Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand

Virginia Gail Toy (Corresponding Author), Rupert Sutherland, John Townend, Michael J Allen, Leeza Becroft, Austin Boles, Carolyn J Boulton, Brett M. Carpenter, Simon C. Cox, Christopher Daube, Dan Faulkner, Angela Halfpenny, Naoki Kato, Stephen Keys, Martina Kirilova, Yusuke Kometani, Timothy Little, Elisabetta Mariani, Ben Melosh, Catriona D MenziesLuiz Morales, Chance Morgan, Hiroshi Mori, Andre Niemeijer, Richard Norris, Dave Prior, Katrina Sauer, Anja M. Schleicher, Norio Shigematsu, Damon A. H. Teagle, Harold Tobin, Robert Valdez, Jack Williams, Samantha Yeo, Laura-May Baratin, Nicolas Barth, Adrian Benson, Carolin Boese, Bernard Celerier, Calum Chamberlain, Ronald Conze, Jamie Coussens, Lisa Craw, Mai-Linh Doan, Jennifer Eccles, Jason Grieve, Julia Grochowski, Anton Gulley, Jamie Howarth, Katrina Jacobs, Lucie Janku-Capova, Tamara Jeppson, Rob Langridge, Deirdre Mallyon, Ray Marx, Cecile Massiot, Loren Mathewson, Jo Moore, Osamu Nishikawa, Brent Pooley, Alex Pyne, Martha Savage, Doug R. Schmitt, Sam Taylor-Offord, Phaedra Upton, Konrad Weaver, Thomas Wiersberg, Martin Zimmer

Research output: Contribution to journalArticle

12 Citations (Scopus)

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 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.
Original languageEnglish
Pages (from-to)497-518
Number of pages21
JournalNew Zealand Journal of Geology and Geophysics
Volume60
Issue number4
Early online date17 Oct 2017
DOIs
Publication statusPublished - 2017

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Keywords

  • Alpine fault
  • New Zealand
  • scientific drilling
  • mylonite
  • cataclasite

Cite this

Toy, V. G., Sutherland, R., Townend, J., Allen, M. J., Becroft, L., Boles, A., ... Zimmer, M. (2017). Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand. New Zealand Journal of Geology and Geophysics, 60(4), 497-518. https://doi.org/10.1080/00288306.2017.1375533