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Relation Between Pyrite and Gold at the Twin Creeks SHMG Deposit, Nevada

By
Grigore Simon
Grigore Simon
Department of Geological Sciences, University of MichiganAnn Arbor, MI 48109
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Stephen E. Kesler
Stephen E. Kesler
Department of Geological Sciences, University of MichiganAnn Arbor, MI 48109
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Dean R. Peltonen
Dean R. Peltonen
Santa Fe Pacific Gold Corp., Twin Creeks MineP.O. Box 69, Golconda, NV 89414
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Stephen L. Chryssoulis
Stephen L. Chryssoulis
AMTEL, 100 Collip CircleUWO Research Park, London, Ontario, Canada N6G 4X8
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Hui Huang
Hui Huang
Department of Chemistry, University of MichiganAnn Arbor, MI 48109
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James E. Penner-Hahn
James E. Penner-Hahn
Department of Chemistry, University of MichiganAnn Arbor, MI 48109
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Published:
January 01, 1997

Abstract

Most gold in sediment-hosted micron gold (SHMG) deposits cannot be imaged by conventional reflected light, secondary electron (SEM), or transmitted electron (TEM) microscopy. Gold particles with a diameter of about 200 Å were observed by Bakken et al. (1989) as inclusions in pyrite, cinnabar, quartz and illite from the Carlin mine, although considerable gold could not be accounted for. Arehart et al. (1993) showed that much of this “invisible” gold at Post/Betze and Gold Quarry is in As-rich growth zones in pyrite, possibly in solid solution. At Twin Creeks, we have observed mat the gold content of ores appears to vary with the texture of pyrite. We report here results of a preliminary study on the relation between gold values and pyrite textures at the Twin Creeks SHMG deposit, based in part on ion probe measurements of gold concentrations in pyrite and X-ray Absorption Near-Edge Spectroscopy (XANES) measurements to determine the oxidation state of gold in the pyrite.

SHMG mineralization in the Megapit (see Fig. 1 of Hallet al., this volume) area of the Twin Creeks deposit, where our work was concentrated, is hosted by calcareous black shales and interlayered volcanic rocks of the Ordovician Comus Formation, which form a large fold. Gold mineralization is concentrated in the nose of this fold and in favorable stratigraphic horizons in the limbs of the fold. Gold is associated with arsenic-bearing pyrite (arsenian pyrite) that was deposited along with various combinations of quartz, adularia, sericite, realgar, orpiment, and stibnite. The Megapit deposit is

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Contents

Society of Economic Geologists Guidebook Series

Carlin-Type Gold Deposits Field Conference

Peter Vikre
Peter Vikre
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Tommy B. Thompson
Tommy B. Thompson
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Keith Bettles
Keith Bettles
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Odin Christensen
Odin Christensen
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Ron Parratt
Ron Parratt
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Society of Economic Geologists
Volume
28
ISBN electronic:
9781934969816
Publication date:
January 01, 1997

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