Petrogenesis of the Neogene bimodal magmatism of the Galatean Volcanic Province, Central Anatolia, Turkey

International audienceA series of geochemical analyses and radiometric age determinations are undertaken on rock samples collected from the Çamlıdere region in the Galatean Volcanic Province of NW Turkey, to better understand the characteristics of the bimodal Early-Middle Miocene volcanism developed near the Late Cretaceous Tethyan Suture Zone. Çamlıdere volcanic rocks consist of large volumes of older (> 20 Ma) calc-alkaline andesites, dacites and rhyolites and pyroclastites, and small volumes of slightly younger (~ 19 Ma) alkaline trachybasalts and basaltic trachyandesites, cropping out as dykes or small lava flows. The older rocks exhibit elevated LILE, LREE and depleted HFSE contents, carrying geochemical characteristics suggesting earlier subduction process. Some samples of the younger mildly alkaline lavas display geochemical characteristics of intraplate magmatism with enrichment of LILE contents with little or no HFSE depletion. Knowing that the Galatean volcanic rocks experienced syn-volcanic extensional tectonics during the Miocene, we think that the reactivation of the old suture zone produced first calc-alkaline series originated from a subduction-modified subcontinental lithospheric mantle, followed by more alkaline products. However, some volcanic rocks suggest penetration of small amounts of asthenospheric melts to this lithospheric mantle source. The regionally known last volcanic phase produced small amounts of alkaline basaltic rocks in Güvem area at about 10 Ma. Volcanic activities ended possibly with, or just after the Güvem event, when the extensional tectonic regime switched to strike-slip faulting in the region, with the inception of one of the major faults of Turkey, the North Anatolian Fault Zone

Alkaline series related to Early-Middle Miocene intra-continental rifting in a collision zone: An example from Polath, Central Anatolia, Turkey

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Geochemical features of multi component mantle source domains beneath Central Anatolia

Extensive volcanic activities were developed in Central Anatolia, due to dynamic nature o f the tectonic regime. Although the most of the volcanic zones are represented by major Stratovolcanoes, severe basaltic magmatism with lack of the central cones, were generated over all the Central Anatolia. In this study, we focus on Sivas mafic product s to shed more light on the mantle components, beneath the central Anatolia , that were not investigated in depth so far. Sivas mafic lavas are the most primitive basaltic products along CAFZ zone (MgO 14 wt%) having OIB - like multi - element signatures. Sr - Nd isotopic study reveals that basaltic lavas close and fall within range of OIB field and indicating the involvement of the common component that was not identified in previous studies. 3 Pb isotopic space ( 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, 208 Pb/ 20 Pb) displa y that Sivas mafic lavas fall in the common mantle (C - mantle, Hanan and Graham, 1996) zone and Indian Ocean Ocean MORB sources. Furthermore, Nd - Hf and Pb isotopic data imply that samples do not fall on the mantle array are enriched in Ba, Th, U and deplete d in K and Rb content, proposing that either the minor amount of sediment contributions or metasoma tic processes. Finally, of all the isotopic data and incompatible element signatures indicate that Sivas mafic materials were possibly derived from the inter action of shallow depleted asthenosphere, the regionally heterogeneous lithosphere, and a common source with the isotopic characteristics of the C component