Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand
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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.
Study Area
| 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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