Title: Geochemistry of Amphiboles from the Precambrian of Karnataka
Abstract: Amphiboles from the Precambrian of Karnataka were analysed for major elements by wet chemical methods. Their cell edges were determined by X-ray powder diffraction technique, using Cr K α radiation. The chemical composition of the amphibole is correlatable with the grade of regional metamorphism. Chemical compositions of the Ca-amphiboles from the northern parts show low alkali and Al + characteristic of tremolite-actinolite group corresponding to greenschist facies. The amphiboles of the middle region are common hornblendes with higher alkali and Al + , characteristic of amphibolite facies. Amphiboles from the southern parts are aluminous and alkali-rich with higher titanium and Fe 3+ /Fe 2+ ratios. They coexist with ortho-or clinopyroxenes, suggesting their formation under granulite facies conditions. The restricted occurrence of sodic amphiboles in the Bababudans, and of cummingtonite-grunerite series in Kudurcmukh iron formations is due to their narrow P-T fields of stability and compositional fields. Anthophyllites from certain horizons of the Precambrian may be regarded as products of metasomatism.
Publication Year: 1976
Publication Date: 1976-03-01
Language: en
Type: article
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Cited By Count: 2
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