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Laxfordian structure, strain distribution and kinematic interpretation of the Kenmore Inlier, Loch Torridon: anatomy of a major Lewisian shear zone

Published online by Cambridge University Press:  03 November 2011

M. Niamatullah  and
R. G. Park
M. Niamatullah
Affiliation:
M. Niamatullah, Department of Geology, University of Baluchistan, Quetta, Pakistan
R. G. Park
Affiliation:
R. G. Park, Department of Geology, University of Keel, Staffordshire ST5 5BG, U.K.
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Abstract

The Kenmore inlier exposes the most intensely deformed part of a major Laxfordian shear zone whose NE margin occurs at Diabaig, N of Loch Torridon. The Laxfordian (post-Scourie dyke) deformation commences with two very intense deformations D1 and D2, producing LS fabrics in dykes and gneisses associated with heterogeneous, locally very large, and typically prolate strains under amphibolite-facies metamorphism. D2 also produced widespread mesoscopic folds. The finite strain was measured at 135 localities using grain-aggregate shapes in Scourie dykes. The combined D1-D2 elongation lineation plunges gently to NW or SE, and the planar fabric appears to have been sub-horizontal before the D3 deformation, which produced NW-SE upright folds under retrogressive metamorphism.

The D1-D2 structure is attributed to a major sub-horizontal shear zone with a top-to-NW movement, a minimum vertical width of 2·5 km and estimated minimum displacement of c. 19 km. The upper (NE) wall of the shear zone at Diabaig exhibits dextral-normal (NE-down) D1 movements. The D2 structures are attributed to superimposition of sub-horizontal movements on earlier inclined D1 fabrics as the shear zone evolves. The D3 refolding reflects a change to a dextral transpressive regime.

Keywords

deformationdextral transpressiveDiabaigelongation lineationfoldsgrainaggregate shapesLS fabricprolate strainScourie dykessuperimposition.
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 81 , Issue 3 , 1990 , pp. 195 - 207
Copyright
Copyright © Royal Society of Edinburgh 1990

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