Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Late Proterozoic-Early Palaeozoic Rb-Sr Whole-rock and Mineral Ages for Granite and Pegmatite, Goalpara, Assam, India


Affiliations
1 Geological Survey of Canada, Ottawa, Canada KIA OE8, Canada
2 Department of Geology, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
3 Department of Geological Sciences, Gauhati University, Guwahati 781014, Assam, India
     

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A granite that cuts the basement gneiss complex yields a five point errorchron giving an age of 647 ± 122 Ma. Uniform Rb-Sr isotopic ratios on the scale of a small quarry (c. 20 m) permit calculation of a maximum age of 850 Ma. Muscovite books from a second of three sets of pegmatite veins to cut the granite yield an Rb-Sr age of 505 ± 5 Ma. Both whole-rock and mineral age data are interpreted as representing times of crystallization and are in the time range of Pan-African activity known from, other fragments of Gondwanaland.
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  • Late Proterozoic-Early Palaeozoic Rb-Sr Whole-rock and Mineral Ages for Granite and Pegmatite, Goalpara, Assam, India

Abstract Views: 193  |  PDF Views: 2

Authors

O. Van Breemen
Geological Survey of Canada, Ottawa, Canada KIA OE8, Canada
D. R. Bowes
Department of Geology, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
C. C. Bhattacharjee
Department of Geological Sciences, Gauhati University, Guwahati 781014, Assam, India
P. K. Chowdhary
Department of Geological Sciences, Gauhati University, Guwahati 781014, Assam, India

Abstract


A granite that cuts the basement gneiss complex yields a five point errorchron giving an age of 647 ± 122 Ma. Uniform Rb-Sr isotopic ratios on the scale of a small quarry (c. 20 m) permit calculation of a maximum age of 850 Ma. Muscovite books from a second of three sets of pegmatite veins to cut the granite yield an Rb-Sr age of 505 ± 5 Ma. Both whole-rock and mineral age data are interpreted as representing times of crystallization and are in the time range of Pan-African activity known from, other fragments of Gondwanaland.