Authors: DURMUŞ BOZTUĞ
Abstract: A number of Upper Cretaceous-Palaeogene alkaline plutons intruded into the crustal metamorphic rocks, the pre-Maastrichtian ophiolitic mélange, and the Cretaceous-Lower Tertiary units are located in the Central Anatolia (CA), Turkey. These alkaline plutons constitute an important association in the post-collisional Central Anatolian Granitoids. The Dumluca, Murmana, Karakeban, Kösedağ, Hasançelebi, Karaçayir and Davulalan plutons constitute the eastern; whereas the Egrialan, Baranadağ, Hamit, Çamsarı, Durmuslu and Bayindir units the western part of this alkaline association. These plutons are mainly composed of silica oversaturated syenitic to monzonitic, and undersaturated syenitic felsic rocks. However, the Dumluca, Murmana and Karakeban plutons also include some undersaturated alkaline mafic rocks which are derived from a different mafic magma source rather than being the early fractionation derivatives of the felsic rocks in these plutons. There are some diversification or subdivisions on the basis of mineralogical-chemical characteristics, wall-rock, silica saturation and associated ore deposit/mineralization in these alkaline plutons. The diversification is thought to be sourced from either some solidification processes which modify the primary composition of any mantle-derived magma, or some different alkaline magma pulses generated by the partial melting of mantle material with different types and degrees of partial melting processes in water-starved environment. The latter consideration seems to be more reasonable due particularly to LIL and F enrichments in these rocks. They apparently indicate "late orogenic" , "within plate granite (WPG)" and "post-collisional" characteristics on the basis of their major and trace element geochemistry. When the mineralogical-chemical data is considered together with the space-time relations in a regional geological setting, one can suggest such a geodynamic model for the CA post-collisional alkaline plutonism: The magma source of this plutonism can be derived from the partial melting of upwelling upper mantle material by the adiabatic decompression mechanism in the passive margin of the Anatolides in a post-collisional lithospheric attenuation environment within a tensional regime immediately after crustal thickening due to Anatolide-Pontide collision along the northward subduction zone of the northern branch of Neo-Tethys.
Keywords: Post-collisional granitoids, alkaline magmatism, mineralogical-chemical classification, diversification in alkaline plutons, alkaline magma genesis, collision of Anatolides and pontides, Central Anatolia-Turkey.
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