Evidence for Pre-Grenvillian high-pressure granulite metamorphism from the northern margin of the Sausar mobile belt in Central India

Abstract

Distinct lithological associations, structural relationships and petrographic and geothemobarometric results indicate the presence of reworked granulites of Pre-Grenvillian age from the northern margin of the Sausar Mobile Belt (SMB) in Central India. In rare residual zones, the mafic granulite-felsic migmatite gneiss association preserves early structures and high-P (∼ 10.5 kbar at ∼ 775°C) granulite histories which appear to pre-date and bear no relation to ∼ 1000 Ma old Sausar orogeny. An isothermal decompression through ∼ 5.5 kbar at 750°C from maximum recorded P-T condition, possibly signifies extensional collapse of the crust, previously thickened through collision. During the Sausar orogeny, the granulites were further tectonically interleaved with younger lithological associations. Widespread retrogression in amphibolite and finally in greenschist facies conditions have all but obliterated granulite mineralogy and structure except in rare low-strain domain.