Displacement-length scaling of brittle faults in ductile shear

Autor(en)

Bernhard Grasemann, Ulrike Exner, Cornelius Tschegg

Abstrakt

Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement-distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow.

Organisation(en)

Institut für Geologie, Department für Lithosphärenforschung

Journal

Journal of Structural Geology

Band

33

Seiten

1650-1661

Anzahl der Seiten

12

ISSN

0191-8141

DOI

https://doi.org/10.1016/j.jsg.2011.08.008

Publikationsdatum

2011

Peer-reviewed

Ja

ÖFOS 2012

105101 Allgemeine Geologie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/3db394f6-33bd-4fd6-93a0-6696ff3254bf