Department or Administrative Unit
Geological Sciences
Document Type
Article
Publication Date
10-17-2017
Journal
New Zealand Journal of Geology and Geophysics
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.
Recommended Citation
Toy, Virginia Gail and Halfpenny, Angela, "Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand" (2017). All Faculty Scholarship for the College of the Sciences. 146.
https://digitalcommons.cwu.edu/cotsfac/146
Comments
This is an Accepted Manuscript of an article published by Taylor & Francis in New Zealand Journal of Geology and Geophysics on October 17, 2017, available online: http://www.tandfonline.com/10.1080/00288306.2017.1375533. Due to copyright restrictions, the version of record is not available for free download from ScholarWorks @ CWU.