Near-surface expression of a young mesothermal gold mineralizing system, Sealy Range, Southern Alps, New Zealand |
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Authors: | A S Templeton D Craw P O Koons C P Chamberlain |
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Institution: | (1) Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA, US;(2) Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand e-mail: dave.craw@stonebow.otago.ac.nz, NZ |
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Abstract: | Carbonate-limonite veins formed in steeply dipping fractures in the upper few hundred metres of basement greywacke in the
actively rising Southern Alps of New Zealand. The veins are found commonly in extensional fractures near to, but not in, major
faults associated with mountain uplift, and/or sinistral faults which bound mountain ranges. Some of the veins contain sulphides
and minor gold deposited as part of incrementally formed fracture fillings. Oxygen isotope ratios of calcite range widely
between +6 and +24‰, and calcite δ13CPDB=−5.5 to −11.5‰. The veins formed from isotopically exchanged crustal fluid with a probable meteoric water component. The
shallow vein network is the near-surface expression of a tectonically induced hydrothermal system which has deposited gold-bearing
veins with a mesothermal style over several vertical kilometres. This vein network has formed in a dilatational zone of the
oblique collisional orogen where near-vertical fractures tap deep-sourced fluids. Similar processes acting at the southern
end of the Southern Alps in the Miocene resulted in locally rich mesothermal quartz-gold veins.
Received: 21 May 1997 / Accepted: 30 June 1998 |
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