On stress and strain in a continuous-discontinuous shear zone undergoing simple shear and volume loss

Fagereng, Ake 2013. On stress and strain in a continuous-discontinuous shear zone undergoing simple shear and volume loss. Journal of Structural Geology 50 , pp. 44-53. 10.1016/j.jsg.2012.02.016

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Abstract

I summarise observations within a continuous-discontinuous shear zone to discuss the local stress and strain conditions experienced within a mixed rheology shear zone undergoing volume loss and deformation approximating simple shear. The Chrystalls Beach Complex, New Zealand, comprises phacoids formed from dismembered beds by layer-parallel extension, enclosed within a relatively incompetent matrix. Local extension is generally subparallel to the regional direction of shortening, and overall it appears that layer-parallel extension is a geometrical necessity in low angle shear zones where significant flattening occurs in response to simple shear accompanied by volume loss. Preferential stress loading of phacoids is predicted by fibre-loading theory, and the failure of phacoids by brittle fracture is thereby governed by fibre stresses transferred from the matrix. The principal stress orientations in a phacoid are likely rotated relative to the matrix, and either parallel or perpendicular to the phacoid-matrix interface. As preferential loading of phacoids decreases the stress level in the matrix, an increased volume fraction of phacoids increases the strength of the shear zone as a whole. However, only small matrix volume fractions are required for the composite to act nearly as weak as the matrix.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Ocean Sciences
Subjects:	Q Science > QE Geology
Uncontrolled Keywords:	Mélanges; Shear zones; Simple shear; Fibre stress; Polyphase rheology
Publisher:	Elsevier
ISSN:	0191-8141
Last Modified:	04 Jun 2017 06:05
URI:	http://orca.cf.ac.uk/id/eprint/56355

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