Cem Yücel

Mehmet Arslan

İrfan Temizel

Emel Abdioğlu

Gilles Ruffet

from a net veined lithospheric mantle in an ongoing extensional setting: Geochronology and geochemistry of Eocene and Miocene volcanic rocks from Eastern Pontides (Turkey)

Keywords: alkaline volcanic rocks, 40 Ar-39 Ar dating, mantle metasomatism, carbonate assimilation, Eastern Pontides

Evolution of K-rich magmas derived

Please cite this article as: Cem Yücel, Mehmet Arslan, İrfan Temizel, Emel Abdioğlu, Gilles Ruffet , Evolution of K-rich magmas derived from a net veined lithospheric mantle in an ongoing extensional setting: Geochronology and geochemistry of Eocene and Miocene volcanic rocks from Eastern Pontides (Turkey). The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Gr(2016Gr( ), doi: 10.1016Gr( /j.gr.2016.12.016 .12.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Introduction

Alkaline rocks constitute less than 1% of all igneous rocks of the Earth's crust [START_REF] Gill | Igneous Rocks and Processes, a pratical guide[END_REF] and can be observed in various geodynamic environments, such as active plate margins (e.g. Indonesia; [START_REF] Varne | Ancient subcontinental mantle: A source for K-rich orogenic volcanics[END_REF][START_REF] Stolz | Magma source components in an arc-continent collision zone: the Flores-Lembata sector, Sunda arc, Indonesia[END_REF], intra-plate (e.g. East African rift; [START_REF] Rosenthal | Petrogenesis of strongly alkaline primitive volcanic rocks at the propagating tip of the western branch of the East African Rift[END_REF] and syn-to post-collisional settings (e.g. Italy, [START_REF] Conticelli | Source contamination and mantle heterogeneity in the genesis of Italian potassic and ultrapotassic volcanic rocks: Sr-Nd-Pb isotope data from Roman Province and Southern Tuscany[END_REF]Conticelli et al., , 2009aConticelli et al., , 2009b;;[START_REF] Gasperini | Upwelling of deep mantle material through a plate window: Evidence from the geochemistry of Italian basaltic volcanics[END_REF].

Besides, alkaline rocks are generally taken into consideration with their unusual mineralogy and distinct trace and rare earth element contents, generally explained by low-degree partial melting of a peridotitic source. They are also notable for their silica-undersaturated features leading to crystallisation of feldspathoid minerals instead of feldspars. These distinct features make interpretation of the origin and evolution of alkaline rocks very difficult, especially for those in subduction zones.

Although the deeper part of the mantle is often believed to be a viable source for silica-undersaturated volcanic rocks based on geochemical [START_REF] Hawkesworth | Crustal contamination versus enriched mantle: 143 Nd/ 144 Nd and 87 Sr/ 86 Sr evidence from Italian volcanics[END_REF][START_REF] Mckenzie | The volume and composition of melt generated by extension of lithosphere[END_REF][START_REF] Hawkesworth | Continental mantle lithosphere, and shallow level enrichment processes in the Earth's mantle[END_REF][START_REF] Bradshaw | Basaltic volcanism in the southern Basin and Range: no role for a mantle plume[END_REF] and thermal considerations (e.g. McKenzie 1989), the origin and processes leading to the formation of leucite and/or analcime-bearing potassic rocks in intra-plate and plate-margin tectonic settings, remain controversial [START_REF] Conticelli | Petrology and geochemistry of potassic and ultrapotassic volcanism in central Italy: petrogenesis and inferences on the evolution of the mantle sources[END_REF][START_REF] Shaw | The petrology and petrogenesis of Roman Province-Type Lavas and ultrapotassic leucitites[END_REF][START_REF] Edgar | Ultra high pressure-temperature melting experiments on an SiO2rich lamproite from Smoky Butte, Montana-Derivation of siliceous lamproite magmas from enriched sources deep in the continental mantle[END_REF]. Metasomatised oceanic or continental lithospheric mantle can be accepted as the alternative source for alkaline magmas (Sun and McDonough, 1989;[START_REF] Halliday | Lead isotope evidence for young trace element enrichment in the oceanic upper mantle[END_REF][START_REF] Halliday | Incompatible trace elements in OIB and MORB and source enrichment in the sub-oceanic mantle[END_REF][START_REF] Niu | Origin of ocean island basalts: A new perspective from petrology, geochemistry, and mineral physics considerations[END_REF][START_REF] Workman | Recycled metasomatized lithosphere as the origin of the enriched mantle II (EM2) end-member: Evidence from the Samoan Volcanic Chain[END_REF][START_REF] Pilet | The metasomatic alternative for ocean island basalt chemical heterogeneity[END_REF][START_REF] Pilet | Metasomatized lithosphere and the origin of alkaline lavas[END_REF][START_REF] Panter | The origin of HIMU in the SW Pacific: Evidence from intraplate volcanism in southern New Zealand and subantarctic islands[END_REF].

The source enrichment can be explained via the addition of melts or fluids from altered oceanic crust and sediments through subduction [START_REF] Chase | Oceanic island Pb:Two-stage histories and mantle evolution[END_REF]Hofman and White;1982;[START_REF] Palacz | Coupled trace element and isotope enrichment in the Cook-Austral-Samoa islands, southwest Pacific[END_REF]1986;[START_REF] Hart | Heterogeneous mantle domains: signatures, genesis and mixing chronologies[END_REF][START_REF] Nakamura | Pb, Nd, and Sr isotopic evidence for a multicomponent source for rocks of Cook-Austral Islands and heterogeneities of mantle plumes[END_REF][START_REF] Hart | Heterogeneous mantle domains: signatures, genesis and mixing chronologies[END_REF][START_REF] Barling | Extreme isotopic variations in Heard Island lavas and the nature of mantle reservoirs[END_REF]1990;[START_REF] Weaver | The origin of ocean island basalt end-member compositions: trace-element and isotopic constraints[END_REF][START_REF] Chauvel | HIMU-EM: The French Polynesian connection[END_REF]. Experimental studies indicate that mantle peridotite including hydrous, incompatible element-rich net veins derived from subducted sediments is an alternative source for alkaline magmas (e.g. [START_REF] Foley | Vein-plus-wall-rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas[END_REF]Mitchel, 1995). Kamafugitic magmas as an ultrapotassic variant of melilitic magmas are considered to be generated by mantle melting under high X CO2 conditions even at low pressure (e.g. [START_REF] Edgar | An experimental study of an olivine ugandite magma and mechanisms for the formations of its K-enriched derivatives[END_REF]Wendlandt andEgler, 1980a, 1980b;[START_REF] Arima | High pressure experimental studies on a katungite and their bearing on the genesis of some potassium rich magmas of the west branch of the African rift[END_REF][START_REF] Lloyd | Partial melting of a phlogopite-clinopyroxenite nodule from south-west Uganda: an experimental study bearing on the origin of a highly potassic continental rift volcanics[END_REF][START_REF] Edgar | The genesis of alkaline magmas with emphasis on their source regions: inferences from experimental studies[END_REF][START_REF] Stoppa | An overview of monogenetic carbonatitic magmatism from Uganda, Italy, China and Spain: volcanologic and geochemical features[END_REF]Schiazza., 2013, Conticelli et al., 2015). Supporting this idea, the capability of producing K-rich granitic or phonolitic melts from carbonated pelites at temperatures of 950-1070°C and high P (2.4 GPa) was recently suggested by [START_REF] Thomsen | Melting of carbonated pelites at 2.5-5.0 GPa, silicatecarbonatite liquid immiscibility, and potassium-carbon metasomatism of the mantle[END_REF]. Furthermore, the source of the most sodic alkaline rocks is generally viewed as convecting asthenosphere modified by enriched lithospheric mantle and crustal material [START_REF] White | Sr and Nd isotope geochemistry of oceanic basalts and mantle evolution[END_REF][START_REF] Mckenzie | Mantle reservoirs and ocean island basalts[END_REF][START_REF] Hart | Heterogeneous mantle domains: signatures, genesis and mixing chronologies[END_REF].

Although there have been different scenarios proposed for the geodynamic evolution of the Eastern Pontides, a well preserved magmatic arc in NE Turkey (e.g. [START_REF] Şengör | Tethyan evolution of Turkey: a plate tectonic approach[END_REF][START_REF] Chorowicz | Black Sea-Pontid relationship: interpretation in terms of subduction[END_REF][START_REF] Bektaş | Migration of the Upper Cretaceous subductionrelated volcanism toward the back-arc basin of the eastern Pontide magmatic arc (NE Turkey)[END_REF][START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF], most workers have reached a consensus on the northward subduction of the northern branch of Neo-Tethys beneath the Eurasian

A C C E P T E D M A N U S C R I P T

3 Plate along the İzmir-Ankara-Erzincan suture zone (IAES) (e.g. [START_REF] Ustaömer | Paleotethyan tectonic evolution of the North Tethyan margin in the central Pontides, N Turkey[END_REF][START_REF] Rice | Late Cretaceous-Early Eocene tectonic development of the Tethyan Suture Zone in the Erzincan area, eastern Pontides, Turkey[END_REF][START_REF] Dilek | Geochemistry and tectonics of Cenozoic volcanism in the Lesser Caucasus (Azerbaijan) and the peri-Arabian region: collision induced mantle dynamics and itsmagmatic fingerprint[END_REF]. Tertiary volcanics are observed on both sides of the IAES, implying that Eocene volcanism was post-collisional. Tertiary volcanic rocks occur both in the northern and southern parts of the Eastern Pontides (e.g., [START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF][START_REF] Arslan | Geochemical and petrochemical characteristics of the Kale (Gümüşhane) volcanic rocks: implications for the Eocene evolution of Eastern Pontide arc volcanism, Northeast Turkey[END_REF][START_REF] Temizel | Mineral chemistry and petrochemistry of post-collisional Tertiary mafic to felsic cogenetic volcanics in the Ulubey (Ordu) area, eastern Pontides, NE Turkey[END_REF][START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]. Post-collisional Middle Eocene volcanism that covers extensive areas from the Western to the Eastern Pontides was revealed by recent detailed studies [START_REF] Robinson | Stratigraphic and structural development of the eastern Pontides, Turkey[END_REF][START_REF] Yılmaz | Geology and tectonics of the Pontides. In: Robinson AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF][START_REF] Şen | Geochemical and petrological characteristics of the Pontide Eocene (?) alkaline province, NE Turkey[END_REF][START_REF] Arslan | Geochemical and petrochemical characteristics of the Kale (Gümüşhane) volcanic rocks: implications for the Eocene evolution of Eastern Pontide arc volcanism, Northeast Turkey[END_REF][START_REF] Altherr | Geochemical and Sr-Nd-Pb isotopic characteristics of Paleocene plagioleucitites from the eastern Pontides (NE Turkey)[END_REF][START_REF] Keskin | Petrology and geochemistry of post-collisional Middle Eocene volcanic units in North-Central Turkey: evidence for magma generation by slab breakoff following the closure of the Northern Neotethys Ocean[END_REF][START_REF] Temizel | Mineral chemistry and petrochemistry of post-collisional Tertiary mafic to felsic cogenetic volcanics in the Ulubey (Ordu) area, eastern Pontides, NE Turkey[END_REF][START_REF] Aslan | U-Pb zircon SHRIMP age, geochemical and petrographical characteristics of tuffs within calc-alkaline Eocene volcanics around Gümüşhane (NE Turkey), Eastern Pontides[END_REF][START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Aydınçakır | Petrography, Geochemistry and Petrogenesis of the Borçka (Artvin, NE Turkey) Area Tertiary Volcanics[END_REF][START_REF] Aydınçakır | Petrogenesis of the postcollisional volcanic rocks from the Borçka (Artvin) area: Implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aydınçakır | The petrogenesis of Early Eocene non-adakitic volcanism in NE Turkey: Constraints on the geodynamic implications[END_REF]Temizal et al., 2016). Besides, narrowly extending Early Eocene [START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF][START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF] and Miocene volcanism were also identified in this area (Arslan et al., 2001;[START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Yücel | Whole rock petrochemistry and 40 Ar-39 Ar geochronology of the Tertiary alkaline volcanics between Trabzon and Giresun areas[END_REF]. Alkaline volcanic rocks in the Trabzon area derived from upper mantle and/or lower crust were first described by [START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF]. [START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF] reported that enriched subcontinental lithospheric mantle can be the source of the Miocene alkaline volcanic rocks.

Although the aforomentioned studies on Tertiary volcanic rocks throughout the Eastern Pontides are mainly about geochemical and isotopic compositions, absolute age relationships, and the petrogenesis of these rocks, the processes responsible for generation of Middle Eocene and Late Miocene alkaline volcanism are still poorly explained. This study concerns the Eocene and Miocene volcanic rocks in the area between Trabzon and Giresun in the northern part of the Eastern Pontides (NE Turkey). Here, we present new 40 Ar-39 Ar ages, whole-rock major and trace element analyses, as well as Sr-Nd-Pb isotope data to understand the genesis of K-rich volcanism through an assessment of petrogenetic processes and their possible geodynamic significance.

Geological outline and local stratigraphy

The Eastern Pontides, in the central part of the Alpine-Himalayan orogenic belt, is of key importance to understand the tectono-magmatic evolution of the Pontides and Eastern Mediterranean.

This orogenic belt lies along the İzmir-Ankara-Erzincan suture zone in NE Turkey (Fig. 1a). During the course of the Alpine orogeny (Laramian phase), the region was affected by the collision of the Tauride-Anatolide platform with the Pontides, which resulted in well-documented igneous records in the active margin of the Neo-Tethyan convergence system in Turkey [START_REF] Şengör | Tethyan evolution of Turkey: a plate tectonic approach[END_REF][START_REF] Bozkurt | Introduction to the geology of Turkey-a synthesis[END_REF]. These tectono-magmatic episodes are discrete pulses with different geochemical compositions, as suggested by temporal and spatial records of the magmatic activity.

Although there have been different interperations in the literature (e.g. [START_REF] Bektaş | Cretaceous rifting of the eastern Pontide carbonate platform (NE Turkey): the formation of carbonates breccias and turbidites as evidences of a drowned platform[END_REF] Eyüboğlu et , 2006), the Eastern Pontides are generally subdivided into northern and southern sub-domains with regards to their structural and lithological features [START_REF] Özsayar | Doğu Pontidler'de Kretase[END_REF][START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF].

A C C E P T E D M A N U S C R I P T 4 al.
The northern part of the Eastern Pontides comprises Late Cretaceous, Middle Eocene, and Miocene units, whereas the southern part is widely dominated by pre-Late Cretaceous units [START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF][START_REF] Şen | Jurassic volcanism in the Eastern Pontides: is it rift related or subduction related?[END_REF]. The Hercynian basement of the Eastern Pontides consists of metamorphic rocks and granitic intrusions [START_REF] Yılmaz | Petrology and structure of the Gümuşhane granite and surrounding rocks, Northeastern Anatolia[END_REF][START_REF] Çoğulu | Petrologic and Geochronologic Studies in the Gümüşhane-Rize region[END_REF][START_REF] Topuz | Carboniferous high-potassium I-type granitoid magmatism in the Eastern Pontides: the Gümüşhane pluton (NE Turkey)[END_REF][START_REF] Ustaömer | Late Palaeozoic-Early Cenozoic tectonic development of the Eastern Pontides (Artvin area), Turkey: stages of closure of Tethys along the southern margin of Eurasia[END_REF][START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF][START_REF] Kaygusuz | U-Pb zircon chronology and petrogenesis of Carboniferous plutons in the northern part of the Eastern Pontides, NE Turkey: constraints for Paleozoic magmatism and geodynamic evolution[END_REF]. Jurassic volcanic and volcano-sedimentary rocks lie unconformably on the basement and mostly crop out in the southern part. Volcanic rocks, which are mainly tholeiitic in character, comprise basaltic, minor andesitic, and trachyandesitic lavas and their pyroclastic equivalents. Jurassic-Cretaceous neritic and pelagic carbonates conformably overlie Jurassic volcanic and volcano-sedimentary rocks. These carbonates are locally overlain unconformably by a Late Cretaceous series comprising sedimentary rocks in the southern part and volcanic rocks in the northern part. The Late Cretaceous volcanic rocks consist of tholeiitic to calcalkaline dacite, rhyolite, and less andesite, basalt, their pyroclastics and alkaline volcanic rocks (e.g., [START_REF] Aydınçakır | Subduction-related Late Cretaceous high-K volcanism in the Central Pontides orogenic belt: Constraints on geodynamic implications[END_REF]. These units are intruded by Late Cretaceous granitoids (e.g., [START_REF] Kaygusuz | Insight into magma genesis at convergent plate margins-a case study from the eastern Pontides (NE Turkey)[END_REF]. Eocene volcanic and volcaniclastic rocks overlie this Late Cretaceous series [START_REF] Güven | Doğu Pontidler'in 1:25000 ölçekli jeolojisi ve kompilasyonu [1:25000 Scale Geology and Compilation of the Eastern Pontide[END_REF]Arslan and Aliyazıoğlu, 2001;[START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF][START_REF] Temizel | Geochronology and geochemistry of Eocene-aged volcanic rocks around the Bafra (Samsun, N Turkey) area: constraints for the interaction of lithospheric mantle and crustal melts[END_REF]. During Paleocene-Early Eocene time, the Eastern Pontides were above sea level probably because of collision [START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Boztuğ | Slow Senonian and fast Paleoceneearly Eocene uplift of the granitoids in the Central Eastern Pontides, Turkey: apatite fission track results[END_REF]. Eocene volcanic and volcaniclastic rocks in the region are intruded by calc-alkaline granitoids of similar age [START_REF] Arslan | Mineralogy, petrography and whole-rock geochemistry of the Tertiary granitic intrusions in the Eastern Pontides, Turkey[END_REF][START_REF] Karslı | Deciphering the shoshonitic monzonites with I-type characteristic, the Sisdağı pluton, NE Turkey: magmatic response to continental lithospheric thinning[END_REF][START_REF] Kaygusuz | Geochronology, geochemistry, and petrogenesis of the Eocene Bayburt intrusions, Eastern Pontide, NE Turkey: implications for lithospheric mantle and lower crustal sources in the high-K calc-alkaline magmatism[END_REF]. Post-Eocene uplift and erosion brought clastic input into locally developed basins in the north [START_REF] Korkmaz | Stratigraphy of Eastern Pontides, NE Turkey[END_REF]. From the end of Middle Eocene times, the region remained largely above sea level and has been affected by minor volcanism and terrigeneous sedimentation until the present [START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF].

Miocene magmatism of the Eastern Pontides was characterised by calc-alkaline to mildly alkaline volcanism [START_REF] Şen | Geochemical and petrological characteristics of the Pontide Eocene (?) alkaline province, NE Turkey[END_REF][START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]Yücel et al., 2014a).

The studied Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas in the northern part of the Eastern Pontides (Fig. 1b,c) have been previously considered as Eocene in aged ("Kabaköy Formation"; [START_REF] Güven | Doğu Pontidler'in 1:25000 ölçekli jeolojisi ve kompilasyonu [1:25000 Scale Geology and Compilation of the Eastern Pontide[END_REF]. The volcanic rocks were separated into Trabzon and Tonya groups by [START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF]. The volcanic rocks around the Trabzon area were attributed to Miocene times (Arslan et al., 2001;[START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Yücel | Whole rock petrochemistry and 40 Ar-39 Ar geochronology of the Tertiary alkaline volcanics between Trabzon and Giresun areas[END_REF] whereas those between Tonya and Giresun areas were ascribed to Eocene times [START_REF] Yücel | Whole rock petrochemistry and 40 Ar-39 Ar geochronology of the Tertiary alkaline volcanics between Trabzon and Giresun areas[END_REF]. The two temporal Tertiary volcanic groups, Eocene (e.g., [START_REF] Güven | Doğu Pontidler'in 1:25000 ölçekli jeolojisi ve kompilasyonu [1:25000 Scale Geology and Compilation of the Eastern Pontide[END_REF][START_REF] Yücel | Whole rock petrochemistry and 40 Ar-39 Ar geochronology of the Tertiary alkaline volcanics between Trabzon and Giresun areas[END_REF] and Miocene (e.g., Arslan et al., 2001;[START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Yücel | Whole rock petrochemistry and 40 Ar-39 Ar geochronology of the Tertiary alkaline volcanics between Trabzon and Giresun areas[END_REF], are characterised by shallow subaqueous to subaerial-volcanic facies, respectively. The Eocene volcanic rocks are represented by volcaniclastics (breccias and tuffs), lavas (pillow lavas and basaltic lavas), and dike-sill-domes (basaltic dikes-sills, andesitic dikes-domes, and

A C C E P T E D M A N U S C R I P T 5 trachytic dikes).
The Miocene volcanic rocks are represented by tuffs and breccias, brecciated lavas, and dikes and sills. The characteristics of these volcanic facies are given in detail by Yücel et al. (2014a). The studied Tertiary volcanic rocks are overlain unconformably by Miocene-Pliocene sedimentary rocks, saprolitic clay occurrences (Arslan et al., 2006), and Quaternary marine alluvium [START_REF] Keskin | Coastal Uplift along the Eastern Black Sea Coast: New Marine Terrace Data from Eastern Pontides, Trabzon (Turkey) and a Review[END_REF]Fig. 1c).

Petrography and mineralogy

The

Analytical techniques

The The selected samples were first crushed using a jaw crusher (0.1-1 cm in diameter), and then ground in a mild-steel mill to obtain rock powder to the grain size of <200 mesh. The samples were wrapped in Al foil to form small packets (11  11 mm) that were stacked up to form columns within which packets of fluence monitors were inserted every 10 samples. Irradiation was performed at the McMaster reactor (Hamilton, Canada) and used 5C high flux location without Cd-shielding. It lasted 13.42 hr (J/h ≈ 3.71 x 10 -4 h -1 ). The irradiation standard was sanidine TCRs (28.608 ± 0.033 Ma; according to [START_REF] Renne | Intercalibration of standards, absolute ages and uncertainties in 40 Ar/ 39 Ar dating[END_REF]Renne et al., , 2010[START_REF] Renne | Joint determination of 40 K decay constants and 40 Ar * / 40 K for the Fish Canyon sanidine standard, and improved accuracy for 40 Ar/ 39 Ar geochronology[END_REF]. The sample arrangement in the irradiation allowed us to monitor the flux gradient with a precision of  0.2 %.

Heating steps were performed with a CO 2 laser probe. All experiments concerned single grains.

The experimental procedure was described by [START_REF] Ruffet | Comparison of 40Ar/39Ar conventional and laser dating of biotites from the North Tre´gor Batholith[END_REF]Ruffet et al. ( , 1995)) [START_REF] Turner | 40 Ar-39 Ar ages from the lunar Maria[END_REF][START_REF] Roddick | The evolution of excess argon in alpine biotites -A 40 Ar-39 Ar analysis[END_REF][START_REF] Hanes | An 40 Ar/ 39 Ar geochronological and electron microprobe investigation of an Archean pyroxenite and its bearing on ancient atmospheric compositions[END_REF] are presented in Supplementary Fig. (e.g. 188, 318, 625) show slight age discrepancies that are within the range of analytical error. As phlogopite ages are systematically slightly older than whole rock ones, it could be seen that these minerals were disturbed by argon in excess (excess/inherited). Isochron calculations do not favour the excess argon hypothesis (cf calculated ( 40 Ar/ 36 Ar) i ratios, Supplementary Fig. 1) but cannot exclude the contention that phlogopites trapped some inherited argon, as these minerals are prone to such a process (e.g. [START_REF] Ruffet | Rb-Sr and 40 Ar-39 Ar laser probe dating of high-pressure phengites from the Sesia zone (western Alps): underscoring of excess argon and new age constraints on the high-pressure metamorphism[END_REF]. Nevertheless, excess argon is more common in metamorphic rocks than in volcanic ones, since outgassing to the atmosphere is easier. It would probably be more sensible viewing a weathering effect disturbing analysed groundmass grains (and K-feldspars, cf. sanidine 188), as suggested by the low calculated ( 40 Ar/ 36 Ar) i ratios (inverse isochron calculations for whole rock grains 188, 318, 625), lower than the atmospheric ratio (298.56 ± 0.31; [START_REF] Lee | A redetermination of the isotopic abundances of atmospheric Ar[END_REF].

It is worth noting that the frequency diagrams of apparent ages and plateau or pseudo-plateau ages of samples from Eocene basaltic and trachytic rocks display two slightly distinct frequency peaks, at ~ 44.7 Ma and ~ 43.8 Ma, suggesting that basaltic rocks could precede trachytic rocks for ~ 1 Ma (Fig. 2).

The youngest ages were obtained from samples of Miocene tephrytic rocks with plateau ages in the range of 6.05 ± 0.06 Ma for foid-bearing brecciated lava, 5.87 ± 0.06 Ma for foid-bearing dike and sill, and 5.65 ± 0.06 Ma for cognate inclusion.

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M A N U S C R I P T 9 5.2

. Major and trace element geochemistry

The major and trace element compositions of the studied Eocene and Miocene volcanic rocks are presented in Supplementary Table 2. The TAS (total alkali versus silica) diagram of Le [START_REF] Bas | A chemical classification of volcanic rocks on the total alkali -silica diagram[END_REF] was used to classify the studied rocks and to determine magma series (Fig. 3a). While Eocene basaltic rocks have a mafic composition, the trachytic rocks present an intermediate character with a higher SiO 2 (55.6-63.8 wt. %) content. The Eocene volcanic rocks display predominantly mildly alkaline affinities, whereas the Miocene teprytic rocks show moderately alkaline affinity (Yücel et al, 2014a). The studied rocks were also checked through the classification diagram of [START_REF] Hastie | Classification of altered volcanic island arc rocks using immobile trace elements: development of the Th-Co discrimination diagram[END_REF] using less mobile elements such as Th and Co, because the LOI (0.7-5.7 wt. % for basaltic, 1.1-5.5 wt.

% for trachytic and 5.2-9.9 wt. % for tephrytic rocks) values of several samples were rather high (Supplementary Table 2). The relatively high LOI contents of the Miocene tephrytic rocks are mostly related to alteration to low-temperature phases (e.g., analcime from leucite; Yücel et al., 2014b), the presence of hydrous phases such as phlogopite, and the minor amount of secondary minerals such as zeolites. In this diagram, while the Eocene basaltic rocks lie mainly in the field of calc-alkaline, high-K and shoshonitic transitional basalts, basaltic andesites and andesites, the trachytic rocks plot in high-K and shoshonitic basaltic andesite/andesite and dacite/rhyolite fields, except for one sample. The Miocene tephrytic rocks with a high-K and shoshonitic character plot into the basalt, basaltic andesite and andesite fields (Fig. 3b). The Eocene volcanic rocks are potassic (K 2 O/Na 2 O=0.7-1.5 for basaltic rocks and 1.1-2.4 for trachytic rocks) and silica-saturated (SiO 2 =44.9-56.8 wt. % for basaltic rocks and 55.6-63.8 wt. % for trachytic rocks), whereas the Miocene tephrytic rocks are sodic-potassic (K 2 O/Na 2 O=0.2-0.7) and silica-undersaturated (SiO 2 =42.0-48.5 wt. %), as indicated by ∆Q versus [START_REF] Peccerillo | Plio-Quaternary magmatism in central-southern Italy: a new classification scheme for volcanic provinces and its geodynamic implications[END_REF][START_REF] Peccerillo | Plio-Quaternary magmatism in Italy[END_REF]. In the AFM diagram (Fig. 4d), both Eocene and Miocene volcanic rocks generally follow the calc-alkaline and shoshonitic trajectories determined by [START_REF] Wimmenauer | Petrography of Magmatic and Metamorphic Rocks[END_REF] with their low FeO * . Using the CaO versus Al 2 O 3 and MgO diagrams of Foley -91, 35-113, 220-452) and HREE (Yb=3-10, 7-14, 5-9) for Eocene basaltic and and Miocene tephrytic rocks resulted in La N /Lu N ratios ranging from 5. 55-10.76, 4.65-11.64 and 36-69, respectively.

K 2 O/Na 2 O diagram (Fig. 3c) of

Sr, Nd and Pb isotope geochemistry

Sr-, Nd-and Pb-isotope ratios of the studied volcanic rocks are presented in Tables 2 and3.

The initial ratio of Sr and Nd isotopes was calculated using 40 Ar-39 Ar ages. Less evolved samples from the Eocene basaltic and trachytic rocks are characterised by initial 87 Sr/ 86 Sr ratios ranging between 0.70389-0.70448 and between 0.70408-0.70425, respectively. The Miocene tephrytic rocks display more radiogenic initial 87 Sr/ 86 Sr ratios, between 0.70518-0.70536. On the other hand, scattering of radiogenic 143 Nd/ 144 Nd ratios of Eocene and Miocene volcanic rocks is limited, varying from 0.51268-0.51279 (εNd i : +1.61 to +3.75) for basaltic rocks, 0.51270-0.51275 (εNd i : +1.84 to +2.81) for trachytic rocks and 0.51267-0.51269 (εNd i : +0.61 to +1.08) for the tephrytic rocks. Within the ( 87 Sr/ 86 Sr) i versus ( 143 Nd/ 144 Nd) i correlation diagram, basaltic and trachytic rocks show less radiogenic Sr isotopic ratios compared to BSE, while the tephrytic rocks plot in partly Sr-enriched quadrant close to mantle array (Fig. 6a). Thus, the basaltic and trachytic rocks have isotopic similarities with the Ulubey (Ordu; (Fig. 6b,c). Furthermore, ∆7/4Pb of the studied volcanic rocks ranges between 52.41-3.30 for basaltic rocks, 52.53-62.14 for trachytic rocks, 46.94-52.53 for tephrytic rocks, when ∆8/4Pb ranges between 10. 68-14.69, 11.04-14.45, 11.81-13.53, respectively.

Discussion

The narrow range of isotopic composition and the large geochemical variations makes the interpretation of the origin and evolution of the volcanic rocks complicated, especially in collisional and post-collisional tectonic settings. The Tertiary volcanic units of the Eastern Pontides orogenic belt have been examined in terms of geochemical and isotopic characteristics by various studies (e.g., [START_REF] Arslan | Geochemistry and petrogenesis of the eastern Pontide volcanic rocks, Northeast Turkey[END_REF][START_REF] Arslan | Geochemical and petrochemical characteristics of the Kale (Gümüşhane) volcanic rocks: implications for the Eocene evolution of Eastern Pontide arc volcanism, Northeast Turkey[END_REF][START_REF] Arslan | Subduction input versus source enrichment and role of crustal thickening in the generation of Tertiary magmatism in the Pontide paleo-arc setting, NE Turkey[END_REF][START_REF] Temizel | Petrology and geochemistry of Tertiary volcanic rocks from the İkizce (Ordu) area, NE Turkey: implications for the evolution of the eastern Pontide paleo-magmatic arc[END_REF][START_REF] Temizel | Mineral chemistry and petrochemistry of post-collisional Tertiary mafic to felsic cogenetic volcanics in the Ulubey (Ordu) area, eastern Pontides, NE Turkey[END_REF][START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF]Temizel et al., 2016). Nevertheless, petrological and geodynamical investigations of the K-rich magmatism maintain their importance, and remain unsolved. In this section, the nature of mantle source and mineralogy and the degree of partial melting will be first discussed; then, we will turn to magma chamber processes such as fractional crystallisation (FC), assimilation coupled with fractional crystallisation (AFC) and magma mixing actualised at crustal magma chambers. This will allow for a discussion of the geodynamic evolution of K-rich Tertiary magmatism at a regional scale.

Fractional crystallisation

Low SiO 2 (< 52 %wt.) and high MgO (> 6 %wt.) contents as well as an Mg number (Mg#) > 65 with high Ni and Cr contents (generally above 100 ppm) characterise near-primitive volcanic rocks (e.g., [START_REF] Frey | Integrated models of basalt petrogenesis: A study of quartz tholeiites to olivine melilitites from South Eastern Australia utilizing geochemical and experimental petrological data[END_REF]

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above may indicate fractionation from a common magma composition. The more silica-rich trachytic rocks were evolved from magmas of more primitive basaltic rocks.

Valuable information about magmatic processes such as fractional crystallisation, assimilation and contamination that control the magma differentiation and its evolution from a primitive nature can be obtained through analyses of the trends of major and trace elements. The observed correlations in the Harker diagrams for Eocene and Miocene volcanic rocks probably reflect the significant role of fractional crystallisation processes during their evolution. The consequent enrichment in LREEs with respect to MREEs and HREEs of the Eocene and Miocene volcanic rocks results in upward concave patterns in the REE diagrams (Fig. 5). MREEs are strongly partitioned, especially in amphibole, which suggests that amphibole and clinopyroxene are part of the fractionated mafic phases (e.g. [START_REF] Gill | Orogenic Andesites and Plate Tectonics[END_REF][START_REF] Thompson | An assessment of the relative roles of crust and mantle in magma genesis: An elemental approach[END_REF][START_REF] Green | Rare Earth element partitioning between clinopyroxene and silicate liquid at moderate to high pressure[END_REF][START_REF] Romick | Amphibole fractionation and magma mixing in andesites and dacites from the central Aleutians, Alaska[END_REF][START_REF] Thirlwall | High field strength element anomalies in arc lavas; source or process[END_REF]. The lack of a sizeable Eu anomaly (Eu N /Eu*=0.81-1.01 for basaltic rocks, 0.81-1.00 for trachytic rocks and 0.88-0.96 for tephrytic rocks), except for three samples from the trachytic rocks (Eu N /Eu*= 0.47-0.54), shows that plagioclase is not a dominant silicate phase during fractional crystallisation.

To model fractional crystallisation processes (Fig. 7), Sc and Rb have been selected for The Rayleigh fractional crystallisation vectors of the Eocene basaltic and trachytic rocks and the Miocene tephrytic rocks have been modelled using [START_REF] Keskin | FC-Modeler: a Microsoft® Excel© spreadsheet program for modeling Rayleigh fractionation vectors in closed magmatic systems[END_REF]'s FC modeller program. Data distributed on FC modelling diagrams suggest that the basaltic rocks follow vectors 2 and 3 (Fig. 7a).

Acording to the modelled vectors of the fractionating mineral assemblage, clinopyroxene and plagioclase are the dominant phases (~ 40-50% cpx and ~ 50% pl); a minor amount of olivine (~10% ol) accompanies these assemblages. As can be seen in Fig. 7b, trachytic rocks, intermediate in

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13 character, follow predominantly vector 4, which corresponds to plagioclase (~55%), amphibole (~30%) and minor amounts of clinopyroxene, biotite and sanidine (~5%, ~5% and ~5% respectively).

Tephrytic rocks which may have evolved by fractional crystallisation from a basic magma, following vectors 2 and 3 (Fig. 7c), which correspond predominantly to clinopyroxene (~70-80%), but also to olivine and a minor amount of plagioclase (~10-30% and ~10% respectively). In light of the data obtained from geochemical variations and FC modelling, clinopyroxene is the dominant mineral as the fractionating phase for basaltic and tephrytic rocks, whereas plagioclase is the main one for the trachytic rocks. Other mineral phases accompanied them in minor amounts. These results are consistent with the detailed petrographic observations reported by Yücel et al. (2014a) for the studied volcanic rocks.

Crustal assimilation

The phenomenon of basaltic magma(s), passing through the thickened crust and staying in magma chambers located at different crustal levels, favours the possibility of crustal assimilation that has an impact upon isotopic and incompatible trace element compositions. The emplacement and stratigraphical features of the studied volcanic rocks reveal a paleoenvironment characterised by a long-term trend of decreasing shallow marine influence from the Middle Eocene to the Miocene periods (Yücel et al., 2014a). Thus, the potential effect of sea water alteration is another phenomenon that needs to be taken into consideration.

The Zr/Hf ratios of primitive mantle and continental crust are ~36.3 and ~11.0, respectively.

The basaltic (Zr/Hf=26.5-41.9) and trachytic (Zr/Hf=31.0-43.0) rocks have ratios similar to primitive mantle, whereas tephrytic rocks are characterised by a higher range (Zr/Hf = 39.5-57.9). The three groups are far beyond continental crust Zr/Hf ratio. The Th/Ce (0.05-0.24 for basaltic, 0.13-0.34 for trachytic and 0.06-0.17 for tephrytic rocks), and Th/La (0.12 -0.46, for basaltic 0.30 -0.67 for trachytic and 0.13 -0.33 for tephrytic rocks) ratios are, with a few exceptions, between primitive mantle and crustal ratios. These observed ratios suggest crustal assimilation coupled with fractional crystallisation. Supporting this idea, the Eocene and Miocene volcanic rocks include some evidence of disequilibrium crystallisation: (1) sieved and rounded, embayed plagioclases, normally and reversely zoned plagioclases and coexisting of these two types in the same samples from the basaltic and trachytic rocks; (2) zoning, resorbed cores and mantles, rounded crystals, and embayed rims in the clinopyroxene in the basaltic, trachytic and tephrytic rocks (Yücel et al., 2014a). The magma ascent through the crust increases the probability of crustal contamination and/or mixing that could produce some of their isotopic and incompatible trace element signatures.

The Sr and Nd isotopic budget of the studied volcanic rocks shows rather complex behaviours with differentiation index such as SiO 2 and MgO. The existence of positive or negative correlations on Sr-Nd isotopes versus several elements or ratios can be used to evaluate the role of FC and AFC

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14 processes for the studied Eocene and Miocene volcanic rocks. All positive or negative trends in Fig. 8 reveal that not only the FC but also the AFC processes are effective in the evolution of the studied Eocene and Miocene volcanic rocks.

To examine crustal assimilation-crystallisation processes, modelling was performed according to equation of De Palolo (1981) using different crustal end-members such as a Palaeozoic-aged granite (T135, [START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF] and a limestone (ERN57, [START_REF] Boari | Transition from ultrapotassic kamafugitic to sub-alkaline magmas: Sr, Nd, and Pb isotope, trace element and 40 Ar-39 Ar age data from the Middle Latin Valley volcanic field, Roman Magmatic Province, Central Italy[END_REF]. Because of a lack of samples representing potential parental magma composition for the Eastern Pontides, sample K-93-56 from western Anatolia (Kula volcanic rocks; [START_REF] Alıcı | Pb-Nd-Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region (western Anatolia, Turkey)[END_REF] was chosen as a reference for a parental magma composition with an OIB-like asthenospheric character. Different theoretical curves were produced for two different values of r=0.2 and r=0.3 (the ratio of the rate of assimilation to the rate of FC) to obtain an immediate estimation of the assimilation rate of crustal material by the ascending magmas. The initial 87 Sr/ 86 Sr and 143 Nd/ 144 Nd ratios of the assimilants (T135, ERN57) were re-evaluated for an age of 45 Ma (Middle Eocene). The value of F represents the ratio of the final mass of magma to its initial mass, and has been marked on each curve decreasing from the parental magma to crustal end-members (Fig. 9a,b). The calculated curves indicate hypothetical trajectories, along which a particular parental magma composition will evolve for different values of D Sr and D Nd (bulk distribution coefficients, Table 5).

As previously mentioned, the composition of primary magmas may be evolved via crustal contamination and/or other magmatic processes. The basement of the studied and surrounding areas is generally composed of Carboniferous granites [START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF], Jurassic-Cretaceous neritic and pelagic carbonates, and thick Late Cretaceous carbonate-bearing formations. The results obtained from AFC modelling using Carboniferous granite and limestone as crustal end-members validate the assimilation of carbonates during evolution of the generally Si-undersaturated Miocene tephrytic rocks. Silica saturation of potassic rocks was controlled by X CO2 during partial melting of the metasomatised mantle source (Wendlandt and Eggler, 1980a, b). Another possibility to generate the silica-undersaturated magmas is carbonatitic metasomatism in the source region (e.g. [START_REF] Litasov | Solidus of alkaline carbonatite in the deep mantle[END_REF][START_REF] Ivanov | The deep water cycle and flood basalt volcanism[END_REF][START_REF] Safonova | Generation of hydrous-carbonated plumes in the mantle transition zone linked to tectonic erosion and subduction[END_REF]. Subducted oceanic crust consists of serpentinites, hydrated sediments, carbonates, and carbonatised basalts can supply water and carbon dioxide to the deep mantle, leading to carbonatitic metasomatism in the source (e.g. [START_REF] Safonova | Generation of hydrous-carbonated plumes in the mantle transition zone linked to tectonic erosion and subduction[END_REF]. However, the reason for the silica undersaturated character of the partial melts is the main question that this character can be generated under the effect of either carbonate assimilation in the crust or carbonatitic metasomatism in the source. Si-undersaturated contaminated magmas can be a consequence of carbonate rock assimilation (e.g. [START_REF] Peccerillo | Interaction between ultrapotassic magmas and carbonate rocks: evidence from geochemical and isotopic (Sr, Nd, O) compositions of granular lithic clasts from the Alban Hills Volcano, Central Italy[END_REF][START_REF] Gozzi | Primary magmatic calcite reveals origin from crustal carbonate[END_REF][START_REF] Prelević | Magmatic response to slab tearing: constraints from the Afyon Alkaline Volcanic Complex, Western Turkey[END_REF][START_REF] Lustrino | Carich carbonates associated with ultrabasic-ultramafic melts: Carbonatite or limestone xenoliths? A case study from the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain)[END_REF]. Experimental studies also show that crystallisation of Ca-rich clinopyroxene resulted in desilication of the melt, and an increase of Si-undersaturation was driven by carbonate syntexis (Prelević et al., 2015, and references therein). The clinopyroxenes from the Miocene tephrytic rocks were classified as salite with high CaO content by Yücel et al. (2014a).

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Besides, occurence of fluor apatite crystals in the Miocene tephrytic rocks (Yücel et al. 2014a) indicates fluorine-rich volatiles during the fractional crystallization associated with carbonate wallrock assimilation of silicate melt. Furthermore, [START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF] reported the presence of calcium rich cancrinite-vishnevite group minerals (generally cancrinite) in the tephrytic rocks. Therefore, crystallisation of such high CaO and/or fluorine and CO 2 bearing minerals in Si-undersaturated rocks may result from the assimilation of carbonate rocks, in agreement with experimental results. Besides, the precence of thick Jurrasic-Cretaceous carbonate-bearing formations in the studied region, the source mineralogy indicating mostly the spinel stability field and the model proposed for crustal magma transport and pathway by Yücel et al. (2014a), may support the increasing possibility of carbonate rock assimilation in the crustal levels.

Nature and characteristics of mantle sources of Eocene and Miocene volcanic rocks

Experimental studies have revealed that K-rich magmas can be produced by partial melting of mantle peridotite including hydrous, incompatible-rich metasomatic veins (e.g. [START_REF] Foley | Vein-plus-wall-rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas[END_REF][START_REF] Mitchell | Melting experiments on a sanidine phlogopite lamproites at 4-7 GPa and their bearing on the sources of lamproitic magmas[END_REF][START_REF] Kirchenbaur | Tectonomagmatic Constraints on the Sources of Eastern Mediterranean K-rich Lavas[END_REF], although there are several hypotheses questioning the formation of these magmas. The metasomatic net veined mantle composition was characterised by a lower melting degree than wall-rock peridotite (e.g. [START_REF] Foley | Vein-plus-wall-rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas[END_REF].

Upper mantle composition and mineralogy can be estimated using REEs due to the different REE partition coefficients of spinel and garnet (Thirwall et al., 1994;[START_REF] Shaw | Petrogenesis of the largest intraplate volcanic field on the Arabian plate (Jordan): a mixing lithosphereasthenosphere source activated by lithospheric extension[END_REF]. Garnet tends to fractionate strongly HREEs in its crystal structure. The melts derived from the garnet stability field generally tend to have high Dy/Yb ratios (> 2.5), whereas a spinel-bearing source has lower Dy/Yb ratios (<1.5; [START_REF] Yang | Late Paleozoic calcalkaline to shoshonitic magmatism and its geodynamic implications, Yuximolegai area, western Tianshan, Xinjiang[END_REF]. Melts with Dy N /Yb N ratios lower than 1.06 generally refer to a spinelbearing source [START_REF] Blundy | Heavy REE are compatible in clinopyroxene on the spinel lherzolite solidus[END_REF].

To investigate the source composition of the Eocene and Miocene volcanic rocks established using the mafic samples from this study, with SiO 2 content lower than wt. 52%. The Miocene tephrytic rocks generally have intermediate Dy N /Yb N ratios ranging from 1.44-1.97, whereas the Eocene basaltic rocks have lower Dy N /Yb N ratios from 1.01-1.53. Thus, intermediate Dy N /Yb N ratios in the tephrytic rocks imply that the melts were derived from garnet-and spinel-bearing peridotite facies, indicating a deeper source region. The lower Dy N /Yb N ratios of the basaltic rocks suggest derivation from a spinel lherzolitic mantle composition. The batch melting equation calibrated by [START_REF] Shaw | Trace element Fractionation during Anatexis[END_REF] was used to determine source mineralogy and the degree of partial melting of the studied volcanic rocks. Two different mineral assemblages, a spinel-bearing lherzolite and a garnet-bearing lherzolite, are used to determine source mineralogy and compositions. The partition coefficients for partial melting modelling calculations are listed in Table 6. In an Yb versus La/Yb diagram (Fig. 10a), the basaltic rocks (SiO 2 <52 wt. %) rocks plot on a line defined by mixing between 10 % melted spinel lherzolite and 3 % melted garnet lherzolite, whereas the tephrytic rocks plot on a line suggesting mixing between

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16 1 % melted spinel lherzolite and 0.1 % melted garnet lherzolite. The budget of alkaline and alkaline earth elements as K, Rb, Sr and Ba is also useful to have an idea about the presence of K-bearing hydrous phases, such as amphibole and phologopite in the mantle source [START_REF] Furman | Erosion of lithospheric mantle beneath the east African rift system; geochemical evidence from the Kivu volcanic province[END_REF].

Fig. 10b (Rb/Sr versus Ba/Rb diagram; [START_REF] Duggen | Post-collisional transition from subduction-to intraplatetype magmatism in the Westernmost Mediterranean: evidence for continental-edge delamination of subcontinental lithosphere[END_REF] can be used to test whether phologopite or amphibole was present or not in the source. The basaltic rocks, with low Ba/Rb ratios, have the signature of phologopite as the hydrous phase in the source, while the precence of amphibole was inferred for the source of the tephrytic rocks from their high Ba/Rb ratios. Therefore, these data suggest that the parental magma of the Eocene basaltic and trachytic rocks was derived from a phologopite-bearing spinel lherzolite source. On the other hand, the melting modelling using trace elements suggests that the parental magmas of the Miocene tephrytic rocks (Dy N /Yb N =1.44 -1.97)

were derived from an amphibole-bearing net veined mantle in the spinel stability field, which was previously metasomatised by melts derived from the garnet stability field.

The origin of the strong depletion in Nb-Ta-Ti and significant enrichment in LILE and LREE contents of the studied volcanic rocks could also be derived from subduction-related metasomatism in the lithospheric mantle (e.g. [START_REF] Foley | The ultrapotassic rocks: characteristics, classification and constraints for petrogenetic models[END_REF][START_REF] Thirlwall | High field strength element anomalies in arc lavas; source or process[END_REF][START_REF] Pearce | Tectonic implications of the composition of volcanic arc magmas[END_REF][START_REF] Turner | Some remarks on magmatic processes beneath island arc volcanoes[END_REF]Alther et al., 2008;[START_REF] Boari | Transition from ultrapotassic kamafugitic to sub-alkaline magmas: Sr, Nd, and Pb isotope, trace element and 40 Ar-39 Ar age data from the Middle Latin Valley volcanic field, Roman Magmatic Province, Central Italy[END_REF]. HFSE depletion is attributed to the retention of these elements in the subducting slab during progressive dehydration, whereas the LILEs and LREEs were transported upward by slab-derived fluids, melts or recycled terrigeneous sediments to fertilise the overlying mantle wedge [START_REF] Peccerillo | Roman Comagmatic Province (Central Italy): Evidence for subduction related magma genesis[END_REF][START_REF] Conticelli | Petrology and geochemistry of potassic and ultrapotassic volcanism in central Italy: petrogenesis and inferences on the evolution of the mantle sources[END_REF][START_REF] Hawkesworth | Mantle and slab contributions in arc magmas[END_REF][START_REF] Münker | Behaviour of high field strength elements in subduction zones: constraints from Kamchatka-Aleutian arc lavas[END_REF][START_REF] Zhao | Geochemical and Sr-Nd-Pb-O isotopic 232 2[END_REF]. Therefore, significant LILE and LREE enrichment of Eocene and Miocene volcanic rocks seem to be consistent with the derivation from subduction-modified lithospheric mantle [START_REF] Pearce | Tectonic implications of the composition of volcanic arc magmas[END_REF]. The systematic decrease of Nb-Ta and Ti anomalies from the Eocene basaltic rocks to the Miocene tephrytic rocks may be caused by different degrees of enrichment in the source during subduction, or by the addition of more primitive melts to a previously metasomatised lithospheric mantle.

The positive εNd (i) values of both Eocene and Miocene volcanic rocks suggest that a depleted mantle or mantle-derived end-member was involved in the petrogenesis, while the conjunction of relatively high ( 87 Sr/ 86 Sr) i values of the Miocene tephrytic rocks seems to imply an additional enriched crustal component [START_REF] Faure | Isotopes: Principles and Applications[END_REF]. Enrichment of a mantle source by subducted sediments can be detected using Pb isotopic ratios because of the low Pb content of the mantle (<0.2 ppm) and high Pb abundances in pelagic sediments (~ 20 ppm; [START_REF] White | Sediment subduction and magma genesis in the Lesser Antilles: isotopic and trace element constraints[END_REF][START_REF] Plank | The geochemical composition of subducting sediment and its consequences for the crust and mantle[END_REF]. The Pb isotope composition of the Eocene basaltic and trachytic rocks plots within the mantle array and overlaps in the field of pelagic sediments; while the Miocene tephrytic rocks plot around the N-African sediments field and Late Cretaceous Everek Hanları (Bayburt) alkaline volcanic rocks. The differences in Pb isotope ratios between the Eocene and Miocene volcanic rocks can be readily explained by the flushing of a depleted mantle source with a subduction component temporally

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and spatially enriched by sediments with high Pb isotope ratios, or from an isotopically more radiogenic asthenospheric mantle.

As previously discussed, subduction-related melt-and/or fluid-like metasomatism appears to be the dominant process in the petrogenesis of the studied rocks; but the characteristics of this efficient component are contentious (e.g. [START_REF] Hawkesworth | U-Th isotopes in arc magmas: implications for element transfer from the subducted crust[END_REF][START_REF] Woodhead | Hafnium isotope evidence for 'conservative' element mobility during subduction zone processes[END_REF][START_REF] Plank | Constraints from Thorium/Lanthanum on sediment recycling at subduction zones and the evolution of the continents[END_REF][START_REF] Kirchenbaur | Tectonomagmatic Constraints on the Sources of Eastern Mediterranean K-rich Lavas[END_REF]. The origin of the metasomatic component of subduction-related magmas can be effectively identified using incompatible trace element ratios [START_REF] Hawkesworth | U-Th isotopes in arc magmas: implications for element transfer from the subducted crust[END_REF]. The modification of the source region by a melt-or fluid-like metasomatic component can be discussed using a Ba/Th versus Th (ppm) diagram (Fig. 11a). The basic samples of the Eocene basaltic rocks (SiO 2 < 52 wt.%) show relatively low Th contents and high Ba/Th ratios, while the Miocene tephritic rocks exhibit relatively high Th contents and low Ba/Th ratios. Although the predominance of subduction related fluid-and melt-like metasomatism in the source may explain such features, the low degree of partial melting of net veined lithospheric mantle source can be efficient for Th enrichment in Miocene tephrytic rocks. On the other hand, the basaltic rock characteristics suggest fluid-like metasomatism in the source region. The Th/Yb versus Ba/La diagram (Fig. 11b) shows that the tephrytic rocks were enriched in Th compared to the basaltic rocks. The enrichment in Th relative to Yb may be explained by complete consumption of phlogopite during melting of hydrous mafic mineral-bearing net veined mantle (e.g. [START_REF] Kirchenbaur | Tectonomagmatic Constraints on the Sources of Eastern Mediterranean K-rich Lavas[END_REF]. Furthermore, the basaltic rocks yield scattered Sr/La ratios in contrast to stable La/Yb ratios (Fig. 11c), suggesting that the source of the basaltic rocks was modified by fluid-like metasomatism, in contrast to the source of the tephrytic rocks derived from net veined mantle.

Illustrated in Figs. 12a and 12b is a three-component mixing model using lower crust (LC), local upper crust (UC; T135, [START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF] and upper mantle (UM) Sr-Nd-Pb isotopic ratios (Table 7). The Eocene basaltic and trachytic rocks plot on the mixing line between the upper mantle and local upper crust, but the Miocene tephrytic rock samples plot outside the mixing line with higher 206 Pb/ 204 Pb ratio. The data obtained from a three-component mixing model reveal that the sources of the Eocene and Miocene volcanic rocks were formed by adding a small amount of crustal material around 3 wt% to the mantle source, leading to the final Sr-Nd-Pb isotopic budget of the studied volcanic rocks. The drift in the mixing model to the outer side of the mixing line between upper mantle and upper crust for the Miocene tephrytic rocks needs the contribution of a more radiogenic (i.e. higher 206 Pb/ 204 Pb ratio) crustal component.

Tectonomagmatic implications

The Eastern Pontides were substantially built during the Alpine-Himalayan orogeny, resulting in a complex tectonic environment. Previous tectonic and geochemical studies (e.g., [START_REF] Şengör | Tethyan evolution of Turkey: a plate tectonic approach[END_REF][START_REF] Boztuğ | Slow Senonian and fast Paleoceneearly Eocene uplift of the granitoids in the Central Eastern Pontides, Turkey: apatite fission track results[END_REF][START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF]; Temizel et al., 2016), which have discussed the geodynamic model, can shed further light on the tectonomagmatic evolution of the Eastern Pontides as a palaeo-magmatic arc developed as a result of the subduction of the Neo-Tethyan oceanic crust beneath the EP [START_REF] Yılmaz | Geology and tectonics of the Pontides. In: Robinson AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF].

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Subduction initiated in Jurassic times, and ended in Paleocene times with the collision between the Pontides and the TAP, and caused the closure of the Neo-Tethyan Ocean. The timing and polarity of subduction and collision between the Pontides and the TAP is still a matter of debate. Accounting for the tectono-magmatic evolution of the region, no available final model reached concurrence due to the lack of detailed structural, geophysical (palaeomagnetic and seismic tomographic) studies, as well as the consecutive contribution of subduction versus mantle geodynamics. Despite contrasting interpretations, most workers [START_REF] Şengör | Tethyan evolution of Turkey: a plate tectonic approach[END_REF][START_REF] Yılmaz | Geology and tectonics of the Pontides. In: Robinson AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Okay | Geology of the eastern Pontides. In: Robinson, AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF][START_REF] Boztuğ | Slow Senonian and fast Paleoceneearly Eocene uplift of the granitoids in the Central Eastern Pontides, Turkey: apatite fission track results[END_REF] believe that Tertiary volcanic rocks in the Eastern Pontides were generated as a result of crustal thickening and subsequent regional uplift related to a Paleocene (~55 Ma) collision. [START_REF] Tokel | Doğu Karadeniz Bölgesinde Eosen yaşlı kalk-alkalen andezitler ve jeotektonizma [Eocene calc-alkaline andesites and geotectonism in Black Sea Region[END_REF] and [START_REF] Robinson | Stratigraphic and structural development of the eastern Pontides, Turkey[END_REF] suggest that the polarity of subduction was northward, and that the collision occurred during Oligocene time (~30 Ma). Alternatively, [START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF] argued that Tertiary volcanic rocks developed by slab window-related processes during ridge subduction in a southward-dipping subduction zone. Besides, the Tertiary volcanism in Western, Eastern Anatolia and Pontides as part of Alp-Himalayan system in the Eastern Mediterranean region was ascribed to post-collisional tectonic settings [START_REF] Yılmaz | Geology and tectonics of the Pontides. In: Robinson AG (ed) Regional and petroleum geology of the Black Sea and surrounding region[END_REF]Arslan and Aliyazıcıoglu, 2001;[START_REF] Keskin | Petrology and geochemistry of post-collisional Middle Eocene volcanic units in North-Central Turkey: evidence for magma generation by slab breakoff following the closure of the Northern Neotethys Ocean[END_REF][START_REF] Kürkcüoğlu | Geochemistry of post-collisional mafic lavas from the North Anatolian Fault zone[END_REF][START_REF] Temizel | Mineral chemistry and petrochemistry of post-collisional Tertiary mafic to felsic cogenetic volcanics in the Ulubey (Ordu) area, eastern Pontides, NE Turkey[END_REF][START_REF] Topuz | Postcollisional adakite-like magmatism in the Ağvanis Massif and implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)[END_REF]Temizel et al., 2012;[START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF]. To explain the relationship between post-collisional extension and magmatism in Turkey, different models have been proposed by many workers; (i) the slab break-off (e.g., [START_REF] Keskin | Magma generation by slab steepening and break off beneath a subductionaccretion complex: an alternative model for collision-related volcanism in Eastern Anatolia, Turkey[END_REF][START_REF] Köprübaşı | Geochemical constraints on the petrogenesis of Cenozoic I-type granitoids in Northwest Anatolia, Turkey: evidence for magma generation by lithospheric delamination in a post-collisional setting[END_REF][START_REF] Altunkaynak | Timing and nature of postcollisional volcanism in western Anatolia and geodynamic implications[END_REF][START_REF] Altunkaynak | Collision-driven slab breakoff magmatism in northwestern Anatolia, Turkey[END_REF][START_REF] Dilek | Cenozoic crustal evolution and mantle dynamics of post-collisional magmatism in western Anatolia[END_REF] and slab tearing (e.g., [START_REF] Prelević | Magmatic response to slab tearing: constraints from the Afyon Alkaline Volcanic Complex, Western Turkey[END_REF]; (ii) slab windowrelated processes (e.g., [START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF]; and (iii) lithospheric delamination (e.g., [START_REF] Aldanmaz | Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey[END_REF][START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aydınçakır | Petrogenesis of the postcollisional volcanic rocks from the Borçka (Artvin) area: Implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]. In these models, magma generation is generally attributed to asthenospheric upwelling and decompressional melting due to partial convective removal of the subcontinental lithospheric mantle (e.g., [START_REF] Altunkaynak | Petrogenesis and time-progressive evolution of the Cenozoic continental volcanism in the Biga Peninsula, NWAnatolia (Turkey)[END_REF]Dilek and Altunkaynak, 2009;Dilek et al., 2009;[START_REF] Dilek | Seismic structure, crustal architecture and tectonic evolution of the Anatolian-African Plate Boundary and the Cenozoic Orogenic Belts in the Eastern Mediterranean Region[END_REF][START_REF] Dilek | Geochemistry and tectonics of Cenozoic volcanism in the Lesser Caucasus (Azerbaijan) and the peri-Arabian region: collision induced mantle dynamics and itsmagmatic fingerprint[END_REF][START_REF] Altunkaynak | Spatial, temporal and geochemical evolution of Oligo-Miocene granitoid magmatism in western Anatolia, Turkey[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF].

Although the slab breakoff model was suggested as viable model to explain the narrow Middle Eocene volcanism throughout the Central Pontides (e.g., [START_REF] Keskin | Petrology and geochemistry of post-collisional Middle Eocene volcanic units in North-Central Turkey: evidence for magma generation by slab breakoff following the closure of the Northern Neotethys Ocean[END_REF], the feasibility of the lithospheric delamination model is suggested to explain the widespread Middle Eocene volcanism in the Eastern Pontides (e.g., [START_REF] Keskin | Petrology and geochemistry of post-collisional Middle Eocene volcanic units in North-Central Turkey: evidence for magma generation by slab breakoff following the closure of the Northern Neotethys Ocean[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]. Besides, the Eastern Pontides are also affected by post-collisional extensional collapse by delamination [START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]. The extensional collapse and ongoing extension resulted in widespread Middle Eocene and rare Miocene

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volcanism in the Eastern Pontides [START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]Yücel et al., 2014a).

Recent petrochemical and isotopic data obtained from Eocene and Miocene volcanic rocks in the Eastern Pontides suggest that the magmas evolved from an enriched mantle source initially metasomatised by fluids and/or melts coming from subducted oceanic lithosphere in a collisional and post-collisional extensional related tectonic setting (Arslan and Aliyazıcıoglu, 2001;[START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF]Temizet at al., 2012;[START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]. The change in stress regime from compressional to extentional and/or heterogeneous composition of lithosperic mantle under the Eastern Pontides orogenic belt could be the cause of the evolution from calc-alkaline volcanism in the southern part to mildly alkaline or calc-alkaline-alkaline transitional volcanism in the northern part during Eocene times, and moderately alkaline volcanism during Miocene times.

Therefore, the composition of lithospheric mantle of the Eastern Pontides may be interpreted as heterogeneous during Tertiary period based on petrochemical and isotopic data. Even if alkaline magmas have a limited volumetric distribution compare to others, they have key role to understand mantle metasomatism and evolution. While alkaline volcanic rocks such as lamproite and kamafugite rocks are generally found in intraplate settings, silica-undersaturated alkaline rocks such as leucitites observed in convergent plate margins are, generally associated with calc-alkaline magmatism [START_REF] Conticelli | Source contamination and mantle heterogeneity in the genesis of Italian potassic and ultrapotassic volcanic rocks: Sr-Nd-Pb isotope data from Roman Province and Southern Tuscany[END_REF]. Melting of a heterogeneous mantle source characterised by the presence of net hydrous phases bearing veined metasomatic domains and surrounding peridotites under a postcollisional tectonic regime results in different melt types. Lamproitic melts are produced by melting of a vein-dominated source, while dilution of the vein melt by increased partial melting of surrounding peridotites produces shoshonitic, high-K and calc-alkaline melts (e.g., [START_REF] Foley | Vein-plus-wall-rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas[END_REF][START_REF] Prelević | Tertiary ultrapotassic volcanism in Serbia: constraints on petrogenesis and mantle source characteristics[END_REF][START_REF] Prelević | Mediterranean Tertiary lamproites derived from multiple source components in postcollisional geodynamics[END_REF][START_REF] Conticelli | Chemical and isotopic composition (Os, Pb, Nd, and Sr) of Neogene to Quaternary calc-alkalic, shoshonitic and ultrapotassic mafic rocks from the Italian Peninsula: inferences on the nature of their mantle sources[END_REF], 2009a[START_REF] Prelević | Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey[END_REF]. [START_REF] Prelević | Mediterranean Tertiary lamproites derived from multiple source components in postcollisional geodynamics[END_REF] support the idea that such hydrous mafic phases bearing net veined mantle is probably present in the entire Alp-Himalayan orogenic belt. The degree of melting also contributes to determining the affinity of the magmas. Alkaline magmas generally ensue from a higher melting degree of lithospheric mantle at a shallower depth, as a result of progressive lithospheric thinning and associated asthenospheric upwelling [START_REF] Kolb | Petrogenesis of mafic to felsic lavas from the Oligocene Siebengebirge volcanic field (Germany): implications for the origin of intracontinental volcanism in Central Europe[END_REF]. The melting processes of the mantle during Tertiary times could be one of the following models: (i) melting triggered by perturbation of the geotherm as a result of heat flow due to asthenospheric upwelling; (ii) decompressional melting of lithospheric mantle because of lithospheric thinning during extension (e.g. [START_REF] Wilson | Tertiary volcanism of the Galatia Province, Central Anatolia, Turkey[END_REF]; and (iii) melting of lithospheric mantle resulting from heat flow facilitated by a mantle plume.

In order to generate parental melts in the Eastern Pontides during Middle Eocene times, the feasible mechanism of lithospheric mantle melting is a perturbation of the geotherm subsequent to an asthenospheric upwelling related to delamination (e.g. [START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF] and/or slab break-off (e.g. [START_REF] Keskin | Petrology and geochemistry of post-collisional Middle Eocene volcanic units in North-Central Turkey: evidence for magma generation by slab breakoff following the closure of the Northern Neotethys Ocean[END_REF][START_REF] Eyüboğlu | Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: implications for slab window melting[END_REF] entire Alp-Himalayan orogenic belt [START_REF] Prelević | Mediterranean Tertiary lamproites derived from multiple source components in postcollisional geodynamics[END_REF]. The metasomatic mineral assemblage has a lower melting point than the surrounding peridotites [START_REF] Foley | Vein-plus-wall-rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas[END_REF].

After collision of TAP and Pontides in Paleocene time, the geodynamic evolution of the region was governed by post-collisional extension, probably caused by strike-slip tectonics. A change in stress regime from compression to extension related to lithospheric delamination controlled by the regional strike-slip movements led to an asthenospheric upwelling that induced an increase in temperature at the base of the lithosphere, resulting in lithospheric mantle and/or lower crustal

melting. An increase in the melting degree of this heterogeneous lithospheric mantle source would lead to melting not only the net veined mantle, but also the surrounding peridotites. The hydrous phases bearing alkaline magmas were produced by melting of a metasomatic veined mantle whereas anhydrous mildly alkaline or alkaline-calcalkaline transitional magmas resulted from a higher melting degree of the surrounding peridotites together with net veined mantle. Tensional fracturing of the lithosphere creates a pathway for ascending magmas that pause at different crustal levels. Hydrous and anhydrous magmas derived from net veined and/or surrounding peridotite experienced mixing processes within deep, middle and shallow level crustal magma chambers (Fig. 13a-d). Nevertheless, Sr-Nd-Pb isotopic data suggest limited crustal assimilation by ascending magmas for Middle Eocene volcanic rocks.

There seems to be a magmatic silence from Middle Eocene (45-41Ma) to Late Miocene (6-5Ma) time in the study area, since there is lack of geochronological data throughout the Eastern Pontides Tertiary magmatism, except for limited Early Oligocene (30Ma; [START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF] and Middle Miocene (16-17 Ma; [START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF] volcanism. Therefore, continuing lithospheric delamination can also be a reliable model for the Miocene volcanism in the Eastern Pontides [START_REF] Aydın | Petrogenesis of the Neogene alkaline volcanics with implications for post-collisional lithospheric thinning of the Eastern Pontides, NE Turkey[END_REF][START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF][START_REF] Aslan | K-Ar age, whole rock and Sr-Nd isotope geochemistry of calc-alkaline volcanics around the Gümüşhane area (NE Turkey): implications for postcollisional volcanism during Tertiary time in the eastern Pontides[END_REF]). However, the distinct geochemical characters and limited distribution and volume of Late Miocene volcanism in the region necessitate an extensional mechanism controlled via strike-slip tectonics to trigger the volcanism during delamination. The collisional and post-collisional events in the Eastern Pontides resulted in a complex crustal architecture during Paleocene-Miocene times. The strike-slip movements have played an important role in shaping the morphology of the region, since E-W-, NE-SW-and NW-SE trending lineaments and block faulted architecture are important extensional tectonic structures of the Pontides crust [START_REF] Bektaş | Doğu Pontid magmatik arkında (KD, Türkiye) neptünyen dayklar ve blok tektoniği[END_REF][START_REF] Maden | Two-and-three-dimensional crustal thickness of the eastern Pontides (NE Turkey)[END_REF]. Besides, [START_REF] Eyüboğlu | Three axial extensional deformation and formation of the Liassic rift basins in the Eastern Pontides (NE Turkey)[END_REF] suggest that these structural trends, which coincide with gravity and magnetic lineament anomalies, control the neotectonic evolution of the Eastern Pontides magmatic arc. This tectonic system can create pathways for magma transport to the surface, and controls the magma residence time and the petrological processes (such as magma mixing and/or contamination) during ascent of magmas through the crust. In the region, some intrusive rocks cropping out along faults zones, similar

A C C E P T E D M A N U S C R I P T 21
to left-lateral NE-SW strike-slip faults [START_REF] Kurt | Doğu Karadeniz Bölgesinin jeodinamik ve Metalojenik Evrimi (Keşap (Giresun)-Çarşıbaşı (Trabzon)-Torul (Gümüşhane) Arasının Jeolojisi), General Directorate of Mineral Research and Exploration of Turkey (MTA)[END_REF], can be regarded as pop-up or flowerstructures. Likewise, the studied Miocene volcanic rocks are limited by two such left-lateral NE-SW strike-slip faults [START_REF] Maden | Two-and-three-dimensional crustal thickness of the eastern Pontides (NE Turkey)[END_REF]Fig. 14a). Such strike-slip faults can generate tensional fractures and extensional areas (Fig. 14b), able to facilitate rising pathways for Miocene volcanism. The extensional tectonics combined with strike-slip movement at the regional scale following (1) 40 Ar-39 Ar geochronology of the studied volcanic rocks reveals that the basaltic and trachytic rocks were emplaced in Middle Eocene (Lutetian) time, when tephrytic rocks erupted during Late Miocene (Messinian) time.

(2) The Eocene volcanic rocks are characterised by narrow initial 87 Sr/ 86 Sr ratios from 0.70389-0.70448 with an εNd (i) range between +1.61 and +3.75 for the basaltic rocks and 0.70408-0.70425 with an εNd (i) range between +1.84 and +2.81 for the trachytic rocks. On the other hand, the tephrytic rocks yielded more radiogenic initial 87 Sr/ 86 Sr ratios, between 0.70518-0.70536 with εNd (i) between +0.61 and +1.08.

(3) Trace element and isotopic AFC modelling revealed that the parental magmas of both the Eocene and Miocene volcanic rocks were mostly affected by fractional crystallisation, rather than assimilation coupled with fractional crystallisation and mixing. Based on petrographic, mineral chemistry and geochemical data, the silica-undersaturated character of the Miocene tephrytic rocks could be attributed to assimilation of carbonate rocks within shallow-level magma chambers, even if this hypothesis is not completely supported by isotopic AFC modelling data.

(4) The parental magmas of the Eocene volcanic rocks are the result of a relatively high melting degree of a net veined mantle and surrounding peridotite source in the spinel stability field, due to an increase in temperature resulting from an asthenospheric upwelling. The parental magmas of the Miocene volcanic rocks are formed by a relatively low melting degree of a net veined mantle domain, previously formed by metasomatic melts derived from a garnet peridotite source, resulting from decompression due to extensional tectonics combined with strike-slip movement at a regional scale, related to ongoing delamination. [START_REF] Okay | Tethyan sutures of northern Turkey[END_REF]. (b) Generalized geological map of the Eastern Pontides showing distribution of the Tertiary volcanic rocks and intrusions (modified after [START_REF] Güven | Doğu Pontidler'in 1:25000 ölçekli jeolojisi ve kompilasyonu [1:25000 Scale Geology and Compilation of the Eastern Pontide[END_REF][START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF]. The square indicates the study area. (c) Geological map of the study area showing distribution of the Eocene and Miocene volcanic rocks (modified from [START_REF] Güven | Doğu Pontidler'in 1:25000 ölçekli jeolojisi ve kompilasyonu [1:25000 Scale Geology and Compilation of the Eastern Pontide[END_REF] and Late Cretaceous units modified from [START_REF] Kurt | Doğu Karadeniz Bölgesinin jeodinamik ve Metalojenik Evrimi (Keşap (Giresun)-Çarşıbaşı (Trabzon)-Torul (Gümüşhane) Arasının Jeolojisi), General Directorate of Mineral Research and Exploration of Turkey (MTA)[END_REF]). (1985), (e, f) CaO (wt.%) vs Al 2 O 3 and MgO classification diagrams of [START_REF] Foley | The ultrapotassic rocks: characteristics, classification and constraints for petrogenetic models[END_REF]. (ΔQ is the algebraic sum of normative quartz (q) minus undersaturated minerals leucite (lc), nepheline (ne), kalsilite (kal) and olivine (ol)). (Sun and McDonough, 1989) multi element spider and chondrite [START_REF] Taylor | The continental crust: its composition and evolution[END_REF] normalized rare earth element diagrams of the Eocene and Miocene volcanic rocks from the Trabzona and Giresun areas. [START_REF] Aydınçakır | Petrogenesis of the postcollisional volcanic rocks from the Borçka (Artvin) area: Implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)[END_REF], Torul volcanic rocks [START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF], Eastern Pontides Southern part Eocene volcanic rocks [START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF], Everek Hanları volcanic rocks (Alther et al., 2008;[START_REF] Eyüboğlu | Late Cretaceous high-K volcanism in the eastern Pontides orogenic belt, and its implications for the geodynamic evolution of NE Turkey[END_REF], Ulubey volcanic rocks [START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF]), Kop Adakites (Eyuboglu et al., 2013), Kale Adakites [START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF]. Data for lithospheric mantle array from [START_REF] Davies | Slab breakoff: a model of lithospheric detachment and its test in the magmatism and deformation of collisional orogens[END_REF]. Compositions of MORB (mid-ocean ridge basalt) and mantle array from [START_REF] Wilson | Igneous Petrogenesis[END_REF], [START_REF] Gill | Orogenic Andesites and Plate Tectonics[END_REF] and [START_REF] Mcculloch | Pb-Sr-Nd-O isotopic constraints on the origin of rhyolites from the Taupo Volcanic zone of New Zealand: evidence for assimilation followed by fractionation of basalt[END_REF]; EMI (enriched mantle type I) and EMII (enriched mantle type II), HIMU(high µυ: mantle with high U/Th ratio), DM (Depleted Mantle) fields and CHUR (Chondritic Uniform Reservoir)-Sr and -Nd reference lines after Zindler and Hart (1986). (b,c) variations in Pb isotope compositions of samples from Eocene and Miocene alkaline volcanic rocks from Trabzon-Giresun areas. Plotted for comparison, the composition of pelagic sediments and MORB are after [START_REF] Peate | Geochemical variations inVanuatu arc lavas: the role of subducted material and a variable mantle wedge composition[END_REF][START_REF] Hofmann | Sampling mantle heterogeneity through oceanic basalts: isotopes and trace elements[END_REF], NHRL (Northern Hemisphere Reference Line) after [START_REF] Hart | A large-scale isotope anomaly in the southern hemisphere mantle[END_REF], EAR (Depleted East European Lithosphere) after [START_REF] Rosenbaum | Multiple enrichment of the Carpathian^Pannonian mantle: Pb-Sr-Nd isotope and trace element constraints[END_REF] [START_REF] Kirchenbaur | Tectonomagmatic Constraints on the Sources of Eastern Mediterranean K-rich Lavas[END_REF] and references therein). The plot of (c) Sr/La vs. La/Yb, (symbols are as in Fig. 3). 7 (symbols are as in Fig. 3). Hofmann, 1988).

A C C E P T E D M A N U S C R I P T

61 (1994)

  studied Eocene and Miocene volcanic rocks are generally observed as volcaniclastics, lava flows, rarely dikes and domes. According to their volcanostratigraphy and facies features,Yücel et al (2014a) discriminated three suites as (1) Eocene basalt, trachybasalt, and basaltic trachyandesite (BTB) suite, which contains basaltic breccia and tuff, pillow lava, basaltic lava, and basaltic dike-sills;(2) Eocene trachyte and trachyandesite (TT) suite, which contains andesitic dikes, domes, and trachytic dikes; (3) Miocene basanite and tephrite (BT) suite, which contains foid-bearing breccia, foid-bearing brecciated lava, and foid-bearing dikes and sills. These discriminations and suite names are kept as Eocene basaltic and trachytic, and Miocene tephrytic rocks here, in order to reveal parental magma(s) and differentiative members in relation to their absolute ages. Petrographically, the common textural features of the Eocene basaltic rocks are microlitic porphyritic, hyalo-microlitic porphyritic, intersertal, glomeroporphyritic and fluidal. The main mineralogical composition of the volcanic rocks is clinopyroxene + plagioclase ± olivine ± brown mica ± hornblende ± Fe-Ti oxide. The Eocene trachytic rocks contain phenocrysts of plagioclase ± sanidine ± brown mica ± hornblende ± clinopyroxene + Fe-Ti oxide ± quartz (<5 %), and show generally microgranular porphyritic, and rare trachytic, hypocrystalline, poikilitic, glomeroporphyritic and sieve textures. General textures of the Miocene tephrytic rocks are microgranular-porphyritic, hyalomicroporphyritic, glomeroporphyritic, microgranular, vesicular, and amygdaloidal. The main mineralogical composition is reflected by clinopyroxene ± olivine ± brown mica ± hornblende ± plagioclase ± sanidine + analcime + Fe-Ti oxide + apatite mineral assemblage. Beside the volcanic facies characteristics, the studied volcanic rocks have been reported in detail with the aspect of petrography and mineral chemistry byYücel et al. (2014a).

  samples were collected from between Trabzon and Giresun in the Eastern Pontides (NE Turkey). They comprise mafic and intermediate volcanic rocks from the remnants of the Eocene and Miocene volcanic rocks composed mainly of volcaniclastics, lava flows, rarely dikes and domes. The most representative and freshest samples were selected for 40 Ar-39 Ar dating, whole-rock major oxides, trace and rare earth element (REE) and Sr-Nd-Pb isotope analyses. Whole-rock major, trace and REEs

( 1987 )

 1987 prepared for classification of alkaline rocks, most of the samples lie within the Roman province (plagioleucitite) field, except for some samples from Eocene trachytic rocks, reflecting an intermediate character and some samples with high MgO and low Al 2 O 3 contents from Eocene basaltic rocks (Fig.3e, f).In the Harker diagrams (Fig.4, Supplementary Fig.2), both the Eocene basaltic and trachytic rocks and the Miocene tephrytic rocks present similar variations. For the Eocene volcanic rocks, TiO 2 MgO, Ni, Sr and Co are negatively correlated; whereas K 2 O, Na 2 O, Th and Rb are positively correlated with SiO 2 when P 2 O 5 , Al 2 O 3 , Hf, Zr, Nb and Ta show curvilinear behaviours. The Miocene tephrytic rocks do not exhibit as smooth a correlation as the Eocene volcanic rocks. P 2 O 5 , MnO, Fe 2 O 3 *, CaO, MgO, Sr, Ni and Co decrease while TiO 2 , Na 2 O, K 2 O, Ba, Hf, Rb, Zr, Nb and Ta show positive curvilinear and scattered behaviour with increasing SiO 2 . A C C E P T E D M A N U S C R I P T 10 In primitive mantle-normalised (Sun and McDonough, 1989) multi-element diagrams (Fig. 5), the Eocene basaltic and trachytic rocks display broadly similar patterns characterised by enrichment in large-ion lithophile elements (LILEs; Sr, K 2 O, Ba, Rb), and Th and Ce and depletion in some high field strength elements (HFSEs; Zr, TiO 2 , Y, Nb, Ta). The Miocene tephrytic rocks have geochemical characteristics similar to those of the Eocene volcanic rocks. Although all volcanic rocks display typical subduction zone signatures (viz. depletions of Nb, Ta and TiO 2 ) the differences in subduction signature between Eocene and Miocene volcanic rocks draw attention. Enrichment in Sr, Ba, Th, Ce and P 2 O 5 for the Miocene tephrytic rocks is more sizeable than that of the Eocene volcanic rocks. Depletion of P 2 O 5 and TiO 2 in some trachyte samples from the Eocene trachytic rocks is more significant than for other volcanic rocks. The studied volcanic rocks present fractionated rare earth element (REE) patterns in chondrite-normalised REE plots. The Miocene tephrytic rocks are characterised by steep light rare earth element (LREE) patterns relative to heavy rare earth elements (HREEs). Despite similar REE patterns, Eocene basaltic and trachytic rocks exhibit less pronounced LREE enrichment than Miocene tephrytic rocks. The enrichment in LREE (La=21

  models. The mantle beneath the Eastern Pontides was metasomatised by fluids derived from a subducted slab during paleo-A C C E P T E D M A N U S C R I P T 20 subduction from Jurassic to Paleocene time. This metasomatic event resulted in the development of hydrous phases bearing net veined mantle in the spinel stability field, as previously reported for the

  collision and delamination led to decompression in an enriched lithospheric mantle characterised by the presence of a net veined metasomatic mineral assemblage, which resulted from metasomatism by melts derived from the garnet stability field. The low partial melting degree of this metasomatic component of the lithospheric mantle with a lower melting point than the surrounding peridotites allows the formation the incompatible element-enriched moderately alkaline melts in the spinel stability field. Tensional fracturing of the lithosphere beneath the Eastern Pontides orogenic belt assures tectonic control on the ascent of small volumes of magma for the Miocene tephritic rocks. The petrological data combined with petrographic and mineral chemistry data reported by Yücel et al. (2014a) indicate that crustal magma chamber processes such as mixing, in three different magma storage regions, are characterised by a polybaric evolutionary path similar to the Eocene ones. Even if Sr-Nd-Pb isotopic data and petrological modelling do not forcefully support assimilation processes, the silica-undersaturated Miocene tephrytic rocks and a petrographical composition characterised by the presence of Ca-rich clinopyroxenes and flourapatite and/or cancrinite-vishnevite group minerals suggest the assimilation of carbonate rocks in shallow-level crustal magma chambers. geochronology, whole-rock and Sr-Nd-Pb isotopic geochemical data from the Trabzon-Giresun area volcanic rocks in the northern part of the Eastern Pontides (NE Turkey) shed a new light on the origin and evolution of Middle Eocene and Miocene volcanic rocks, enabling us to reach the following conclusions:

Figure 1 .

 1 Figure Captions

Figure 2 .

 2 Figure 2. Distribution of apparent ages acquired by step heating of whole-rock, phlogopite and sanidine fractions of (a) the Eocene basaltic and trachytic, and (b) the Miocene tephrytic rocks (AP is apparent age).

Figure 3 .

 3 Figure 3. Classification of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas based on the (a) Na 2 O + K 2 O (wt.%) vs SiO 2 (wt.%) diagram (Le Bas et al., 1986), (b) Th (ppm) vs Co (ppm) diagram (Hastie et al., 2007), (c) K 2 O/Na 2 O vs ΔQ diagram[START_REF] Peccerillo | Plio-Quaternary magmatism in central-southern Italy: a new classification scheme for volcanic provinces and its geodynamic implications[END_REF][START_REF] Peccerillo | Plio-Quaternary magmatism in Italy[END_REF], (d) AFM ternary diagram tholeitic-alkaline-calc-alkaline-shoshonitic dividing lines fromWimmanuer (1985), (e, f) CaO (wt.%) vs Al 2 O 3 and MgO classification diagrams of[START_REF] Foley | The ultrapotassic rocks: characteristics, classification and constraints for petrogenetic models[END_REF]. (ΔQ is the algebraic sum of normative quartz (q) minus undersaturated minerals leucite (lc), nepheline (ne), kalsilite (kal) and olivine (ol)).

Figure 4 .Figure 5 .

 45 Figure 4. Major oxides (wt. %) Harker variation diagram plotted against SiO 2 (wt. %) of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas (symbols are as in Fig. 3)

Figure 6 .

 6 Figure 6. (a) ( 143 Nd/ 144 Nd) i versus ( 87 Sr/ 86 Sr) i diagram showing the Eocene and Miocene volcanic rocks from Trabzon and Giresun areas with the samples from other alkaline and calc-alkaline volcanic rocks of Borçka volcanic rocks[START_REF] Aydınçakır | Petrogenesis of the postcollisional volcanic rocks from the Borçka (Artvin) area: Implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)[END_REF], Torul volcanic rocks[START_REF] Kaygusuz | Geochemical and Sr-Nd isotopic characteristics of post-collisional calc-alkaline volcanics in the Eastern Pontides (NE Turkey)[END_REF], Eastern Pontides Southern part Eocene volcanic rocks[START_REF] Arslan | 40 Ar-39 Ar dating, whole-rock and Sr-Nd-Pb isotope geochemistry of post-collisional Eocene volcanic rocks in the southern part of the Eastern Pontides (NE Turkey): Implications for magma evolution in extension-induced origin[END_REF], Everek Hanları volcanic rocks(Alther et al., 2008;[START_REF] Eyüboğlu | Late Cretaceous high-K volcanism in the eastern Pontides orogenic belt, and its implications for the geodynamic evolution of NE Turkey[END_REF], Ulubey volcanic rocks[START_REF] Temizel | Petrochemistry, geochronology and Sr-Nd isotopic systematics of the Tertiary collisional and post-collisional volcanic rocks from the Ulubey (Ordu) area, eastern Pontide, NE Turkey: implications for extension-related origin and mantle source characteristics[END_REF]), Kop Adakites (Eyuboglu et al., 2013), Kale Adakites[START_REF] Karslı | Generation of the early Cenozoic adakitic volcanism by partial melting of mafic lower crust, Eastern Turkey: implications for crustal thickening to delamination[END_REF]. Data for lithospheric mantle array from[START_REF] Davies | Slab breakoff: a model of lithospheric detachment and its test in the magmatism and deformation of collisional orogens[END_REF]. Compositions of MORB (mid-ocean ridge basalt) and mantle array from[START_REF] Wilson | Igneous Petrogenesis[END_REF],[START_REF] Gill | Orogenic Andesites and Plate Tectonics[END_REF] and[START_REF] Mcculloch | Pb-Sr-Nd-O isotopic constraints on the origin of rhyolites from the Taupo Volcanic zone of New Zealand: evidence for assimilation followed by fractionation of basalt[END_REF]; EMI (enriched mantle type I) and EMII (enriched mantle type II), HIMU(high µυ: mantle with high U/Th ratio), DM (Depleted Mantle) fields and CHUR (Chondritic Uniform Reservoir)-Sr and -Nd reference lines after Zindler andHart (1986). (b,c) variations in Pb isotope compositions of samples from Eocene and Miocene alkaline volcanic rocks from Trabzon-Giresun areas. Plotted for comparison, the composition of pelagic sediments and MORB are after[START_REF] Peate | Geochemical variations inVanuatu arc lavas: the role of subducted material and a variable mantle wedge composition[END_REF][START_REF] Hofmann | Sampling mantle heterogeneity through oceanic basalts: isotopes and trace elements[END_REF], NHRL (Northern Hemisphere Reference Line) after[START_REF] Hart | A large-scale isotope anomaly in the southern hemisphere mantle[END_REF], EAR (Depleted East European Lithosphere) after[START_REF] Rosenbaum | Multiple enrichment of the Carpathian^Pannonian mantle: Pb-Sr-Nd isotope and trace element constraints[END_REF], North African sediments after Pe-Piper (1994), DM (depleted mantle), HIMU and enriched (EMI and EMII) mantle afterZindler and Hart (1986). Field of arc systems (compiled in[START_REF] Wilson | Igneous Petrogenesis[END_REF] Winter, 2001)

Fig. 3 )

 3 Figure9. (a, b) ( 87 Sr/ 86 Sr) i versus ( 143 Nd/ 144 Nd) i diagrams (g, h, using Paleozoic aged granite (T135) from[START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF] and limestone (ERN57) from[START_REF] Boari | Transition from ultrapotassic kamafugitic to sub-alkaline magmas: Sr, Nd, and Pb isotope, trace element and 40 Ar-39 Ar age data from the Middle Latin Valley volcanic field, Roman Magmatic Province, Central Italy[END_REF] as a upper crustal assimilant, respectively) showing isotopic AFC (assimilation-fractional crystallization) for the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas. The representative AFC curves are for various combinations of a volcanic arc basalt as hypothetical parental magma (K-93-56,[START_REF] Alıcı | Pb-Nd-Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region (western Anatolia, Turkey)[END_REF] and bulk distribution coefficients (D Sr , D Nd ). Tick marks indicate the ratio of the final mass of magma to its initial mass (F) and are given in intervals of 5 % and 10 % to a maximum of 95 % (r = 0.2 and 0.3 for figure a curves r=0.3 for figure b curves). Other parameters are indicated in the Table6(symbols are as in Fig.3)

Figure 11 .

 11 Figure 11. The importance of sediment or fluid like metasomatism in the petrogenesis of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas; (a) the plot of Ba/Th vs. Th (ppm), the shaded areas represent the arc volcanic rocks worldwide. (b) Th/Yb vs. Ba/La diagram, the shaded areas indicate the oceanic arc volcanic rocks[START_REF] Kirchenbaur | Tectonomagmatic Constraints on the Sources of Eastern Mediterranean K-rich Lavas[END_REF] and references therein). The plot of (c) Sr/La vs. La/Yb, (symbols are as in Fig.3).

Figure 12 .

 12 Figure 12. (a) ( 87 Sr/ 86 Sr) i versus 206 Pb/ 204 Pb, and (b) εNd i versus 206 Pb/ 204 Pb diagrams showing a threecomponent mixing model between upper/lower crust and upper mantle for the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas. Tick marks on mixing lines are at 10% intervals and the parameters for the mixing calculation are presented in Table7(symbols are as in Fig.3).

Figure 13 .Figure 14 .

 1314 Figure 13. Schematic cartoons showing the favoured geodynamic model for the Eocene and Miocene volcanism in the Eastern Pontides, accompanied by post-collisional extension regime due to delamination of lithosphere: (a) post-collisional extensional stage due to delamination, forming the Eocene volcanism (ca.50-45 Ma, Arslan et al., 2013), (b) schematic illustration of partial melting and pre-eruptive crystallization paths and magmatic processes in crustal chambers for Eocene volcanism, (c) ongoing post-collisional extensional stage, forming Miocene-Pliocene volcanism (ca. 15-5 Ma, Arslan et al., 2013), (d) schematic illustration of partial melting and pre-eruptive crystallization paths and magmatic processes in crustal chambers for Miocene volcanism.

  Figure 1

  1. A summary of age determinations is given in Table 1. The great majority of the obtained age spectras have a flat pattern over more than 80% of the degassed 39 Ar K . Few show low apparent ages in the low temperature steps, probably

	related to degassing of some weathering phases (e.g. 511 whole rock). Rarely higher but decreasing
	apparent ages (e.g. 777 whole rock) are probably related to some limited 39 Ar K recoil, occurring during
	irradiation, on phases degassing in the low-temperature domain. All these age spectra allow plateau
	age calculations that are, on the whole, validated by isochron calculations. Nevertheless, some whole-
	rock experiments from basaltic rocks yield age spectra with slightly decreasing apparent ages from the
	low-to the intermediate-temperature steps with pseudo-plateau ages (PPA) in the high-temperature
	steps (e.g. whole rocks 301, 363 and 642). Such a pattern characterises 39 Ar K recoil with a broader
	extent than e.g. 777 whole rock. This is easy to recognise with isochron diagrams, as this recoil effect
	leads to a concave trajectory of successive degassing steps in the place of a simple straight line (e.g.
	363 wholerock). Nevertheless, the high-temperature PPA provides rather good estimates of the true
	age of the analysed material, as suggested by their good agreement with results from isochron
	calculations. Eocene basaltic rock samples yielded ages between 44.21 ± 0.18 and 43.97 ± 0.18 Ma for
	pillow lavas, between 44.75 ± 0.18 and 44.15 ± 0.17 Ma for basaltic lavas and between 45.31 ± 0.18
	and 43.86 ± 0.19 Ma for basaltic dikes and sills. Eocene trachytic rock samples yielded ages between
	43.90 ± 0.17 Ma and 42.95 ± 0.17 Ma for andesitic dike and domes, and between 44.87 ± 0.22 Ma and
	41.32 ± 0.12 Ma for trachytic dike. Some phlogopite/whole rock pairs from samples of trachytic rocks

  tephrytic rocks have higher radiogenic lead isotope compositions than those of the Eocene volcanic rocks; all plot above the Northern Hemisphere Reference Line (NHRL;[START_REF] Hart | A large-scale isotope anomaly in the southern hemisphere mantle[END_REF] with relatively enriched 207 Pb/ 204 Pb ratios. The isotopic budget of the Eocene basaltic and trachytic rocks presents a close relationship with the Eastern Pontides Southern part Eocene volcanic rocks, whereas the Miocene tephrytic rocks exhibite similarities with the Late Cretaceous Everek Hanları volcanic rocks

	Temizel et al., 2012) and Borçka (Artvin; Aydınçakır and Şen, 2013) volcanic rocks when tephrytic
	rocks exhibit similarities with Torul (Gümüşhane; Kaygusuz et al., 2011) and the Eastern Pontides
	Southern Part Eocene volcanic rocks (Arslan et al., 2013).
	The lead isotope ratios exhibit narrow ranges e.g., 206 Pb/ 204 Pb =18.72-18.79,

207

Pb/ 204 Pb=15.

63-15.67, 208

Pb/ 204 Pb= 38.79-38.92 for the basaltic rocks, 206 Pb/ 204 Pb =18.78-18.80, 207 Pb/ 204 Pb=15.64-15.67, 208 Pb/ 204 Pb= 38.87-38.97 for the trachytic rocks and 206 Pb/ 204 Pb =18.89-18.95, 207 Pb/ 204 Pb=15.66-15.68, 208 Pb/ 204 Pb= 38.94-39.06 for the tephrytic rocks. The Miocene

A C C E P T E D M A N U S C R I P T

  . The studied Eocene and Miocene volcanic rocks are quite different, with low

	Mg# (16.6-55.9 for basaltic rocks, 5.4-37 for trachytic rocks and 23.4-44.6 for tephrytic rocks),
	generally low Ni (0.7-143 ppm for basaltic rocks, 0.2-16.2 ppm for trachytic rocks and 3.7-31.3 ppm
	for tephrytic rocks) and Cr (1.3-72.2 ppm for basaltic rocks, 1.4-4.2 ppm for trachytic rocks and 1.4-
	13.2 ppm for tephrytic rocks) contents. The Eocene basaltic and trachytic rocks form consecutive
	trends, but the basaltic rocks, within discrimination diagrams (Figs. 3, 4 and Supplementary Fig. 2),

appear to be more primitive compared to the trachytic rocks. Moreover, the overlap between basaltic and trachytic rocks ranging from 46.75-58.54 SiO 2 wt. % and observed consecutive trends mentioned

  Ti oxides, whereas negative CaO correlation parallel to Sr and negative K 2 O and Na 2 O trends with increasing SiO 2 are probably linked to plagioclase, phologopite and K-feldspar joined fractionations. Negative Nb, Rb, Ba or negative P 2 O 5 correlations with increasing SiO 2 probably result from phlolopite and apatite fractionations, respectively.

	The decrease in MgO, Fe 2 O 3	* , Co and Ni
	with increasing SiO 2 is probably related to olivine fractionation. The CaO and MgO decrease with
	increasing SiO 2 reflects clinopyroxene fractionation. The negative trends in Fe 2 O 3	* , TiO 2 and MgO
	may be related to fractionation of Fe-

Table 4 .

 4

Eocene basaltic rocks, Sr and Dy for Eocene trachytic rocks, and Sc and Nb for Miocene tephrytic rocks. Rb and Nb are strongly incompatible for mineral phases crystallising from magmas with basic compositions. Sc is highly partitioned into amphibole, clinopyroxene and biotite, but not into olivine and plagioclase. Sr, strongly partitioned in plagioclase, exhibits compatible behaviour during fractional crystallisation processes for magmas with intermediate compositions. Although Dy is strongly partitioned in hydrous mafic mineral phases such as amphibole, it generally comes into prominence with incompatible character for intermediate magma compositions. The K d values of Rb, Sc, Sr, Nb, Dr for amphibole, plagioclase, clinopyroxene, olivine, biotite and sanidine are given in

  Sc, Sr, Nb, Dy and Sr for amphibole, plagioclase, clinopyroxene, olivine, biotite and sanidine were compiled from[START_REF] Rollinson | Using Geochemical Data: Evaluation, Presentation, Interpretation[END_REF], GERM Partition Coefficient (Kd) Database of Earth Reference Data and Models website (http://earthref.org/; see the references therein) and[START_REF] Keskin | FC-Modeler: a Microsoft® Excel© spreadsheet program for modeling Rayleigh fractionation vectors in closed magmatic systems[END_REF]. amp: amphibole; pl: plagioclase; ol: olivine; bio: biotite; cpx: clinopyroxene; Sa: sanidine (symbols are as in Fig.3). (a, b) ( 87 Sr/ 86 Sr) i versus ( 143 Nd/ 144 Nd) i diagrams (g, h, using Paleozoic aged granite (T135) from[START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF] and limestone (ERN57) from[START_REF] Boari | Transition from ultrapotassic kamafugitic to sub-alkaline magmas: Sr, Nd, and Pb isotope, trace element and 40 Ar-39 Ar age data from the Middle Latin Valley volcanic field, Roman Magmatic Province, Central Italy[END_REF] as a upper crustal assimilant, respectively) showing isotopic AFC (assimilation-fractional crystallization) for the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas. The representative AFC curves are for various combinations of a volcanic arc basalt as hypothetical parental magma (K-93-56,[START_REF] Alıcı | Pb-Nd-Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region (western Anatolia, Turkey)[END_REF] and bulk distribution coefficients (D Sr , D Nd ). Tick marks indicate the ratio of the final mass of magma to its initial mass (F) and are given in intervals of 5 % and 10 % to a maximum of 95 % (r = 0.2 and 0.3 for figure a curves r=0.3 for figure b curves). Other parameters are indicated in the Table6(symbols are as in

	, North African sediments after Pe-Piper (1994), DM (depleted mantle), HIMU and enriched (EMI and EMII) mantle after Zindler and Hart (1986). Field of arc systems (wt.%) (d) ( 143 Nd/ 144 Nd) i versus Sm/Nd, (e) ( 143 Nd/ 144 Nd) i versus Nb (ppm), (f) 207 Pb/ 204 Pb versus MgO (wt.%) diagrams showing possible fractional crystallization (FC) and/or assimilation-fractional crystallization (AFC) trends for the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas (symbols are as in Fig. 3). (compiled in Wilson, 1989; Winter, 2001) Figure 8. (a) ( 87 Sr/ 86 Sr) i versus Nb/Ta, (b) ( 87 Sr/ 86 Sr) i versus Sr (ppm), (c) ( 87 Sr/ 86 Sr) i versus SiO 2 Figure 9.

Figure 7. (a) Sc vs. Rb (for the Eocene basaltic rocks), (b) Sr vs. Dy (for the Eocene trachytic rocks), (c) Sc vs. Nb (for the Miocene tephrytic rocks) diagrams displaying theoretical Rayleigh fractionation lines. The FC-Modeller program of Keskin (2002) was used to calculate the plot of line. Kd values of Rb,

Table Captions Table 1 .

 Captions1 40 Ar-39 Ar age spectrum of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas.

Table 2 .

 2 Sr and Nd isotopic analysis of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas.

Table 3 .

 3 Pb isotopic analysis of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas.

Table 4 .

 4 Compiled Kd values used in fractional crystallization (FC) modelling calculation.

Table 5 .

 5 ( 143 Nd/ 144 Nd) i , ( 87 Sr/ 86 Sr) i , Sr (ppm) and Nd (ppm) compositions assumed for the end member components in the AFC calculation.

Table 6 .

 6 Partition coefficient (D), normative weight fractions of minerals and source modal composition data used in partial melting modelling calculation.

Table 7 .

 7 The compositions assumed for the end member (upper mantle, upper crust, lower crust) components of Sr-Nd-Pb isotopic mixing model.

Table 1

 1 The errors in the J values (0.2 %) are included in the plateau age calculations. Uncertainties are given at the 2σ level.

	Sample Material	Rock name	Step	Inverse isochrone age (Ma)	Plateau age (Ma)

Table 2

 2 Uncertainties for the 87 Sr/ 86 and 143 Nd/ 144 Nd ratios are 2σ m errors in the last two digits (in parentheses). ɛNd(0) and ɛNd(t) values are calculated relative to CHUR with present-day values of 143 Nd/ 144 Nd = 0.512638 and 147 Sm/ 144 Nd = 0.1967(Jacobsen and Wasserburg, 1980). Nd single stage model ages (T DM ) are calculated with a depleted mantle reservoir and present-day values of 143 Nd/ 144 Nd = 0.513151 and 147 Sm/ 144 Nd = 0.219 (Liew and

																		T
			Sa mpl e	Rb (p pm )	Sr (pp m)	87 Rb / 86 Sr	87 Sr/ 86 Sr	(±2 σ m )	( 87 Sr/ 86 Sr) i	Sm (p pm )	Nd (p pm )	147 Sm/ 146 Nd	143 Nd/ 144 Nd	(±2 σ m )	( 143 Nd/ 144 Nd) i	ɛ N d(0)	ɛ N d(t)	D M ( G
																		a)
			301	43. 7	67 5.0	0.18 7248	0.70 4130	11	0.704 013	4.2 1	19. 7	0.129 204	0.512 772	5	0.5127 34	2.6 0	2.6 4	0. 68
			363	45. 8	46 5.4	0.28 4628	0.70 4112	10	0.703 933	3.5 4	14. 4	0.148 630	0.512 813	5	0.5127 70	3.4 2	3.4 5	0. 79
			141	79. 6	67 0.8	0.34 3221	0.70 4479	10	0.704 261	4.2 7	21. 3	0.121 201	0.512 738	5	0.5127 03	6	2.0 0	0. 68
	rocks Basaltic	260 511 399	96. 0 81. 4 11 0.1	93 5.6 66 5.5 11 90.	0.29 6776 0.35 3785 0.26 7465	0.70 4330 0.70 4705 0.70 4294	10 10 9	0.704 144 0.704 480 0.704 130	5.6 1 3.9 1 5.4 2	26. 0 18. 1 25. 1	0.130 452 0.130 603 0.130 553	0.512 764 0.512 719 0.512 764	4 5 5	0.5127 26 0.5126 80 27	2.4 5 1.5 7 2.4 6	2.4 9 1.6 1 2.4 9	0. 71 0. 79 0. 71
			642	39. 3	77 6.4	0.14 6400	0.70 3987	10	0.703 893	4.7 5	24. 1	0.119 163	0.512 821	5	0.5127 86	3.5 6	3.6 1	0. 53
			508	14 1.1	49 4.9	0.82 4666	0.70 4818	10	287	5.7 9	29. 9	0.117 075	0.512 731	5	0.5126 96	1.8 1	1.8 5	0. 66
			801	93. 8	63	0.42 7323	0.70 4587	10	0.704 315	8	24. 3	0.116 441	0.512 828	5	0.5127 94	0	3.7 5	0. 51
			232	17 0.8	51 0.0	0.96 8697	0.70 4857	9	0.704 253	4.6 5	26. 1	0.107 715	780	5	0.5127 49	2.7 6	2.8 1	0. 53
			233	17 2.0	46 4.8	1.07 0371	0.70 4901	10	0.704 248	4.2 2	2	0.114 926	0.512 734	4	0.5127 02	1.8 7	1.9 2	0. 64
	rocks	777	18 1.7	57 4.8	0.91 4333	0.70 4768	10	0.704 198	4.8 0	24. 4	0.118 935	0.512 730	5	0.5126 96	1.8 0	1.8 4	68
	Trachytic	675 188	12 6.9 18 9.8	63 9.5 26 1.1	0.57 3957 2.10 2734	0.70 4578 0.70 5440	10 10	0.704 220 0.704 206	4.5 9 5.7 4	22. 6 28. 7	0.122 790 0.120 918	0.512 749 0.512 771	5 5	0.5127 14 0.5127 38	2.1 7 2.5 9	2.2 1 2.6 3	0. 67 0. 62
			318	12 6.4	65 0.5	0.56 2020	0.70 4428	10	0.704 079	5.9	29. 6	0.121 122	0.512 753	5	0.5127 18	2.2 4	2.2 8	0. 65
			625	28 4.0	15 4.7	5.31 1462	0.70 7564	10	0.704 252	5.1 6	27. 2	0.114 694	0.512 743	5	0.5127 10	4	2.0 9	0. 63
			603	25. 0	22 72. 1	0.03 1827	0.70 5309	10	0.705 306	12. 30	93. 0	0.079 960	0.512 669	5	0.5126 66	0.6 0	0.6 1	0. 55
	Tephry.	rocks	721	78. 9	22 71. 8	0.10	0.70 5371	10	0.705 362	13. 42	87. 4	0.092 831	0.512 693	5	0.5126 89	1.0 7	1.0 8	0. 58
			726	52. 2	31 58. 5	0.04 7805	0.70 5182	10	0.705 178	11. 32	76. 5	0.089 462	0.512 682	5	0.5126 78	0.8 5	0.8 6	0. 58

Table 3 Sample Pb(ppm) 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb

 3

	Δ8/4	Δ7/4

Table 5 .

 5

	End member	IC 0 (parental magma)	IC A (local continental crust)	IC A (continental crust)	Total Partition coefficient (∑D) D1 D2 D3 D4
	Sr (ppm)	887.2	59.1	386	Sr	1.60 1.20 1.20 0.15
	Nd (ppm)	34.5	23.1	3.85	Nd 0.95 1.15 1.85 2.00
	Sample no:	K-93-56	T135 (granite)	ERN-57 (limestone)	For all continental crust
	87 Sr/ 86 Sr	0.703114	0.728225	0.708768	modelling
	143 Nd/ 144 Nd	0.512941	0.512121	0.512115
		Alıcı et al. (2002)	Kaygusuz et al. (2012)	Boari et al. (2009)

Table 6 . Mantle Sources Modal proportions Normative weight fractions of minerals (i) in the partial melts

 6 Garnet lherzolite Ol 0.598 Opir 0.211 Kpir 0.076 Grt 0.115 Ol 0.05 Opx 0.2 Cpx 0.3 Grt 0.45 Spinel lherzolite Ol 0.578 Opir 0.27 Kpir 0.119 Spl 0.033 Ol 0.1 Opx 0.27 Cpx 0.5 Spl 0.13

	Partition coefficients	D La	D Yb	Partition coefficient (D) values are from Keskin (1994), McKenzie and O'Nions (1991, 1995) and GERM (Geochemical Earth
	Olivine	0.0004	0.0015	Reference Model) website. at http://earthref.org/databases/KDD/
	Orthopyroxene	0.002	0.049	Source compositions: Primitive mantle REE composition
				(McDonough and Sun, 1995) was chosen for all partial melting
	Clinopyroxene	0.0435	0.313	scenarios
	Garnet	0.01	4.3	Ol: olivine. Opx: orthopyroxene. Cpx: clinopyroxene. Grt: garnet. Spl: spinel
	Spinel	0.01	0.01	Garnet and spinel lherzolite composition are from Thirlwall et al.

Acknowledgement

This study is a part of the PhD thesis of the first author. The authors gratefully acknowledge the Turkish Scientific Research Council (TUBITAK-ÇAYDAG; Project no: 108Y204) and the Karadeniz Technical University (BAP Project no: 771). We would also like to thank to Dr. Nafiz Maden (Gümüşhane University, Turkey) for geophysical interpretations. We thank associate editor Inna Safonova and anonymous reviewers for their critical and constructive comments to improve our paper.

A C C E P T E D M A N U S C R I P T

Supplementary Figure Captions

Supplementary Figure 1. 40 Ar-39 Ar Age spectra and plateau and inverse isochrones ages acquired by step heating of whole-rock, phlogopite and sanidine fractions of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas. The age error bars for each temperature steps are at the 1r level and do not include errors in the J-values. The errors in the J-values (0.2 %) are included in the plateau age calculations.

Supplementary Figure 2. Trace (ppm) and rare earth element (ppm) Harker variation diagram plotted against SiO 2 (wt. %) of the Eocene and Miocene volcanic rocks from the Trabzon and Giresun areas (symbols are as in Fig. 3)

Supplementary Table Captions

Supplementary Table 1. Analytical data and parameters used for calculations (isotopic ratios measured on K, Ca and Cl pure salts; mass discrimination; atmospheric argon ratios; J parameter; decay constants) and reference sources for the studied Eocene and Miocene volcanic rocks.

Supplementary Table 2. The major and trace element composition of the studied Eocene and Miocene volcanic rocks. (1995). Pb concentration is from Rudnick and Fountain (1995). Sr-Nd-Pb isotope data and Pb concentration of upper crust are from (T135, Carboniferous aged granite; [START_REF] Kaygusuz | Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey[END_REF].

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