Guilhem Hoareau
email: guilhem.hoareau@univ-pau.fr

Nemo Crognier

Brice Lacroix

Charles Aubourg

Nick M W Roberts

Nathan Niemi

Mathieu Branellec

Nicolas Beaudoin

Isabel Suárez Ruiz

Combination of ∆47 and U-Pb dating in tectonic calcite veins unravel the last pulses related to the Pyrenean Shortening (Spain)

Keywords: Clumped isotopes, carbonate U-Pb geochronology, veins, fractures, Pyrenees

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The links between fracture development and fluid flow in foreland fold and thrust belts has been the subject of active research over the last decades (e.g. [START_REF] Roure | Incidence and Importance of Tectonics and Natural Fluid Migration on Reservoir Evolution in Foreland Fold-and-Thrust Belts[END_REF] references therein; [START_REF] Lacroix | Syntectonic fluid-flow along thrust faults: Example of the South-Pyrenean fold-and-thrust belt[END_REF][START_REF] Lacroix | Multi Fluid-Flow Record during Episodic Mode I Opening: A Microstructural and SIMS Study (Cotiella Thrust Fault, Pyrenees)[END_REF]Evans and Fischer, 2012;Beaudoin et al., 2014[START_REF] Beaudoin | U-Pb dating of calcite veins reveals complex stress evolution and thrust sequence in the Bighorn Basin, Wyoming, USA[END_REF][START_REF] Crognier | Syn-orogenic fluid flow in the Jaca basin (south Pyrenean fold and thrust belt) from fracture and vein analyses[END_REF][START_REF] Cruset | From hydroplastic to brittle deformation: Controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)[END_REF]. However, in low-temperature systems the precipitation conditions are often obscured by the scarcity of reliable mineral geothermometers and geochronometers, and by the variable impacts of temperature, precipitation rate, and fluid composition, on authigenic mineral composition (e.g. [START_REF] Dromgoole | Iron and Manganese Incorporation into Calcite: Effects of Growth Kinetics, Temperature and Solution Chemistry[END_REF]Saulnier et al., 2012;[START_REF] Crognier | Syn-orogenic fluid flow in the Jaca basin (south Pyrenean fold and thrust belt) from fracture and vein analyses[END_REF].

Clumped isotope thermometry ideally recovers the temperature of carbonate formation without making assumptions about the composition of precipitating water and / or oxygen composition of another mineral phase, as required for conventional stable isotope thermometry [START_REF] Ghosh | 13 C-18 O Bonds in Carbonate Minerals: A New Kind of Paleothermometer[END_REF]. The recent development of calibrations to temperatures higher than 100°C (e.g., [START_REF] Bonifacie | Experimental calibration of the dolomite clumped isotope thermometer from 25 to 350°C, and implications for a universal calibration for all (Ca, Mg, Fe)CO3 carbonates[END_REF][START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF] has allowed Δ47 clumped isotope application to the field of fluid migration along tectonic structures, i.e. the Moab fault (e.g., [START_REF] Bergman | Tracing Paleofluid Sources Using Clumped Isotope Thermometry of Diagenetic Cements Along the Moab Fault, Utah[END_REF][START_REF] Hodson | Temperature and Composition of Carbonate Cements Record Early Structural Control on Cementation in a Nascent Deformation Band Fault Zone: Moab Fault, Utah, USA[END_REF], the San Andreas Fault Zone [START_REF] Luetkemeyer | Constraints on paleofluid sources using the clumped-isotope thermometry of carbonate veins from the SAFOD (San Andreas Fault Observatory at Depth) borehole[END_REF], or the Cotiella and Lower Pedraforca thrust faults in the Pyrenees [START_REF] Lacroix | Multi Fluid-Flow Record during Episodic Mode I Opening: A Microstructural and SIMS Study (Cotiella Thrust Fault, Pyrenees)[END_REF]Cruset el al., 2020). It is also very recently that U-Pb dating of calcite cements by LA-ICPMS has been employed to successfully date brittle faulting and diagenetic cements (e.g., [START_REF] Roberts | U-Pb Geochronology of Calcite-Mineralized Faults: Absolute Timing of Rift-Related Fault Events on the Northeast Atlantic Margin[END_REF][START_REF] Beaudoin | U-Pb dating of calcite veins reveals complex stress evolution and thrust sequence in the Bighorn Basin, Wyoming, USA[END_REF][START_REF] Mangenot | An emerging thermo-chronometer for carbonate-bearing rocks: Δ47/(U-Pb)[END_REF][START_REF] Macdonald | Clumped-isotope palaeothermometry and LA-ICP-MS. U-Pb dating of lava-pile hydrothermal calcite veins[END_REF][START_REF] Cruset | From hydroplastic to brittle deformation: Controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)[END_REF]. When combined together these techniques may considerably refine the diagenetic and fluid-flow history of sedimentary basins, and increase our understanding of past diagenetic alteration, especially along fault systems [START_REF] Lawson | Deciphering the diagenetic history of the El Abra Formation of eastern Mexico using reordered clumped isotope temperatures and U-Pb dating[END_REF][START_REF] Mangenot | An emerging thermo-chronometer for carbonate-bearing rocks: Δ47/(U-Pb)[END_REF][START_REF] Macdonald | Clumped-isotope palaeothermometry and LA-ICP-MS. U-Pb dating of lava-pile hydrothermal calcite veins[END_REF][START_REF] Cruset | From hydroplastic to brittle deformation: Controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)[END_REF].

Here, we focus on the South Pyrenean Frontal Thrust (SPFT), outlined by the Sierras Exteriores (Spain), a complex alignment of folds and thrusts making the most external part of the South-Pyrenean fold and thrust belt. Although its tectonic and sedimentary evolution has been extensively documented (e.g. Turner, 1988[START_REF] Garrido | Synchronous Detachment Folds and Coeval Sedimentation in the Prepyrenean External Sierras (Spain): A Case Study for a Tectonic Origin of Sequences and Systems Tracts[END_REF][START_REF] Arenas | Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics (north-eastern Iberia): controls on basin margin fans and fluvial systems[END_REF][START_REF] Oliva-Urcia | Rotational basement kinematics deduced from remagnetized cover rocks (Internal Sierras, southwestern Pyrenees)[END_REF][START_REF] Oliva-Urcia | New magnetostratigraphic dating of the Palaeogene syntectonic sediments of the westcentral Pyrenees: tectonostratigraphic implications[END_REF], 2019), only a few studies have focused on the thermal or paleohydrological history of the SPFT [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF][START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF]. This example is particularly suitable to test whether the combination of Δ47 clumped isotopes and U-Pb dating of carbonates (∆47/U-Pb thermochronometry) can bring valuable information about the thermal and fluid-flow evolution in complex fault systems.

In this contribution, ∆47/U-Pb thermochronometry of calcite veins from the SPFT are combined with fracture analysis, fluid-inclusion microthermometry and thermal modeling to define the temperature and timing of vein formation, and to unravel the origin of calciteprecipitating fluid within the tectonic frame of the area.

Geological Context

The South Pyrenean Frontal Thrust is located at the southern front of the Pyrenees, a double-verging asymmetric fold and thrust belt which developed from the Late Cretaceous to the Early Miocene during the convergence between the Iberian and European plates [START_REF] Choukroune | Main Results of the Ecors Pyrenees Profile[END_REF][START_REF] Muñoz | Evolution of a continental collision belt: ECORS-Pyrenees crustal balanced cross-section[END_REF][START_REF] Beaumont | Factors Controlling the Alpine Evolution of the Central Pyrenees Inferred from a Comparison of Observations and Geodynamical Models[END_REF][START_REF] Teixell | Crustal structure and evolution of the Pyrenean-Cantabrian belt: A review and new interpretations from recent concepts and data[END_REF] (Figure 1A). Most of the central and southern part of the Pyrenees is affected by a series of southverging thrusts and folds (e.g., Labaume et al., 2016 and references therein;Munoz et al., 2002Munoz et al., , 2013Munoz et al., , 2018)). The Axial Zone is made of imbricated thrust units of Paleozoic basement, which connect southward to thrust units affecting Mesozoic to Cenozoic sediments, forming the South Pyrenean Zone (SPZ), which overrides the Ebro foreland basin [START_REF] Teixell | The Ansó transect of the southern Pyrenees: basement and cover thrust geometries[END_REF][START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF][START_REF] Teixell | Crustal structure and evolution of the Pyrenean-Cantabrian belt: A review and new interpretations from recent concepts and data[END_REF]. In the west-central Pyrenees, the SPZ corresponds to the Jaca-Pamplona piggyback basin. From north to south, basement thrusts affecting the SPZ along the eastern Jaca basin transverse include the Eaux-Chaudes-Lakora thrust (Ypresian-Bartonian), the Gavarnie thrust (Priabonian-Rupelian), the Broto thrust (Rupelian-Chattian), and the Fiscal and Guarga thrusts (late Rupelian-Aquitanian) [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF][START_REF] Oliva-Urcia | Dating the northern deposits of the Ebro foreland basin; implications for the kinematics of the SW Pyrenean front[END_REF] and references therein) (Figure1B). The emergence of the SPFT, forming the Sierras Exteriores in the study zone, was contemporaneous to the Broto and Fiscal-Guarga basement thrusts (~33 -20 Ma), and accumulated at least 22 km of shortening [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF]. It subdivided the SPZ in the Jaca-Pamplona basin and the Ebro basin.

The Sierras Exteriores consist of a complex WNW-ESE alignment of thrusts, which cross several anticline folds (from the east to the west: Gabardiella, Pico del Aguila, Bentué de Rasal, Santo-Domingo anticlines) [START_REF] Anastasio | Thrusting, halotectonics, and sedimentation in the External Sierra, southern Pyrenees, Spain[END_REF][START_REF] Garrido | Synchronous Detachment Folds and Coeval Sedimentation in the Prepyrenean External Sierras (Spain): A Case Study for a Tectonic Origin of Sequences and Systems Tracts[END_REF], 2000;[START_REF] Arenas | Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics (north-eastern Iberia): controls on basin margin fans and fluvial systems[END_REF] (Figure 1C,D,E). The Gabardiella, Pico del Aguila, Bentué de Rasal and Rasal anticlines formed along with Eaux-Chaudes and Gavarnie thrust activities, and have been interpreted to have formed on oblique ramps of south-verging thrusts (e.g., [START_REF] Pueyo | Rotation Velocity of a Thrust: A Paleomagnetic Study in the External Sierras (Southern Pyrenees)[END_REF], or as a result of westward propagation of deformation during early Bartonian to Priabonian times [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF][START_REF] Mochales | Rotational velocity for oblique structures (Boltaña anticline, Southern Pyrenees)[END_REF]. They have a rough N-S axial orientation, explained by a syn-growth clockwise rotation of up to 40° [START_REF] Pueyo | Rotation Velocity of a Thrust: A Paleomagnetic Study in the External Sierras (Southern Pyrenees)[END_REF][START_REF] Huyghe | Paleogene Propagation of the Southern Pyrenean Thrust Wedge Revealed by Finite Strain Analysis in Frontal Thrust Sheets: Implications for Mountain Building[END_REF]. The WNW-ESE Santo Domingo anticline formed during Rupelian to Aquitanian times, coeval to the Broto and Fiscal thrusts [START_REF] Oliva-Urcia | Dating the northern deposits of the Ebro foreland basin; implications for the kinematics of the SW Pyrenean front[END_REF]. The folds were affected by the emergence of cover thrusts collectively labeled as the Sierras Exteriores thrust by [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF]. These thrusts correspond to the cover equivalent of the Fiscal-Guarga thrusts, and form the SPFT. Although their activity is clearly recognized between the Rupelian and the Aquitanian (e.g., [START_REF] Oliva-Urcia | Dating the northern deposits of the Ebro foreland basin; implications for the kinematics of the SW Pyrenean front[END_REF], minor, active compressive tectonics has been proposed to have taken place at least until the Burdigalian, as the uppermost Aquitanian continental deposits of the Uncastillo Formation are folded and thrusted (e.g., the Domingo-Gabardiella thrust sytem; Millán [START_REF] Garrido | Actividad tectónica registrada en los depósitos terciarios del frente meridional del Pirineo central. Translated title: Tectonic activity recorded in the tertiary deposits of the southern front of the central Pyrenees[END_REF][START_REF] Arenas | Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics (north-eastern Iberia): controls on basin margin fans and fluvial systems[END_REF]. In the Pico del Aguila fold, this complex evolution was associated with the development of a polyphase fracture network from the Paleocene to the Oligocene, associated with a multi-stage fluid flow history involving both local waters and the ingress of meteoric water from the surface [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF].

From the early Eocene to the Miocene, the activity of the successive southwardverging thrusts was contemporaneous with deposition of several thousand meters of syntectonic sediments in the Jaca-Pamplona basin, above Triassic to Paleocene pre-tectonic sediments (e.g., [START_REF] Soler-Sampere | Líneas Generales De La Geología Del Alto Aragón Occidental[END_REF][START_REF] Carbayo | [END_REF][START_REF] De Rojas | Mapa Geológico De España a Escala[END_REF][START_REF] Samso | Mapa Geológico De España a Escala[END_REF][START_REF] Teixell | Mapa Geológico De España a Escala[END_REF]Montes andBarnolas, 1992, 2002;[START_REF] Garrido | Synchronous Detachment Folds and Coeval Sedimentation in the Prepyrenean External Sierras (Spain): A Case Study for a Tectonic Origin of Sequences and Systems Tracts[END_REF], 2000;[START_REF] Arenas | Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics (north-eastern Iberia): controls on basin margin fans and fluvial systems[END_REF][START_REF] Oliva-Urcia | New magnetostratigraphic dating of the Palaeogene syntectonic sediments of the westcentral Pyrenees: tectonostratigraphic implications[END_REF], 2019; The thermal evolution of the SPFT remains poorly constrained. According to [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF], the Triassic deposits presently outcropping in the Sierras Exteriores were buried up to ~5 km. Assuming a geothermal gradient of 24 °C/km typical of foreland basins [START_REF] Allen | Basin analysis: principles and application to petroleum play assessment[END_REF], this would correspond to maximum temperatures of ~140 °C in the studied zone. Such temperature is grossly consistent (i) with the temperatures of ~80-100 °C proposed by [START_REF] Cantarelli | Tectonic-sedimentation Burial History and Exhumation of the Southern Sector of the Central-western Pyrenees[END_REF] in the Belsué-Atarés and Arguis-Pamplona Formations north of the Rasal anticline (~4 km burial), (ii) with the absence of resetting of apatite fission track ages in Belsué-Atarés sandstones sampled east of the Arguis anticline [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF], and (iii) with the low precipitation temperatures of veins sampled in the Pico del Aguila anticline by [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF] (T < 100°C).

Methodology

Sampling and analytical strategy

The initial sampling strategy was intended to increase knowledge of the thermal evolution of the Sierras Exteriores. 17 outcrops of Triassic to Rupelian sedimentary rocks were selected to sample bulk rocks and/or calcite veins (Figure 1B,C,D). 9 bulk rocks appeared suitable for the measurement of vitrinite reflectance (VR) or Rock-Eval (RE) Tmax values, and were used to build 1D thermal models of the study area. 10 tectonic calcite veins scattered along the Sierras Exteriores were selected to assess fluid temperature conditions both from fluid inclusion data and from ∆47 clumped isotope analysis (SE1, SE2, SE3, SE4, SE10, SE12, SE13, A21, A22, and A56). Among the veins, three were previously sampled in the Pico del Aguila anticline (A21, A22, and A56, corresponding to sites 436, 439 and 467, respectively, in [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF]). Vein sampling was associated with the analysis of fracture and vein orientations where outcrop conditions permitted (7 veins out of 10: sites SE4, SE10, SE12, SE13, A21, A22, A56), in order to link vein formation to the main tectonic events recorded in the Sierras Exteriores. Given the maximal burial temperatures obtained from VR, RE Tmax values and thermal modelling (T > 100°C; see Results section), U-Pb dating of these calcite veins was then performed to estimate the degree of ∆47 solid-state reordering which, depending on the thermal history, can lead to erroneous ∆47 temperatures (T∆47) [START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF].

Analytical methods

Petrographic and microstructural characteristics of the veins were studied on polished thick-and thin-sections using optical microscopy and cathodoluminescence (CL). CL images were acquired using an OPEA Cathodyne coupled to a Nikon BH2 microscope at the University of Pau and Pays de l'Adour (LFCR, France). Analytical conditions were with an accelerating voltage of 12.5 kV and an intensity of 200-300 mA.

Fluid-inclusion petrography was performed on doubly polished thick sections (100 µm) of the vein samples using a Linkam automatic THMSG600 cooling-heating stage coupled to a Nikon LV-150-ND microscope and a Nikon MK1 camera (University of Pau, LFCR, France). Calibration of the microthermometric stages used synthetic fluid inclusions (FIL, Leoben, Austria), including, (1) pure water (ice melting temperature (Tm) = 0.0 °C; critical homogenization temperature (Th) = 374.1 °C), (2) H2O-CO2 inclusions (CO2 melting temperature = -56.6 °C; hydrate melting temperature = +9.9 °C) and (3) H2O-NaCl inclusions (eutectic temperature (Te) = -21.2 °C). Accuracy was ±0.1 °C at temperature between -56.6 and +25 °C and ±2 °C at +374 °C. Progressively heating up to Th was followed by freezing of the inclusions, and their slow heating to tentatively determine their Te and Tm.

Carbon and oxygen isotopes as well as ∆47 clumped isotopes compositions of the 10 vein calcite samples were performed at the University of Michigan. About 6 mg of microdrilled carbonate powder was loaded into a manual multi-sample rotary carrousel. Each sample was then dropped into ~20 ml of anhydrous 105 wt. % phosphoric acid maintained at 75°C. Extracted CO2 was purified following cryogenic procedures (propanol and liquid N2 mixture at -95°C) under vacuum conditions as defined in [START_REF] Ghosh | 13 C-18 O Bonds in Carbonate Minerals: A New Kind of Paleothermometer[END_REF] and [START_REF] Huntington | Methods and Limitations of 'Clumped' CO2 Isotope (Δ47) Analysis by Gas-Source Isotope Ratio Mass Spectrometry[END_REF], to remove residual water vapor. CO2 was then purified to remove any hydrocarbon and halocarbon contaminants by passing through Porapak™ resin at ~ -35°C for 15 min. Finally, purified CO2 was transferred to a vial for storage for no more than 24 hr before analysis. CO2 masses 45-49 were measured on a dual-inlet Thermo-Finnigan MAT 253 mass spectrometer following the methods of [START_REF] Huntington | Methods and Limitations of 'Clumped' CO2 Isotope (Δ47) Analysis by Gas-Source Isotope Ratio Mass Spectrometry[END_REF]. Δ47 values were calculated using the stochastic reference heated gas and equilibrated CO2-water (at 25°C) lines produced during the relevant analysis period (March 2014, September 2014and January 2015). Heated gas was produced by heating CO2 gases of different isotopic compositions in a furnace for 2 hr. Each isotopologue analysis required ~2 ½ hr of mass spectrometer time to achieve precisions on the order of 10-6 for Δ47 values and each carbonate sample was analyzed at least 3 times in order to reduce uncertainties in derived Δ47 temperature values.

Final temperature values were corrected empirically for acid fractionation factor at 75°C [START_REF] Guo | Isotopic Fractionations Associated with Phosphoric Acid Digestion of Carbonate Minerals: Insights from First-Principles Theoretical Modeling and Clumped Isotope Measurements[END_REF]. Δ47 results are normalized to the Universal Reference Frame as proposed by [START_REF] Dennis | Defining an Absolute Reference Frame for 'Clumped' isotope Studies of CO2[END_REF] using CO2-H2O equilibration at 25°C andheated CO2 at 1000°C. Δ47 values are converted into temperatures using the Δ47-temperature calibration of [START_REF] Bonifacie | Experimental calibration of the dolomite clumped isotope thermometer from 25 to 350°C, and implications for a universal calibration for all (Ca, Mg, Fe)CO3 carbonates[END_REF].

For the host rock samples, O-and C-isotopes analysis was performed at the ISTeP (Paris, France), using a Kiel IV Carbonate device connected to a mass spectrometer delta V advantage. About 40 µg of calcite powder was reacted with 104% phosphoric acid at 70 °C in individual vials. The CO2 sample gas produced was purified in an automatic cryogenic system. Instrument calibration was performed using the standard NBS 19 and an in-house standard (Marceau). The analytical precision determined by analysis of NBS 19 was 0.07‰ for δ 18 O and 0.03‰ for δ 13 C. Carbon and oxygen isotopic composition are reported as relative to Vienna Pee Dee Belemnite (VPDB).

U-Pb geochronology via the in-situ LA-ICP-MS method was conducted at the Geochronology & Tracers Facility, NERC Isotope Geosciences Laboratory (Nottingham, UK). The method utilizes a New Wave Research 193UC excimer laser ablation system, coupled to a Nu Instruments Attom single-collector sector-field ICP-MS. The laser parameters used are a 100 μm static spot, fired at 10Hz, with a ~7-8 j.cm 2 fluence, for 30 seconds of ablation. Normalization uses standard sample bracketing to NIST 614 glass for Pb-Pb ratios, and the WC-1 carbonate reference material for 206 Pb/ 238 U ratios [START_REF] Roberts | WC-1: A calcite reference material for LA-ICP-MS U-Pb geochronology[END_REF]. Normalisation is based on the measured/accepted ratio derived from the session-based drift-corrected mean of the primary WC-1 reference material. An additional carbonate material, Duff Brown, was measured in most sessions to provide a control on accuracy and precision. No common lead correction is made; those ages that are deemed robust (based on low MSWD), are determined from lower intercepts on a Tera-Wasserburg plot. Age results are based in lower intercept ages with systematic uncertainties (decay constants, reference material age uncertainty, long-term method reproducibility) propagated. Resulting ages have uncertainties quoted as age ± x/y, where x is without systematic uncertainties and y is with (see [START_REF] Horstwood | Community-Derived Standards for LA-ICP-MS U-(Th-)Pb Geochronology -Uncertainty Propagation, Age Interpretation and Data Reporting[END_REF]. Additional information is available in the Supplementary Material.

Vitrinite reflectance analyses were performed at the INCAR laboratory (Oviedo, Spain), using reflected white light and an oil immersion objective (50x) in an MPV-Combi-Leitz optical microscope. The petrographic pellets were prepared using a procedure described in the ISO norm (ISO-7404-2, 2009). These pellets are formed by 10-15 g of rock, grounded until a particle size of about 1 mm, blended with a synthetic resin composed by styrene and phthalic anhydride. Rock particles stiffened in the resin in a random statistical orientation.

The resulting samples were polished and put for minimum 24 hours in a silica-gel drier before microscopic analysis. All samples were examined under reflected white light. The reflectance was measured in incident white light on vitrinite particles of unaltered / unoxidized samples, following the ISO-7404-5 (2009) and ASTM-D7708-11 (2011) norms.

Rock-Eval pyrolysis was made using a Rock Eval 6 (VINCI Technologies), at the ISTeP (Paris, France), in order to obtain RE Tmax values, which corresponds to the temperature at which the largest quantity of hydrocarbons is released upon cracking.

Results

Analysis of fracture and vein orientation

The statistical analysis of the fracture network was focused on measurements of joints and veins that exhibit no evidence of shear, at sites SE4, SE10, SE12, and SE13. These data were complemented with previously published data from 3 sites (A21, A22, A56) [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF]. The three stereograms proposed for each site (Figure 2) correspond to the present-day orientations, and to orientations corrected for deformation recorded in the Sierras Exteriores (folding of strata, and regional tilting due to activation of the Guarga thrust, taken as a plane N110°E/30°NE (strike/dip) following [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF]. Examples of field photographs of joints and veins are presented in Figure 3A to 3D.

For this study, the veins were sampled in stratigraphic levels ranging from the Triassic to the Priabonian. In the Bartonian / Priabonian Arguis-Pampelune marls (sites A21 and A22), most veins are oriented N060°E, and become vertical after unfolding and backtilting. To a lesser extent, N170°E striking fractures are also found. Note that vein A22 was interpreted as a right-lateral fault by [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF]. In the Lutetian Guara limestones (sites SE4 and A56), the fracture patterns are similar at both sites, with N110°E preferential orientation, along with a minor N170°E trending set. The latter is orthogonal to bedding in current bedding attitude, whereas the other one is not. In the Cretaceous Adraen Bona formation (site SE12), most fractures are vertical after unfolding and backtilting, trending along the N170°E and N110°E directions. In the middle Triassic (Muschelkalk) beds (sites SE10 and SE13), the fractures are vertical after the same corrections, and 4 trends of fractures striking N060°E, N140°E, N170°E and N040°E are recognized. The N060°E-striking fractures are restricted to the Triassic and Bartonian / Priabonian beds, whereas the N110°E-striking fractures are found both in the Muschelkalk and Eocene limestones. Finally, the N170°E-striking fractures has been measured in all lithologies, and the N140°E-striking fractures are only seen at SE10.

Vein petrography

Nine of the 10 collected veins consist to either mode I extensional veins or mode Imode II transtensional shear veins according to the nomenclature of [START_REF] Bons | A Review of the Formation of Tectonic Veins and Their Microstructures[END_REF]. Only one vein (SE2) corresponds to the mode II (shear vein). Extensional veins (SE1, SE3, SE4, SE10, SE12, SE13, A21 and A56) correspond to mm-to cm-thick veins, filled by granular, blocky or elongated-blocky calcite. Among them, 2 veins (SE1, A56) show evidence of crackseals events, indicating precipitation coeval to fracture opening. The former one displays multiple crack-seals on the borders and elongated blocky calcite crystals, defining a stretching vein [START_REF] Bons | A Review of the Formation of Tectonic Veins and Their Microstructures[END_REF] (Figure 3E). The latter one is filled by blocky crystals, mixed with pieces and trails of host-rock (Figure 3F). One vein (SE4) is characterized by blocky crystals affected by several stylolites parallel to the vein walls (Figure 4A). The other extensional veins are filled with blocky calcite without evidence of syn-opening precipitation (Figure 4E).

The transtensional shear vein (A22) has a thickness of 2.5 cm. It presents a first generation of elongated blocky crystals slightly oblique to the vein walls, corresponding to a first stage of opening (Figure 4B). It is followed by elongated blocky crystals evolving to large blocky crystals towards the center of the vein, corresponding to a second stage of opening and calcite precipitation.

The shear vein (SE2) corresponds to a cm-thick body featuring slickenfibres.

Microscopically, it comprises stacked (sub)-millimeter thick sheets parallel to the macroscopic vein, formed by the lateral succession of numerous sub-millimetric rhombshaped veinlets separated from each other by thin, locally discontinuous, host-rock bands (Figure 4C), similar to the description of [START_REF] Bons | A Review of the Formation of Tectonic Veins and Their Microstructures[END_REF]their Fig. 12).

Five veins (A56, SE2, SE4, SE12, SE13) present a homogeneous CL, supporting a single precipitation stage or precipitation from waters with similar composition [START_REF] Machel | Application of Cathodoluminescence to Carbonate Diagenesis[END_REF]. They have a dull orange-red color in CL, except SE13 where the CL is extinct. The five other veins present at least two distinct colors. Among these, three veins (A21, SE3, SE10) show concentric CL zoning in the blocky calcite grains, reflecting precipitation under variable redox conditions or variations in precipitation kinetics [START_REF] Machel | Application of Cathodoluminescence to Carbonate Diagenesis[END_REF]. In A21 and SE3 veins, the CL zonings remain in orange tones (Figure 4E). In SE10 vein, they evolve from orange, to dull and bright yellow, supporting multi-precipitation stages (Figure 4D).

Finally, in A22 vein, the CL varies slightly between the 2 cement precipitation stages (dull orange on the borders to brighter orange to the center of the vein) (Figure 4B), whereas for SE1 the fringe of crystals having partially filled some voids have an orange CL brighter than in the rest of vein (Figure 3E).

Fluid inclusion petrography and microthermometry

All veins show small primary and secondary fluid inclusions (generally below 5 µm), making phase transition temperatures difficult to measure. Only 3 samples (SE2, SE10 and SE12) presented primary two-phase aqueous inclusions with Th in the range 75˚C-83°C for sample SE2 (n = 5), 125-185°C for sample SE10 (n = 4) and 79-95°C for sample SE12 (n = 6) (Figure 5A; Table S1). For SE10, most primary fluid inclusions were all liquid, suggesting that the few two-phase inclusions are the results of variable inclusion stretching. The other veins show only single-phase primary inclusions, generally suggesting trapping temperatures below 50°C, or up to ~100°C for very small inclusions (< 3 µm) [START_REF] Goldstein | Systematics of Fluid Inclusions in Diagenetic Minerals[END_REF]. The same conclusion applies to the secondary inclusions, which are all liquid in all the veins. No Te and Tm could be measured.

Stable and ∆47 clumped isotopes

For the analyzed veins, the δ 18 O and δ 13 C values range between -9.24‰ and +2.69 ‰ VPDB, and between -4.47‰ and +1.22‰ VPDB, respectively (Figure 5C; Table S1). Their ∆47 values range from 0.696‰ to 0.532‰, which can be converted to precipitation temperatures between 21˚C and 88 ˚C (Figure 5B; Table S1). For the three veins presenting two-phase aqueous fluid inclusions, the T∆47 values are in good agreement with the homogenization temperatures (Figure 5B).

For the host rocks, the isotopic composition range between -2.37‰ and +2.71‰ VPDB for δ 13 C, and between -6.52‰ and -2.73 ‰ VPDB for δ 18 O (Figure 5C).

Carbonate U-Pb dating

Two to 6 transects of spot ablations were performed in 8 of the 10 vein samples selected for U-Pb dating. 6 samples (SE3, SE4, SE10, A21, A22, A56) gave meaningful, accurate ages (that we define as being younger than the depositional age of the enclosing rocks and older than present within 2 sigma uncertainties, and as having MSWD below 2), for at least one transect. Note that sample A21 is included in the successful samples, despite a MSWD of 2.5. The ages obtained range from 60.7±2.9 Ma to 14.4±2.7 Ma (Figure 6; Table S1 andS2). They correspond to one transect (A56, SE10), or from the combination of two transects giving ages similar within uncertainty (A21, A22, SE3, SE4). All veins but one show precipitation ages younger than ~24 Ma (23.8 Ma to 11.7 Ma if the age uncertainties are considered).

Maturity of organic matter

Accurate vitrinite reflectance values could be measured on only 3 samples (1 coal sample in the Triassic (site SE11) and 2 limestone samples in the Cretaceous (site SE12))

(Figure 1). The values are 0.32±0.04% (1s) for sample SE11, and 0.34±0.03% and 0.44±0.10% for sample SE12 (n = 12) (Figure S2). For Rock-Eval analyses, measurements were performed on 17 powdered samples mostly from the northern part of the study zone.

Only 7 samples yielded reliable RE Tmax values varying from 431 to 443°C (Figure 1B, Table S3).

Discussion

5.1. Timing of joint and vein emplacement in the SPFT: structural measurements versus U-Pb dating Our novel data of fracture orientation (i.e., joints and veins), combined with existing interpretation of the Pico del Aguila anticline (sites A21, A22 and A56; [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF] allow to propose a sequence of deformation in the Sierras Exteriores. Based on fracture orientations and their link with local fold axis orientation, we first discuss whether the main fractures sets, which comprise the vein analyzed, formed before, during or after folding (see [START_REF] Tavani | A review of deformation pattern templates in foreland basin systems and fold-and-thrust belts: implications for the state of stress in the frontal regions of thrust wedges[END_REF]. We propose that at 4 sites, there are 2 main fracture sets developed before folding, or during early folding: one set trending ~N060°E comprising fractures at high-angle to bedding (A21, A56, SE10, SE13), and one set trending ~N170°E (SE10, SE12, SE13). At 2 sites (A22 and SE4), the dominant fracture sets are identified as being late-to post-folding in origin. For site A22, [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF] have shown that the veins result from the reactivation of former joint during Guarga thrusting. For site SE4 (located at the eastern tip of the Santo Domingo anticline), our interpretation is based both on the presentday vertical orientation of the main set, and on its mean strike similar to the fold axis (~N110).

Where U-Pb dating was successful (A21, A22, A56, SE4, SE10), we can refine this interpretation with absolute age constraints. For sites A21 and A56, formation of the ~N060°E directed fractures (which include the veins dated) during early folding of the Pico del Aguila anticline, as proposed by [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF], would correspond to the Bartonian (~38-41 Ma). U-Pb ages show that these fractures actually are cemented with calcite dated to ~14-16 Ma. For sample A21 (14.7 ± 2.7 Ma), whether the cement is contemporaneous or younger than the opening of the fracture cannot be answered from petrographic observations. However, for sample A56, the young age (16.6 ± 1.1 Ma), added to evidence of syn-tectonic calcite precipitation, suggest that the fracture developed only after the activation of the Guarga thrust (i.e., post-folding), or that have may seal -the crack reactivated an inherited fracture. For site SE10 (Triassic Muschelkalk beds located south-west of the Pico del Aguila anticline), relation to folding of the early ~N060°E-striking set would lead to interpret it as related to Layer Parallel Shortening (LPS; sensu [START_REF] Bergbauer | A new conceptual fold-fracture model including prefolding joints, based on the Emigrant Gap anticline, Wyoming[END_REF]. U-Pb dating (60.7 ± 2.9 Ma) demonstrates that instead, these fractures developed prior to LPS, before regional clockwise rotation, leading us to interpret them as the across-strike set of fractures of the foreland forebulge (sensu [START_REF] Tavani | A review of deformation pattern templates in foreland basin systems and fold-and-thrust belts: implications for the state of stress in the frontal regions of thrust wedges[END_REF]. Accordingly, the other fractures of this site (~N170°E-striking) correspond to the along-strike set. For sample A22, the interpretation of a post-folding vein development is compatible with the measured U-Pb age (18.8 ± 5.0 Ma). Finally, for site SE4, the main fracture set likely formed at the end of Santo Domingo folding. According to Oliva-Urcia et al ( 2019), this fold developed during Chattian-Aquitanian times (~20-27 Ma), slightly older than our U-Pb age of 17.3 ± 3.4 Ma.

Petrographic evidence of vertical stylolites in the vein demonstrates clearly that tectonic shortening was still ongoing after vein precipitation, i.e. at least during the Burdigalian.

The consequences of the interpretations proposed above are twofold. First, although based only on a limited set of data, the ages obtained by U-Pb dating of calcite veins have bring decisive insights into the sequence of deformation recorded in the SPFT. For some veins (A56 and SE10), absolute age determinations were in contradiction with the interpretations based solely on the study of fracture sets (i.e., younger and older, respectively).

We propose that the structural approach to determining relative joint/vein ages in folds should be systematically associated with absolute dating of vein precipitation for greater reliability, as proposed by [START_REF] Beaudoin | U-Pb dating of calcite veins reveals complex stress evolution and thrust sequence in the Bighorn Basin, Wyoming, USA[END_REF] in the Bighorn Basin (USA). Second, U-Pb dating alone suggests that the SPFT may still have recorded tectonic shortening after 17.3 ± 3.4 Ma at least in the Santo Domingo area, as shown by the results obtained on sample SE4. This age is slightly younger than the minimum age of ~20 Ma proposed by Oliva-Urcia et al. ( 2019) in their paleomagnetic and tectono-sedimentary study of the Uncastillo Formation at the southern flank of the Santo Domingo anticline. However, it is in accordance with observations that in the same anticline, the uppermost conglomerates of the Uncastillo Formation were folded and thrusted by the Domingo-Gabardiella thrust system, suggesting deformation during the Burdigalian [START_REF] Garrido | Actividad tectónica registrada en los depósitos terciarios del frente meridional del Pirineo central. Translated title: Tectonic activity recorded in the tertiary deposits of the southern front of the central Pyrenees[END_REF][START_REF] Arenas | Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics (north-eastern Iberia): controls on basin margin fans and fluvial systems[END_REF]. The other veins that formed after the Aquitanian (A21, A56, SE3) have ages similar to that of sample SE4 within uncertainties, and may also have formed in response to compressive deformation in the SPFT. However, in the absence of petrographic evidence of such deformation, alternative scenarios of joint/vein development may also be considered. For A21 and SE3 veins, which do not present evidence of syn-opening precipitation, they include the possibility of a time gap between fracture opening and calcite precipitation, as locally observed in the Bighorn Basin [START_REF] Beaudoin | U-Pb dating of calcite veins reveals complex stress evolution and thrust sequence in the Bighorn Basin, Wyoming, USA[END_REF]. For all three samples, joints may have formed earlier (during the Bartonian for A21 and A56) before being reactivated as veins.

Finally, for SE3 vein, in the absence of statistical analysis of the fracture network, the development of joint/vein during post-tectonic exhumation cannot be excluded [START_REF] Engelder | Loading paths to joint propagation during a tectonic cycle: an example from the Appalachian Plateau[END_REF]Twiss and Moores, 2006). Nevertheless, our results suggest that fractures can record subtle deformations that would have remained unrevealed with other methods such as the study of tectono-sedimentary relationships. Absolute U-Pb dating of veins provides a robust time frame to these movements, allowing to refine previous interpretations of the tectonic evolution of geologically complex areas such as the SPFT.

Thermal evolution of the SPFT and impact on T∆47 values

1D Thermal modelling of the SPFT

Little quantitative data is available on the thermal evolution of the Sierras Exteriores area. To our knowledge only [START_REF] Cantarelli | Tectonic-sedimentation Burial History and Exhumation of the Southern Sector of the Central-western Pyrenees[END_REF] has proposed maximum burial temperatures of ~80-100°C in the Belsué-Atarés and Arguis-Pamplona Formations, based on vitrinite reflectance and illite crystallinity. To better constrain this thermal evolution, we used our vitrinite reflectance (VR) and RE Tmax values to perform 1D thermal models along 4 virtual stratigraphic wells (San-Felices, Riglos, Nueno and Pico del Aguila from west to east) constructed from compilations of thickness and age of deposition data available in the literature (Figure 7; see the Supplementary Material for details of the approach). The VR measured at the base of each virtual stratigraphic well (0.3 to 0.4%) are abnormally low given thickness of the stratigraphic pile (> 1.5 km before uplift-related erosion), and the VR measured in the Campodarbe Formation (0.3±0.1%) by [START_REF] Izquierdo-Llavall | On the Origin of Cleavage in the Central Pyrenees: Structural and Paleo-Thermal Study[END_REF]. The delay or suppression of vitrinite reflectance has been recognized in various geological contexts and lithologies, and is commonly explained by a hydrogen-rich vitrinite composition or by the development of overpressures [START_REF] Price | Suppression of vitrinite reflectance in amorphous rich kerogen -A major unrecognized problem[END_REF][START_REF] Carr | Suppression and Retardation of Vitrinite Reflectance, Part 1. Formation and Significance for Hydrocarbon Generation[END_REF]. For this reason, only the thermal models built with the values of RE Tmax have been retained. The RE Tmax values measured in the upper part of the sedimentary columns (431 to 443°C) are all consistent with the onset of the oil window, equivalent to VR of at least ~0.5-0.6% [START_REF] Lafargue | Rock-Eval 6 applications in hydrocarbon exploration, production, and soil contamination studies[END_REF]. Using these values in the models results in temperatures of 120 to 140°C at the base of the virtual stratigraphic wells at ~28 Ma, corresponding to the onset of the Fiscal-Guarga thrust [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF], and taken as the time of maximum burial before exhumation of the Sierras Exteriores. Such values are equivalent to a VR of ~1.1 to 1.3% (Figure 7). They require adding to the composite logs a substantial thickness of sediments ( 1to 2 km) that would currently be eroded, leading to an initial thickness of ~2.5 to 3.5 km for the Campodarbe Formation. These values are compatible with those measured on either side of the Sierras Exteriores (Millán Garrido et al., 1995), as are the burial temperature estimates based on RE Tmax values compatible with [START_REF] Cantarelli | Tectonic-sedimentation Burial History and Exhumation of the Southern Sector of the Central-western Pyrenees[END_REF] estimates and Labaume et al.

(2016) reconstructions. Exhumation rates in the southern Pyrenees from the Upper Oligocene are little constrained, notably due to debates about the thickness, spatial extent and timing of the erosion of late-and post-orogenic continental deposits (e.g., [START_REF] Coney | Syntectonic burial and post-tectonic exhumation of the southern Pyrenees foreland fold-thrust belt[END_REF][START_REF] Babault | Origin of the highly elevated Pyrenean peneplain[END_REF]. Therefore, we chose to apply two different, simple exhumation scenarios to the wells. The first scenario implies a temperature of 40°C (1.5 km of burial) at 20 Ma and a current temperature of 15°C at the surface (based on [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF]. In the second scenario, we consider a linear temperature decrease between ~28 Ma and present times. Using these constraints, thermal modelling suggests that all dated veins except SE10 are likely to have precipitated in thermal equilibrium with their host rock (Figure 8).

Modelling the effects of solid-state reordering on T∆47

It is well known that carbonates can undergo solid-state reordering during diagenesis, resulting in the alteration of their initial ∆47 values (e.g. Passey and Henkes 2012; [START_REF] Stolper | The Kinetics of Solid-State Isotope-Exchange Reactions for Clumped Isotopes: A Study of Inorganic Calcites and Apatites from Natural and Experimental Samples[END_REF][START_REF] Lawson | Deciphering the diagenetic history of the El Abra Formation of eastern Mexico using reordered clumped isotope temperatures and U-Pb dating[END_REF][START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF]. Based on an experimental approach, [START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF] demonstrate that the kinetic of reordering of carbonate can be constrained by the reaction-diffusion model proposed by [START_REF] Stolper | The Kinetics of Solid-State Isotope-Exchange Reactions for Clumped Isotopes: A Study of Inorganic Calcites and Apatites from Natural and Experimental Samples[END_REF]. This model incorporates both diffusion of isotopes through the crystal lattice and isotope-exchange reactions between adjacent carbonate groups (see Stolper and Eiler 2015 for a complete description). Here, we use a temperature history reordering model (THRM) to explore the kinetic re-ordering of ∆47 of the studied calcite veins, by integrating the reaction-diffusion model of [START_REF] Stolper | The Kinetics of Solid-State Isotope-Exchange Reactions for Clumped Isotopes: A Study of Inorganic Calcites and Apatites from Natural and Experimental Samples[END_REF] (using the numerical code from [START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF] with the thermal history derived from our 1D thermal modelling, and when available, the measured U-Pb ages.

It is worth noting that among the 6 veins dated, the 5 ones having ages younger than 23.8 Ma were formed during exhumation, about 9 to 13 Ma after maximum burial (taken as ~28 Ma). According to the 1D thermal model, they did not encompass temperatures higher than 80°C. Experimental and theoretical considerations have shown that clumped isotope reordering is very limited at such low temperatures (< 100°C; e.g., Passey and Henkes 2012; [START_REF] Stolper | The Kinetics of Solid-State Isotope-Exchange Reactions for Clumped Isotopes: A Study of Inorganic Calcites and Apatites from Natural and Experimental Samples[END_REF][START_REF] Lloyd | Experimental calibration of clumped isotope reordering in dolomite[END_REF]. For these veins, the T∆47 values, which lie below ~80°C, reflect the true precipitation temperature (Table S1). In contrast, the THRM suggests that the vein sample SE10, dated at ~61 Ma, has undergone significant reordering resulting in a measured T∆47 higher than the temperature at the time of precipitation, due to burial temperatures higher than 100°C at ~28 Ma. Assuming precipitation temperature identical to the enclosing rocks temperature of ~40°C (as deduced from 1D thermal modelling at 61 Ma), the T∆47 values calculated by the THRM can vary between ~45 and ~80°C, if considering the 2σ uncertainties at the output of the model (Figure 9A). This temperature range is similar to measured T∆47 values (Table S1). Considering different temperature conditions of SE10 vein precipitation (for example, 20 and 80°C) results in different reordering pathways, but the final modelled T∆47 temperatures can yet be similar to the measured T∆47 values. The same conclusion can be drawn for the 4 veins that could not be dated (SE1, SE2, SE12 and SE13). Taking SE2 as an example, temperatures calculated with the THRM fall in the same measured T∆47 range (77-97°C) if the veins formed between ~75°C and ~110°C during burial (Figure 9B), or if they formed between ~80°C and ~110°C during exhumation (Figure 9C). The measured T∆47 can then be equally explained by precipitation at different temperatures and ages (between ~32 Ma and ~24 Ma). Therefore, reordering modelling shows that modelled present-day ∆47 temperatures can result from various reordering pathways depending on the age of precipitation (i.e. no significant reordering for late precipitation, or consequent reordering for early precipitation), even for a thermal peak limited in both duration and intensity (< 10 Ma at 100-140°C). In general, the example of the SPFT demonstrates that the use of clumped isotope reordering models based on thermal history should be systematically applied in clumped isotope studies of sedimentary basins, if there is evidence of burial temperature exceeding ~100°C, especially when the ages of carbonates are not precisely constrained.

Paleohydrology of the SPFT during late tectonics

In order to gather information on the paleohydrology recorded in the Sierras Exteriores during the last tectonic pulses, we derive the δ 18 O values of the waters at the origin of the precipitation of calcite veins (δ 18 Ow). To do this, we use both the T∆47 and δ 18 O values of calcite veins and the oxygen isotope fractionation factor of [START_REF] Kim | Equilibrium and nonequilibrium oxygen isotope effects in synthetic carbonates Geochim[END_REF].

For the reasons mentioned in the previous section, we focus on the 5 samples for which we obtained precise and recent U-Pb ages. For these veins, the δ 18 Ow shows large variations with values ranging from -4.5‰ to +10.3‰ VSMOW (Figure 5D). All the veins considered in this study are hosted within marine sediments. δ 18 Ow values of unaltered marine water source should be ~ -1‰ VSMOW (Zachos et al., 2001). Such values are not recorded in our studied veins suggesting either that (i) the water has been isotopically altered by interaction with the host sediments, or (ii) the veins record water incursions from external reservoirs. The most negative values observed in the SE3 and A56 veins (mean values of -2.6 and -4.5‰, respectively) are compatible with a meteoric source [START_REF] Longstaffe | Stable Isotope Studies of Diagenetic Processes[END_REF], which require infiltration of external water. Considering the young precipitation age of these veins (~16-18 Ma), and therefore their formation after the uplift of the area during the Priabonian [START_REF] Labaume | Tectonothermal history of an exhumed thrust-sheet-top basin: An example from the south Pyrenean thrust belt[END_REF], the incursion of meteoric waters from the surface is not surprising (e.g., [START_REF] Beaudoin | Fluid Systems and Fracture Development During Syn-Depositional Fold Growth: An Example from the Pico Del Aguila Anticline, Sierras Exteriores, Southern Pyrenees, Spain[END_REF][START_REF] Roure | Incidence and Importance of Tectonics and Natural Fluid Migration on Reservoir Evolution in Foreland Fold-and-Thrust Belts[END_REF][START_REF] Lacroix | Syntectonic fluid-flow along thrust faults: Example of the South-Pyrenean fold-and-thrust belt[END_REF]. The very low T∆47 obtained for SE3 vein, which requires the incursion of water colder than the enclosing rock, further reinforces this interpretation. The 3 other veins which formed after 25 Ma (SE4, A21, A22) have δ 18 Ow values between +4.7 and +10.3‰. These high values are consistent with water isotopically buffered by host rocks during burial history, or with the involvement of highly evaporated water [START_REF] Bradbury | Ancient fluid flow within foreland terrains[END_REF][START_REF] Longstaffe | Stable Isotope Studies of Diagenetic Processes[END_REF]. If fluid flow has occurred, it has not acted long enough or in a volume sufficient to maintain an oxygen isotopic imbalance of oxygen with the host rocks (e.g., [START_REF] Bradbury | Ancient fluid flow within foreland terrains[END_REF].

The δ 13 C values of the youngest veins are generally homogeneous, ranging from -0.9 to +0.9‰, values compatible with waters of marine origin or having been isotopically buffered by marine carbonate rocks. Only the SE3 vein shows a significant difference with its host rock (+0.1 versus -1.6‰), which is once again in the direction of an incursion of water in isotopic imbalance with the surrounding rock. To summarize, the late veins studied show two distinct paleohydrological regimes, with either evidence of meteoric water circulation or the presence of isotopically buffered waters and therefore possibly of more local origin. The recording of these two sources of fluids in tectonic veins is consistent with other continental fold and thrust belts (e.g., Roure et al., 2005 and references therein;[START_REF] Travé | Fluid Systems in Foreland Fold-and-Thrust Belts: An Overview from the Southern Pyrenees[END_REF][START_REF] Cruset | From hydroplastic to brittle deformation: Controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)[END_REF]. Examples include the Canadian Rockies [START_REF] Garven | The Role of Regional Fluid Flow in the Genesis of the Pine Point Deposit, Western Canada Sedimentary Basin[END_REF], the Mexican fold and thrust belt [START_REF] Fitz-Diaz | Insights into fluid flow and water-rock interaction during deformation of carbonate sequences in the Mexican fold-thrust belt[END_REF]), the Albanides (Vilasi et al., 2009), but also the central and eastern South Pyrenean fold and thrust belt, as shown in the Jaca and Cotiella thrusts [START_REF] Lacroix | Syntectonic fluid-flow along thrust faults: Example of the South-Pyrenean fold-and-thrust belt[END_REF]Travé et al., 1997) or the Lower Pedraforca thrust sheet [START_REF] Cruset | From hydroplastic to brittle deformation: Controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)[END_REF]. In all these settings, and as we infer in the SPFT, marine-derived or isotopically buffered waters were dominant in volume, but topographic highs acted as recharge areas for meteoric waters, which flowed downward along faults, or in aquifers, to locally replace the initial fluids.

Concerning sample SE10 and the 4 undated veins, because of the possibility of clumped isotope reordering, only their δ 13 C values can be tentatively used to decipher the origin of the water that allowed their precipitation. The measured values are generally close to those observed for younger veins, consistent with marine or buffered water. Only SE10 vein has a δ 13 C value significantly lower than that of the host rock (-4.5‰ versus -0.6‰). It indicates an organic origin of part of the carbon that could be soil derived or produced by microbially-mediated redox reactions [START_REF] Hoefs | Stable isotope geochemistry[END_REF].

Finally, the δ 18 O of host rocks is too negative compared to those expected for marine sediments, with values below -2.4‰ (Figure 5C). For the Arguis-Pamplona marls, low values could be explained at least in part by the presence of a detrital carbonate fraction with negative signature. For the other formations, corresponding to platform carbonates, they necessarily indicate an alteration of the initial isotopic composition. It could result from burial recrystallization related to temperature increase, or from a partial reset during the ingress of large volumes of water in isotopic disequilibrium with the carbonates (e.g., [START_REF] Bradbury | Ancient fluid flow within foreland terrains[END_REF]. A precise determination of the diagenetic evolution of the deposits involved in the SPFT would be necessary to determine the timing and conditions of such peculiar isotopic evolution, as well as to link it with the long-term evolution of calciteprecipitating water within the tectonic frame of the southern Pyrenees.

Conclusions

The example of the South Pyrenean Frontal Thrust demonstrates the potential of ∆47/U-Pb thermo-chronometry to determine the conditions of fracture development and associated vein precipitation in tectonically complex areas such as fold and thrust belts. The ages obtained, which range between ~61 Ma and ~14 Ma, are sometimes clearly distinct from the estimates derived from the microstructural study of fractures, highlighting the relevance of absolute dating in fracture analysis. Most studied veins formed during the late exhumation of the area (age < 28 Ma), and the most recent ages obtained likely record the last tectonic pulses of the southern Pyrenees. This late formation makes it possible to validate the vein T∆47 values, which were not modified by reordering during burial. Calculation of the oxygen isotopic compositions of the waters shows that the veins record either the incursion of meteoric water from the surface, or the presence of waters of more local origin that have interacted with the surrounding rocks. The modelling of the thermal evolution of the SPFT indicates that during maximum burial at around 28 Ma, temperatures could reach 120-140°C at the base of the series. For undated or older veins, clumped isotope reordering models suggest that such temperatures have been sufficient to significantly alter clumped isotopes values, excluding their use as a reliable thermal marker or paleohydrological tracer. Thus, in areas where temperatures higher than 100°C have been reached, the use of clumped on diagenetic calcite veins or cements should systematically be accompanied by the modelling of clumped isotope reordering. In this purpose defining the thermal history of the area under investigation is a mandatory pre-requisite, and determining the precipitation ages with the U-Pb method is a definite advantage.

Figure captions

  see also references used for thermal modelling in the Supplementary Material) (Figure1B). Based on the references cited above, in the Sierras Exteriores, pre-tectonic sediments include middle Triassic carbonates, upper Triassic shales and evaporites (10-100 m), upper Cretaceous limestones (Adraen-Bona Formation, 50-250 m), and Cretaceous / Paleocene continental deposits (Garumnian Formation, 10-100 m). Overlying syn-folding deposits are marked by significant variations in thickness. They include marine Lutetian platform limestones (Guara Formation; 50-800 m), grading upward into the marine marls of the Arguis-Pamplona Formation (Bartonian; 300-1000 m), and deltaic sandstones (Belsué-Atarès and Yeste-Arrés Formations, Bartonian-Priabonian, 10-200 m). Emersion of the entire Jaca-Pamplona basin during the Priabonian-Chattian was marked by the westward progradation of the Campodarbe conglomerates (~1000-3500 m), uncomfortably overlain by the Uncastillo conglomerates (late Chattian-Aquitanian, ~200-500 m).

Figure 1 .

 1 Figure 1. A: Simplified geological map of the Pyrenees (modified from Filleaudeau, 2011).

Figure 2 :

 2 Figure 2: Results of fracture analysis in 7 of the 10 studied sites. Results are presented on 3

Figure 3 :

 3 Figure 3: A. Close field view of vein SE3 (arrows). B. Field photograph of vein SE10

Figure 6 :

 6 Figure 6: Tera-Wasserburg diagrams for the 6 veins successfully dated by the U-Pb method.

Figure 7 :

 7 Figure 7: Results of 1D thermal modelling for the four virtual time-correlated sedimentary

Figure 8 :

 8 Figure 8: Time-temperature paths for the rocks hosting the 10 veins analyzed for clumped

Figure 9 :

 9 Figure 9: A. Modelling of the reordering behavior of calcite T∆47 (THRM) using the

Acknowledgements

This work benefited from a PhD grant of the French Ministry of Research (MESR) to NC. All analyses and field work performed in the course of this study were funded by a "CNRS excellence chair" grant to GH. The manuscript greatly benefited from the reviews of P. Granado and two anonymous reviewers.

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TABLES

Table S1: Results of isotopic, microthermometric and U-Pb dating measurements for the studied veins and their host-rocks.