Stress estimates and fault history from quartz microstructures

Blenkinsop, Thomas G. ORCID: https://orcid.org/0000-0001-9684-0749 and Drury, M. R. 1988. Stress estimates and fault history from quartz microstructures. Journal of Structural Geology 10 (7) , pp. 673-684.

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Abstract

Fault plane structures and microstructures have been examined from a fault in Cambro-Ordovician quartzites exposed on the north coast of the Cantabrian zone, N.W. Spain. Along the fault there is a 2–3 cm wide cataclasite zone bounded by plastically deformed intact quartzite, which is restricted to a few metres from the fault plane. In thin section, the cataclasite consists of angular fragments of quartz in a fine-grained matrix of quartz cement. Cathodoluminescence reveals extensive intra- and transgranular microcracking. Deformation lamellae (D.L.) are widespread in the intact quartzite; electron microscopy shows that they are defined by a banded dislocation substructure. The microstructures indicate a fault history consisting of plastic deformation restricted to a metre-scale zone, followed by cataclasis and dilational fracture. The early plasticity is interpreted as evidence for the propagation of a process zone. The D.L. are used as an indicator of power-law-breakdown creep, which occurs above a critical normalized stress, estimated as at least 170 MPa from available data. Dislocation densities also indicate a stress higher than 116 MPa. The process zone as defined by formation of D.L. is modelled using fracture mechanics theory. For the likely size of the zone, the remote applied stress for fault propagation is shown to be less than 100 MPa.

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/50639

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