High-temperature crustal anatexis in a clockwise P – T – t path: isotopic evidence from a granulite–granitoid suite in the Eastern Ghats belt, India

Abstract

The high-grade metamorphic belt of the Eastern Ghats, India, displays polyphase deformation structures, a complex metamorphic record and dehydration melting in different crustal protoliths. High-temperature melting in pelitic and greywacke-like precursors in a clockwise P – T path, decompression and subsequent isobaric cooling have recently been described from the south–central sector of this belt. In this contribution, high-temperature melting has been dated at c . 1162 Ma by Sm–Nd whole-rock isotopic compositions of granitoids. Subsequent isobaric cooling could have occurred between 988 and 900 Ma as indicated by U–Pb ages of zircon and monazite in pelitic granulites. Thus, a prolonged orogenic cycle of at least 250 Ma is envisaged. Additionally, isotopic disequilibrium between whole rock and minerals in sapphirine granulites could have resulted from rapid melting and been further enhanced by a prolonged reaction history of the sapphirine granulite.