Geochemical and Sr-Nd Isotopic Characteristics of Post-Collisional Calc-Alkaline Volcanics in the Eastern Pontides (NE Turkey)

Authors : Abdullah KAYGUSUZ, Mehmet ARSLAN, Wolfgang Siebel Cüneyt ŞEN

Pages : 137-159

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Major, trace element, K-Ar age and Sr-Nd isotopic data are presented for the Eocene Torul volcanics in the eastern Pontide orogenic belt insert ignore into journalissuearticles values(NE Turkey);. The studied rocks are composed of basaltic andesitic, andesitic, trachyandesitic, and minor trachydacitic lavas associated with their pyroclastics. These rocks contain plagioclase insert ignore into journalissuearticles values(An2-44);, hornblende insert ignore into journalissuearticles values(Mg#= 0.78-0.98);, clinopyroxene insert ignore into journalissuearticles values(Wo43-46 En41-43 Fs10-15);, biotite, quartz, and minor sanidine phenocrysts. K-Ar ages on hornblendes ages range from 43.99 insert ignore into journalissuearticles values(±2.59); to 33.45 insert ignore into journalissuearticles values(±2.32); Ma, within the Middle to Late Eocene. The volcanic rocks show calc-alkaline affinities and have medium to high K contents. They are enriched in large ion lithophile insert ignore into journalissuearticles values(LILE); and light rare earth elements insert ignore into journalissuearticles values(LREE);, with pronounced depletion of high field strength elements insert ignore into journalissuearticles values(HFSE);. The chondrite-normalized REE patterns insert ignore into journalissuearticles values(Lacn/Lucn= 4.0-9.8); show low to medium enrichment, indicating similar sources for the rock suite. Initial 87Sr/86Sr values vary between 0.70457 and 0.70511 and initial 143Nd/144Nd values between 0.51264 and 0.51278. The main solidification processes involved in the evolution of the volcanics consist of fractional crystallization with minor amounts of crustal contamination ± magma mixing. All evidence supports the conclusion that the parental magmainsert ignore into journalissuearticles values(s); of the rocks probably derived from an enriched upper mantle, previously modified by subduction- induced metasomatism in a post-collisional geodynamic setting.
Keywords : Turkish J Earth Sci, 20, 2011, 137 159 Turkish J Earth Sci, vol 20, iss 1