A granulite-facies normal shear zone exposed in the Arunta Inlier of central Australia; implications for deep-crustal deformation during oblique divergence
A granulite-facies normal shear zone exposed in the Arunta Inlier of central Australia; implications for deep-crustal deformation during oblique divergence (in Crustal cross sections; from the western North American Cordillera and elsewhere; implications for tectonic and petrologic processes, Robert B. Miller (editor) and Arthur W. Snoke (editor))
Special Paper - Geological Society of America (2009) 456: 267-286
- Arunta Block
- Australasia
- Australia
- continental crust
- crust
- deformation
- extension
- fabric
- facies
- faults
- foliation
- geometry
- granulite facies
- high temperature
- inliers
- lineation
- lower crust
- Northern Territory Australia
- oblique orientation
- plate boundaries
- plate divergence
- plate tectonics
- reconstruction
- rotation
- shear zones
- structural analysis
- temperature
- theoretical models
- Mount Hay Block
- Capricorn Ridge shear zone
The Mount Hay block is a approximately 12-km-thick, deep continental crustal section exposed in the Arunta inlier in central Australia. The -4-km-wide, granulite-facies (770-776+ or -38 degrees C) Capricorn ridge shear zone cross-cuts the dominant granulite-facies fabric of the Mount Hay block. In its present geometry, the Capricorn ridge shear zone contains a steeply south-southeast-dipping foliation, steeply east-southeast-plunging lineation, and south-side-up shear-sense indicators. When post-granulite-facies tilting is removed, the shear zone restores to a shallowly to moderately (30-50 degrees ) dipping, normal shear zone in which the lineation is oblique to the inferred Proterozoic plate boundary, suggesting oblique divergence. The field observations and reconstruction indicate that strain can be localized in the high-temperature, deep-crustal roots of extensional fault systems. This geometry of a discrete, moderately dipping, deep-crustal shear zone is consistent with simple-shear conceptual models of crustal extension.
