Sapphirine and hogbomite in overprinted kyanite-eclogites of central Rhodope, N. Greece; first evidence of granulite-facies metamorphism

Sapphirine and hogbomite were found within overprinted kyanite-eclogites of central Rhodope. Sapphirine is characterized as peraluminous and occurs in association with rutile (+ ilmenite) + plagioclase. Hogbomite coexists either with kyanite + rutile (+ ilmenite) + plagioclase or with rutile + Fe-Mg-spinel. Sapphirine and, in part, hogbomite were probably formed by reaction between kyanite, omphacite and corundum, during the overprint. Some hogbomite also grew by reaction between rutile and Fe-Mg-spinel. Formation of the sapphirine is considered to have taken place above 700 degrees C at high pressures (ca. 10-15 kbar), implying that the eclogites entered the granulite-facies field. The rocks studied record the highest overprinting temperatures in the Rhodope.