Rb-Sr Ages on the Granite and Pegmatitic Minerals from Bastar-Koraput Pegmatite Belt, Madhya Pradesh and Orissa, India

isotopic date on 12 samples of the Paliam and Darba granites of the Bastar Craton in Central India have defined an isochron age of 2308 ± 48 Ma. with initial Sr-isolopic ratio of 0.7354 ± 0.0097. Mineral ages on perthite, biolile and muscovite from tin- and rare metal-minearlised as well as non-minearlised pegmatites of the Bastar-Koraput Pegmatite belt within this craton have indicated two important dates of about 2050 and 1620 Ma. These dates are interpreted as (a) emplacement of the granite around 2300 Ma., (b) derivation of the pegmatites from this parent granite around 2050 Ma and (c) reselling of Rb-Srsystem at about 1620 Ma., concomitant with the metamorphic/uplift event in the nearby Eastern Ghats. The very high initial ⁸⁷Sr/⁸⁶Sr ratio of 0.735 for granite indicates thai they are crustal derived, possibly from a metasedimentary source.