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Authors
Affiliations
1 Geochronology and Isotope Geology Division, Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, IN
2 Chemical Laboratory, Geological Survey of India, 27, Jawaharlal Nehru Road, Calcutta 700016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 4 (1980), Pagination: 188-193
Abstract
Lamprophyric dyke rocks occurring in the Indian Gondwanas (Permian-Lower Cretaceous) form a consanguinous suite ranging from ultrabasic mica-peridotite to micro-syenitic assemblages. Chemical characters include low SiO2 (ca. 40% or less), high (FeO+MgO) and high MgO/FeO and K2O/Na2O ratios. The petrographic and chemical characters have been discussed in a broad framework after Rock (1977). K-Ar radiometric ages on four biotite separates and one whole rock from three different localities range from 105 to 121 Ma and are believed to represent true crystallisation ages.