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



Toy, Virginia Gail, Sutherland, Rupert, Townend, John, Allen, Michael J ORCID: 0000-0001-5068-3661, Becroft, Leeza, Boles, Austin, Boulton, Carolyn, Carpenter, Brett, Cooper, Alan, Cox, Simon C
et al (show 60 more authors) (2017) Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand. NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS, 60 (4). pp. 497-518.

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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.

Item Type: Article
Uncontrolled Keywords: Alpine Fault, New Zealand, scientific drilling, mylonite, cataclasite
Depositing User: Symplectic Admin
Date Deposited: 15 Dec 2017 16:52
Last Modified: 19 Jan 2023 06:50
DOI: 10.1080/00288306.2017.1375533
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3012278