Commodities
PrimarySilver, Gold
SecondaryZinc, Lead, Copper
Commodity typeM
Deposit
Deposit typefault zone
Model129: Detachment-fault-related polymetallic Cu-Au-Ag-Pb-Zn deposits
Deposit sizeS
Orebody formsubhorizontal lenses
Ore controlOre is associated with shear zones dating from a period of regional extensional faulting about 15-10 Ma.
Materials
Ore mineralsGold
GangueQuartz, Calcite, Hematite, Clay
Geology
Host rockMonzonite,Mafic Intrusive Rock,Andesite,Dacite · "Nelson Monzonite", "Patsy Mine Volcanics"
Associated rockGneiss,Schist
StructureThe northern Eldorado Mountains are characterized by many west-dipping listric normal faults which sole into a west-dipping detachment, all formed about between 15 and 10 Ma due to regional extension. The structural style changes markedly in the southern Eldorado Mountains, where Tertiary volcanic strata dip west and are cut by east-dipping listric faults. The Eldorado Canyon and mining district are located between the two structurally distinct areas and represent an ?accommodation zone?., The deposit is bounded on all sides by post-mineral, high-angle faults.
Tectonic settingThe deposit is situated within a probable structural ?accommodation zone? marking the boundary between different styles of faulting in the northern El Dorado mountains and the southern portion of the range.
AlterationPropylitic alteration is widespread throughout the host rocks. Anomalous gold also occurs in zones of local silicification, argillic alteration, and quartz-alunite veining.
Economic & production
Development statusPast Producer
First production1863
Last production1970
Discovery year1857
Identification
Deposit ID10310510
MRDS IDM031039
Alternate namesWBG deposit (Wall Street-Black Hawk-Gracey)
RegionNA
Data scoreB
Coordinates35.71, -114.84082
References
Koschmann and Bergendahl, 1968Longwell and others, 1965Robinson, J.P., 1996, in Coyner, A.R., and Fahey, P.L., eds., Geology and ore deposits of the American Cordillera, 1995; symposium proceedings: Reno, Geological Society of Nevada, v. 1, p. 567-579Wyman, R.V., 1987, in Johnson, J. L., ed., Bulk Mineable Precious Metal Deposits of the Western United States, Geological Society of Nevada, p. 109-113.AMH 1997 entry for Nelloro Corp.Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Significant deposits of gold, silver, copper, lead, and zinc in the United States: U.S. Geological Survey Open-File Report 90-206A, 33 p.; 98-206B. one 3.5 inch diskette.