Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand. Issue 4 (2nd October 2017)

• Record Type: Journal Article
• Authors: Toy, Virginia Gail; Sutherland, Rupert; Townend, John; Allen, Michael J.; Becroft, Leeza; Boles, Austin; Boulton, Carolyn; Carpenter, Brett; 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, Andre; Norris, Richard; Prior, David; 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; Jacobs, Katrina; Janku-Capova, Lucie; Jeppson, Tamara; Langridge, Robert; Mallyon, Deirdre; Marx, Ray; Massiot, Cécile; Mathewson, Loren; Moore, Josephine; Nishikawa, Osamu; Pooley, Brent; Pyne, Alex; Savage, Martha K.; Schmitt, Doug; Taylor-Offord, Sam; Upton, Phaedra; Weaver, Konrad C.; Wiersberg, Thomas; Zimmer, Martin;
• Is Part Of: New Zealand journal of geology and geophysics. Volume 60:Issue 4(2017)
• Page Start: 497
• Page End: 518
• Publication Date: 2017-10-02
• Subjects: Alpine Fault -- New Zealand -- scientific drilling -- mylonite -- cataclasite; Geology -- New Zealand -- Periodicals; Geology -- Periodicals; Geophysics -- Periodicals; Geofysica; Geologie; Geology; Geophysics; New Zealand; Periodicals; 559.3
• DOI: 10.1080/00288306.2017.1375533
• Languages: English
• ISSNs: 1175-8791

Abstract

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.