- Title
- Crystallographic preferred orientation of quartz deformed at granulite conditions: the Kalinjala Shear Zone, Port Neill, South Australia
- Creator
- Wilson, C. J. L.; Hunter, N. J. R.; Luzin, V.
- Relation
- Australian Journal of Earth Sciences Vol. 69, Issue 8, p. 1119-1131
- Publisher Link
- http://dx.doi.org/10.1080/08120099.2022.2076740
- Publisher
- Taylor & Francis
- Resource Type
- journal article
- Date
- 2022
- Description
- Crystallographic preferred orientations of quartz aggregates in mylonitic orthogneisses from the highest strained central region of the Kalinjala Shear Zone, Port Neill South Australia, are products of a combination of constrictional and flattening strains. These rocks were deformed under granulite facies peak metamorphic conditions, reaching pressures of ∼1.0GPa and temperatures of ∼800±50 °C. Neutron diffraction textural and fabric analysis methods reveal a dominant single c-axis maximum parallel to the Y-strain axis. This is accompanied by a symmetric orthorhombic pattern, where the c-axis fabrics and corresponding pole figure densities of {a}, {m}, {r} and {z} planes are arranged around the XY foliation plane. These fabrics from coexisting adjacent layers suggest that the activation of prism- slip is characteristic for these high-temperature deformation conditions. A small asymmetry in the [c], {a} and {m} pole figures suggests a minor component of dextral shearing. The c-axis pattern is weakened where the foliation is dominated by secondary phases, such as concentrations of biotite mica. The opening angles obtained from cross-girdle c-axis patterns produce temperature estimates that are ∼100 °C lower than the peak metamorphic temperature of ∼800±50 °C, but closer to temperatures related to a component of flattening strain. These c-axis patterns are consistent with other structural characteristics and can be related to the late-stage flattening strains during the Kimban Orogeny. KEY POINTS Mylonitic orthogneisses are deformed under granulite facies conditions. Quartz fabrics were measured by bulk neutron diffraction and optical methods. Mylonite c-axis fabrics can be related to the high-temperature deformation and activation of the prism-< a > slip system. Crystal preferred orientations indicate a large component of flattening strain superimposed on the dextral shearing observed in the Kalinjala Shear Zone.
- Subject
- kalinjala shear zone; quartz crystallographic preferred orientations (CPO); quartz deformation; microstructure; neutron diffraction; fabric analysis
- Identifier
- http://hdl.handle.net/1959.13/1486522
- Identifier
- uon:51877
- Identifier
- ISSN:0812-0099
- Language
- eng
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