Chromite-Chlorite Intergrowths in Peridotite at Chimwadzulu Hill, Malawi

H. W. Haslam, R. R. Harding and A. E. Tresham
Institute of Geological Sciences, 64-78 Gray's Inn Road, London, WC1X 8NG
Institute of Geological Sciences, Exhibition Road, London, SW7 2DE

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 re-crystallized, depleted in Al2O3 and MgO and correspondingly enriched in FeO, Fe2O3, and Cr2O3, giving rise to the observed chromite-chlorite association.

Mineralogical Magazine; September 1976 v. 40; no. 315; p. 695-701; DOI: 10.1180/minmag.1976.040.315.03
© 1976, The Mineralogical Society
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