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

S. Chakravarti ¹, S. Mukherjee ¹

Affiliations
1 Department of Geology, University of Calcutta, Calcutta, IN

Abstract

No Abstract.

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S. Mukherjee ¹, B. K. Bandyopadhyay ¹

Affiliations
1 Department of Geology, Calcutta University, Calcutta, IN

Abstract

The presence of a Gonditic rock unit is reported from Manbazar, Purulia district, West Bengal. It occurs as a distinct band cofolded with the associated metapelites into an isoclinal antiform followed to the west by a complimentary synform with granitic rocks occupying the antiformal core. The metasediments including the gonditic unit were metamorphosed under Upper Greenschist Facies conditions of regional metamorphism. Mineralogically it is composed mainly of quartz, spessartite, piedmontite, braunite, magnetite, specularite and ilmenite. The minerology and textural relationships indicate moderately high temperature and high oxygen fugacity under which the original sediments were metamorphosed.

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Tandra Bhaumik ¹, S. Mukherjee ¹, Abhijit Basu ²

Affiliations
1 Department of Geology, Calcutta University, Calcutta 700 019, IN
2 Department of Geology, Indiana University, Bloomington, IN 47405, US

Abstract

A nepheline syenite pluton is reported from the area around Santuri, Purulia District. Microcline, phenocrystic mesoperthite, sodic oligoclase and nepheline are the predominant minerals. Biotite, barkevikite, apatite and calcite are the common accessory minerals. Nine rock samples have been chemically analysed. The nepheline syenites are miaskitic. Available data suggest a magmatic origin. The alkaline melt was emplaced latetectonically along fissures developed during the last stage of deformation. The alkaline rocks of the present area exhibit a striking resemblance to many of the nepheline syenites occurring along the Eastern Ghats.

Keywords

Petrology, Nepheline Syenites, Alkaline Rocks, Santuri Purulia Dt. West Bengal.

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