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Picritic basalts from the Palaeocene lava field of west-central Skye, Scotland: evidence for parental magma compositions

Published online by Cambridge University Press:  05 July 2018

Brian R. Bell  and
Ian T. Williamson
Brian R. Bell
Affiliation:
Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, Scotland
Ian T. Williamson
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, England
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Abstract

Mineral chemistry and whole-rock compositional data are reported for two lavas of picritic basalt from the Palaeocene lava field of west-central Skye, Scotland. Whole-rock compositions for both flows plot on Thompson's (1982) 9 kbar cotectic for olivine + plagioclase + clinopyroxene + liquid. Both flows contain highly forsteritic olivine phenocrysts (c. Fo89), which enclose early-precipitated crystals of chrome-spinel (Al2O3: c. 25 wt.%; Cr2O3: c. 36 wt.%; FeO + Fe2O3: c. 20 wt.%; MgO: c. 15 wt.%). The olivine compositions indicate equilibrium with picritic basalt magma compositions, as represented by the whole-rock compositions of both lavas. A high-pressure origin for the chrome-spinels is suspected on the basis of their textural association and aluminous composition. Compositional comparisons between the whole-rock and mineral chemistry characteristics of both flows and a picritic basalt chill facies of the temporally- and spatially-associated Rum Igneous Complex suggests that similar parental magmas were involved.

Keywords

basaltpicritemagma compositionSkyeScotland
Type
Petrology
Information
Mineralogical Magazine , Volume 58 , Issue 392 , September 1994 , pp. 347 - 356
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1994

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