Authors: NURDAN S. AYDIN, M. CEMAL GÖNCÜOĞLU, AYHAN ERLER
Abstract: Magmatic, metamorphic and ophiolitic rock assemblages in Central Anatolia ar e collectively named as the Central Anatolian Crystalline Complex (CACC). Magmatic rocks form significant portion of the CACC and display a range of fabrics, mineralogies and compositions. However , composite granitoid intrusions, such as the Yozgat, Agaçör en, Ekecikdağ and Cefalıkdağ, dominate the geology of the complex. Overall, ther e ar e two main types of Central Anatolian Granitoids (CAG): a) the C-type (crustal) leucog ranites and b) the H-type (hybrid) hornblende ± K-feldspar megacrysts ± mafic micr ogranular enclave bearing granites. The emplacement of granitoid magmatism was followed by the syenitoid magmatism wher e the quartz syenitoids (e.g., the Idisdaği Intrusion) predate the feldspathoid bearing syenitoids (e.g., the Atder e Intrusion). The type of magmatism in the CACC varies fr om peraluminous, metaluminous to alkaline/peralkaline through time. The C-type granitoids represent the early granitoid phase of the CACC and are consider ed to be products of the syncollisional magmatism. The H-type granitoids and the syenitoid intrusions represent the advanced and final stages of the post-collisional magmatism, respectively . The C-type granitoids are likely derived from uppercrustal sedimentary protolith by partial melting induced by crustal thickening with or without intrusion of mantle-derived mafic melts. Most of the field and petrographic features of the H-type granitoids requir e mantle-derived mafic magma contributions in the genesis of these rocks which can be explained in terms of mafic magma underplating of lower crust as a result of lithospheric delamination. Transition from silica-saturated to silica -undersaturated magmatism can be attributed to variation of availability of water in the melting zone. In general, the nature of magmatism in the CACC and related magmatic pr ocesses and the relative contributions of source material varied through time.
Full Text: PDF