Implications of a Newly Dated ca. 1000-Ma Rhyolitic Tuff in the Indravati Basin, Bastar Craton, India

AbstractA rhyolitic tuff with a minimum thickness of about 2.5 m occurs at the top of the sedimentary succession of the Indravati Group in south-central India. The tuff is a high-K, low-Na rhyolite with dominantly K-feldspar phenocrysts. Cathodoluminescence color of the quartz phenocrysts is blue. U-Pb isotopic analyses (LA MC-ICPMS) of magmatic zircons separated from the tuff give a weighted-mean average 207Pb/206Pb age of Ma that we interpret as the age of crystallization. We conclude that the closure age of the Indravati succession is ca. 1000 Ma, very similar to that of the Chhattisgarh and Vindhyan successions. The age of this tuff is identical, within analytical errors, to those of the Sukhda and Dhamda Tuffs in the Chhattisgarh Basin some 350 km away. We suggest that these three tuffs represent a ca. 1000-Ma rhyolitic flare-up, possibly related to the assembly of Rodinia and docking of India and East Antarctica.