.91	1.87	0.89		0.70		2.74							-0.25	1.50			-1.15	-0.91	0.85		-0.92			-3.01		-2.32	-1.39			0.10	1.28	1.23		-1.06	1.34	0.79	0.41	1.68	3.44		0.58	0.57	2.85
	Stage	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_II	CC_II	LS	LS	LS	ZD	ZD	ZD	ORE	LS		ORE					CCD_II	CCD_I			CCD_II	CCD_II	CCD_II	CCD_II	CCD_II			CCD_II		CCD_II	CCD_II			CCD_I	CCD_I	CCD_I		WC	CC_I	ZD	ZD	CC_I	LS	LS	CCD_I	CCD_I	LS	CCD_I		CCD_II	CCD_II
	Sample No.	RV61A	RV61	RV62A	RV62	RV62B	RV63	RV63B	RV63C	RV64A	RV64	RV64B	RV64C	RV65A	RV65	RV65B	R219	R220A	R221	R222	R223	R224	R225	R226	R227A	R228A	R229	R230	R231A	R231B	R232A	R233	R234A	R235	R236	R237A	R238	R239A	R239B	R240	R241	R242A	R242B	R242C	R243	R245A	R246A	R247A	R247B	R248A	R248B	R249	R250A	R250B	R250C	R251	R252	R253	R254
	Site	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	VEIN	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (A_B)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_I (B_C)	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II

) TiO2 (%) Al2O3 (%) Fe2O3 (

%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (

ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)

		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00	0.00	0.00				0.00						0.00	0.00			0.00							0.00			0.00	0.00	0.00	0.00					0.00	0.00								0.00	0.00	0.00
		7.01	2.20	5.12	3.30	9.29	4.06	6.03	5.10	4.92		4.18	2.97	5.10	3.38	5.19				5.88						2.03	1.40			1.93							1.75			10.31	3.50	1.95	16.73					1.23	1.91								0.88	9.00	38.76
		0.26	0.00	0.06	0.00	0.00	0.12	0.25	0.06	0.80		0.50	0.00	1.55	0.00	1.07				0.62						0.00	0.00			0.00							0.00			0.00	0.00	0.00	0.00					0.00	0.00								0.00	0.00	0.00
		0.80	1.16	1.51	0.95	0.66	0.72	2.35	0.87	0.89		1.75	0.80	1.34	1.65	1.41				0.83						0.62	0.75			1.07							1.58			2.04	1.14	0.36	1.46					21.81	12.40								0.36	1.31	1.56
		45.10	36.78	37.93	40.68	37.77	39.21	46.01	45.88	33.76		43.30	31.94	38.65	36.39	306.55				227.13						51.31	45.81			47.97							38.39			140.78	31.73	56.64	35.37					116.07	155.67								40.54	38.99	39.72
		0.20	0.00	0.10	0.00	0.00	0.40	0.10	0.00	0.40		0.30	0.00	0.50	0.00	0.20				1.00						0.00	0.00			0.00							0.00			0.00	0.00	0.00	0.00					0.00	0.00								0.00	0.00	0.00
		774	120.7	158.0	104.1	74.2	46.5	125.9	655	17.5		35.0	28.4	44.3	23.0	18.5				14.32						260.7	374.8			496							399.34			492	40.9	178.3	4827					4.69	5.40								25.69	34.14	47.93
		1.38	0.27	0.60	0.62	0.20	0.73	1.10	2.29	1.39		3.56	0.54	3.21	3.69	2.28				1.74						0.21	1.11			2.09							1.19			0.75	0.43	0.44	0.33					1.74	0.07								0.56	5.11	8.00
		0.93	0.13	0.39	0.25	1.04	1.63	2.14	1.12	1.98		5.39	1.15	3.65	3.07	3.27				1.62						1.15	2.42			2.99							2.67			1.87	0.75	1.15	0.75					0.06	0.02								0.92	6.20	10.12
		0.12	0.18	0.08	0.35	0.25	0.06	0.20	0.10	0.16		0.24	0.25	0.27	0.39	0.20				0.15						0.23	0.30			0.13							0.08			0.09	0.02	1.70	0.27					0.08	0.26								0.02	0.37	0.56
		45.92	46.31	46.21	45.60	43.86	45.24	45.64	46.04	46.08		44.11	45.39	46.32	43.74	42.43				42.61						45.55	46.59			48.35							46.28			43.99	46.07	47.25	42.60					44.57	41.41								47.18	46.41	47.77
		0.01	0.00	0.01	0.00	0.00	0.01	0.01	0.01	0.01		0.01	0.00	0.02	0.04	0.02				0.02						0.00	0.00			0.00							0.00			0.00	0.00	0.01	0.01					0.00	0.00								0.00	0.05	0.11
		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.01		0.00	0.01	0.01	0.03	0.01				0.02						0.01	0.01			0.01							0.01			0.01	0.01	0.01	0.00					0.01	0.00								0.01	0.04	0.06
		0.03	0.03	0.03	0.03	0.02	0.02	0.03	0.03	0.03		0.04	0.03	0.03	0.03	0.02				0.02						0.03	0.04			0.04							0.04			0.01	0.03	0.04	0.02					0.01	0.00								0.03	0.04	0.04
		30.79	29.44	30.84	29.37	28.60	31.01	31.85	31.10	30.96		33.15	29.41	30.85	28.00	54.32				55.37						30.01	30.19			31.35							31.87			49.57	29.91	31.76	33.73					56.37	51.80								30.20	28.87	30.70
		21.26	21.26	21.44	20.66	19.62	21.53	21.21	21.12	21.77		21.79	20.44	21.44	19.95	1.28				0.61						20.16	20.98			21.75							19.49			4.67	20.70	20.46	14.78					0.31	0.70								21.51	21.76	21.70
		0.06	0.06	0.06	0.07	0.04	0.04	0.06	0.06	0.04		0.02	0.03	0.04	0.04	0.01				0.00						0.05	0.05			0.05							0.06			0.02	0.06	0.07	0.12					0.01	0.01								0.04	0.04	0.05
		1.15	0.59	0.62	0.70	0.44	0.37	1.22	1.30	0.45		0.09	0.22	0.63	0.55	0.06				0.03						0.40	0.48			0.81							0.84			0.08	0.81	1.76	2.21					0.01	0.01								0.59	0.56	0.78
		0.01	0.03	0.03	0.04	0.03	0.03	0.02	0.03	0.06		0.07	0.04	0.17	0.21	0.11				0.08						0.04	0.05			0.04							0.03			0.01	0.04	0.05	0.04					0.01	0.01								0.03	0.28	0.23
		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.01	0.01	0.00				0.00						0.00	0.00			0.00							0.00			0.00	0.00	0.00	0.00					0.00	0.00								0.00	0.01	0.02
	SiO2 (%	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.01		0.00	0.00	0.11	0.00	0.07				0.06						0.00	0.00			0.00							0.00			0.00	0.00	0.00	0.00					0.00	0.00								0.00	0.00	0.00
	Sr87/Sr86 stoich.					49.99							50.07														49.82			50.56													49.85												0.708436		50.22
	δ18O		-15.10		-14.72	-15.43							-17.77		-15.39					-11.61		-9.46	-13.96	-11.32		-14.90	-13.57			-13.75	-12	-12.77					-13.38	-14.34	-14.15	-13.99	-14.71	-13.22	-11.82	-14.2	-13.78			-19.43	-20.22	-15.30		-14.42	-6.69		-8.42		-14.63	-15.43	-14.55
	δ13C		1.04		0.61	-0.13							-0.46		1.10					3.55		-0.94	1.35	-3.61		1.13	2.05			1.53	1.59	1.13					0.83	1.01	1.08	-1.71	0.85	1.49	-1.16	1.16	1.39			0.89	0.27	0.86		2.65	-5.34		-4.56		0.74	0.78	1.01
	Stage	CCD_I	ZD	ZD	ZD	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I		CCD_II	CCD_II	ZD	ZD	LS				LS	CC_I	TC	CCD_I	ORE	LS	CCD_I	CCD_I			CCD_I	CC_I	CC_I					CCD_I	CCD_I	CCD_I	ORE	CCD_I	CCD_I	ORE	CCD_I	CCD_I			WC	WC			LS	TC		TC		CCD_I	CCD_I	CCD_I
	Sample No.	R255	R256A	R256	R256B	R257A	R257	R258	R259	R260	R261	R262	R263A	R263	R263B	R264	R265	R266	R267	R268A	508A	539A	539B	539C	R269	R270A	R270B	R271	R271b	R272A	R272B	R272C	R273	R274	R275	R276	R277A	R277B	R277C	R277aA	R277aB	R278A	R278B	R279A	R279B	R280	R282	R283A	R284A	R284B	R284b	R285A	R285B	R286	R287A	R288	R290A	R290B	R291A
	Site	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_II	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III

) TiO2 (%) Al2O3 (%) Fe2O3 (

%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (

ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)

	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.00	0.00	0.00	0.00			0.00	0.00					0.00		0.00	0.00	0.00				0.00
	0.96									2.99	0.60	85.17				3.25	9.45					5.87			20.76		4.12	5.53	2.71	32.49			13.57	12.14					12.26		1.32	1.56	0.87				1.14
	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.00	0.00	0.00	0.00			0.00	0.00					0.00		0.00	0.00	0.00				0.00
	1.09									1.96	1.16	1.53				0.00	0.66					0.21			2.03		0.20	2.55	3.02	2.34			1.96	4.07					2.38		3.41	1.18	0.46				5.68
	37.94									92.41	27.05	38.04				678.57	139.09					508.95			39.09		746.58	20.58	38.29	39.77			38.98	24.90					36.59		55.37	70.00	29.73				35.44
	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.00	0.00	0.00	0.00			0.00	0.00					0.00		0.00	0.00	0.00				0.00
	17.08									12.00	68.55	25.34				3.19	133					33.28			1689		14.86	7072	49.68	170.2			3124	3201					202		13.87	8.96	7.28				7.19
	1.14									0.19	1.60	0.67				0.24	0.53					0.26			1.41		0.50	3.19	0.76	0.37			5.46	21.31					0.37		82.51	1.36	0.38				0.81
	1.72									0.29	2.43	2.44				0.00	0.90					0.28			1.89		0.09	4.10	6.84	2.05			3.13	26.45					1.97		10.03	2.02	0.96				0.02
	0.04									0.29	0.40	0.22				0.22	0.41					0.25			1.08		0.01	0.16	0.49	0.28			0.05	2.03					0.22		0.14	0.05	0.01				0.01
	48.65									40.63	43.10	44.07				41.26	42.76					41.95			42.36		44.48	43.53	45.23	46.09			47.62	41.54					44.57		48.76	47.88	47.32				47.39
	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.01		0.00	0.01	0.00	0.00			0.01	0.11					0.00		0.00	0.00	0.00				0.00
	0.01									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.01	0.01	0.00	0.00			0.02	0.04					0.00		0.01	0.01	0.01				0.01
	0.04									0.01	0.03	0.03				0.00	0.02					0.00			0.01		0.01	0.01	0.01	0.01			0.03	0.01					0.02		0.03	0.03	0.03				0.03
	31.96									48.87	29.31	28.93				52.21	30.85					53.10			39.01		56.32	49.73	28.54	27.86			46.17	42.85					30.08		36.01	33.55	30.02				29.76
	21.60									2.09	18.41	19.58				0.27	17.00					0.26			10.77		0.27	4.13	20.91	22.19			10.44	7.26					19.21		18.79	19.75	21.78				22.02
	0.04									0.01	0.01	0.01				0.00	0.06					0.01			0.06		0.01	0.08	0.08	0.06			0.08	0.03					0.02		0.02	0.06	0.04				0.07
	0.41									0.00	0.03	0.00				0.00	1.38					0.01			1.31		0.00	1.62	0.04	0.59			1.85	1.55					0.14		0.06	0.92	0.44				0.66
	0.03									0.02	0.05	0.03				0.01	0.05					0.01			0.03		0.01	0.06	0.02	0.04			0.07	2.84					0.03		0.03	0.07	0.02				0.02
	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.00	0.00	0.00	0.00			0.00	0.09					0.00		0.00	0.00	0.00				0.00
	0.00									0.00	0.00	0.00				0.00	0.00					0.00			0.00		0.00	0.00	0.00	0.00			0.00	0.00					0.00		0.00	0.00	0.00				0.00
											49.76																		49.9	50.2									51.13				49.85				50.18
									0.708768									0.708363				0.708815																	0.708265								0.708267
	-15.7								-18.83			-18.59	-15.82	-14.54		-19.59	-12.85	-14.20	-10.72			-17.86	-9.14	-15.81	-10.35		-17.29	-7.43	-15.69	-15.51	-13.76		-11.45	-7.23					-18.16	-14.23	-18.29	-15.12	-16.43				-13.69
	0.99								-0.64			-1.10	0.46	-0.16		1.10	2.45	0.75	2.95			0.79	-3.82	-0.79	-2.77		0.74	-5.58	-0.38	0.47	0.00		-3.2	-3.94					-0.93	0.98	0.32	0.95	1.12				1.13
	CCD_I								WC	WC	CCD_II	CCD_II	CCD_I	CCD_I		WC	CCD_I	CCD_I	CCD_I			WC	DEDOL	WC	ORE		WC	ORE	CCD_I	CCD_I			ORE	ORE					CCD_II	CCD_I	CCD_II	CCD_I	CCD_I				CCD_I
	R292A	R293	R294	R295	R296	R297	R298	R299	R300A	R300C	R300D	R301A	R302A	R302B	R303	R304A	R304B	R305A	R305B	R306	R307	R308A	R309aA	R309aB	R309aC	R309b	R310bA	R310bB	R311A	R311B	R311C	R312L	R312PA	R312PB	R313	R314	R315	R316	R317A	R317B	R319A	R319B	R320A	R321	R323	R324	R325A
	MO_III	MO_III	MO_III	MO_III	MO_III	MO_III	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_IV	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')	MO_VII (A_A')

) TiO2 (%) Al2O3 (%) Fe2O3 (

		0.00	0.00	0.00	0.00	0.00	0.00			0.00		0.00			0.00				0.00		0.00	0.00	0.00		0.00		0.00	0.00		0.00	0.00		0.00	0.00	0.00		0.00	0.00	0.00	0.00	0.00	0.00	0.00	80.10	81.60	82.40	0.00		0.00	0.00	0.00	0.00		0.00
		0.92	1.44	6.39	4.39	3.77	5.18			4.26		5.51			1.29				1.15		1.14	1.08	1.44		8.63		3.41	4.86		1.87	4.71		2.16	2.98	7.01		8.88	0.82	7.48	12.94	2.65	4.88	1.59	5.65	4.64	4.47	5.44		3.00	1.79	0.39	5.58		4.87
		0.00	0.00	1.18	0.26	0.16	0.32			0.08		0.36			0.00				0.00		0.00	0.00	0.00		4.54		0.23	0.63		0.00	0.66		0.00	0.00	1.95		5.03	0.00	3.52	0.00	0.11	1.06	0.00	2.86	3.05	1.90	0.00		0.00	0.00	0.00	0.00		0.00
		0.65	1.10	1.80	3.35	1.77	2.30			0.08		1.52			0.95				1.83		1.45	2.84	2.34		2.35		2.46	2.72		3.57	3.24		1.95	1.44	2.46		2.22	2.64	3.84	5.03	3.63	4.69	1.79	2.56	2.34	2.30	1.08		1.42	0.92	1.39	1.67		1.85
		250.55	30.21	224.72	43.55	36.94	46.96			405.71		263.65			33.18				41.30		33.27	40.08	30.76		41.60		39.04	47.88		62.04	44.47		50.44	1.60	1.60		57.39	44.78	51.76	56.35	46.95	42.95	42.87	75.40	75.90	65.60	28.08		31.75	32.58	27.61	28.83		30.69
		0.00	0.00	0.70	0.30	0.30	0.30			0.40		0.20			0.00				0.00		0.00	0.00	0.00		2.90		0.50	0.70		0.00	0.50		0.00	0.00	0.80		4.30	0.00	3.90	0.00	0.40	1.10	0.00	2.80	3.00	2.10	0.00		0.00	0.00	0.00	0.00		0.00
		3.78	7.22	4.93	17.84	8.40	7.69			3.08		262.7			5.03				102.5		253	325	31830		848		17781	220		384.6	972		7161	106042	117776		9568	201	4451	3833	548	830	92.6	336	453	445	36.9		35.3	9.7	8.7	59.3		8.99
		0.66	0.82	5.02	0.81	0.62	0.87			0.71		3.22			1.04				1.05		1.19	1.73	3.65		5.95		4.56	3.70		1.06	2.87		4.24	383.41	-2.45		7.59	0.38	5.08	12.00	1.29	2.77	2.40	3.52	2.65	2.16	0.63		5.61	0.33	2.39	8.07		2.39
		0.47	1.40	6.68	0.79	3.48	3.75			0.16		3.46			2.12				3.27		2.46	4.49	4.26		15.29		14.74	13.07		5.48	16.36		1.90	2.41	7.05		16.82	2.86	10.93	16.00	8.33	12.57	7.63	1.93	2.00	1.42	0.78		5.95	0.70	4.51	10.09		3.41
		0.01	0.04	0.28	0.04	0.05	0.04			0.06		0.11			0.04				0.07		0.07	0.33	0.21		0.35		0.58	0.32		0.13	0.74		0.05	0.07	0.23		0.55	0.08	0.52	0.58	0.43	0.39	0.28	0.66	0.39	0.39	0.02		0.28	0.02	0.18	0.32		0.22
		45.71	47.31	43.00	46.08	45.80	45.04			40.76		42.71			48.55				47.56		47.25	45.11	42.34		43.82		44.49	45.37		46.94	45.42		46.49	1.13	35.13		45.01	48.07	44.95	46.29	46.10	45.87	48.53	44.75	44.23	44.97	47.58		46.38	47.49	48.94	47.44		47.55
		0.00	0.00	0.01	0.01	0.01	0.01			0.00		0.01			0.00				0.00		0.00	0.00	0.01		0.05		0.01	0.01		0.00	0.01		0.00	0.00	0.01		0.02	0.00	0.02	0.03	0.00	0.01	0.00	0.01	0.01	0.01	0.00		0.09	0.00	0.00	0.06		0.01
		0.01	0.01	0.02	0.00	0.00	0.00			0.00		0.00			0.01				0.01		0.01	0.01	0.01		0.10		0.00	0.02		0.01	0.01		0.01	0.01	0.03		0.13	0.01	0.11	0.28	0.01	0.03	0.02	0.05	0.06	0.04	0.01		0.06	0.01	0.01	0.03		0.09
		0.01	0.03	0.02	0.03	0.02	0.02			0.01		0.01			0.03				0.04		0.04	0.03	0.03		0.03		0.02	0.03		0.03	0.02		0.02	0.01	0.00		0.03	0.02	0.02	0.03	0.02	0.03	0.02	0.03	0.03	0.02	0.03		0.04	0.04	0.04	0.04		0.04
		56.19	30.42	54.27	31.62	31.39	33.40			55.95		54.99			30.94				30.44		29.45	28.99	28.58		31.66		31.37	31.26		29.53	30.85		30.35	0.30	0.28		30.80	30.75	30.28	30.12	30.78	31.11	30.97	30.74	30.56	30.99	31.94		28.52	29.35	31.32	33.19		30.37
		1.49	21.48	1.68	20.18	20.75	19.37			0.36		1.48			22.24				21.69		22.12	20.49	18.24		22.09		22.05	21.96		21.78	21.72		20.78	0.82	0.23		21.28	21.94	21.05	20.76	21.46	21.78	22.20	19.56	19.09	19.58	20.63		21.99	22.41	22.33	19.61		21.73
		0.02	0.04	0.01	0.07	0.05	0.05			0.01		0.01			0.06				0.08		0.02	0.05	0.05		0.02		0.04	0.05		0.06	0.04		0.06	0.03	0.05		0.03	0.05	0.05	0.05	0.05	0.05	0.03	0.05	0.05	0.05	0.07		0.03	0.03	0.02	0.02		0.04
		0.06	0.41	0.11	0.91	0.87	0.77			0.00		0.16			0.60				1.63		0.01	0.58	1.03		0.17		0.04	0.58		0.88	0.53		0.53	0.25	0.68		0.71	0.30	0.76	0.71	0.61	0.50	0.04	1.05	1.02	1.05	1.27		0.93	0.26	0.01	0.58		0.63
		0.02	0.02	0.14	0.04	0.03	0.03			0.01		0.04			0.03				0.05		0.03	0.04	0.03		0.33		0.02	0.07		0.03	0.06		0.03	0.05	0.17		0.46	0.03	0.42	0.98	0.04	0.12	0.05	0.27	0.26	0.18	0.03		0.32	0.03	0.02	0.35		0.33
		0.00	0.00	0.01	0.00	0.00	0.00			0.00		0.00			0.00				0.00		0.00	0.00	0.00		0.02		0.00	0.00		0.00	0.00		0.00	0.00	0.01		0.02	0.00	0.02	0.03	0.00	0.00	0.00	0.01	0.01	0.01	0.00		0.01	0.00	0.00	0.01		0.01
	SiO2 (%	0.00	0.00	0.13	0.00	0.00	0.00			0.00		0.00			0.00				0.00		0.00	0.00	0.00		0.48		0.00	0.04		0.00	0.05		0.00	0.00	0.25		0.75	0.00	0.79	0.00	0.00	0.16	0.00	3.35	3.46	1.89	0.00		0.00	0.00	0.00	0.00		0.00
	Sr87/Sr86 stoich.		50.19																																														50.48	51.59
	δ18O	-13.99	-15.11						-17.43	-17.09					-14.87	-16.6		-9.4	-12.57	-12.86	-17.12	-13.17	-12.26						-14.8	-14.94	-16.18		-15.29	-1.88		-3.11	-15.69	-15.26		-15.9			-17.47	-16.72	-15.29	-15.19	-14.44		-16.12	-16.13	-18.09	-16.65		-15.1
	δ13C	1.67	1.34						1.71	0.82					1.04	2.24		-3.05	1.17	1.43	-0.61	1.06	-0.58						0.8	1.33	-0.59		0.6	-2.57		-1	0.27	0.91		-0.21			-2.67	0.76	1.41	1.63	1.07		0.97	0.31	0.47	0.43		1.69
	Stage		CCD_I	LS	CCD_I	CCD_I	CCD_I			WC		LS			CCD_I	LS			CCD_I		CCD_II	CCD_I	ORE		CCD_II		CCD_II	CCD_I	CCD_I	CCD_I	CCD_I		CCD_I	wrong	ORE	ORE	DS	CCD_I	CCD_I	DS	CCD_I	CCD_I	CCD_II	ZD	ZD	ZD	CCD_I		CCD_I	CCD_I	CCD_II	CCD_I		CCD_I
	Sample No.		R345B	R346	R347	R348	R349	R349x	R350A	R350B	R350b	R351	R352	R353	R354A	R354B	R355	R356A	R356B	R357A	R358A	R359A	R360A	R361	R365	R365a	R366	R367	R368A	R368B	R369A	R370	R371xC	R371A	R371A	R371B	R372A	R373A	R373A	R373B	R374	R375	R376A	R500A	R500B	R500C	R378A	R381	R382A	R382B	R383A	R383B	R384	R392A
	Site		MO_VIIa	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_VIII	MO_V	MO_V	MO_V	MO_V	MO_V	MO_V	MO_V	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MO_IX	MA_III	MA_III	MA_III	MA_III	MA_III	MA_III	MA_III	MA_I

%) MnO (%) MgO (%) CaO (%) Na2O (%) K2O (%) P2O5 (%) CO2 (%) Sc (ppm) V (

ppm) Cr (ppm) Zn (ppm) Rb (ppm) Sr (ppm) Y (ppm) Zr (ppm) Ba (ppm) Pb (ppm)

	0.00			0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00		0.00		0.00	0.00	0.00		0.00
	6.66			4.73	1.85	4.32	3.46	1.65	4.62	2.38	4.49	6.53	4.68	3.71	3.94	3.77	3.72	3.94	6.68	3.43	0.77	0.74	7.65		0.69	5.48		5.44		0.86	5.78	1.67		4.74
	2.76			1.11	0.00	1.16	1.09	0.00	0.06	0.00	0.16	0.20	0.74	0.16	0.18	0.15	0.08	0.23	0.03	0.27	0.00	0.00	0.00		0.00	0.65		0.83		0.00	1.53	0.00		2.82
																RANERO VEIN SECTION
	1.64	1.40 Serial 0.61 0.46	0.31	0.28 POZALAGUA QUARRY SITE AND RANERO FRONT SECTION 0.69 0.69 0.50 0.43 2.09 0.91 1.66 4.80 0.60 1.25 3.65 0.11 1.04 3.73 1.81 2.62 1.39 1.23 0.72 1.21 0.56 1.51 RANERO FAULT SECTION SAMPLE POROSITY PERMEABILITY
	33.46	273.84 No. 327.15 Serial 26.50 No.	25.68 Serial 328.98 37.44 27.64 No. NUMBER 35.13 40.79 222.95 28.66 102.73 NUMBER 45.92 34.97 39.35 39.43 27.36 ROCK TYPE 25.18 53.00 24.26 41.41 205.41 ROCK TYPE 264.58 32.96 POROSITY 221.04 48.69 (%) (%) 177.84 POROSITY PERMEABILITY (mD) (mD) PERMEABILITY No. ROCK TYPE (%) (mD)
	2.50			1.00	0.00	0.30	0.10	0.00	0.40 1	0.00	0.30 RV-48 0.10 0.90 0.30	0.10 RQ27 0.10 0.20 0.30	0.40	0.20	0.00 LS 0.00	0.00		0.00 CCD-II 0.20 0.40		0.00	0.60 0.35 0.00	0.30	2.1	0.58	0.16
				1							RC-2								ZD.								2.7			0.82
	48.63			46.5	7.4	50.3	29.5	11.6	41.8 2	17.6	51.3 RV-49 42.8 31.3 49.3	29.5 RQ39 36.1 26.6 33.7	56.6	11.7	6.2 CC-I 21.6 43.2		4.1 CCD-II 10.2 10.2		5.2	8.5 1.0 8.5		10.7	1	0.35	0.13
	2.88			1.83 2	0.47	0.97	0.60	0.42	0.85 3	0.47	0.68 RC3 0.64 1.22 RV-51 0.80	0.59 RQ40 0.84 0.80 1.00	0.64	0.54 DEDOL. 0.64 0.62 25.00 CCD-I	0.54 CCD-II 1.42 1.82		43.21	1.52 7.3 27.71 2.0		2.63	4.5	1.54 0.12	0.43
	5.06			3.67 3	0.66	1.65	1.08	0.09	0.38 4	0.08	0.75 RC-4 0.60 1.48	1.53	0.57 RT70 1.65 0.44 1.56	0.45	0.46 CCD-I 2.70 5.97 55.45	4.74 DEDOL. 2.68 3.22		0.30	3.63 3.3 0.21		4.39	6	0.06	0.12
	0.37			0.23 4	0.04	0.05	0.03	0.01	0.02 5	0.01	0.03 RC-5 0.03 0.17 RV52	0.06	0.04 RT74H 0.23 0.02 0.07	0.02	0.02 CCD-I 0.10 0.36 1.46 CC-I		0.19 CCD-II 0.13 0.13		0.01	0.16 2.5 0.01 0.5		0.25	1.65	0.14 2.14	0.23
	46.42			43.00 5	44.74	45.93	45.87	44.09	45.87 7 6	46.39	46.11 RC-6 45.76 42.78 RV-53 45.99	45.36 RQ26 46.64 46.22 46.09 RQ28	46.01 APPENDIX-V 44.40 46.69 46.47 41.36 47.81 39.76 40.76 47.31 42.16 49.98 39.40 DS 0 CCD-I 4.8 CCD-II 8.28 LS 0.5	0.60 0.05	0.078 0.19
	0.01			0.01	0.00	0.01	0.01	0.00	0.00	0.00	0.01 RV-54 0.00 0.03 0.01	0.00	0.00	0.00	0.01	0.01	0.01 CCD-I 0.00 0.00 0.00		0.00	0.01		0.01		0.00	0.01 1.3 0.00		0.02	0.24
	0.03 0.06		0.01 0.03 6 Porosity/permeability data from Ranero 0.01 0.01 0.03 0.01 0.02 0.00 0.01 0.01 0.02 0.00 0.02 0.01 0.02 0.00 0.02 0.00 0.01 0.02 0.02 0.00 0.02 0.00 0.03 0.00 0.03 0.00 0.02 0.00 0.03 0.00 0.02 0.00 0.03 0.01 0.03 0.02 0.02 0.42 0.02 0.01 0.01 0.00 0.01 0.01 0.03 0.01 0.01 0.01 0.05 0.01 0.02 0.01 8 RQ34 CCD-II 3.8 0.21 RC-7 CCD-I 2.3 0.09 9 RQ46 CCD-II 1.6 RV55 CCD-I 3.7 0.77 0.16 7 RC-8 CCD-I 4.22 0.33 area RQ30 DS 3.3 0.14 RV57 CCD-II 1.744 0.84
	31.14			50.94 8	56.57	31.44	31.29	55.77	32.49	29.89	31.02 RC9 32.82 54.08	30.73	35.83 RT77 30.90 31.69 31.72	32.15	31.86 CCD-I 30.05 30.87 36.23		31.75 CCD-II 51.80 56.35		30.38	51.96	33.15 7		50.34	3.42	0.79	0.12
											RV-59						CCD-I								1.0			0.04
	20.72			3.52 9	0.32	21.17	21.65	0.30	20.44	21.01	21.12 RC-10 19.98 1.48 21.11	16.08 RQ24 20.89 21.24 20.92	19.69	21.68 CCD-I 21.17 20.38 11.85		20.98	5.75 LS	1.31		21.50	3.92 2.6 21.95		7.98	0	1.23	0.14
	0.04			0.01 10 0.01	0.05	0.05	0.01	0.05	0.06	0.06 RC-11 0.06 0.01 0.06 RV-60	0.05 RQ29H 0.06 0.06 0.07	0.07	0.05 CCD-I 0.03 0.02 0.03 DEDOL.	0.03	0.02 ZD	0.01		0.07	0.03 2.6 0.09 2.4		0.02	3.7	0.20 0.06	0.17
	0.61			0.19 11 0.01	0.99	0.77	0.01	0.66	0.79	1.16 RC-12 1.10 0.06 1.28 RV-61	0.88 RQ35 1.02 0.69 1.34 RQ33	1.24	0.80 CCD-I 0.01 0.05 1.72 CCD-I		0.13 CCD-II 0.18 0.14 ZD		0.84	0.45 3.4 1.13 3.0		0.16	3.5 3.1	1.50 0.38	0.27 0.28
	0.28			0.17 12 0.03	0.04	0.02	0.01	0.02	0.02	0.02 RV-62 0.02 0.11 0.04	0.01	0.01	0.01	0.02	0.02	0.02 CCD-I 0.02 0.12 3.62		0.05	0.16		0.10		0.03	0.15 1.0 0.05		0.26	0.10
											RC-13	RQ41		CCD-I		CCD-II			2.9			11	0.18	0.9
	0.01			0.01 13 0.00	0.00	0.00	0.00	0.00	0.00	0.00 RC-14 0.00 0.00 0.00 RV63	0.00 RQ43 0.00 0.00 0.00	0.00	0.00 CCD-I 0.00 0.00 0.12 CCD-I		0.00	0.00 ZD	0.00		0.00	0.01 4.5 0.00 0.16	0.01	2.13	0.47 0.29	0.075
	0.34			0.18 14 0.00	0.00	0.00	0.00	0.00	0.00	0.00 RV64 0.00 0.09	0.00	0.00 RQ44 0.00 0.00 0.00	0.00	0.00	0.00 LS 0.00	0.00		0.00	0.34 ZD	0.17		0.00	0.16 0.5 0.00		0.40	3.24	1.44	0.17
										50.19	RC-15	RT68		CCD-I	DEDOL.			5.77		6.6	0.63	0.22
				15						RC-17 RV65I	RT69		CCD-I ZD		CCD-I 0.708152			5.9 3.2			0.9	0.31 0.37	0.13
		-16.57	-15.36	-14.49 16 -17.29			-17.07		-14.53 RV-65V RC-18							-17.49 CC-II -18.76 -10.72 ZD		-18.99		-12.5			-14.36	-14.57 0.2 2.31 -13.41		0.03 0.49
		0.04	1.21	1.75 17 1.22			1.00		1.04	999								0.08 ZD 0.78	-2.64		1.34		-0.9			1.21	1.2 11.6 2.06		1.64
											RC21							CCD-I								0.5			0.64
	CCD_I	CCD_I	CCD_I	LS	WC	CCD_I	CCD_I	WC	CCD_I	CCD_I	CCD_I	CCD_I	LS	CCD_I	DEDOL	CCD_I	CCD_I	CCD_I	CCD_I	CCD_I	CCD_II	CCD_II	DEDOL		CCD_II	LS	DEDOL	LS		CCD_I	LS	CCD_I	LS	LS
											RC22							CCD-I								1.9			0.40
	R392A	R392B	R393A	R393B	R394A	R395	R397	R398A	R398	R398B	R399	R400	R401	R403	R404	R405	R406	R407	R408	R410	R411A	R411B	R411C	R412	R413A	R413	R413B	R414	R415	R416A	R416	R416B	R416C	R417
	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_I	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II	MA_II

métrie, avec une pro por tion mo laire de CaCO 3 va riant de 50 à 52%. Les cal cai res si tués à proxi mi té des do lo mies montrent des com po si tions iso to pi ques ap pau vries en ␦ 18 O, si mi lai res à cel les des do lo mies, et tra dui sant un réé qui li brage pen dant la do lo mi ti sa tion. La re cris tal li sa tion semble avoir ré duit la po ro si té pri mi tive dans les do lo mies non pla nai res à tex ture mo saïque, et la cal cite tar dive comble l'es sen tiel de la po ro si té ré si duelle, com pli quant l'in ter pré ta tion des mesu res pé tro phy si ques. L'o ri gine des flui des res pon sa bles de la do lo mi ti sa tion peut être cherchée dans les ni veaux éva pori ti ques pro fonds du Trias, les dia pirs sa li fè res du Keu per et/ou dans des ro ches ignées ma gné sien nes.

Acknowledgments

We are indebted to Michael Joachimski (Department of Geology, University of Erlangen), Christophe Renac (Géologie, Université Jean Monnet, Saint Etienne) for stable isotope analyses. Thanks are also due to Eric Kohler (Geochemistry, IFP Energies nouvelles) for XRD analyses, followed by valuable discussions. Herman Nijs (Geology, K. U. Leuven) and Chantal Perrache (Géologie, Université Jean Monnet, Saint Etienne) are also acknowledged for thin sections preparation. Lastly, we thank two reviewers (Benoit Vincent and Veerle Vandeginste) for their valuable comments, which lead to a much improved finished product. This work is part of the PhD studies, partially financed by Petrobras and IFP Energies nouvelles.

ACKNOWLEDGEMENTS

The authors would like to thank Statoil SA for giving permission to publish these results. We are also grateful to D. Morrow, D. Cantrell and an anonymous reviewer. Their comments helped to improve the quality of this paper.

Acknowledgements

This contribution consists of a group-work involving various academic and industrial groups which have been studying the dolomite features that are exposed in the Ranero area (northern Spain). These groups include the University of Basque Country, Spanish Research Council (CSIC), TOTAL, IFP Energies nouvelles (France), Statoil, the Katholieke Universiteit Leuven (Belgium), and St Etienne School of Mines (France).

The idea of writing up a common paper has emerged from a workshop that was held at IFP Energies nouvelles on the 31 st of May and 1 st of June, 2010, devoted to the hydrothermal dolomites of Ranero and nearby regions in Cantabria and the Basque Country. During this workshop, it was agreed to present a joint-paper aiming at consolidating a common conceptual model for the Ranero hydrothermal dolomites. The authors would like to thank their academic and industrial institutions for allowing them to publish some results of their research work.

Hydrothermal dolomites in the Early Albian (Cretaceous) platform carbonates (N.W Spain): Nature and origin of dolomites and dolomitising fluids M. M. SHAH 123 , F. H. NADER 1 , D. GARCIA 2 , R. SWENNEN 3 , R. Ellam 4 1 IFP Energies nouvelles, 1 et 4, Av. de Bois Préau, 92852, Rueil-Malmaison, France (mumtaz-muhammad.shah@ifpen.fr) 2 Centre SPIN -ENSMSE, Département GENERIC, 158, cours Fauriel, 42023 Saint-Etienne, France Chapter:

CONCLUSIONS AND PERSPECTIVES

Field investigations, petrographic studies, geochemical as well as isotope analyses and fluid inclusion studies of fault-related hydrothermal dolomites in the late Albian slope-to-platform carbonates in the Karrantza valley, (NW Spain) resulted in the following conclusions:

• Excellent exposures in the study area (especially in the Pozalagua quarry) helped in the establishing comprehensive paragenetic sequence (Swennen et al., in press), which facilitated the in depth study of various dolomite and calcite phases.

• Integrated studies resulted in the identification of two distinct phases of dolomites, which preand post-date calcite phases. Initially, hydrothermal karst-filling by lath-like, banded calcite (CC-I) followed by coarse crystalline, twinned calcite (CC-II). Initial phase of calcitization is followed by dolomitization event related to fracture-and fault development. Two sets of bedding-parallel stylolites pre-and post-date dolomitization. First phase of dolomite consisted of medium to coarse crystalline, ferroan-rich pervasive dolomite (CCD-I), which contains Ferich core (CCD-Ia) and relatively Fe-poor (CCD-Ib). CCD-Ia containing ferroan rim, which readily dedolomitized by late meteoric calcite. Zebra dolomite (ZD) and internal sediments (DS) formed by the replacement of pre-existing limestone and believed to be its origin before CCD-I.

Second phase of dolomite formation resulted in coarse crystalline, non-ferroan saddle dolomite (CCD-II). The termination of dolomitization event is marked by pyrite precipitation. Coarse crystalline, white calcite (WC) usually occurred as pore-fillings in the brecciated dolomite, hence confirming its post-tectonic formation.

• Post-diagenetic alterations include cataclastic deformation, dissolution and precipitation of late, meteoric calcite (TC).

• Mineralization includes scarce Galena-Barite ore, which pre-dates dolomitization, and more frequent, although unevenly distributed, Sphalerite-Galena (MVT ore) coeval with CCD-I dolomitization.

• The broad range of depleted δ 18 O values (-19 to -10‰ V-PDB) is consistent with multiphase dolomitization and dolomite recrystallization (Nielsen et al., 1994). The estimated salinity of the primary inclusions of these dolomite facies are up to three to four time greater than seawater (12 -21 eq. wt. % NaCl; Shah et al., 2010), which eliminates meteoric water as possible explanation for depleted δ 18 O values and temperature increase is the likely cause for the depleted δ18O values as argumented by the high T H values (Shah et al., 2010).

APPENDIX-III