Proterozoic Crustal Evolution of the Chotanagpur Granite Gneissic Complex, Jharkhand-Bihar-West Bengal, India: Current Status and Future Prospect

The Chotanagpur Granite Gneiss Complex (CGGC) of the east Indian shield records vestiges of deep-crustal processes over 1200 Myr of the Proterozoic Eon. In this article the existing geological and geochronological information on the CGGC are reviewed and a plausible tectonic model that explain the evolution of this important crustal segment is presented. Based on published geological and geochronological information a threefold subdivision of the CGGC is proposed. These subdivisions, from south to north, are designated as Domain I, Domain II and Domain III. The three domains are characterized by their gross lithology, metamorphic and deformational history. Domain I, which is dominated by high-grade migmatitic gneisses containing enclaves of supracrustal and magmatic rocks, record the most complete geological information. Detrital zircons in metapelitic (Khondalite) enclaves constrains that the sedimentary basins were formed on an older crust during ca. 1700–1680 Ma. Geological and geochronological information identified the following magmatic events—felsic magmatism at ca. 1750–1650 Ma, anorthosite intrusion at ca. 1550 Ma, ferroan granite intrusion at ca. 1450 Ma, alkali syenite and granitoids magmatism at ca. 1000–925 Ma, finally mafic magmatism and emplacement of pegmatite. Three major tectonothermal events are recorded; an ultra-high temperature (UHT) metamorphism at mid-crustal level (~1000 °C, ~7 kbar) at ca. 1650 Ma; high pressure granulite metamorphism (~800 °C, 12–9 kbar) at ca. 950 Ma and an upper amphibolite-granulite grade metamorphism at ca. 870–780 Ma. The nature of magmatism and the style of metamorphism hitherto reported suggest growth and extension of the CGGC in response to the Proterozoic supercontinent cycles (Columbia and Rodinia). This study also demonstrates that India and Antarctica formed a coherent landmass before 1000 Ma.