Architecture of Proterozoic shear zones in the Christie Domain, western Gawler Craton, Australia: Geophysical appraisal of a poorly exposed orogenic terrane

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• 作者：Nicholas G. Direen ; Allan G. Cadd ; Patrick Lyons and Jonathan P. Teasdale
• 关键词：Coorabie Orogeny ; Gawler Craton ; Gravity ; Magnetics ; Oblique slip tectonics ; Proterozoic ; Rodinia ; Southern Australia
• 刊名：Precambrian Research
• 出版年：2005
• 出版时间：30 November 2005
• 年：2005
• 卷：142
• 期：1-2
• 页码：28-44
• 全文大小：1416 K

文摘

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.