Geochronological research about the relation of Proterozoic rocks, western of Kolkata, with 1700Ma rocks in Nepal.

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In peninsular India, there are Proterozoic Lavas extending large area. The ages of these rocks are reported 1500-1600 Ma by K-Ar and Rb-Sr dating methods and we have reported the relation of these rocks to the Dwar Khola dolerite (1600-1800Ma 40Ar-39Ar ages) from Siwalik of Sub-Himalaya, situated about 400km north, before. We have collected these samples in 2003 and report 40Ar-39Ar age results in this paper.These volcanic rocks are situated in the Proterozoic metamorphic and granitic rocks and divided 4 parts ((Dalma, Dhanjori and Jagarnathpur, Ongabila). Plateau ages about 1700-1800 Ma as those of Nepal dolerites cannot be obtained.All age spectrum show disturbed pattern by metamorphism or excess Ar pattern.From these results, we conclude 5 ages for these volcanic rocks.1)1800-2000Ma ; original age same as those of Nepal Dolerites.2)1550-1670Ma ; original age or metamorphic age3)1400Ma ; metamorphic age4)950-1050Ma ; metamorphic age which is recognized in intruded rocks in Napier Complex, Antarctica.5)450-550Ma ; metamorphic age corresponding to the Pan African Metamorphism.