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The Lower Eastern Layered Series of Rhum

Published online by Cambridge University Press:  01 May 2009

John W. Faithfull
John W. Faithfull
Affiliation:
Department of Geological Sciences, University of Durham, South Road, Durham, DH1 3LE, U.K.
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Abstract

The Lower Eastern Layered Series (LELS) comprises approximately units 1–5 of previous workers. Remapping has revealed considerable along-strike lithological variation in the units of the LELS. It is suggested, on the basis of field and geochemical evidence, that two layers formerly regarded as ‘conformable intrusive sheets of fine-grained olivine gabbro’, may be evolved alii valite layers rather than later intrusions. Xenolith suites, in these layers and elsewhere, indicate a component derived from the roof or walls of the magma chamber. Cryptic variation is more extensive in the LELS than in other parts of Rhum: olivine forsterite content varies from 85.6 to 70, and clinopyroxene Mg×100/(Mg+Fe) varies from 88 to 74. Postcumulus effects and subsolidus re-equilibration have altered the initial compositions of the mineral phases. The data are consistent with a model of repeated replenishment by picritic magma, although the replenishing liquids may have been slightly less magnesian than those subsequently available, during the formation of the upper ELS.

Type
Articles
Information
Geological Magazine , Volume 122 , Issue 5 , September 1985 , pp. 459 - 468
Copyright
Copyright © Cambridge University Press 1985

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