Zeibright Mine

Site Name

Primary: Zeibright Mine

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Commodity

Primary: Gold
Secondary: Copper

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Location

State: California
County: Nevada
District: Emigrant Gap District

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Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.
Administrative Organization: Nevada County Planning Department

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Donner Mine Camp, Incorporated
Info Year: 2007

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Hydrothermal vein
Operation Type: Underground
Discovery Year: 1890
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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Physiography

Not available

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Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

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Orebody

Form: Tabular

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Structure

Type: R
Description: Melones Fault Zone

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Alterations

Alteration Type: L
Alteration Text: None specifically reported, although there is a vague reference by MacBoyle (1919) to the slate wallrock being ?slightly changed at contact with the ledge.?

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Rocks

Name: Volcanic Rock (Aphanitic)
Role: Host
Description: dike
Age Type: Host Rock
Age Young: Mesozoic

Name: Slate
Role: Host
Age Type: Host Rock
Age Young: Devonian
Age Old: Ordovician

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Pyrite
Ore: Chalcopyrite
Ore: Pyrrhotite
Gangue: Quartz

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Comments

Comment (Development): The mine is known to have been in operation in 1902 based on a report in the Mining and Scientific Press (1902). The name was derived from the first mine owners, F. Zeitler and W.F. Englebright. From 1918 to 1934, the Zeibright Mine was operated by the Bear Valley Mining Company. According to records filed in the Online Archive of California (http://oac.cdlib.org/), the mine was subsequently owned and operated by the Empire Star Mines Company and Newmont from 1934 to the 1950?s. It was worked extensively during the 1930?s when large tonnages of low-grade ore were mined. These tonnages included 10,285 in 1934, 129,866 in 1936, and 260,479 in 1939. There were approximately 200 employees in 1939. In 1940, a tailings dam failed (this facility was possibly at the Omega Diggings, about three miles northwest of the mine), which caused suspension of mining and milling, although development of ore bodies continued. For many years, the mine property has been operated as a camp for youth groups. A clean-up operation at the property was ordered by the U.S. EPA in 2006 to remove lead and arsenic contamination at the site?s former assay building. (http://www.epa.gov/compliance/resources/newsletters/cleanup/cleanup29.pdf) Amalgamation, flotation, and cyanidation processes were used at this mine.

Comment (Economic Factors): Clark (1970) estimated production at the Zeibright Mine to be in excess of $1 million. There was significant production during the 1930?s.

Comment (Geology): Structure Most Upper Jurassic and older basement rocks of the northern Sierra Nevada were metamorphosed and deformed during the Jurassic-Cretaceous Nevadan Orogeny. Deformation features in the lithotectonic blocks of the northern Sierra Nevada are best developed in the Eastern, Central, and Feather River Peridotite Belts, where they have been collectively described as the "Foothills Fault System" (Clark, 1960). Compressive deformation produced northwesterly trending faults, folds, and regional greenschist facies metamorphism (Harwood, 1988). Many of the intrusive granitic plutons of the Sierra Nevada were also part of this compressive episode. Most of the dominant faults dip steeply east and display reverse displacement. Regionally, the metamorphic rocks display northerly trending and steeply dipping foliation, bedding, and contacts. LOCAL GEOLOGY The Zeibright Mine is situated within the metasedimentary terrane of the Lower Paleozoic Shoo Fly Complex. The ore deposit consists of a quartz vein-dike complex that is emplaced in slate wallrock. The vein complex reportedly is nearly perpendicular in orientation and averages about 20 feet in width. On his economic geology map of the Colfax folio, Lindgren (1900) showed two north-trending quartz veins very near the deposit at the Zeibright Mine. The vein complex at the Zeibright Mine may be of similar strike. It appears to be part of a regional group of northerly trending veins that extends from Blue Canyon northward through the Washington and Graniteville mining districts. According to Logan (1941), the ore is present in an ?impregnated dike? that carries bands of quartz on both walls; there was no ore outside the dike. Besides native gold, the ore deposit contains auriferous pyrite, chalcopyrite, and pyrrhotite. Concentrations of the sulfides are not known, but are assumed to be low. MacBoyle (1919) reported an ore shoot that extended at least 400 feet down-dip and had a length on the vein of about 160 feet.

Comment (Environment): The Zeibright Mine is situated in a forested area on the north slope of the canyon of the Bear River.

Comment (Workings): According to Logan (1941), the vein was initially developed by adits, one of which was 990 feet long. Subsequent mining was accomplished through a vertical shaft that reached 1,750 feet in 1940 (the current depth may be about 1,900 feet). Stoping at that time reached a depth of 800 feet.

Comment (Geology): REGIONAL GEOLOGY The northern Sierra Nevada is home to numerous lode and placer gold deposits. It includes the famous lode districts of Alleghany, Johnsville, Sierra City, Grass Valley, and Nevada City and the famous placer districts of La Porte, North Columbia, Cherokee, Michigan Bluff, Forest Hill, and Dutch Flat. The geological and historical diversity of most of these deposits and specific mine operations are covered in numerous publications produced over the years by the U.S. Bureau of Mines, U.S. Geological Survey, California Division of Mines and Geology (now California Geological Survey), and others. A regional geologic map covering the area is the 1:250,000-scale Chico Quadrangle compiled by Saucedo and Wagner (1992). Schweickert and others (1999) provided a more recent overview of the region.

Comment (Deposit): The Zeibright Mine is situated within the metasedimentary terrane of the Lower Paleozoic Shoo Fly Complex. The ore deposit consists of a quartz vein-dike complex that is emplaced in slate wallrock. The vein complex reportedly is nearly perpendicular in orientation and averages about 20 feet in width. It is assumed to have a northerly strike, similar to a regional group of veins that extends from Blue Canyon northward through the Washington and Graniteville mining districts. The ore is reportedly present in an ?impregnated dike? that carries bands of quartz on both walls; there appears to be no ore outside the dike. Besides native gold, the ore deposit contains auriferous pyrite, chalcopyrite, and pyrrhotite. Concentrations of the sulfides are not known, but are assumed to be low. MacBoyle (1919) reported an ore shoot that extended at least 400 feet down-dip and had a length on the vein of about 160 feet.

Comment (Geology): Stratigraphy The northern Sierra Nevada basement complex has a history of both oceanic and continental margin tectonics recorded in sequences of oceanic, near-continental, and continental volcanism and sedimentation that have been divided into four lithotectonic belts; the Western Belt, Central Belt, Feather River Peridotite Belt, and Eastern Belt (Day and others, 1988). The Western Belt is composed of the Smartville Complex, a late Jurassic volcanic arc complex (Beard and Day, 1987), consisting of basaltic to intermediate pillow flows overlain by pyroclastic and volcaniclastic rock units with diabase, metagabbro, and gabbro-diorite intrusives. The Cretaceous Great Valley sequence overlies the belt to the west, and to the east it is bounded by the Big Bend-Wolf Creek Fault Zone. East of the Big Bend-Wolf Creek Fault Zone is the Central Belt, which is in turn bounded to the east by the Goodyears Creek Fault and its extension to the south along the west side of the Feather River Peridotite Belt. This belt is structurally and stratigraphically complex and consists of metasedimentary, metavolcanic, and plutonic rocks of Paleozoic to Mesozoic age, including a sliver of Calaveras Complex on its east side. The Feather River Peridotite Belt separates the Central Belt from the rocks of the Eastern Belt for almost 95 miles along the northern Sierra Nevada (Day and others, 1988). Its eastern margin coincides with the Melones Fault Zone of Clark (1960). Much of the ultramafic intrusives have been serpentinized. The Eastern Belt, or "Northern Sierra Terrane," is composed primarily of Devonian-to-Jurassic metavolcanic rocks, siliciclastic metasedimentary rocks of the Lower Paleozoic Shoo Fly Complex, and Mesozoic granitic rocks of the Sierra Nevada batholith. The Upper Devonian-Jurassic rocks unconformably overly the Shoo Fly Complex and are of island-arc origin (Brooks, 2000). They consist of the Devonian-Permian Taylorsville Sequence, Permian-Triassic Arlington, Goodhue, and Reeves Formations, and the Jurassic Sailor Canyon Formation. The Zeibright Mine is within the Shoo Fly Complex. Regionally, the northern Sierra Nevada experienced a long period of Cretaceous to early Tertiary erosion, after which it underwent extensive Oligocene to Pliocene volcanism. The oldest Tertiary units are basal Eocene auriferous gravels, preserved in basement paleochannels, and associated bench gravels deposited by the predecessors of the modern Yuba and American Rivers. In contrast to the earlier volcanism, Tertiary volcanism was continental and deposited on top of the eroded metamorphic rocks, channel deposits, and Mesozoic intrusives. An important widespread unit of intercalated rhyolite tuffs and intervolcanic channel gravels is the Oligocene-Miocene Valley Springs Formation. The youngest volcanic unit, the Miocene-Pliocene Mehrten Formation, consists largely of andesitic flows and breccias overlying the Valley Springs Formation. Pliocene-Pleistocene westward uplift of the Sierra Nevada caused existing drainages to carve deep river gorges. During this process, the modern rivers became charged with placer gold deposits from both newly eroded basement rocks and from the reconcentration of the Eocene placers. The discovery of these modern Quaternary placers in the American River is what sparked the California Gold Rush.

Comment (Commodity): Ore Materials: Native gold and auriferous sulfides (pyrite, chalcopyrite, and pyrrhotite)

Comment (Commodity): Gangue Materials: Quartz, dike rock

Comment (Identification): There are two ?Zeibright? mines, one on the USGS 7.5-minute Blue Canyon quadrangle and the other on the Washington quadrangle. The deposit described here refers to that on the Blue Canyon quadrangle. This mine is considered the more significant of the two.

Comment (Location): Location selected for latitude and longitude is the Zeibright Mine adit symbol adjacent to the Bear River as shown on the USGS 7.5-minute Blue Canyon quadrangle.

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References

Reference (Deposit): Beard, J. S. and Day, H. W., 1987, The Smartville intrusive complex, Sierra Nevada, California: The core of a rifted volcanic arc: Geological Society of America Bulletin, v. 99, no. 6, p. 779-791.

Reference (Deposit): Brooks, E. R., 2000, Geology of a late Paleozoic island arc in the Northern Sierra terrane, in Brooks, E. R. and Dida, L.T., editors, Field guide to the geology and tectonics of the northern Sierra Nevada: California Division of Mines and Geology Special Publication 122, p. 53-110.

Reference (Deposit): Clark, L. D., 1960, Foothills fault system, western Sierra Nevada, California: Geological Society of America Bulletin, v. 71, p. 483-496.

Reference (Deposit): Clark, W.B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 45-46.

Reference (Deposit): Day, H. W. and others, 1988, Metamorphism and tectonics of the northern Sierra Nevada, in Ernst, W. G., editor, Metamorphism and crustal evolution of the western United States (Rubey Volume VII): Prentice-Hall, Englewood Cliffs, New Jersey, p. 738-759.

Reference (Deposit): Harwood, D.S., 1988, Tectonism and metamorphism in the northern Sierra Terrane, northern California, in Ernst, W. G., editor, Metamorphism and crustal evolution of the western United States (Rubey Volume VII): Prentice-Hall, Englewood Cliffs, New Jersey, p. 764-788.

Reference (Deposit): Lindgren, W., 1900, Colfax folio, California: U.S. Geological Survey Atlas of the U.S., Folio 66, 10 p.

Reference (Deposit): Logan, C.A., 1941, Nevada County: 37th Annual Report of the State Mineralogist, California Journal of Mines and Geology, p. 431.

Reference (Deposit): Schweickert, R.A., Hanson, R.E., and Girty, G.H., 1999, Accretionary tectonics of the Western Sierra Nevada Metamorphic Belt, in Wagner, D.L. and Graham, S.A., editors, Geologic field trips in northern California: California Division of Mines and Geology Special Publication 119, p. 33-79.

Reference (Deposit): Saucedo, G.J. and Wagner, D.L., 1992, Geologic map of the Chico Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 7A, scale 1:250,000.

Reference (Deposit): MacBoyle, E., 1919, Nevada County: 16th Annual Report of the State Mineralogist, California State Mining Bureau, p. 260-261.

Reference (Deposit): Mining and Scientific Press, 1902, Placer County: Mining and Scientific Press, v. 85, no. 10, p. 135.

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