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

S. S. Bose ¹

Affiliations
1 R & D Unit, A.M.S.E. Wing, Geological Survey of India, 2, Church Street, Bangalore 560 001, IN

Abstract

Geochemical maps for copper, based on 355 samples comprising B horizon soils and ferruginous nodular concretions collected from a depth of 0.3 to 1.5 m along predetermined traverse lines in the test areas,have brought out anomaly zones of restricted strike lengths delineating the possible trend of sub-surface mineralization. Cumulative probability plots have indicated bimodal density distribution for the Dudhiasol West Block and polymodal complex distribution for the Kesarpur Block. Critical assessment of threshold values of partitioned populations on the probability plots, helped in suggesting priority areas for follow-up exploration. Geophysical prospecting carried out in these areas has broadly corroborated the geochemical data. Subsequent drilling has substantiated much of the geochemical findings.

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S. V. Srikantia ¹, S. S. Bose ¹

Affiliations
1 Geological Survey of India, No.2, Church Street, Bangalore 560001, IN

Abstract

The Banasandra Komatiites occur within the Kibbanahalli arm of the Chitradurga supracrustal Belt in Karnataka. They apparently overlie the Bababudan Group and the Peninsular Gneiss and occur in two isolated exposures, (i) east of Birasandra, and (ii) near Kodihalli - Kunikenahalli. Ultramafic rock types include pillowed serpentinites, spinifex-textured komatiite, massive and schistose serpentinite and talc-tremolite-chlorite schist. Certain quartz-antigorite (birbirite ?), quartz-amphibole, and high-magnesian chlorite rocks are also closely associated with the ultramafics. The major element chemistry of the Banasandra komatiites compares with those of Barberton, S. Africa, Munro Township, Canada and of W. Australia. The exact relationship between these komatiites and the Bababudan volcanics is not clear for lack of continuous outcrops. Field evidences point to possible tectonic emplacement.

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