Camanche District

Site Name

Primary: Camanche District

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Commodity

Primary: Gold
Secondary: Platinum
Secondary: Silver

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Location

State: California
County: Amador
District: Camanche

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Land Status

Land ownership: Federal
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: U.S. Bureau of Reclamation

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: U.S. Bureau of Reclamation.

Owner Name: Various private owners

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Production

Not available

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Deposit

Record Type: District
Operation Category: Past Producer
Deposit Type: Stream placer
Operation Type: Surface
Discovery Year: 1849
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: Placer Au-PGE

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Orebody

Form: Irregular

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Structure

Type: R
Description: Bear Mountains fault zone, Melones fault zone

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Alterations

Not available

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Rocks

Name: Gravel
Role: Host
Description: Stream
Age Type: Host Rock
Age Young: Quaternary

Name: Gravel
Role: Host
Description: terrace and shoreline
Age Type: Host Rock
Age Young: Tertiary

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Analytical Data

Not available

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Materials

Ore: Gold
Gangue: Zircon
Gangue: Garnet
Gangue: Quartz
Gangue: Magnetite
Gangue: Ilmenite

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Comments

Comment (Development): Placer gold deposits in the creeks of the Camanche district were first worked during the early years of the gold rush and hydraulic mining of the terrace gravels followed. The town of Comanche was named for a town in Iowa. Later, the Chinese mined the river gravels and reworked the old tailings. From 1904 to 1923, the American Dredging Company operated three bucket-line dredges on the Mokelumne River. Several dredging operators worked the gravels afterward, including Camanche Placers, Ltd (1931-?, one bucket-line), Gold Gravel Products (1935), Gold Hill Dredging Co. (1936-1951, two bucket-lines), Lancha Plana Gold Dredging Co. (1926-1940, one bucket-line), and Wallace Dredging Co. (1935-1940, two bucket-lines) (Clark, 1970). Dredging operations ended in 1951.

Comment (Commodity): Ore Materials: Placer Gold

Comment (Commodity): Gangue Materials: Quartz, igneous and metamorphic gravels, magnetite, ilmenite, zircon, and garnet

Comment (Deposit): The Camanche district is noted for its rich placer gold deposits within river and floodplain gravels of the modern Mokelumne River. The placer gold was derived from erosion of bedrock gold-quartz veins in the Mother Lode and East Gold belts of the Sierra Nevada and from reworked auriferous gravels deposited by the ancestral Tertiary Mokelumne River. Gravel deposits were generally 6 to 50 feet deep and of low grade, yielding 10 to 25 cents per yard. Dragline and bucket dredging were the principal means of mining.

Comment (Economic Factors): No information is available regarding the early placer production in the Comanche district. Production from the later dredging operations conducted in the 1900s is estimated to be about $10 million (Clark, 1970). Values recovered by dredging ranged from 10 to 25 cents per yard.

Comment (Location): Location selected for latitude and longitude is the community of Camanche on the USGS 7.5 minute Wallace quadrangle

Comment (Geology): REGIONAL GEOLOGY The Camanche District is within the Sierra Nevada foothills, where bedrock consists of north trending tectonostratigraphic belts of metamorphosed sedimentary, volcanic, and intrusive rocks that range in age from late Paleozoic to Mesozoic. Locally, the Mesozoic rocks are capped by erosional remnants of Eocene auriferous gravels and once extensive volcanic rocks of Tertiary age. The structural belts, which extend about 235 miles along the western side of the Sierra, are flanked to the east by the Sierra Nevada Batholith and to the west by sedimentary rocks of the Cretaceous and Jurassic Great Valley sequence. The structural belts are internally bounded by the Melones and Bear Mountains fault zones. All the belts are characterized by extensive faulting, shearing, and folding. In Amador and Calaveras counties, rich mesothermal gold-quartz veins of the Mother Lode Belt are responsible for most of the gold produced. However, rich placer gravels of the ancestral Tertiary Mokelumne and Calaveras rivers and their current recent counterparts were also exploited, primarily by hydraulic mining and dredging respectively. The placer gold was derived from the upstream erosion of the Mother Lode and East Gold belt bedrock veins. Mother Lode Belt mineralization is generally characterized by steeply dipping gold-bearing quartz veins that traverse western El Dorado through Tuolumne counties. The Mother Lode veins are generally enclosed in Mariposa Formation slate with associated greenstone. The vein system ranges from a few hundred feet to a mile or more in width. Within the zone are numerous discontinuous or linked veins, which may be parallel, convergent, or en echelon. The veins commonly pinch and swell. Few can be traced more than a few thousand feet. Mother Lode type veins fill voids created within faults and fracture zones and consist of quartz, gold and associated sulfides, ankerite, calcite, chlorite, and sericite (Clark and Carlson, 1956). The Melones Fault zone separates the Mother Lode Belt from the East Gold Belt. The East Belt is dominantly argillite, phyllite and phyllonite, chert, and metavolcanic rocks of Paleozoic-Mesozoic age that have been assigned to the Calaveras Complex by most investigators. Lode deposits of the East Belt consist of many individual gold quartz veins within rocks of the Calaveras Complex, Shoo Fly complex, or in granitic rocks. Most of the veins trend northward and dip steeply. East Belt veins are smaller and narrower than those of the Mother Lode, but commonly are more chemically complex, and richer in grade. 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 of the Tertiary units are Eocene auriferous gravels, which were preserved in paleochannels eroded into basement and adjacent bench gravels deposited by the predecessors of the modern Mokelumne and Consumnes rivers. In contrast to the earlier volcanism, Tertiary volcanism was continental and deposited on top of the eroded basement 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 overlying the Valley Springs Formation.

Comment (Workings): Little specific information is available regarding the individual mining operations in the Camanche district. The earliest placer mining was by means of a miner's pan. By 1850, rockers were in use throughout the district. Rockers were quickly supplemented and replaced by the long tom. By the early 1850s, hydraulic mining became the dominant method of mining the gravels. Hydraulic mining persisted until the Sawyer Decision in 1884 severely curtailed hydraulic mining. While some hydraulic mining operations continued, this method of mining virtually ceased by 1905. In 1904, the American Dredging Company introduced bucket-line dredging of the unconsolidated Quaternary gravels. By the 1930s, dragline dredging came into prominence since it allowed the working of many small properties that were not rich or large enough to warrant the capital investment in a bucket-line dredge. Clark and Lydon (1962) and Logan (1927) provide a more detailed description of the equipment and techniques employed in each of these mining methods.

Comment (Identification): The Camanche district extends along the Mokelumne River from the former historic community of Lancha Plana in Amador County southwestward through the Camanche area to Clements in San Joaquin County, a distance of about 12 miles (Clark, 1970). Most of district was inundated under Comanche Reservoir when the Camanche Dam was constructed on the Mokelumne River in 1964. Auriferous Quaternary-age river and floodplain gravels deposited by the modern Mokelumne River were the principal deposits. As much as 50 feet thick, these low-grade gravels yielded 10 to 25 cents per yard and were largely exploited by dragline and bucket dredging operations between 1904 and 1951. Tertiary-age auriferous gravels of the ancestral Mokelumne River were also exploited by hydraulic mining methods until hydraulic mining was curtailed by the Sawyer decision in 1884. Tertiary gravels included ancient river gravels as well as deltaic and shoreline sands near the ancient river's mouth where it entered the Ione Sea. No information is available regarding the early placer production in the Camanche district. Production from the later dredging operations is estimated to be about $10 million (Clark, 1970). Values

Comment (Geology): Pliocene-Pleistocene uplift of the Sierra Nevada caused existing drainages to cut down through the volcanic Valley Springs - Mehrten sequence and carve deep river gorges into the underlying basement rocks. During this process, the modern rivers became charged with placer-gold deposits from both newly eroded basement rocks and from the reconcentration of the eroded Tertiary placers. The discovery of these modern Quaternary placers in the American River is what sparked the California Gold Rush, which led to the discovery of similar deposits in Mokelumne River gravels in the Camanche district. LOCAL GEOLOGY The principal placer deposits of the Camanche district consist of unconsolidated Quaternary gravels in and adjacent to the current Mokelumne River, its floodplain deposits and those of tributary streams. Secondary deposits included older terrace and Tertiary shoreline gravels associated with the ancestral Mokelumne River. In the western portions of the dredging fields, the gravels ranged from 6 to 50 feet deep while, in the east, they were 6 to 25 feet deep, averaging about 20 feet. The gravels are underlain by a false bedrock of volcanic lava ash and clay. Overburden consists of from one to ten feet of silt and soil. Values recovered by dredging ranged from 10 to 25 cents per yard. The gold was fine-grained and 850 to 900 in fineness (Clark, 1970). Associated with the gold are heavy, resistant minerals such as magnetite, ilmenite, zircon, and garnet, as well as minor amounts of silver and platinum-group metals.

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References

Reference (Deposit): Clark, W. B., 1955, San Joaquin County, Gold Hill dredges: California Journal of Mines and Geology, Vol. 51, no. 1, p. 37-39.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 33.

Reference (Deposit): Clark. W. B., and Lydon, P.A., 1962, Mines and mineral resources of Calaveras County, California: California Division of Mines and Geology County Report No. 2, p. 76-93.

Reference (Deposit): Logan, C.A., 1927, Calaveras County, American Dredging Compnay: California State Mining Bureau, 23nd Report of the State Mineralogist, p. 198.

Reference (Deposit): Winston, W.B., 1910, Gold Dredging in California, Calaveras County: California Mining Bureau Bulletin 57, p. 205-208.

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California Gold

"Where to Find Gold in California" looks at the density of modern placer mining claims along with historical gold mining locations and mining district descriptions to determine areas of high gold discovery potential in California. Read more: Where to Find Gold in California.