Metamorphic evolution and geochemistry of kyanite eclogites in central Rhodope, northern Greece

Abstract

 In central Rhodope of northern Greece, kyanite eclogites were discovered in the area of Thermes. They are strongly overprinted and exhibit a multi-stage development of minerals and mineral assemblages formed during successive stages of the exhumation. The initial high-pressure assemblage was garnet+omphacite+kyanite+zoisite+phengite+rutile+quartz. Corundum, Fe-Mg-spinel, sapphirine and högbomite occur as products of a first, high-temperature overprint, still at high pressures, whereas various symplectites [corundum-plagioclase (pl), spinel-pl, sapphirine-pl, clinopyroxene-pl, biotite-pl, amphibole-pl] grew during subsequent stages of the exhumation. Diablastic amphibole+plagioclase formed as end-products of the amphibolitization. According to geochemical data, the protoliths of the kyanite eclogites were basalts to basaltic andesites with “volcanic arc” affinities. For the high-pressure stage of metamorphism, minimum PT conditions were around 19 kbar, 700°C, while for the initial stages of the overprint, high-pressure granulite-facies conditions prevailed (T>800°C, at P>15 kbar). The PT conditions of the amphibolite facies were 8–11 kbar, 580–690°C. The kyanite eclogites of Thermes record the highest temperatures of metamorphism within the whole of Rhodope.