High-pressure/low-temperature metamorphic rocks of Turkey

Okay A.

Memoir of the Geological Society of America, vol.164, no.1, pp.333-347, 1986 (Scopus) identifier


Five major high-pressure metamorphic complexes are recognised in Turkey. The Tavsanli Zone in western Turkey is the largest and most important HP/LT metamorphic belt. It consists of a thick basal marble unit overlain by metabasite, metachert, and metashale. HP/LT metamorphism is generally prograde with abundant development of lawsonite, sodic amphibole, and sodic pyroxene in the metabasic rocks. The HP/LT metamorphic rocks are tectonically overlain by a non-metamorphic ophiolite nappe. The metamorphic Alanya nappes, situated on the Mediterranean coast in southern Turkey, consist of three superimposed flat-lying nappes; only the intermediate nappe (Sugozii Nappe), comprising abundant garnet-micaschists and rare bands of metabasite, shows an early eclogite/blueschist facies metamorphism overprinted by a later greenschist facies metamorphism, which also affected the other two nappes and welded them into one unit. Unlike the Tavsanli Zone, Alanya blueschists are allochthonous and consist mainly of shallow-water sedimentary rocks. The age of metamorphism in the Alanya nappes and in the Tavsanli Zone is mid-Cretaceous. The Bitlis Massif in eastern Turkey is the third major high-pressure metamorphic complex of the Taurides. Rare lenses and bands of kyanite-eclogites in the Precambrian basement of the Bitlis Massif indicate that the Bitlis Massif has undergone a Precambrian eclogite facies metamorphism, evidence of which was mostly destroyed by the Alpine greenschist facies metamorphism. The Karakaya Complex of the Pontides has an extensive distribution in northern Turkey, and consists of metabasite, marble, and metagreywacke. It has undergone a high pressure greenschist facies metamorphism during Triassic time with local development of crossite in metabasic rocks. Elekdg blueschists in north-central Turkey consist of an ophiolite nappe with serpentinite, gabbro and diabase, and an ophiolitic melange metamorphosed in blueschist facies. Glaucophane-bearing eclogites are also described from the Elekdg area. Turkish blueschists share two common features with many other Alpine HP/LT metamorphic complexes; the short time span of the HP/LT metamorphism, and blueschist protoliths consisting mainly of sedimentary rocks deposited on continental crust. These features, which differentiate these blueschists from the Circum-Pacific HP/LT metamorphic complexes, are probably a reflection of the peculiar characteristics of the Tethys ocean.