California · Napa, Yolo County
Producer

McLaughlin Mine

Napa, Yolo County, California, United States
SilverGoldMercuryZincLeadCopperThalliumArsenicAntimonyIron
⌖ Show on mapUSGS source ↗
Commodities
PrimarySilver, Gold
SecondaryMercury
TertiaryZinc, Lead, Copper, Thallium, Arsenic, Antimony, Iron
Commodity typeM
Deposit
Deposit typeHot spring; hydrothermal vein
Model104: Hot-spring Au-Ag
Orebody formWedge
Ore controlBoth precious-metal and cinnabar mineralization in the deposit are controlled by association with the Stony Creek Fault. The fault served as a pathway for migration of mafic magmas and metal-bearing hydrothermal fluids as well as a locus of dilational fractures, which were eventually filled with silicic veins.
Materials
Ore mineralsElectrum, Pyrargyrite, Gold, Pyrite, Miargyrite, Freibergite, Polybasite, Cinnabar, Metacinnabar, Mercury, Chalcedony, Quartz, Adularia, Alunite, Stibnite, Arsenic, Realgar, Orpiment, Arsenopyrite, Sphalerite, Chalcopyrite, Galena
GangueOpal
Geology
Host rockSerpentinite,Mudstone,Tectonic Melange,Basalt,Andesite,Mixed Clastic/Volcanic Rock · "Coast Range Ophiolite", "Knoxville Formation", "Clear Lake Volcanics"
StructureStony Creek Fault\n\nOR (alternatively)\n\nThe segment of the Stony Creek Fault associated with the ore deposit dips moderately (30o-45o) to the northeast, although it is near vertical along strike to the northwest and southeast of the deposit. Tosdal and others (1996) believed that the precious-metal-bearing veins associated with the fault formed during two distinct stages, which resulted from a major change in the regional stress field. The first stage produced a local pressure shadow in the fault zone, which was invaded by hydrothermal fluids to form the high-grade sheeted vein complex. The second stage produced a larger but lower-grade set of veins spread over a 6,000-foot segment of the fault zone. The metalliferous veins are mostly within the tectonic melange in the immediate footwall side of the fault, although some mineralization is present in hydrothermally Knoxville Formation on the immediate hanging wall side of the fault. Width of the deposit appears to be restricted to the southwest by a large mass of serpentinite melange in the footwall and to the northeast by non-altered Knoxville Formation in the hanging wall. Vein thicknesses range from less than an inch to about two feet, but typically are no more than six inches. In general, stage 1 veins strike northeasterly, while stage 2 veins strike southeasterly., Changes from barren rock to high-grade ore were notably very abrupt. Ore grade was observed to correlate more with density of veins rather than type of veins; the sheeted vein complex was notable for its multiple episodes of cross-cutting (at least five have been recognized). The main ore body extended to about 1,000 feet depth, although Sherlock and others (1995) show detected gold down to at least 1,600 feet.
Tectonic settingCollision transform fault
AlterationEarly Phase: \nSilica-Carbonate; quartz, chalcedony, calcite, dolomite \n\nCoeval Phase: \nSilicic; quartz, chalcedony, opal\nPotassic; adularia\nSericitic; sericite\nArgillic; montmorillonite\nAdvanced argillic; alunite\n\nLate Phase: \nArgillic; kaolinite, marcasite, barite\n
Economic & production
Development statusProducer
Discovery year1978
Identification
Deposit ID10310645
Alternate namesManhattan
RegionNA
Data scoreA
Coordinates38.83705, -122.3613
References
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