Browns Valley Mining District, Yuba Co., California, USAi

Regional Level Types
Browns Valley Mining District	Mining District
Yuba Co.	County
California	State
USA	Country

A former lode Au-Ag mining district located in sec. 16, T16N, R5E, MDM, around the town of Browns Valley, including along the eastern slope of Browns Valley Ridge, N of the Yuba Gold Field and N of the Yuba River, about 12 miles northeast of Marysville. Now owned by the county (Yuba County Planning Department). Discovered in 1850.

NOTE: Location selected for latitude and longitude by the USGS MRDS staff is the Donnebrouge Mine shaft symbol on the USGS 7.5-minute Browns Valley quadrangle. This mine was one of the most important producers in the district.

The relevent MRDS database record summarizes, on the whole, the characteristics of many individual lode mines and prospects that comprise the Browns Valley District. There is no single mine that represents a dominant property of the district.

The Browns Valley Mining District is situated in the lowest western foothills of the Sierra Nevada near the edge of the Central Valley. Most of the mines are concentrated at the east base of Browns Valley Ridge in a ravine that drains southward a little over a mile to intersect the Yuba River. Vegetation is mixed oak woodland and grass. There are scattered rural residences and ranches in the district.

This district comprises many small lode-gold mines at or within two miles of the settlement of Browns Valley. Known individual mines and prospects are listed above under "Other Names." the more notable producers were the Hibbert and Burris, Donnebrouge, Pennsylvania, and Jefferson. A few placer mines are also present (Cleveland, Lone Jack ). Useful references on mines in this district include Waring (1919) and O'Brien (1952). Available information on mines in this district is somewhat sparse.

•This district was discovered during the Gold Rush when miners exploited placer deposits. In 1850, one miner reportedly recovered several thousand dollars from a quartz vein. Lode mining was prevalent through the 1860's and 1870's, and was then intermittent through World War I. The Donnebrouge Mine reopened in the 1940's and was intermittently active until at least 1970. History of the district subsequent to 1970 is uncertain. A ?Brown?s Valley Mine? was operated in the 1930?s by the Empire Star Mines Company (http://content-backend-a.cdlib.org/view?docId=kt3v19n6jq&chunk.id=c01-1.7.8.4) Amalgamation processes were used at some of the mines.

Mineralization of the district is a series of lode Au deposits (Deposit model code 273; USGS model code 36a; deposit model name: Low-sulfide Au-quartz vein; Mark 3 model number 27), hosted in Jurassic diorite/diabase, gabbro and greenstone of the Smartville Complex; and Mesozoic serpentinite and granodiorite. Local rocks include Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains).

Regional structures include the Swain Ravine-Spenceville Fault Zone. Local structures include a few reports of faults associated with quartz veins, relationships unclear.

The ore deposits of the Browns Valley District are situated at the far western edge of the Western Sierra Nevada Metamorphic Belt within metaigneous rocks of the Mesozoic Smartville Complex. The deposits appear to be distributed over an area of a few square miles. They comprise a set of north-south-striking and east-west-striking fissure-filling quartz veins that cut the complex. The veins contain native gold and very low percentages of sulfide minerals, which include pyrite, chalcopyrite, galena, and sphalerite. Vein thicknesses generally range from inches to 4 feet, but may be as much as 18 feet. Some veins exhibit ribbon structure.

REGIONAL GEOLOGY: The Browns Valley District is situated in the northern portion of the Sierra Nevada Foothills Gold Belt. This belt averages 50 miles wide and extends for about 150 miles in a north-northwest orientation along the western slope of the Sierra Nevada Mountains. The Browns Valley District is almost 20 miles directly west of the Grass Valley District, home to California's two largest underground gold mines, the Empire and the Idaho-Maryland. Regionally, the Foothills Gold Belt approximately coincides with the Sierra Nevada Foothills Metamorphic Belt, which in this area can be subdivided into four major lithotectonic belts: Western Belt, Central Belt, Feather River Peridotite Belt, and Eastern Belt (Schweickert and others, 1999). The Western Belt in this area consists mainly of metamorphosed volcanic, sedimentary, and intrusive rocks of the Mesozoic Smartville Complex (Beard and Day, 1987). It is separated from the Central Belt by the Wolf Creek Fault Zone. The Central Belt consists of a complicated assemblage of Paleozoic-Mesozoic metasedimentary, metavolcanic, and metaplutonic rocks that have been intruded locally by Mesozoic plutonic rocks. The Central Belt is separated from the East Belt by the Feather River Peridotite Belt, which coincides in part with the Melones Fault Zone, a major structural boundary of the western Sierra Nevada. Rocks in this belt are largely peridotite and serpentinite, with lesser amounts of metasedimentary and metavolcanic rocks locally. The East Belt is dominantly metasedimentary and metavolcanic rocks of Paleozoic-Mesozoic age. Most of the metamorphic rocks in the belt in this area have been assigned to the Lower Paleozoic Shoo Fly Complex. The metamorphic complexes are intruded in places by Mesozoic plutonic rocks. On the west, near the Browns Valley District, the Sierra Nevada Foothills Metamorphic Belt is overlain by Cenozoic sedimentary deposits that cover the floor of the Central Valley. The Browns Valley District lies within the Western Belt, which in this area is composed of north-northwest-striking metaigneous rocks of the Smartville Complex. Most of the rocks are of mafic to intermediate volcanic or shallow intrusive origin. They are interpreted to be part of a rifted island arc. Part of the complex is intruded by an appendage of the Mesozoic Swedes Flat Pluton. The belt is also cut by several north-northwest-striking fault zones. Dips of foliation and bedding are generally vertical or nearly so, while strikes are dominantly NNW.

LOCAL GEOLOGY: The Browns Valley District is situated in the westernmost part of the Smartville Complex, which consists here mainly of metamorphosed mafic and intermediate marine volcanic rocks and shallow intrusive rocks. Metamorphosed felsic volcanic rock, serpentinite, and granodiorite were reported to be intersected in a few of the mines, although it is not clear if the granodiorite is part of the metamorphic complex or is a much younger body intrusive into it. A few NW-trending fault zones are shown to pass through the district, and there are reports of faults in some of the mines. Individual ore deposits in the district typically consist of quartz veins, some of which exhibit ribbon structure. The most common wallrock observed is diabase and diorite, with fewer reports of greenstone, gabbro, serpentinite, and ?porphyry.? the wallrock is reportedly very hard in some of the mines, with gouge in places; there is no mention in the documents reviewed of any alteration, however. Ore shoots typically had lengths of a few hundred feet maximum. Quartz veins in the mines of the district are reported in published literature to strike north-south with moderate (35-50 degrees) dips to the east or west; a few veins strike NNW. There are a few reports of east-west strikes also. Lindgren (1895), however, shows dominantly east-west strikes of quartz veins in the district. At one of the most productive mines in the district, the Donnebrouge, a strike of N35W and dip of N25E was reported (O?Brien, 1952). Thicknesses of veins range from inches to 18 feet, although most are less than 4 feet. Ore in the mines of the district was composed mostly of native gold and minor amounts of auriferous sulfides (pyrite, chalcopyrite, galena, and some sphalerite). Ore mined during the 1950?s at the Donnebrouge Mine reportedly graded from $10 to $60 per ton in parts of the workings. Overall, ore in the district probably averaged about 1-3% sulfides, although there was a report of 12% at one mine.

Workings information: Mines and prospects in this district were developed through standard underground methods that included shafts, winzes, raises, and drifting. Ore and waste were removed by conventional stoping; in some operations, waste and mill tailings were used as backfill in the underground workings. Waring (1919) provides the most detail overall for mines in the district. The deepest workings are probably at the Pennsylvania Mine, which reportedly reached an inclined depth of at least 1,600 feet. The nearby Donnebrouge Mine was worked to at least 1,500 feet deep on the incline. Otherwise, mines appear to have been less than 1,000 feet deep. Drifts turned from the shafts were typically hundreds of feet in length although a few were possibly as much as a few thousand feet in length.

Production information: Total production from lode mines in the Browns Valley District was estimated by Clark (1970) to be about $3 million to $5 million. (at $35/troy oz = 2.7 to 4.5 tonnes Au (PS)).

Analytical data: Gold was reportedly 0.763 fine at the Hibbert and Burris Mine. At the Donnebrouge Mine, about 80% of the ore values were as native gold. At least some of the concentrates were shipped to the smelter at Shelby near San Francisco.

Regions containing this locality

Pacific Ocean	Ocean
North America Plate	Tectonic Plate

References

USGS MRDS Record:10400280

Localities in this Region