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

D. B. Nadagouda ¹, R. S. Hanagodimath ¹

Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580 003, IN

Abstract

Grunerite is a characteristic mineral of metamorphosed iron-rich siliceous sediments. Though it occurs commonly in the oxide, silicate and carbonate facies of banded iron formations, its association with ankerite, garnett siderite and magnetite appears to be somewhat rare. Detailed petrographic, optical ana chemical studies together with X-ray diffraction pattern of the separated amphibole from the ankerite-siderite-garnet assemblage from Huliyar indicate that the amphibole belongs to the grunerite end member [82% Fe₇Si₈O₂₂(OH₂)] of the cummingtonite-grunerite series.

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D. B. Nadagouda ¹, R. S. Hanagodimath ¹, T. C. Devaraju ¹

Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580 003, IN

Abstract

The banded Iron-formation, corresponding mostly to oxide facies, exposed in the south-western parts of Chitradurga belt has been studied with respect to their field, petrographic, mineralogical and petrochemical aspects. It is concluded that, these iron-formations are essentially the results of chemical precipitation of iron and silica derived from continental weathering of basic rocks under anaerobic, quiet, below-wave base marine conditions. The banding is attributed to cyclic changes in climatic conditions.

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