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Paragenesis of a Cordierite-Garnet Granulile from Assam, India

Published online by Cambridge University Press:  01 May 2009

G. G. K. Sastri
G. G. K. Sastri
Affiliation:
Director of Geology and Mining, Government of Gujarat, Ahamadabad-16 (India).
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Abstract

A cordierite-garnet granulite from Assam, India, carries optically positive cordierite, garnet, spinel, biotite, and sillimanite. The optics of the cordierite are: α = 1·534, β = 1·540, γ = 1·548, 2V = + 81°, while the composition of the garnet inferred from the writer's charts, in terms of the end-members, is Al73Py20Sp2An3Gr2. The development of an iron-rich garnet in association with a magnesium-rich cordierite is discussed, and data are presented to show that such garnets have a restricted compositional range. It is doubtful if the FeO/MgO ratio in a cordierite-garnet assemblage can be used for interpretation of the physical conditions governing the formation of the host rock.

Type
Articles
Information
Geological Magazine , Volume 100 , Issue 4 , August 1963 , pp. 331 - 336
Copyright
Copyright © Cambridge University Press 1963

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