Abstract
The Koolyanobbing shear zone is one of a number of northwest‐trending, crustal‐scale, ductile shear zones located in the Archaean granitoid‐greenstone terrains of the Yilgarn Craton, Western Australia. It is between 6 and 15 km wide and based on aeromagnetic data, may be in excess of 650 km long. At Koolyanobbing, in the Southern Cross Province, the shear zone is defined by an approximately 6 km wide zone of mylonitic rocks, formed by intense deformation of banded monzogranite to tonalite. The shear zone comprises a series of alternating zones of foliated granitoid, protomylonite, mylonite and ultramylonite that indicate a progressive increase in strain towards the centre of the shear zone. Within granitoid gneiss, to the north of Koolyanobbing, high‐ and low‐strain zones appear to be symmetrically disposed about the centre of the Koolyanobbing shear zone. However, a zone of high strain also occurs adjacent to the Koolyanobbing greenstone belt. Kinematic indicators (asymmetrical pressure shadows, S‐C and ...
Published Version
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