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

Open Access Open Access  Restricted Access Subscription Access
Open Access Open Access Open Access  Restricted Access Restricted Access Subscription Access

Lamprophyres from Indian Gondwanas - K-Ar Ages and Chemistry


Affiliations
1 Geochronology and Isotope Geology Division, Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, India
2 Chemical Laboratory, Geological Survey of India, 27, Jawaharlal Nehru Road, Calcutta 700016, India
     

   Subscribe/Renew Journal


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.
Subscription Login to verify subscription
User
Notifications
Font Size

Abstract Views: 178

PDF Views: 2




  • Lamprophyres from Indian Gondwanas - K-Ar Ages and Chemistry

Abstract Views: 178  |  PDF Views: 2

Authors

Amitabha Sarkar
Geochronology and Isotope Geology Division, Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, India
D. K. Paul
Geochronology and Isotope Geology Division, Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, India
M. N. Balasubrahmanyan
Geochronology and Isotope Geology Division, Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, India
N. R. Sengupta
Chemical Laboratory, Geological Survey of India, 27, Jawaharlal Nehru Road, Calcutta 700016, India

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.