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Chromite-chlorite intergrowths in peridotite at Chimwadzulu Hill, Malawi

Published online by Cambridge University Press:  05 July 2018

H. W. Haslam ,
R. R. Harding  and
A. E. Tresham
H. W. Haslam
Affiliation:
Institute of Geological Sciences, 64-78 Gray's Inn Road, London, WCIX 8NG
R. R. Harding
Affiliation:
Institute of Geological Sciences, Exhibition Road, London, SW7 2DE
A. E. Tresham
Affiliation:
Institute of Geological Sciences, Exhibition Road, London, SW7 2DE
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Summary

Chromiferous spinel and chlorite are associated and sometimes intergrown in serpentinized peridotites at Chimwadzulu Hill. The peridotites probably crystallized from a melt under the conditions of the spinel-lherzolite facies (O'Hara, 1967) in which the stable aluminous phase is spinel. The spinel that formed was probably a chromite with some Al2O3 and MgO. At lower temperatures aluminous spinel is unstable in the presence of olivine and orthopyroxene, chlorite being the stable aluminous mineral. It is thought that the chlorite crystallized under the conditions of medium-grade metamorphism that prevailed when the rocks were emplaced, and at the same time the spinel recrystallized, depleted in Al2O3 and MgO and correspondingly enriched in FeO, Fe2O3, and Cr2O3, giving rise to the observed chromite-chlorite association.

Type
Research Article
Information
Mineralogical Magazine , Volume 40 , Issue 315 , September 1976 , pp. 695 - 701
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1976

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References

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