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

Ranadhir Mukhopadhyay ¹, Sridhar D. Iyer ¹, R. Banerjee ¹, R. K. Drolia ²

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN
2 National Geophysical Research Institute Hyderabad - 500 007, IN

Abstract

No Abstract.

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S. Mukhopadhyay ¹, R. Banerjee ²

Affiliations
1 Department of Geological Sciences, Jadavpur University, Calcutta 700 032, IN
2 National Institute of Oceanography, Dona Paula, Goa 403 004, IN

Abstract

A rapid method of sample preparation for ferromanganese nodules and crusts mounting is presented here, by using laminated polyester resin, cobalt napthanate and methyl ethyl ketone peroxide. With this technique vacuum impregnation is not required. Any naturally soft and brittle material can be successfully mounted by this procedure.

Keywords

Ferromanganese Nodule, Petrographic Methods.

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R. Banerjee ¹, S. D. Iyer ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa, 403 004, IN

Abstract

The petrography of the basalts collected in dredge hauls from the Carlsberg Ridge (3° 37' N and 64° 07' E) show systematic variations in their textural and mineralogical assemblages, from an outennost vitreous glassy to a holocrystalline interior through a variolitic zone. The silica-alkalies relation show these basalts to be of sub-alkaline nature. Variable normative compositions and Mg number, increase in alkali index, differences in Al₂O₃/CaO and FeO*/MgO ratios, variable trace element concentrations, together with variable relations of P₂O₅ TiO₂ , Ni and Cr with MgO indicate a process of fractional crystallisation of a primary magma. Chemically and mineralogically these rocks have a closer affinity to those of the other parts of the Mid-Indian Ocean Ridge.

Keywords

Petrography, Carlsberg Ridge, Trace Element Geochemistry.

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R. Banerjee ¹, S. D. Iyer ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN

Abstract

Pillow basalts from the Carlsberg Ridge at 3°35'N contain disseminated chalcopyrite, pyrite, and magnetite. The euhedral shape of the pyrite grains indicate them to be early formed and grown unobstructed while magnetite occurs as skeletal crystals. These opaque minerals indicate their origin from a rapidly cooled silicate melt and probably resulted by a process of liquid immiscibility during lava emplacement.

Keywords

Carlsberg Ridge, Basalts, Pelrology, Indian Ocean.

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