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

N. P. Nathan ¹, R. Bhaskaran ², K. N. Rao ³

Affiliations
1 Geological Survey of India, Op TN, Ponds, Kerala, IN
2 Geological Survey of India, Chennai - 600 090, IN
3 Petrology Division, S R Geological Survey of India, Hyderabad - 500 068, IN

Abstract

No Abstract.

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K. T. Vidyadharan ¹, S. Paranthaman ¹, K. N. Rao ², T. C. Devaraju ³, T. T. Alapieti ⁴, R. J. Kaukonen ⁴

Affiliations
1 Geological Survey of India, Bangalore, IN
2 Geological Survey of India, Hyderabad, IN
3 Department of Studies in Geology, Karnatak University, Dharwad - 580 003, IN
4 Institute of Geosciences, University of Oulu, P 0 Box 3000, FI

Abstract

No Abstract.

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S. K. Bhushan ¹, K. N. Rao ², K. T. Vidyadharan ³

Affiliations
1 MSPL Limited, Baldota Enclave, Abheraj Baldota Road, Hospet – 583 203, IN
2 F-2, Sree Essen Residency, 186/3 RT Vijay Nagar Colony, Hyderabad, IN
3 310/Block-B, Maharaja Residency, Mangalore, IN

Abstract

The present paper documents the petrography, mineral chemistry and petrochemistry of the acid volcanics of St.Mary group of islands. These are essentially characterized by pyroxene bearing rhyolites with average 73.49 wt.% SiO₂. All the rhyolites from these islands are acmite normative, hence peralkaline with phenocrysts of zoned plagioclase and sometimes hypersthene/augite. There is depletion of LREE with moderate negative Eu anomaly. The enhancement of HFSE elements indicates their compatibility with continental crust. These rhyolites have high equilibrium temperature (915°C) at relatively lower oxygen fugacity (10^-16). The acidic lava flows are anorogenic, within plate rhyolites, generated during northern migration of Indian plate over Marion hotspot.

Keywords

Acid Volcanics, Petrography, Geochemistry, St. Mary Islands, Karnataka.

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