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Age of Mineralization at the Twin Creeks SHMG Deposit, Nevada

By
Chris M. Hall
Chris M. Hall
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Grigore Simon
Grigore Simon
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Stephen E. Kesler
Stephen E. Kesler
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Published:
January 01, 1997

Abstract

This paper will explore the significance of thermochemical sulfate reduction (TSR) to the origin of sedimenthosted disseminated gold (SHDG) deposits. TSR provides a means of generating abnormally high concentrations of H2S at moderate temperatures (e.g., 100 to 200°C). A high H2S content is a prerequisite for mobilizing gold and other metals associated with SHDG deposits (Ag, Hg, Sb, As), and is also necessary to form ore bodies with a high Au/Ag ratio. Field and sulfur-isotopic evidence supporting the TSR hypothesis will be reviewed. The discussion will focus on SHDG deposits in the Carlin Trend and similar deposits in China, as well as the Hemlo gold deposit, Ontario, a possible Archean analog of this deposit type. If valid, the TSR hypothesis has significance to the minerals exploration industry as a means to discriminate between favorable vs. unfavorable source rocks.

Mineralization at Twin Creeks mine is hosted by rocks of the Ordovician Comus Formation, which consists of dolomitic to calcareous black shales with tuffaceous interbeds and interlayered basalt flows and sills. These rocks have been deformed into a northwest-trending fold system with a known length of about 4.5 km (3 miles). Gold mineralization post -dates this folding, and is concentrated in the nose of this fold and in favorable stratigraphic horizons in the limbs of the fold. In the most intensely mineralized part of the deposit, the Megapit, the fold is cut into three sections by right-lateral the TC (northern) and DZ (southern) faults trending NE-SW (Fig. 1) and dipping steeply to

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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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