Microfabric memory of vein quartz for strain localization in detachment faults: A case study on the Simplon fault zone

Haertel, Mike; Herwegh, Marco (2014). Microfabric memory of vein quartz for strain localization in detachment faults: A case study on the Simplon fault zone. Journal of structural geology, 68, pp. 16-32. Pergamon 10.1016/j.jsg.2014.08.001

[img] Text
Herwegh.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (8MB) | Request a copy

This manuscript deals with the adaptation of quartz-microfabrics to changing physical deformation conditions, and discusses their preservation potential during subsequent retrograde deformation. Using microstructural analysis, a sequence of recrystallization processes in quartz, ranging from Grain-Boundary Migration Recrystallization (GBM) over Subgrain-Rotation Recrystallization (SGR) to Bulging Nucleation (BLG) is detected for the Simplon fault zone (SFZ) from the low strain rim towards the internal high strain part of the large-scale shear zone. Based on: (i) the retrograde cooling path; (ii) estimates of deformation temperatures; and (iii) spatial variation of dynamic recrystallization processes and different microstructural characteristics, continuous strain localization with decreasing temperature is inferred. In contrast to the recrystallization microstructures, crystallographic preferred orientations (CPO) have a longer memory. CPO patterns indicative of prism <a> and rhomb <a> glide systems in mylonitic quartz veins, overprinted at low temperatures (�400 �C), suggest inheritance of a high-temperature deformation. In this way, microstructural, textural and geochemical analyses provide information for several million years of the deformation history. The reasons for such incomplete resetting of the rock texture is that strain localization is caused by change in effective viscosity contrasts related to temporal large- and small-scale temperature changes during the evolution of such a long-lived shear zone. The spatially resolved, quantitative investigation of quartz microfabrics and associated recrystallization processes therefore provide great potential for an improved understanding of the geodynamics of large-scale shear zones.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Other Institutions > Teaching Staff, Faculty of Science
08 Faculty of Science > Institute of Geological Sciences > Tectonics

UniBE Contributor:

Herwegh, Marco

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0191-8141

Publisher:

Pergamon

Language:

English

Submitter:

Marco Herwegh

Date Deposited:

01 May 2015 13:11

Last Modified:

06 Oct 2015 09:50

Publisher DOI:

10.1016/j.jsg.2014.08.001

BORIS DOI:

10.7892/boris.59491

URI:

https://boris.unibe.ch/id/eprint/59491

Actions (login required)

Edit item Edit item
Provide Feedback