Petrochemistry and Geochronology of Pink Granite from Songsak, East Garo Hills, Meghalaya

The pink granite of Songsak area, East Garo Hills district, Meghalaya, intrusive into Precambrian gneisses is inferred to be S-type, peraluminous, low calcium, postkinematic granite. It is characterised by initial ⁸⁷Sr/⁸⁶Sr ratio of 0.728±.002, high K₂0, high differentiation index and presence of normative corundum. The major mineral constituents are perthitic microcline, fresh interstitial microcline, orthoclase with different degree of triclinisation, two generations of quartz and biotite. Sericitization of feldspars, presence of muscovite, rare chiastolite, fluorite and uraninite are other characteristics of the pink granites. Whole rock Rb-Sr dating assigns an age of 500±40 m.y,