Thermal Evolution of the Permo−Triassic Karakaya Subduction-accretion Complex Between the Biga Peninsula and the Tokat Massif (Anatolia)

The results of the combined application of a series of analytical methods (clay mineralogy, vitrinite reflectance, Raman microspectroscopy) placed tight constraints on the thermal evolution of the Karakaya Complex of northern Anatolia, a mostly Permo-Triassic subduction-accretion complex resulting from the progressive closure of the Palaeotethys. The thermal evolution of the Karakaya Complex is the result of Permian-Triassic subduction-accretion processes, and was not significantly affected by later Alpine-age tectonism, as shown by Liassic shallow-water siliciclastic and carbonate deposits overlying unconformably the Karakaya Complex which did not undergo any significant burial. The Lower Karakaya Complex, comprising metabasite and subordinate marble and phyllite, experienced maximum temperatures ranging from 340 to 497° C, in agreement with independently determined thermobarometric reconstructions. The entire Upper Karakaya Complex, previously considered unmetamorphosed or slightly metamorphosed, was affected by zeolite to lower greenschist facies metamorphism (120-376° C). The coherent results of this study show that Raman thermometry has great potential for palaeotemperature determination at low temperature ranges (200-350° C).