Metamorphic evolution of the Chotanagpur Granite Gneiss Complex of the East Indian Shield: current status

Abstract

AbstractGeological information on the Chotanagpur Granite Gneiss Complex (CGGC) has been reviewed with a view to: (a) identifying the different metamorphic episodes; (b) developing an event stratigraphy in the high-grade blocks; and (c) correlating the different metamorphic episodes with the globally extensive orogenic processes. Integrating the existing geological information, the geological evolution of the high-grade block of the CGGC has been divided into four stages associated with four distinct metamorphic events (MI−MIV). The earliest metamorphic event (MI) that is recorded in granulite enclaves in the regionally extensive felsic gneisses culminated in ultrahigh temperatures (>900 °C at c. 5–8 kbar) at around 1.87 Ga. In the second stage, voluminous felsic magmas were intruded – the MI granulites – and were metamorphosed to form migmatitic felsic gneisses (MII) within about 1.66–1.55 Ga. The third stage witnessed intrusions of a suite of anorthosite and porphyritic granitoids (c. 1.55–1.51 Ga), followed by high-grade metamorphism (700±50 °C, 6.5±1 kbar, MIII) during approximately 1.2–0.93 Ga. The fourth stage (MIV) is marked by the intrusion of a suite of mafic dykes, followed by infiltration-driven metamorphism (600–750 °C at 7±1) during 0.87–0.78 Ga. The proposed metamorphic events have been correlated with the supercontinental cycles in the Proterozoic time.