Document Type
Article
Department or Administrative Unit
Geological Sciences
Publication Date
10-17-2017
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
Journal
New Zealand Journal of Geology and Geophysics
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.