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Tabular intrusion and folding of the late Archaean Murehwa granite, Zimbabwe, during regional shortening

Blenkinsop, Thomas G. and Treloar, P. J. 2001. Tabular intrusion and folding of the late Archaean Murehwa granite, Zimbabwe, during regional shortening. Journal of the Geological Society 158 (4) , pp. 653-664. 10.1144/jgs.158.4.653

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Abstract

The Murehwa granite belongs to the late Archaean Chilimanzi suite of granites that occupy more than 50% of the Zimbabwe craton. The granite has compositional layers on metre to tens of metre scales with generally shallow dips, and dip directions towards the centre of the granite near its margins. The layering is systematically folded about sub-horizontal east–west axes. Microcline phenocrysts are generally strongly aligned parallel to the layering, but locally crosscut the layering because they are axial planar to the folds. Crystals are not significantly deformed: fabrics are thus magmatic. The granite was intruded in a tabular sheet that may have been only about 6 km thick and fed by dykes, contrary to previous concepts of diapirism/ballooning for some Archaean granites of the Zimbabwe craton. The systematic orientation of magmatic folds and axial planar fabrics demonstrate that the granite was intruded during regional north-south shortening. This shortening is consistent with the orientation of cratonic-scale fractures that were intruded by the Great Dyke within 25 Ma of the intrusion of the Murehwa granite. The granite may have intruded in a relatively short interval of less than 1–26 Ma, within the longer duration of the entire Chilimanzi granite event.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: granites; intrusions; magmatic fabric; folding; crustal shortening
Publisher: Geological Society of London
ISSN: 0016-7649
Last Modified: 04 Jun 2017 05:19
URI: http://orca-mwe.cf.ac.uk/id/eprint/50677

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