Pvr. Babu et al., RB-SR AGES ON THE GRANITE AND PEGMATITIC MINERALS FROM BASTAR-KORAPUTPEGMATITE BELT, MADHYA-PRADESH AND ORISSA, INDIA, Journal of the Geological Society of India, 42(1), 1993, pp. 33-38
Rb-Sr isotopic date on 12 samples of the Paliam and Darba granites of
the Bastar Craton in Central India have defined an isochron age of 230
8 +/- 48 Ma. with initial Sr-isotopic ratio of 0.7354 +/- 0.0097. Mine
ral ages on perthite, biotite and muscovite from tin- and rare metal-m
inearlised 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) emplacem
ent of the granite around 2300 Ma., (b) derivation of the pegmatites f
rom this parent granite around 2050 Ma and (c) resetting of Rb-Sr syst
em at about 1620 Ma .. concomitant with the metamorphic/uplift event i
n the nearby Eastern Ghats. The very high initial Sr-87/Sr-86 of 0.735
for granite indicates that they are crustal derived, possibly from a
metasedimentary source.