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Field Trip Day Two SEG Getchell Region: Road Log, Twin Creeks Mine Turnoff to Getchell Mine

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Published:
January 01, 2000

Cumulative Miles

0.0 Log begins at yield sign at Getchell/Twin Creeks mine Road fork: head due north on the mine road. See Day One for log up to the turnoff.

Looking west, the south end of the Summer Camp oxide gold open pit is visible behind the Summer Camp waste dump further north. The southern Getchell property boundary is 500 ft south of the open pit. The Summer Camp orebody was discovered in 1984, and mined in 1989–1990. It produced 2.2 M tons grading 0.034 opt. Ore-grade sulfide material (0.2 opt Au) is still exposed on the pit floor and makes up a small satellite resource. Gold ore is hosted in silicified and mineralized hornfelsed Comus formation carbonaceous mudstones and calcareous mudstones along the north-south, east-dipping Getchell fault and intersecting northeast- and southwest-striking faults.

Looking northwest, the Riley open pit and underground workings are visible along the range front. Riley is the largest of the tungsten mines that occur along the margins of the Osgood Mountain stock. Scheelite was discovered here in 1917 but was not mined until 1943. The Riley pits expose stratabound and discordant scheelite in garnetite and clinopyroxene (diopside) skarn in limestone protoliths along the intrusive contact of the Cretaceous (92 m.y.) Osgood Mountain stock. From here, the layering you can see in the highwalls of the pits is relic bedding of the stratigraphy that forms dip slopes among the open pits. The open pits are in the footwall of the Getchell fault, well exposed near the mine shack. The Getchell fault dips 45° E, essentially parallel to the bedded exposures in the pit highwalls. The historical Riley shaft head frame is just visible at the north end of the workings near the range front.

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Contents

Society of Economic Geologists Guidebook Series

Part I. Contrasting Styles of Intrusion-Associated Hydrothermal Systems: Part II. Geology & Gold Deposits of the Getchell Region

John H. Dilles
John H. Dilles
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Mark D. Barton
Mark D. Barton
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David A. Johnson
David A. Johnson
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John M. Proffett
John M. Proffett
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Marco T. Einaudi
Marco T. Einaudi
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Elizabeth Jones Crafford
Elizabeth Jones Crafford
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Society of Economic Geologists
Volume
32
ISBN electronic:
9781934969854
Publication date:
January 01, 2000

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