Extreme Hydrothermal Conditions Near an Active Geological Fault, DFDP-2B Borehole, Alpine Fault, New Zealand
Abstract
The DFDP-2B borehole sampled rocks above and within the upper part of the Alpine Fault, New Zealand, to a depth of 893 m in late 2014. The experiment was the first to drill a major geological fault zone that is active and late in its earthquake cycle. We determined ambient fluid pressures 8-10% above hydrostatic and a geothermal gradient of 130-150 °C/km in rocks above the fault. These unusual ambient conditions can be explained by a combination of: rock advection that transports heat from depth by uplift and oblique slip on the fault; and fluid advection through fractured rock, driven by topographic forcing, which concentrates heat and causes fluid over-pressure in the valley. Highly-anomalous ambient conditions can exist in the vicinity of active faults, and earthquake and mineralization processes occur within these zones.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2015
- Bibcode:
- 2015AGUFM.T11G..03S
- Keywords:
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- 3653 Fluid flow;
- MINERALOGY AND PETROLOGY;
- 7230 Seismicity and tectonics;
- SEISMOLOGY;
- 8004 Dynamics and mechanics of faulting;
- STRUCTURAL GEOLOGY;
- 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS