40Ar-39Ar geochronology and petrogenesis of postcollisional trachytic volcanism along the İzmir-Ankara-Erzincan Suture Zone (NE, Turkey)

Authors : GÖNENÇ GÖÇMENGİL, Zekiye KARACIK, Şengül Can GENÇ, Mehmet Zeki BİLLOR

Pages : 1-31

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :The obliteration of the Neo-Tethyan Ocean and collision of the microplates along the northern part of Turkey led to the development of the İzmir-Ankara-Erzincan suture zone insert ignore into journalissuearticles values(IAESZ);. After the collision of Pontides with the Central-Anatolian Crystalline Complex insert ignore into journalissuearticles values(CACC); in the Paleocene, a new phase of extension and volcanism concomitantly developed along the northern insert ignore into journalissuearticles values(Almus; Pontides); and southern insert ignore into journalissuearticles values(Yıldızeli; CACC); sides and along the IAESZ during the Middle Eocene time interval. The first products of the Middle Eocene volcanism in these areas are represented by calc-alkaline to alkaline insert ignore into journalissuearticles values(basic-intermediate); volcanic and volcanoclastic units together with late-stage trachytic dikes, plugs, and stocks. The mantle source area of both volcanic units displays a metasomatized character, which was dominantly fluxed by sediment-sourced melts. The partial melting of the metasomatized source area gave rise to first-stage basic-intermediate volcanism in the crustal levels. Simultaneously with the generation of the first-stage volcanism, basaltic trachyandesitic shallow-seated magma mushes were also developed. The reactivation of these shallow-seated mushes by late-stage extensional tectonics gave rise to the development of trachytic volcanism in both regions, which have a high-K to shoshonitic character. Almus trachytic lavas are phenocryst-poor and have differentiated Mg# numbers insert ignore into journalissuearticles values(avg. 26);. On the other hand, Yıldızeli trachytic lavas have a broad compositional range insert ignore into journalissuearticles values(benmoreite to latite);; they are phenocryst-rich and show more basic character insert ignore into journalissuearticles values(Mg# avg. 40);. Trachytic volcanism in both areas is largely controlled by fractional crystallization of similar basaltic trachyandesitic parental magma with minor assimilation of the upper crustal lithologies. 40Ar-39Ar ages from sanidine phenocrysts from both areas also confirm that trachytic volcanism in both regions developed nearly coevally in different tectonic blocks insert ignore into journalissuearticles values(~41?40 Ma);. Generation of similar volcanism on the different tectonic blocks during the postcollisional stage was probably governed by a regional-scale delamination and/or lithospheric removal-related tectonomagmatic processes.
Keywords : Postcollisional magmatism, Middle Eocene, potassic magmatism, 40Ar 39Ar geochronology, geochemical modeling