Sleeper Mine

Humboldt County, Nevada, United States

GoldSilverBarium-BariteBismuthCopperLeadTelluriumZincCobaltNickelMolybdenumSulfurArsenicSeleniumAntimonyMercuryThalliumPotassium

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Description

John Wood, an AMAX geologist, made the discovery and staked the claims.\n

Commodities

PrimaryGold, Silver

TertiaryBarium-Barite, Bismuth, Copper, Lead, Tellurium, Zinc, Cobalt, Nickel, Molybdenum, Sulfur, Arsenic, Selenium, Antimony, Mercury, Thallium, Potassium

Commodity typeB

Deposit

Deposit typehydrothermal -vein, -stockwork/stringers, -breccia filling

Model150: Epithermal vein, Comstock

Deposit sizeM

WorkingsSurface

Orebody formtabular to disseminated to irregular

Ore controlBrittle rocks (mainly rhyolite porphyry) were required for deposition of gold in open tension fractures and as stockwork veins and hydrothermal breccias.

Materials

Ore mineralsGold

GangueQuartz, Adularia, Stibnite, Pyrite, Marcasite, Opal, Cristobalite, Sericite, Alunite, Kaolinite, Barite, Illite, Jarosite

Geology

Host rockRhyolite,Porphyry,Andesite,Phyllite,Slate,Quartzite · Auld Lang Syne Group

StructureIn the northern Slumbering Hills, Triassic sedimentary rocks are weakly folded and form a N20E-trending monocline that dips 45 east., The Sleeper Deposit occurs within a N20E-striking range front fault zone that dips 45-85 and terminates the NW side of the range. This fault zone hosted extensive hydrothermal alteration and mineralization and localized the Sleeper Gold Deposit. A normal fault which strikes N50W and dips 72 south intersects the range front fault zone in the vicinity of the Sleeper Deposit.

AlterationAlteration of rhyolitic host rock consists predominantly of silicification, argillic alteration, acid leaching, and supergene alteration. Replacement and open-space filling by silica minerals are the most prominent and diagnostic alteration styles at Sleeper. Early silicification, accompanied by pyrite, resulted in pervasive replacement of plagioclase phenocrysts and groundmass by opaline silica. Alunite occurs in some early silicified rocks, but possibly was a later addition. Silicification of several types accompanied ore stages. Late-stage silicification in the form of opal is controlled by post-ore faults and fractures and is barren of gold. This late opal typically contains abundant light-colored alunite, kaolinite, or jarosite. Small amounts of native sulfur are enclosed in the late silica. Hypogene argillic alteration occurs peripheral to zones of early silicification; commonly there is a transition zone from 3 to 50 m wide of clay-altered plagioclase in silicified groundmass. The broad argillized zones are barren of Ag and Au, and contain little sulfide and no silica veinlets. Feldspar phenocrysts and aphanitic groundmass in argillized zones commonly are altered to clay minerals, most commonly kaolinite, smectite, and illite. Plagiocalse phenocrysts have been replaced by fine-grained clay minerals and alunite. Sanidine is locally altered to sericite or kaolinite. Groundmass is generally altered to very fine grained silica-clay mixtures. Thoroughly acid-leached rocks with sponge-like texture of more than 90% silica occur in local zones along post-ore faults. Subsequently, opal, alunite, and jarosite were deposited in the porous rocks. \nThe prominent red coloration of upper pit walls reflects supergene destruction of sulfides and local redistribution of iron into fractures. Pyritic tuffs have been oxidized to tan alunite+jarosite+limonite-bearing mixtures. Feldspars are altered to white clays along open fractures and voids later filled by phases of unusual composition, some rich in Cl (as NaCl and AgCl), and various combinations of Al, Mn, and Co As oxides or sulfates. \n\nPropylitically altered tuffaceous sediments, andesitic lava flows, and metasedimentary basement rocks underlie the rhyolitic host rock.

Economic & production

Development statusProducer

Production years1986 - 1996

First production1986

Last production1996

Discovery year1982

Identification

Deposit ID10310319

MRDS IDW700408

Alternate namesWest Wood, Bedrock Casino, Northeast areas, Sleeper Pit, Wood Pit

RegionNA

Data scoreA

Coordinates41.3338, -118.0524

References

Quade, Jack, 1985 - Attempted field examination report (locked gate, guard).Nash, J.T., Utterback, W.C., and Saunders, J.A., 1991, Geology and Geochemistry of the Sleeper Gold Deposits, Humboldt County, Nevada, an interim report, in Raines, G.L., et al., eds., Geology and Ore Deposits of the Great Basin, The Geological Society of Nevada, Reno, p. 1063-1084.Amax Annual Corporate Report for 1990, p. 18-19.Wood, J.D., 1988, Geology of the Sleeper Gold Deposit, Humboldt County, Nevada, in Schafer, R., et al., eds., Bulk Mineable Precious Metal Deposits of the Western United States, The Geological Society of Nevada, Reno, p. 293-302.Wood, J.D., 1987, Technical Aspects of the Sleeper Gold Discovery, Nevada, in Mining Technology and Policy Issues: 1986 International Mining Show, Las Vegas, Nevada, American Mining Congress, Washington, D.C., 3 pp.Mining Magazine, January, 1989, p. 44.Staff, 1988, Directory of Nevada Mine Operations Active During Calendar Year 1987: Nevada Division Of Mine Inspection, 84 pMetal Market Consultants, Inc., 1987, Gold Situation Map.Minesearch Annual, 1984-1985, Vol. VII, p. 418-420; Metals Economics Group, Boulder, Co.Bonham, H.F., 1986, NBMG Field Examination Report, 5/86, and sample analyses.Bonham, H.F., 1986, NBMG Map 91.Bonham, H.F., 1988, in NBMG MI-1987.NBMG Mining District File 123, Numerous Press Clippings and news releasesNBMG, 1994, MI-1993-2002Nevada Division of Minerals, 1994Mining Record, March 24, 1993Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Database of significant deposits of gold, silver, copper, lead, and zinc in the United States; Part A, Database description and analysis; part B, Digital database: U.S. Geological Survey Open-File Report 98-206, 33 p., one 3.5 inch diskette.Saunders, James, 1994, Silica and gold textures in Bonanza Ores of the Sleeper Deposit, Humboldt County, Nevada: Econ. Geol. vol 89, pp. 628-638.http://www.x-cal.com/sleeper.htmCrafford, A.E.J. (ed.), 2003, GSN Road Log 2, Interstate 80 Eastbound, Fernley (Exit 48) to Golconda (Exit 194).AMAX GOLD INC FORM 10K, 3/29/90AMAX GOLD INC FORM 10K, 3/30/89AMAX GOLD INC PROSPECTUS, 7/87DEMULL, THOMAS J. ORE PROCESSING AT AMAX GOLD'S SLEEPER MINE, 12/87.NEV. DIV. MINE INSPECTION, 1991, DIRECTORY OF NEVADA MINE OPERATIONS ACTIVE DURING CALENDAR YEAR 1990, P. 45.HAMILTON, S. K. AND J. D. WOOD. THE SLEEPER GOLD-SILVER DEPOSIT DISCOVERY THROUGH FEASIBILITY, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES. NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.POOLER, A. F. ENGINEERING AND OPERATIONS AT AMAX GOLD'S SLEEPER MINE, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES. NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.STANFORD, W. D., AND T. J. DEMULL. AMAX GOLD'S SLEEPER MINE DEVELOPMENT AND CONSTRUCTION, IN ASSAYS TO ASSETSUTTERBACK, W. C. GEOLOGY OF THE SLEEPER GOLD DEPOSIT, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES.AMERICAN MINES HANDBOOK, 1996, PP. 19, 20, 21.RANDOL MINING DIRECTORY, 1994/95, U.S. MINES & MINING COMPANIES, P351.RANDOL MINING DIRECTORY, 1996/97, U.S. MINES & MINING COMPANIES, P272.1995/96, NEVADA MINES DIRECTORY, PP. 2, 25.THE NORTHERN MINER, VOL., #9, APRIL 28, 1997, P10.AMAX GOLD INC., 1996 FORM 10-K, P8, AND ANNUAL REPORT.AMAX GOLD INC., 1995 ANNUAL REPORT; & FORM 10-K REPROT.