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

Abstract.

The Pan-African basement of the Menderes Massif comprises a regular lithological succession that reaches a thickness of 8 km, the oldest units of which 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 studies, were predominantly clastic sediments of litharenitic composition. Geochemical data indicate that the protoliths for the leptite-gneisses were of cratonic provenance. Because they have undergone Pan-African polymetamorphism and are intruded by approximately 550 Ma gneisses of granitic origin, it is believed that the time of deposition of their protoliths was Late Proterozoic. Relict parageneses indicate that the Pan-African metamorphism reached granulite-facies conditions in the leptite-gneisses. Supracrustal sedimentary origin of these rocks require that these rocks, formerly termed leptite and/or leptite-gneiss, should be renamed sillimanite–garnet gneiss and/or paragneiss.