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Igneous stratigraphy and internal structure of the Little Minch Sill Complex, Trotternish Peninsula, northern Skye, Scotland

Published online by Cambridge University Press:  01 May 2009

Sally A. Gibson  and
Adrian P. Jones
Sally A. Gibson
Affiliation:
School of Geological Sciences, Kingston Polytechnic, Kingston upon Thames, KT1 2EE, U.K.
Adrian P. Jones
Affiliation:
School of Geological Sciences, Kingston Polytechnic, Kingston upon Thames, KT1 2EE, U.K.
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Abstract

Detailed sampling of the Little Minch Sill Complex reveals that it is composed of both single and multiple sills. These are formed of three main, genetically related units: picrite, picrodolerite and crinanite, which are the result of differentiation of an alkali-olivine basalt magma (approximately 10% MgO) in an upper-crustal magma chamber. Variations in igneous stratigraphy and the presence of internal chills in the Trotternish sills suggest that they were emplaced by multiple intrusion and subsequently differentiated in situ. Changes in petrography adjacent to pegmatite veins and textures within picrite units indicate compaction and filter-pressing were important processes after emplacement. Rhythmic layering (1 cm to 1 m thick) is conspicuous in the sills near contacts but does not involve cryptic mineral variation. Such modal layering may be more common than realised in relatively small-scale intrusions and maybe modelled in terms of in situ differentiation under conditions of significant undercooling in a changing thermal gradient at the synthetic for-sterite-diopside-anorthite eutectic.

Type
Research Article
Information
Geological Magazine , Volume 128 , Issue 1 , January 1991 , pp. 51 - 66
Copyright
Copyright © Cambridge University Press 1991

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