Rb-Sr and Sm-Nd dating of different metamorphic events from the Sausar Mobile Belt, central India: implications for Proterozoic crustal evolution

Sr and Nd isotopic studies of various rock suites and their mineral separates in and around the Sausar Mobile belt, Central India, have revealed that (1) the last amphibolite facies metamorphism (≡main Sausar metamorphism) occurred during 800-900 Ma and has more or less reset the Rb-Sr isotopic clock in this whole terrain whereas older Sm-Nd isotopic signatures were mostly unaffected; (2) the main Sausar Group of rocks is bounded both in the North and the South by two granulite belts of different crustal histories at least up to ∼1100 Ma; (3) the Northern granulite belt experienced peak metamorphism during pre 1100 Ma, followed by steep decompression and subsequent cooling around 1100 Ma; (4) peak metamorphism in the Southern granulite belt occurred at ∼2672 Ma. This was followed by emplacement of a vast basic igneous body (represented as metagabbro) and subsequent cooling around ∼1400 Ma. These two granulite belts were juxtaposed with each other during the Neo-Mesoproterozoic which is correlatable with high pressure metamorphism in the northern granulite belt. This tectonic movement might have been triggered by Mesoproterozoic rifting of the southern Bastar craton, resulting in basic magmatism in the southern granulite belt. Mafic dykes were emplaced during subsequent readjustment of the crust and amphibolite facies reactivation (∼main Sausar event) of granulites in the whole terrain. Lithological and tectonic arrangements, metamorphic history along with the present geochronological data from CITZ point towards an evolutionary history similar to the Grenville Province of Canada.