Chemistry of calcic amphiboles from the area around Terakanambi,southern Karnataka |
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Authors: | N Shadakshara Swamy B Mahabaleswar |
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Institution: | (1) Department of Geology, Bangalore University, 560056 Bangalore, India |
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Abstract: | Chemial analyses of twelve amphiboles from the area around Terakanambi are presented. Results indicate that they are ferro-hornblende
and ferro-pargasitic hornblende types in banded iron formations; magnesio hornblende in ultramafic rocks and edenite; and
ferroan pargasite and ferroan pargasitic hornblende types in calcamphibolites. Titanium content in the amphiboles of the present
study is relatively low compared to results from similar zones elsewhere. The lower titanium content of the amphiboles may
be attributed to either bulk chemical composition or to low oxygen fugacity. Mg/Fe ratios vary considerably and it is mainly
controlled by host rock composition. The plots of calcic amphiboles on (lOONa/Ca + Na)/(100 Al/Si + Al) and Aliv/Alvi diagrams indicate that they are of medium to low pressure type. |
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Keywords: | Calcic amphiboles Terakanambi high grade terrain chemical analyses |
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