Cordierite-bearing strongly peraluminous Cebre Rhyolite from the eastern Sakarya Zone, NE Turkey: Constraints on the Variscan Orogeny

摘要: Abstract The Cebre Rhyolite with an outcropping area up to 12 km2 is one of the rare extrusions in Variscan basement Sakarya Zone. unit consists high-K calc alkaline rhyolites (SiO2 = 74–82 wt.%). Abundant phenocrysts quartz and K-feldspar are accompanied by subordinate cordierite phenocrysts, muscovite microphenocrysts biotite microcrysts set a fine-grained groundmass. Three types rock fragments (xenoliths) have been recognized; (i) porphyritic, (ii) equigranular hypabyssal (iii) hypocrystalline fragments. Zircon U–Pb dating indicates that was extruded at 332.8 ± 4.38 Ma, which post-dates low temperature metamorphism pre-dates emplacement I-type granitic intrusions (325–303 Ma).The samples strongly peraluminous A/CNK values ranging from 1.48 2.95 A/NK 1.49 2.99. They very high K2O (3.72–7.42 wt.%) Al2O3 (10.77–14.11 wt.%) contents, but CaO (0.02–0.21 wt.%), Na2O (0.05–0.78 wt.%) MgO (0.3–0.21 wt.%) contents. show geochemical affinity upper continental crust, e.g., enrichment large ion lithophile elements (LILEs; K, Rb, U, Th, Pb), depletion field strength (HFSEs; Nb, Ta, Ti), Sr, P Eu, ԐNd(t) (− 3.06 − 8.75) isotope ratios Sr(t)(87Sr/86Sr = 0.70499–0.70915) Pb(t) (206Pb/204Pb = 16.41–17.570, 207Pb/204Pb = 15.54–15.59, 208Pb/204Pb = 36.20–37.22) similar those lower crust. Geochemical data indicate generated melting metapelitic rocks some addition intermediate metaigneous derived magma. As geodynamic model, we propose Orogeny Turkey occurred collision Gondwana arc/terrane separated southern margin Laurussia. This followed shortly after splitting oceanic lithosphere into two pieces sinking down asthenosphere. Rapid upwelling asthenosphere space emptied previous provided heat for anatexis metasedimentary