Ar-40-Ar-39 age of carbonatite-alkaline magmatism in Sung Valley, Meghalaya, India

Ar-40-Ar-39 analyses of one alkali pyroxenite whole rock and two phlogopite separates of calcite carbonatites from the Sung Valley carbonatite-alkalin e complex, which is believed to be a part of the Rajmahal-Bengal-Sylhet (RB S) flood basalt province, yielded indistinguishable plateau ages of 108.8 /-2.0 Ma, 106.4 +/-1.3 Ma and 107.5 +/-1.4 Ma, respectively. The weighted m ean of these ages, 107.2 +/-0.8 Ma, is the time of emplacement of this comp lex. This implies that Sung Valley complex and probably other such complexe s in the Assani-Meghalaya Plateau postdate the main flood basalt event (i.e ., the eruption of tholeiites) in the RBS province by similar to 10 Ma.