Virtual Field Trip: Alpine Fault
Alpine Fault mylonites and pseudotachylytes, Harold Creek
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Quartzo-feldspathic mylonite with winged porphyroclast of feldspar indicating dextral movement |
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Broken up mylonite intruded by pseudotachylyte or friction melt, the result of momentary high temperatures developed during coseismic frictional sliding |
The convergence across the Alpine Fault has resulted in the uplift and exhumation of an extensive mylonite zone, formed at depths of 25-30 km. The zone outcrops immediately east of the fault and is up to 1 km wide. A zone of cataclasite and gouge up to 50 m thick bounds the mylonites to the west, and ultramylonite and mylonite grade eastwards into protomylonite and eventually into amphibolite facies Alpine Schist which forms the western flanks of the Southern Alps.
More comprehensive recent data about the mylonite sequence, and the pseudotachylytes it hosts can be found on Virginia Toy's PhD page.