Geology
Host rockChert,Argillite,Limestone,Siltstone,Quartzite,Shale · Havallah Formation
Associated rockGranodiorite,Ash-Flow Tuff,Alluvium
StructureThe Havallah Sequence of the Buffalo Valley Mine has a homoclinal appearance. With certain exceptions, beds strike NW to slightly east of north and generally dip 45-65 SW or West. Buffalo Valley Mine is situated in a fault block that is bounded on the east by the western range-bounding fault of Battle Mountain and on the west by another west-dipping normal fault, which is known locally as the Front Fault., Golconda Thrust
AlterationContact metamorphic effects in the upper structural unit of the Havallah Sequence: non-calcareous silty lithologies are converted to biotite hornfels; slightly calcareous, siliceous and argillaceous siltstones are metamorphosed to calc-silicate hornfelses (diopside + quartz plagioclase, clinozoisite, epidote). Sulfides are restricted to later fractures. Endoskarn: sulfide-poor calc-silicate mineral assemblages which occur as alteration products of porphyry dikes are common west and southwest of the open pit, rare in the open pit, and absent east and north of the pit. In some hand specimens, endoskarn alteration can be observed as envelopes about individual quartz veins, e.g. plagioclase-quartz-pyroxene-bearing inner envelopes (hornblende destroyed) and relict hornblende-stable outer envelopes. Potassic alteration: shreddy hydothermal biotite is abundant in dikes in the open pit and the degree of biotization is independent of proximity to quartz veins. Prograde skarn: a few unequivocal but rare examples of coarse grained garnet-pyroxene skarn have been exposed in the center of the open pit, interbedded with calc-silicate hornfels. These skarns contain pyrite, although it is unclear whether it was deposited synchronous with skarn silicates. Retrograde skarn: pyroxene hornfels and less commonly basalt and biotite hornfels locally are intensely altered to dark green chlorite, pyrite, and nontronite(?). This assemblage has been reported to carry free gold.
References
Roberts, R.J., and Arnold, D.C., Ore Deposits of the Antler Peak Quadrangle, Humboldt and Lander Counties, Nevada: U.S.G.S. Prof Paper 459-B.Quade, J. and Bentz, J.; Field Exam May 11, 1982Seedorff, E., Bailey, C. R. G., Kelley, D., and Parks, W., 1991, Buffalo Valley Mine: a Porphyry-Related Gold Deposit, Lander County, Nevada, 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. 969-987.Horizon Gold Shares Inc., Annual Report for 1987.Horizon Gold Shares Inc., Annual Report for 1988.Horizon Gold Shares Inc., Annual Report For 1989.Horizon Gold Shares Inc., Form 10-K for 1990.Horizon Gold Shares Inc., Form 10-K for 1991.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.Johnston, Ivan, and others, 1999, Geology and gold mineralization of the Buffalo Valley area, northwestern Battle Mountain Trend; Trenton Canyon Mine; North Peak Mine; Buffalo Valley Mine; Redline gold skarn deposit; Copper Canyon gold skarn, a review; Marigold Mine; Geological Society of Nevada, Special Publication, vol.31, 261 pp., 1999.Denver Mining Record, 9/14/94 and 11/30/94.Doebrich, Jeff, 1995, Geology and Mineral Deposits of the Antler Peak n7.5-minute quadrangle, Lander County, Nevada, NBMG Bull 109, 44 p.Geological Society of Nevada, 1999, Geology and Gold Mineralization of the Buffalo Valley Area, Northwestern Battle Mountain Trend; GSN Special Publication No. 31, 1999 Fall field trip Guidebook.