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

New Zealand Journal of Geology and Geophysics
By: , and 



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.

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Publication type Article
Publication Subtype Journal Article
Title Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand
Series title New Zealand Journal of Geology and Geophysics
DOI 10.1080/00288306.2017.1375533
Volume 60
Issue 4
Year Published 2017
Language English
Publisher Taylor & Francis
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center, Pacific Coastal and Marine Science Center
Description 22 p.
First page 497
Last page 518
Country New Zealand
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