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Caledonian and Knoydartian overprinting of a Grenvillian inlier and the enclosing Morar Group rocks: structural evolution of the Precambrian Proto-Moine Nappe, Glenelg, NW Scotland

Krabbendam, M.; Ramsay, J.G.; Leslie, A.G.; Tanner, P.W.G.; Dietrich, D.; Goodenough, K.M.. 2018 Caledonian and Knoydartian overprinting of a Grenvillian inlier and the enclosing Morar Group rocks: structural evolution of the Precambrian Proto-Moine Nappe, Glenelg, NW Scotland. Scottish Journal of Geology, 54 (1). 13-35. https://doi.org/10.1144/sjg2017-006

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Abstract/Summary

The Grenville and Caledonian orogens, fundamental to building Laurentia and Baltica, intersect in northern Scotland. The Precambrian Glenelg Inlier, within the Scottish Caledonides, preserves a record of Grenvillian, Knoydartian and Caledonian orogenesis. Based on new mapping and re-interpretation of previous mapping, we present a structural model for the evolution of the Glenelg Inlier. The inlier can be divided into Western Glenelg gneiss comprising orthogneiss with no record of Grenville-age metamorphism, and Eastern Glenelg gneiss with ortho- and paragneiss, affected by Grenvillian eclogite-facies metamorphism. The basement gneisses and their original cover of psammitic, Neoproterozoic Morar Group (Moine) rocks were deformed by three generations of major ductile folds (F1–F3). In medium-strain areas F2 and F3 folds are broadly coaxial and both face to the west; in higher strain areas F2 and F3 folds are oblique to each other. By restoring post-F1 folds and late faults, the Glenelg gneiss inliers are seen to form the core of a major recumbent SSE-facing F1 isoclinal fold nappe – the Proto-Moine Nappe. The upper limb of this nappe is a thick, right-way-up sequence of moderately strained Morar Group rocks whereas the lower, inverted limb comprises intensely deformed, migmatitic Morar Group rocks. Within the constraints of published geochronology, the Proto-Moine Nappe is likely Pre-Caledonian and may have originated during the early Neoproterozoic Knoydartian Orogeny.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1144/sjg2017-006
ISSN: 0036-9276
Date made live: 02 Nov 2018 10:17 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/521422

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