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- 저자 : Eyuboglu, Yener (검색결과 3 건)
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Eocene granitoids of northern Turkey: Polybaric magmatism in an evolving arc–slab window system
Eyuboglu, Yener,Dudas, Francis O.,Thorkelson, Derek,Zhu, Di-Cheng,Liu, Ze,Chatterjee, Nilanjan,Yi, Keewook,Santosh, M. Elsevier 2017 Gondwana research Vol.50 No.-
<P><B>Abstract</B></P> <P>The Eastern Pontides Orogenic Belt offers critical clues on the origin of Early Cenozoic continental arc magmatism in the Alpine-Himalayan system. Systematic geological, geochemical and chronological studies indicate that there are three subgroups among the Early Cenozoic intrusions in the Eastern Pontides Orogenic Belt - Late Paleocene-Early Eocene adakitic intermediate-felsic intrusions, Eocene mafic intrusions, and Eocene non-adakitic granitoid intrusions. Here we focus on the petrology and geodynamic setting of the Eocene non-adakitic granitoid intrusions that are well exposed in a belt between the Thanetian-Ypresian adakitic intrusions in the south and the Lutetian gabbroic intrusions in the north. We also present data on enclaves and surrounding Eocene volcanics. The studied intrusions can be grouped into two main categories, based on their field and petrographical characteristics: granodiorite and monzodiorite-dominated and syenite-dominated bodies. They can be further subdivided into four groups of differing K<SUB>2</SUB>O content: low-K<SUB>2</SUB>O (Çevrepınar, Kaletaş, Sarıçiçek and Üzengili), mixed (Sorkunlu, Kozluk and Tamdere), and high-K<SUB>2</SUB>O (Dölek, Meşebaşı, Çakırbağ and Arslandede) rocks are granodioritic and monzodioritic, whereas shoshonitic (Kösedağ, Meydanlı and Bademli) bodies are syenitic. Zircon U-Pb age determinations reveal that these granitoids were emplaced into crustal rocks of the Eastern Pontides Orogenic Belt between 47 and 42Ma, in Lutetian time, simultaneously with the gabbroic intrusions in the north. Mineral compositions and P-T calculations are consistent with the interpretation that crustal melting or magma storage started at mid-crustal depth (~25km), with a magma system that subsequently extended to shallow levels (<4km). The studied granitoids, enclaves and volcanics exhibit geochemical signatures typical of subduction-related arc magmas, however, the shoshonitic intrusions are younger than most of the other Lutetian intrusions, and indicate a temporal change in arc magmatism. The Sr-Nd-Pb isotopic data indicate that the Lutetian rocks are mixtures of three or four end-member compositions. Considering all geological, geochemical and chronological data, we conclude that the Early Cenozoic magmatism was generated by slab window processes related to ridge subduction in a south-dipping subduction zone below the Eastern Pontides Orogenic Belt.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Non-adakitic granitoids were emplaced into crustal rocks between 47 and 42 Ma. </LI> <LI> Crustal melting or magma storage started at mid-crustal depth, with a magma system that subsequently extended to shallow levels. </LI> <LI> Non-adakitic granitoids, enclaves and volcanics have characteristic signatures of subduction-related arc magmas. </LI> <LI> They were generated by slab window processes related to ridge subduction in a south-dipping subduction zone. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Eyuboglu, Y.,Santosh, M.,Yi, K.,Tuysuz, N.,Korkmaz, S.,Akaryali, E.,Dudas, F.O.,Bektas, O. Elsevier 2014 Ore geology reviews Vol.59 No.-
The Meso-Cenozoic geodynamic evolution of the eastern Pontides orogenic belt provides a key to evaluate the volcanogenic massive sulfide (VMS) deposits associated with convergent margin tectonics in a Cordilleran-type orogenic belt. Here we present new geological, geochemical and zircon U-Pb geochronological data, and attempt to characterize the metallogeny through a comprehensive overview of the important VMS mineralizations in the belt. The VMS deposits in the northern part of the eastern Pontides orogenic belt occur in two different stratigraphic horizons consisting mainly of felsic volcanic rocks within the late Cretaceous sequence. SHRIMP zircon U-Pb analyses from ore-bearing dacites yield weighted mean <SUP>206</SUP>Pb/<SUP>238</SUP>U ages ranging between 91.1+/-1.3 and 82.6+/-1Ma. The felsic rocks of first and second horizons reveal geochemical characteristics of subduction-related calc-alkaline and shoshonitic magmas, respectively, in continental arcs and represent the immature and mature stages of a late Cretaceous magmatic arc. The nature of the late Cretaceous magmatism in the northern part of the eastern Pontides orogenic belt and the various lithological associations including volcaniclastics, mudstones and sedimentary facies indicate a rift-related environment where dacitic volcanism was predominant. The eastern Pontides VMS deposits are located within the caldera-like depressions and are closely associated with dome-like structures of felsic magmas, with their distribution controlled by fracture systems. Based on a detailed analyses of the geological, geophysical and geodynamic information, we propose that the VMS deposits were generated either in intra arc or near arc region of the eastern Pontides orogenic belt during the southward subduction of the Tethys oceanic lithosphere.
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