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Authors
Affiliations
1 Institute of Geochemistry SB RAS, Irkutsk-33, Box 4019, RU
2 Geology Department, St Xavier's College, Mumbai-400001, IN
3 Graduate School of Science and Technology, Niigata University, Niigata 950-2181, JP
4 Department of Geology, University of Madras, Chennai-600025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 72, No 3 (2008), Pagination: 312-324
Abstract
Benstonite-Ba-Sr carbonatites are found only in two localities in the world the Murun massif in Siberia and Jogipatti in Tamil Nadu, South India. The specific feature of these carbonatites is high BaO (20-35%) and SrO (up to 10% as in the Murun carbonatites) concentrations. These carbonatites jointly with calciocarbonatite varieties occur in caibonatite-alkaline complexes of Siberia and South India. However, carbonatites of South India and Siberia differ in terms of the chemical composition, especially the trace and rare earth element contents. In South India (Tamil Nadu area), carbonatites are found in three alkaline massits Samalpatti, Sevathur, and Elagiii. Benstonite carbonatites are found only in the Samalpatti massif as a small dyke. In the Murun massif carbonatites are separated from the silicate rocks and occur as a residual silicate-carbonate complex. It comprises microclinites, pyroxene-microclines, quartz-microcline- pyroxene-calcites, which contain calcite carbonatites and charoite rocks as schleiren and dykes. Benstonite carbonatites form a horizontal body of 40 m thick in the southwestern part of the complex. We examined and compared the geological and geochemical features of these two areas where Bensonite occurs in association with other carbonatites and discuss their origin. The Indian carbonatites crystallized as the plutonic phase while Siberian ones formed in the near-surface area and effused on the Earth's surface.
Keywords
Benstonite, Carbonatites, Geochemistry, Sevathur, Samalpatti, Tamil Nadu.
