Mine detail: Bald Mountain Mine

Previously called 'North Area DepositsPit 1Pit 2Pit 3Pit 5BF Claim GroupOne-Five depositTwo-Three deposit'

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Location

Lat / long:

39.96659, -115.59589

Resource(M)

Primary:	Gold, Silver
Tertiary:	Zinc, Arsenic, Antimony, Mercury, Bismuth, Tellurium, Copper
Ore:	Gold
Gangue:	Quartz, Pyrite, Marcasite
Orebody form:	pipe-like to tabular
Discovery year:	1977

Production

Operation type:	Surface
Deposit type:	sediment-hosted gold
Production size:	Large
Development status:	Producer
Production years:	1983; 1985 - present 2006
First production started:	1983

Geology

Host rock:	Dunderberg Shale, Secret Canyon Shale, Carlin member, Windfall Formation
Host type:	Shale,Limestone,Porphyry,Dolomite
Associated rock:	Bald Mountain Stock
Associated type:	Granite
Structure:	The Bald Mountain district is located in an area of thinned crust along the eastern side of the Late Proterozoic rift that split the North American craton. It is also in the west-central portion of the Late Devonian-Early Mississippian Antler foreland basin, and near the eastern edge of deformation related to the late Paleozoic Humboldt orogeny. To the west of the Bald Mountain district, geologic interpretations are dominated by recognition of Paleozoic deformation, whereas to the east, interpretations emphasize Mesozoic contraction and plutonism and Tertiary extension., The Bald Mountain district is disrupted by structures that range in age from Jurassic to Quaternary faults that cut alluvial fans. Neogene extensional faults that in part reactivated older structures dominate the present-day topography. High-angle normal faults bound the north- to northeast-trending basins that characterize the area and form a series of horsts and grabens. The dominant structural trend is N45W, but there are NE-, N-S, and E-W-trending structures as well. Intense pre- and post-mineral faulting at Bald Mountain has resulted in a complex structural setting, dominantly controlled by intersecting NW and NNE trending deep crustal features
Tectonic:	The Bald Mountain district is located in an area of thinned crust along the eastern side of the Late Proterozoic rift that split the North American craton. It is also in the west-central portion of the Late Devonian-Early Mississippian Antler foreland basin, and near the eastern edge of deformation related to the late Paleozoic Humboldt orogeny.
Alteration processes:	Alteration consists predominantly of silicification, argillization, and potassic alteration. The main alteration feature at Bald Mountain is the large halo of silicification and strong argillization. Potassic alteration is recognized at depth. In the North area deposits, the sedimentary rocks are variably hornfelsed and were locally pervasively argillized. Siliciclastic rocks are decalcified within ore zones with minor silicification adjacent to ore zones. Pervasive secondary iron oxides resulted from the oxidation of marcasite and pyrite in the host rocks. Higher grade ore is indicated by chocolate-brown goethite.

References

MRDS	M233723
DEP	10310370
Reference	{Deposit:: The Geological Society of Nevada 1996 Spring Field trip, Geology and Gold Deposits of Eastern Nevada, GSN Special Publication No. 23.}{Deposit:: Hose, Blake, and Smith, 1976, Geology and Mineral Resources of White Pine County, Nevada, NBMG Bulletin 85.}{Deposit:: Hill, J. M., 1916, Notes on some Mining Districts in Eastern Nevada, USGS Bull. 648, p. 152-161.}{Deposit:: Dean, D. A., Benedetto, K. M. F., Durgin, D. C., 1991, Part Two: Ely - Bald Mountain - Ely Road Log, in Buffa, R. and Coyner, A., eds., Geology and Ore Deposits of the Great Basin - Field Trip Guidebook Compendium, The Geological Society of Nevada, Reno, p. 136-162.}{Deposit:: Lowe, N. T., Raney, R. G., and Norberg, J. R., Principal Deposits of Strategic and Critical Minerals in Nevada, USBM Information Circular 9035, p. 75.}{Deposit:: A Study of Active U. S. Gold Mines, July, 1986, Metals Economics Group, Boulder, Co, p. 288-291.}{Deposit:: Placer Dome Inc., Annual Report for 1987.}{Deposit:: Placer Dome Inc., Annual Report for 1988.}{Deposit:: Placer Dome Inc., Annual Report for 1989.}{Deposit:: Placer Dome Inc., Annual Report for 1990.}{Deposit:: Bonham, H., Bentz, J., and Smith, P., 1981, Field Examination, June 28, 1981.}{Deposit:: NBMG, 1982, Open File Report 82-9.}{Deposit:: Pay Dirt, Oct, 1982.}{Deposit:: Nevada Mining Association Bulletin, 1983.}{Deposit:: Division of Mine Inspection, 1983, Directory of Nevada Mining Operations Active During Calendar Year 1983.}{Deposit:: Jones and Papke, 1984, Active Mines and Oil Fields in Nevada - 1983, NBMG Map M84.}{Deposit:: NBMG, 1994, MI-1993}{Deposit:: Long, 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. NBMG MI-2002}{Deposit:: Royal Gold Inc. press release, March 2003.}{Deposit:: Adella Harding, Elko Daily Free Press Mining Quarterly, Fall 2002.}{Deposit:: Nutt, C.J., Hofstra, A.H., Hart, K.S., and Mortensen, J.K., 2000, Structural setting and genesis of gold deposits in the Bald Mountain-Alligator Ridge area, east-central Nevada, in Cluer, J.K., Price, J.G., Struhsacker, E.M., Hardyman, R.F., and Morris, C.L., eds., Geology and Ore Deposits 2000: The Great Basin and Beyond: Geological Society of Nevada Symposium Proceedings, May 15-18, 2000, p. 513-537.}{Deposit:: Hitchborn and others, 1996, Geology and Gold Deposits of the Bald Mountain Mining District, White Pine County, Nevada, in Geology and Ore Deposits of the American Cordillera Symposium Proceedings, eds. A. Coyner and P. Fahey.}{Deposit:: BLM, 2004, Bald Mountain Mine Exploration Program Programmatic Environmental Assessment NV040-04-023, Case File # N78825.}
Reporter	LaPointe, D. D. , Schruben, Paul G.