Havelock geology : the Alpine Fault Zone between the Cook and Karangarua Rivers, South Island, New Zealand
The section of the Alpine fault between the Cook and Karangarua Rivers provides further information on the structure of the fault zone. Exposures of the fault have been revealed in a recent slips at Havelock Creek. A complete hanging-wall section ranging through schist derived gouge to cataclasite, 'green mylonite', metabasite and schist mylonites, and protomylonite overthrusts Quaternary sediments at the surface. The distribution of fault rocks along strike shows a systematic segmentation of the fault trace into alternating thrust and tear sections: thrust sections occur on the true right of major drainages and tear sections along the ridges, left of the drainages, suggesting a correlation with topography. Thrust sections have the entire series of gouge - cataclasite - mylonite - proto-mylonite, whereas the tear segments are lacking in highly mylonitized rocks. A model is presented which explains this behavior. The fault zone records evidence of high fluid flow. Elevated fluid pressures possibly created by a low permeability metabasite cap, retrogression in the 'green mylonite' zone, with late stage cross cutting quartz-carbonate veins, and numerous, low discharge cold-springs are present. There is no evidence of dry, brittle deformation in this area. Pseudotachylyte distribution along strike is related to the nature of the foot-wall rocks. Also notable in this area is overthrust nappes that help to constrain the convergence rates.
63 leaves : ill. (some col.), maps ; 30 cm.
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POLYGON ((169.828417060000106 -43.553464555999938,169.895909864000032 -43.504482134999932,169.907183143000111 -43.496421052999949,169.949188023000033 -43.498623423999959,169.950441554000122 -43.504031123999937,169.951052545000039 -43.506666576999976,169.92381208900008 -43.533036587999959,169.908256459000086 -43.532395657999984,169.878646926000101 -43.554837382999949,169.839289507000103 -43.584628854999949,169.821517136000011 -43.583950897999955,169.822340365000059 -43.56849531599994,169.822928801000103 -43.557442292999951,169.828417060000106 -43.553464555999938))
McAdoo, Brian Garland, 1969-, “Havelock geology : the Alpine Fault Zone between the Cook and Karangarua Rivers, South Island, New Zealand ,” Otago Geology Theses, accessed March 1, 2021, http://theses.otagogeology.org.nz/items/show/264.