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Ultrabasic eruptives with alnöitic-kimberlitic affinities from Malaita, Solomon Islands

Published online by Cambridge University Press:  14 March 2018

J. B. Allen
Affiliation:
Mineral Resources Division, Overseas Geological Surveys, London
T. Deans
Affiliation:
Mineral Resources Division, Overseas Geological Surveys, London

Summary

A detrital assemblage of magnesian ilmenite, pyrope, chrome-diopside, rutile, and zircon has been traced to outcropping ultrabasic alkaline rocks, hitherto unknown in the Melanesian region. Analyses and descriptions of these ‘kimberlite indicator minerals’ are given. The host rocks comprise alnöite, an alnöite breccia with calcite matrix, and a magnesian ankaratrite, which are described, with chemical analyses. Emphasis is laid on the abundance of ultrabasic inclusions and xenocrysts and the replacements and transformations they have undergone. Malaita Island promises to contribute significantly to the understanding of the relations between alnöite, melilite basalts, and kimberlites.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1965

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