Abstract:

Medium-grade metamorphic rocks crop out over a large area under the Neogene sedimentary and volcanic rocks in the central Biga Peninsula in northwest Turkey. These Çamlıca metamorphics consist dominantly of quartz-micaschists with minor calc-schist, marble, quartzite and metabasite. Some of the metabasites in the Çamlıca metamorphics preserve an early eclogite-facies mineral assemblage of garnet + omphacite + glaucophane + rutile ± paragonite, strongly overprinted by greenschist-facies mineral assemblages. The conditions of the eclogite-facies metamorphism have been determined as 510 ± 50°C temperatures and a minimum pressure of 11 kbar, based on the garnet-clinopyroxene Fe-Mg partitioning and the jadeite content of omphacite, respectively. The high phengite content of the potassic white micas in the quartz-micaschists and the close interlayering of quartz-micaschists and the metabasites suggest that the whole of the Çamlıca metamorphics has undergone regional eclogite-facies metamorphism. Rb-Sr phengite ages from three quartz-micaschist samples from the Çamlıca metamorphics range from 65 to 69 Ma and indicate a Maastrichtian age for the eclogite-facies metamorphic event. The Çamlıca metamorphics probably are a part of the Rhodope metamorphic complex, which exhibits a similar lithostratigraphy and metamorphic history.

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