Petrology across a calcareous rock-anortho site interface from the Chilka Lake Complex, Orissa: Implications for Neo-Proterozoic crustal evolution of the northern Eastern Ghats Belt

摘要

Mineral assemblages, reaction textures and consideration of deduced mineral reactions in appropriate petrogenetic grids in calc-silicate rocks occurring at the contact of the 0.79 Ga Chilka Lake anorthosite pluton, northeastern part of the Eastern Ghats Belt, India, reveal UHT-metamorphism (T>1000 degrees C) at mid-crustal depths (corresponding to 7 +/- 1 kbar). This 0.79 Ga thermal metamorphism completely erased imprints of an earlier (0.96 Ga) granulite facies metamorphism in the calc-silicate rocks. The anorthosite and UHT contact metamorphic rocks were overprinted by amphibolite-granulite facies tectonothermal re-working at 0.69-0.66 Ga. Both the anorthosite-induced UHT metamorphism and the high-grade Pan-African re-working are unique for the Eastern Ghats Belt. These new observations provide clues regarding integration and disintegration of Rodinia and Indo-Antarctic correlation in the Precambrian.