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Authors
Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, 1-1-153, Begumpet, Hyderabad 500 016, IN
2 Atomic Minerals Division, Department of Atomic Energy, West Block VII, R. K. Puram, New Delhi 110022, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 10 (1984), Pagination: 655-665
Abstract
The Andaman ophiolite suite, consists of ultramafic to mafic plutonites, basic volcanics and chert beds. Ophiolites were emplaced as linear belts along major and deep 'seated N-S-trending fault zones in eugeosynclinal flysch series of the Port Blair Group. Ultramafic plutonites include dominant serpentinile and minor dunite, harzburgite and Tare pyroxenite, with the last three exhibiting different degrees of serpentinization. Among the mafic and related plutonites, olivine-gabbro and gabbro are dominant. A layered complex, comprising olivine-gabbro, gabbro, anorthositic gabbro and anortho- site. is recorded near Kodiaghat in South Andaman island.
Low grade metamorphic effects under the greenschist facies conditions and metasomatic alteration, of varying intensity culminating finally in near-total serpentinization together with high-temperature contact metamorphism are recorded.
A model involving partial melting of a CO2-Saturated upper mantle material of 'Spinel-peridotite at about 20 K bar pressure leading to the formation of an alkalic basalt that got separated and extruded first from a probable hot-spot within the Indian Ocean Plate is suggested. This was followed by the intrusion of ultramafics along deep seated N-S trending fault zones in the eugeosyncline involving vertical tectonics. The Andaman ophiolites were not involved in any obduction or large scale lateral migration, and hence may be considered as belonging to an autochthonous-type, in contrast to many on-land allochthonous ophiolites.
