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Significant shortening by pressure solution creep in the Dwyka diamictite, Cape Fold Belt, South Africa

Fagereng, Ake 2014. Significant shortening by pressure solution creep in the Dwyka diamictite, Cape Fold Belt, South Africa. Journal of African Earth Sciences 97 , pp. 9-18. 10.1016/j.jafrearsci.2014.04.022

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Abstract

The Dwyka diamictite preserves a record of horizontal shortening related to the development of the Cape Fold Belt at subgreenschist conditions. This shortening was accommodated by folding and thrust faulting, but pressure solution may also have contributed significantly to bulk deformation. Cleavage within the Dwyka group is, in the studied part of the Karoo Basin, subvertical to moderately south dipping, and approximately axial planar to regional folds. The cleavage is anastomosing, leading to the development of ‘tombstone cleavage’, and defined microscopically by thin seams of fine grained dark material. X-ray diffraction analyses show that the diamictite matrix is made up of quartz, feldspars, muscovite and chlorite. Element maps further indicate that the cleavage is defined predominantly by phyllosilicates and minor oxides, implying that it is made up of relatively insoluble material and hydrothermal alteration products. Overall, the cleavage therefore formed by dissolution and removal of mobile elements. This indicates that pressure solution likely accommodated a significant component of shortening during the Cape Orogeny, and provides an example of low temperature cleavage development during orogenesis.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: Folds; Diamictite; Karoo; Fold-and-thrust belt; Pressure solution
Additional Information: Pdf uploaded in accordance with the publisher’s policy at http://www.sherpa.ac.uk/romeo/search.php(accessed 02/07/2014)
Publisher: Elsevier
ISSN: 1464-343X
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 28 April 2014
Last Modified: 29 Jun 2019 15:55
URI: http://orca-mwe.cf.ac.uk/id/eprint/59557

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