Nevada · Mineral County
Producer

Borealis Mine

Mineral County, Nevada, United States
GoldSilverZincCopperNickel
⌖ Show on mapUSGS source ↗
Description

S. W. Ivosevic of H.O.M.Co.

Commodities
PrimaryGold
SecondarySilver
TertiaryZinc, Copper, Nickel
Commodity typeM
Deposit
Deposit typevolcanic-hosted disseminated
Model104: Hot-spring Au-Ag
Deposit sizeM
Orebody formtabular to irregular
Ore controlOre-controlling features include NE-trending structures, fracturing, paleo-hot springs activity; and the intersection of 3 fault systems.
Materials
Ore mineralsGold, Cinnabar, Chalcopyrite, Chalcocite, Sphalerite, Covellite, Tetrahedrite, Tennantite, Enargite, Matildite, Nagyagite, Niccolite, Alunite, Feldspar, Barite, Pyrite, Hematite, Montmorillonite, Kaolinite, Marcasite, Arsenopyrite, Pyrrhotite
GangueQuartz
Geology
Host rockAndesite,Tuff,Volcanic Breccia (Agglomerate)
StructureMajor regional structural trends affecting the mine area are the Walker Lane shear zone and the Borealis Trend., NE-trending faults with subordinate N-S and E-W- striking structures.
AlterationHost rock alteration consists mainly of pervasive silicification, alunitization, kaolinization, oxidation, argillization, and propylitization. The conduit for hydrothermal fluids was a 100-200 ft. wide core zone of silica breccia with abundant iron oxide minerals. The silica breccia zone narrows downward and grades downward into oxidized quartz-sulfide and unoxidized quartz-pyrite alteration. Argillic and propylitic alteration zones develop outward from core. Barren opal and chalcedonic silica overlie deposit.
Economic & production
Development statusProducer
Production years1981-1990
First production1981
Last production1990
Discovery year1930
Identification
Deposit ID10310350
MRDS IDM035782
Alternate namesDeep Ore Flats, East Ridge, Freedom Flats, Gold View, Graben, Jaimes Ridge, Northeast Ridge orebodies
RegionNA
Data scoreB
Coordinates38.38325, -118.75957
References
Reid, R. F., Jr., 1984, The geology of the Borealis deposit: GSA Abstracts with Programs, 97th Ann. Mtg, Reno, NV.NBMG Mining District File 200, Items 8, 9, Press Clippings.Tooker, E.W., 19?, In USGS Bull 1646.Strachan, D.G., 19?, Geologic Discussion of the Borealis Gold Deposit, Mineral Co., Nevada, in USGS Bull 1646.Bulk-Mineable Precious Metals Symposium, 1987, Field Trip Guidebook.NBMG, 1994, MI-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.Golden Phoenix Co. website, 2006.Gryphon Gold website, 2006.Struhsacker, Eric, guidebook editor, 1994, Geological Society of Nevada Special Publication #20, Gold Deposits of the Central Walker Lane, Nevada: mineralization Style and Mine Closure Planning.Eng, T., 1991, Geology and Mineralization of the Freedom Flats Gold Deposit, Borealis Mine, Mineral County, in Raines and others, Geology and Ore Deposits of the Great Basin, Symposium Proceedings, Reno, NV: Geological Society of Nevada, v. 2, p. 995-1019.