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| Titel |
Bedrock Geology of the DFDP-2B Drill-Site, Central Alpine Fault, New Zealand |
| VerfasserIn |
Virginia Toy, Rupert Sutherland, John Townend |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145957
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| Publikation (Nr.) |
 EGU/EGU2017-9942.pdf |
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| Zusammenfassung |
| Bedrock was encountered at drilled depths (MD) of 238.5–893.2 m (vertical depths of 238.4–818.0 m) in DFDP-2B, Whataroa River, Westland, New Zealand. Continuous sampling and onsite description of whole cuttings samples and thin sections allowed identification that the borehole terminated within amphibolite facies, Torlesse Composite Terrane-derived mylonites >200-400 m above the Alpine Fault principal slip zone (PSZ). The most diagnostic macro-and micro-structural features were the occurrence of shear bands and reduction in mean quartz grain sizes toward the Alpine Fault. Onsite optical microscopy and subsequent offsite electron microscopy both demonstrate: (i) reduction in grain size and (ii) change in composition to greater mica:quartz+feldspar, most markedly at 720 m MD (vertical depth of 695 m), inferred to result from either heterogeneous sampling due to variations in drilling parameters, or a change in rock type across a minor fault. Major oxide variations suggest the Alpine Fault alteration zone, as defined during DFDP-1, was not sampled. |
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