Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand
Toy, Virginia Gail; Sutherland, Rupert; Townend, John; Allen, Michael John; Becroft, Leeza; Boles, Austin; Boulton, Carolyn; Carpenter, Brett M.; Cooper, Alan; Cox, Simon C.; Daube, Christopher; Faulkner, Daniel R.; Halfpenny, Angela; Kato, Naoki; Keys, Stephen; Kirilova, Martina; Kometani, Yusuke; Little, Timothy; Mariani, Elisabetta; Melosh, Benjamin; Menzies, Catriona D.; Morales, Luiz; Morgan, Chance; Mori, Hiroshi; Niemeijer, André; Norris, Richard; Prior, David J.; Sauer, Katrina; Schleicher, Anja M.; Shigematsu, Norio; Teagle, Damon A H; Tobin, Harold; Valdez, Robert; Williams, Jack; Yeo, Samantha; Baratin, Laura May; Barth, Nicolas; Benson, Adrian; Boese, Carolin; Célérier, Bernard; Chamberlain, Calum J.; Conze, Ronald; Coussens, Jamie; Craw, Lisa; Doan, Mai Linh; Eccles, Jennifer; Grieve, Jason; Grochowski, Julia; Gulley, Anton; Howarth, Jamie; DFDP-2 Science Team
(2017) New Zealand Journal of Geology and Geophysics, volume 60, issue 4, pp. 497 - 518
(Article)
Abstract
During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5–893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the
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borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200–400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.
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Keywords: Alpine Fault, cataclasite, mylonite, New Zealand, scientific drilling, Taverne, Geophysics, Geology, Earth and Planetary Sciences (miscellaneous)
ISSN: 0028-8306
Publisher: Taylor and Francis Ltd.
(Peer reviewed)
