Geometry, classification and kinematics of S-C and S-C′ fabrics in the Mushandike area, Zimbabwe

Blenkinsop, Thomas G. ORCID: https://orcid.org/0000-0001-9684-0749 and Treloar, P. J. 1995. Geometry, classification and kinematics of S-C and S-C′ fabrics in the Mushandike area, Zimbabwe. Journal of Structural Geology 17 (3) , pp. 397-408.

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Abstract

Planar fabrics in small dextral shear zones in the Mushandike area of the Zimbabwe Archaean craton consist of a sigmoidal primary foliation S displaced by discrete shears C or C′. These planar fabrics can be divided into porphyroclastic, megacrystic and banded types, depending mainly on the values of the angles between S- and C- or C′-surfaces, the structures that define S-surfaces, and the spacing of C- or C′-surfaces. The values of the angles between the foliations are proposed as the basis for a general classification of planar fabrics in shear zones. The values of the angles depend on microstructures and strain. Microstructural evidence shows that slip did not occur on S-surfaces, but only on C- or C′-surfaces. A model for the development of the fabrics proposes that S-surfaces lie parallel to the XY plane of the local finite strain ellipsoid in domains of simple shear between C- or C′-surfaces. C′-surfaces may form in the orientation of a Coulomb failure surface. The field evidence suggests that an increase in bulk strain is at least partly accommodated by an increase in local strain in domains between C- or C′-surfaces as the S-surfaces rotate with the local finite strain ellipsoid.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Publisher:	Elsevier
ISSN:	0191-8141
Last Modified:	24 Oct 2022 12:08
URI:	https://orca.cardiff.ac.uk/id/eprint/50650

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