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Abstract

Large-scale Mesoproterozoic crustal shear zones are partially exposed from beneath cover sequences in the Christie Domain
of the northwestern Gawler Craton, southern Australia. These structures are associated with gravity and magnetic anomalies that
allow them to be mapped under cover, and their three-dimensional geometry and kinematics to be evaluated. Gravity and magnetic
forward modelling indicate that these shear zones form an imbricate oblique thrust stack with combined top-to-the-southeast, left
lateral transport. The longest shear zones in the stack penetrate the crust to at least 15 km depth, and dip to the northwest at 70◦;
their inferred sense of motion are consistent with kinematic indicators from sparse outcrops. From northwest to southeast, the
stack includes crustal slices bound by the Karari Fault Zone, Tallacootra and Blowout Shear Zones, Colona and Coorabie Fault
Zones and the Muckanippie Shear Zone. These structures separate discrete tectonometamorphic packages within the previously
undifferentiated Christie Gneiss of the Archean Mulgathing Complex, and imply several generations of transport of material from
the lower and middle crust.
Three-dimensional inversion of gravity data indicates that the Muckanippie Shear Zone, a shallowly rooted second-order splay
of the Coorabie Fault Zone has an antithetic dip (to the southeast), and is part of a positive flower structure.
Cross-cutting relationships, coupled with recent reconnaissance geochronology, suggest that the western Gawler Craton, part of
the Mawson Continent, was under a long-lasting oblique slip deformational regime after ca. 1590 Ma. This tectonic reworking is
correlated with episodic pervasive metamorphism and deformation recorded elsewhere in the Gawler Craton between ca. 1550 and
1450 (Coorabie Orogeny), pointing to a complex history of stabilization in Proterozoic Rodinia.
The Tallacootra, Colona and Coorabie structures are all cut at a high angle to their strikes by Mesozoic rift faults of the Southern
Rift System, and may form piercing points in reconstructions of Gondwana, and earlier Rodinia configurations.

Item Type:	Article
Authors/Creators:	Direen, NG and Cadd, A G and Lyons, P and Teasdale, JP
Keywords:	Coorabie Orogeny; Gawler Craton; Gravity; Magnetics; Oblique slip tectonics; Proterozoic; Rodinia; Southern Australia
Journal or Publication Title:	Precambrian Research
ISSN:	0301-9268
DOI / ID Number:	https://doi.org/10.1016/j.precamres.2005.09.007
Additional Information:	Crown Copyright © 2005 Published by Elsevier B.V. All rights reserved. The definitive version is available at http://www.sciencedirect.com
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