Revision of "Leptite-gneisses" in the Menderes Massif: a supracrustal metasedimentary origin

The Pan-African basement of the Menderes Massif comprises a regular litholo gical succession that reaches a thickness of 8 km, the oldest units of whic h are, in ascending order, so-called leptite-gneisses, a quartzite-sequence transition zone and mica schists. New findings suggest that the protoliths for the leptite-gneisses, proposed to be of volcanic origin in previous st udies, were predominantly elastic sediments of litharenitic composition, Ge ochemical data indicate that the protoliths for the leptite-gneisses were o f cratonic provenance. Because they have undergone Pan-African polymetamorp hism and are intruded by approximately 550 Ma gneisses of granitic origin, it is believed that the time of deposition of their protoliths was Late Pro terozoic. Relict parageneses indicate that the Pan-African metamorphism rea ched granulite-facies conditions in the leptite-gneisses. Supracrustal sedi mentary origin of these rocks require that these rocks, formerly termed lep tite and/or leptite-gneiss, should be renamed sillimanite-garnet gneiss and /or paragneiss.