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Amphiboles in alkaline rocks of Koraput, Orissa

Published online by Cambridge University Press:  14 March 2018

Mihir Kumar Bose
Mihir Kumar Bose*
Affiliation:
Dept. of Geology, Presidency College, Calcutta
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Summary

The chemistry and optics of the amphiboles in alkaline rocks of Koraput, Orissa, India, are described. The variation in chemical characters of the amphiboles is consistent with the variation in rock composition. With progressive fractionation the mineral shows increasing replacement of magnesium by iron while Ca is not affected by such replacement. The trend in variation is comparable to that in pyroxenes of alkaline basaltic magmas. The entry of Ti into the structure of amphibole appears to be favoured by alumina activity and concentration of Ti in the magma. Optical characters vary with the iron : magnesium ratio and titanium content of the mineral. The water content of the magma had an important influence on the composition of the mafic minerals in the rocks.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 33 , Issue 265 , June 1964 , pp. 912 - 917
Copyright
Copyright © 1964, The Mineralogical Society

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References

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