Extreme 34S depletions in ZnS at the Mike gold deposit, Carlin Trend, Nevada: Evidence for bacteriogenic supergene sphalerite
- Thomas M. Bawden*1,
- Marco T. Einaudi*1,
- Benjamin C. Bostick*1,
- Anders Meibom*1,
- Joseph Wooden*2,
- John W. Norby3,
- Michael J.T. Orobona*3 and
- C. Page Chamberlain*4
- 1Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
- 2U.S. Geological Survey, Stanford University, Stanford, California 94305, USA
- 3Newmont Mining Corporation, P.O. Box 669, Carlin, Nevada 89822, USA
- 4Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
Abstract
We identified submicrometer-sized framboidal sphalerite (ZnS) below the base of supergene oxidation in a Carlin-type gold deposit of Eocene age in Nevada, United States, where the framboidal sphalerite forms a blanket-like body containing >400,000 metric tons of zinc. Framboidal sphalerite <0.1 μm in diameter, formed in the early Miocene, ranges from <0.1 to 0.35 mol% FeS; the δ34S values range from −25‰ to −70‰, the lowest values measured in a marine or terrestrial environment. These S isotope data demonstrate the involvement of sulfate-reducing bacteria and provide the first documentation that sphalerite can form significant supergene sulfide-enrichment blankets.
Footnotes
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↵*Present addresses: Corresponding author: Bawden—Global Mineral Resources, P.O. Box 193135, San Francisco, California 94119-3135, USA. orestrikeyahoo.com. Bostick—Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA. Norby—JN Resources, LLC, 784 Holyoke Drive, Spring Creek, Nevada 89815, USA. Orobona—Hibbing Taconite Company, P.O. Box 589, Hibbing, Minnesota 55746, USA
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- Accepted July 5, 2003.
- Received May 15, 2003.
- Revision received June 27, 2003.
- Geological Society of America
