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Geology and petrology of the mafic volcanic rocks within the Karakaya complex from central (Ankara) and nw (Geyve and Edremit) Anatolia

Sayıt, Kaan
This study aims to reveal the geochemical signatures of the basic igneous rocks with well-determined age within the Karakaya Complex in Central and NW Anatolia and also exhibit the relationships between the studied units in terms of geological and petrographical features. The Karakaya Complex comprise a number of tectono-stratigraphic units in the studied regions (the Olukman Melange, the Bahçecik Formation, the Ortaoba Unit and the informally named pillow basalt-limestone association) and the pre-Karakaya basement unit (the Eymir Complex). The basic igneous rocks have been all intensely affected by hydrothermal metamorphism as reflected by the secondary products strongly overprinting the primary mineral phases and most of them exhibit vesicular structures which are filled by mainly calcite. The primary mineral assemblage dominating the basaltic rocks is clino-pyroxene, plagioclase and olivine, whereas secondary phases are characterized by actinolite, pistacite, zoisite/clinozoisite group and chlorite. Kaersutite, as a late stage magmatic mineral, is distinctive for Ti-augite bearing İmrahor basalts; on the other hand, the diabase dykes include hornblende as an essential primary phase. The basic rocks are represented by three groups; sub-alkaline, alkaline and transitional. The alkaline samples from İmrahor, Hasanoğlan, Kadirler and Ortaoba are of Anisian age and akin to oceanic-island basalts (OIB). The sub-alkaline and transitional samples from İmrahor and Ortaoba reflect P-MORB features and are younger than the first group. The diabase dykes cross-cutting the Eymir Complex, on the other hand, are too dissimilar, indicating back-arc basin signatures. Based on the data obtained from this study, the Karakaya Complex is characterized by a number of tectonic components (seamount, plume-related mid ocean ridge and back-arc basin) with different ages and origins,