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

October 17, 2017

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.

Publication Year 2017
Title Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand
DOI 10.1080/00288306.2017.1375533
Authors Virginia G. Toy, Rupert Southerland, John Townend, Michael J. Allen, Leeza Becroft, Austin Boles, Carolyn Boulton, Brett Carpenter, Alan K. Cooper, Simon C. Cox, Christopher Daube, Daniel R. Faulkner, Angela Halfpenny, Naoki Kato, Stephen Keys, Martina Kirilova, Yusuke Kometani, Timothy Little, Elisabetta Mariani, Benjamin Melosh, Catriona D. Menzies, Luiz Morales, Chance Morgan, Hiroshi Mori, Andre Niemeijer, Richard Norris, David Prior, Katrina Sauer, Anja Schleicher, Norio Shigematsu, Damon A.H. Teagle, Harold Tobin, Robert Valdez, Jack Williams, Samantha Yeo, Laura-May Baratin, Nicolas C. Barth, Adrian Benson, Caroline Boese, Bernard Celerier, Calum J. Chamberlain, Ronald Conze, Jamie Coussens, Lisa Craw, Mai-Linh Doan, Jennifer L. Eccles, Jason Grieve, Julia Grochowski, Anton Gulley, Jamie Howarth, Katrina D. Zamudio, Lucie Janku-Capova, Tamara Nicole Jeppson, Robert M. Langridge, Deirdre Mallyon, Ray Marx, Cecile Massiot, Loren Mathewson, Josephine Moore, Osamu Nishikawa, Brent Pooley, Alex Pyne, Martha K. Savage, Doug Schmitt, Sam Taylor-Offord, Phaedra Upton, Konrad C. Weaver, Thomas Wiersberg, Martin Zimmer
Publication Type Article
Publication Subtype Journal Article
Series Title New Zealand Journal of Geology and Geophysics
Index ID 70226533
Record Source USGS Publications Warehouse
USGS Organization Geology, Minerals, Energy, and Geophysics Science Center; Pacific Coastal and Marine Science Center