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

R. Ramasamy ¹

Affiliations
1 Tamil Nadu State Dept. of Geology and Mining Chennai, IN

Abstract

No Abstract.

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R. Ramasamy ¹

Affiliations
1 Department of Geology and Mining, Madras 32, IN

Abstract

Vogesite occurs as a melanocratic dyke rock in close proximity to carbonatite outcrops of Sevvattur. Vogesite was formed as a late magmatic differentiate of a monzonitic magma under CO₂-rich wet subvolcanic conditions. Postmagmatic fluids enriched in acidic components permeated through the rock causing development of lamprophyric character.

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R. Ramasamy ¹

Affiliations
1 Tamil Nadu State Department of Geology and Mining, Madras - 600 032, IN

Abstract

Dyke rocks of olivine-tephrite and carbonate-tephritein association with soda-trachyte and carbonatite occur in Kudangulam area near Cape Comorin, Tamil Nadu. Based on Rittmann's τ and σ-values K₂/SiO₂, and co-variationof alkalies and silica, and ratios (CaO:MgO, Ca:Na:K, 100Mg/(Mg+Fe) and cpx/ol(vol%) the tephrites resemble the olivine poor nephelinite suite, normally found in carbonatite-ultra alkalic rock associations.

Keywords

Tephrite, Trachyte, Carbonatite, Nephelinite, Tamil Nadu.

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S. Saravanan ¹, R. Ramasamy ²

Affiliations
1 18, Natesan Salai, Madras, 600 083, IN
2 Tamil Nadu State Department of Geology and Mining, Madras 600 032, IN

Abstract

Shonkinite occurring in the carbonatite complex of Tiruppattur, Tamil Nadu is essentially composed of equal proportions of anorthoclase and augite with accessories of olivine, hastingsite, biotite, apatite and magnetite. The carbonatite complex comprises alkaline rocks emplaced in two adjacent structural basins of Sevvattur and Jogipatti. The chemical composition of shonkinite is intermediate between melanocratic rocks, alkali syenites and soda-rich alkali syenites of the Sevvattur structural basin and highly potassic alkaline rocks of the Jogipaui structural basin. Both these basins constitute the carbonatite complex of Tiruppattur. The study of geochemistry of clinopyroxenes in the co-magmatic alkaline series of the carbonatite complex reveals that both the groups of alkaline rocks were derived from shonkinitic parent magma by convection current aided differentiation and fractionation of mafic cumulates with intermittent immiscible separations of carbonate and silicate liquids.

Keywords

Alkaline rocks. Clinopyroxene, Geochemistry, Tiruppattur, Tamil Nadu.

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R. Ramasamy ¹

Affiliations
1 Tamilnadu State Department of Geology and Mining, Madras-600 032, IN

Abstract

Amtdst a chamockitic terrain, a new occurrence of carbonatite-metasomatic complex has been reported from Kudangulam area, near Cape Comorin, Tamil Nadu. Petrography and geochemistry of the metasomatic rocks formed around the carbonatites indicate that the carbonatitic melt associated with fenitizing solution degassed through deep faults present in this area by reactivation of continental rifting during Post-Tertiary Period.

Keywords

Carbonatites, Fenites, Metamorphism, Kudangulam, Tamil Nadu.

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R. Ramasamy ¹

Affiliations
1 Tamilnadu State Department of Geology and Mining, Madras - 600 032, IN

Abstract

Occurrence of dyke rocks of carbonatites in charnockites and granite gneisses near Kudangulam village situated 20 km NE of Cape Comorin, Tamil Nadu is reported. Petrography and Chemical composition of these rocks reveal that coarse grained curbonatites were formed under subvolcanic miarolitic crystallization from a degassed carbonatitic melt.

Keywords

Petrology, Carbonatite, Volcanic Rocks, Tamil Nadu.

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L. G. Gwalani ¹, R. Ramasamy ², S. C. Patel ³, P. Sangurmath ⁴

Affiliations
1 University Department of Geology, Nagpur, IN
2 Tamilnadu State Dept. of Geology & Mining, Madras, IN
3 Indian School of Mines, Dhanbad, IN
4 Mineral Exploration Corporation Ltd. Hyderabad, IN

Abstract

No Abstract.

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