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Mineral fractionation and pre- and post-emplacement processes in the uppermost part of the Shiant Isles Main Sill

Published online by Cambridge University Press:  05 July 2018

C. M. B. Henderson ,
F. G. F. Gibb  and
K. A. Foland
C. M. B. Henderson*
Affiliation:
Department of Earth Sciences, University of Manchester, Manchester M13 9PL, UK
F. G. F. Gibb
Affiliation:
Environmental & Geological Sciences, University of Sheffield, Sheffield S3 7HF, UK
K. A. Foland
Affiliation:
Department of Geological Sciences, Ohio State University, Columbus, Ohio 43210, USA
*
*E-mail: [email protected]
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Abstract

Reinvestigation of the top 25 m of the 165 m thick Shiant Isles Main Sill requires reinterpretation of its internal structure, especially of the last unit emplaced – the granular olivine picro-dolerite. New mineral analyses allow re-assessment of the magmatic processes involved in the intrusion and differentiation of this classic multiple sill. C-shaped vertical mineral composition profiles, which occur in olivine-rich, alkaline basaltic sills, reflect reaction between phenocrysts and variable composition liquids. A case is made for vertical migration of interstitial liquids within and across the boundaries of intrusive units, for the mixing of such liquids from adjacent units, and for their influence on mineral chemistry on both sides of the interface.

Keywords

picro-doleriteolivinemineral fractionationinterstitial liquidShiant Isles
Type
Research Article
Information
Mineralogical Magazine , Volume 64 , Issue 5 , October 2000 , pp. 779 - 790
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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