Pine Tree-Josephine Mine

Site Name

Primary: Pine Tree-Josephine Mine

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Commodity

Primary: Gold
Secondary: Silver
Secondary: Copper
Tertiary: Lead
Tertiary: Zinc
Tertiary: Nickel
Tertiary: Cobalt

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Location

State: California
County: Mariposa
District: Bagby 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: Mariposa County Planning Department

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Hydrothermal vein and replacement; hydrothermal stockwork
Operation Type: Underground
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: Low-sulfide Au-quartz vein

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Orebody

Form: Tabular, irregular

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Structure

Type: R
Description: Main and subsidiary (Mother Lode fault zone) branches of the Melones Fault Zone

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Alterations

Alteration Type: L
Alteration Text: Carbonate; ankerite, quartz, sericite, Cr-mica, pyrite Chloritic; chlorite, talc

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Rocks

Role: Host
Age Type: Host Rock
Age Young: Late Jurassic

Name: Diorite
Role: Associated
Description: Meta-
Age Type: Associated Rock
Age Young: Jurassic

Name: Serpentinite
Role: Associated
Age Type: Associated Rock
Age Young: Mesozoic

Name: Graywacke
Role: Associated
Description: Meta-
Age Type: Associated Rock
Age Young: Jurassic

Name: Slate
Role: Associated
Age Type: Associated Rock
Age Young: Jurassic

Name: Greenstone
Role: Associated
Age Type: Associated Rock
Age Young: Jurassic

Name: Schist
Role: Host
Description: Ankerite-quartz-mariposite
Age Type: Host Rock
Age Young: Cretaceous

Name: Schist
Role: Host
Description: Ankerite-
Age Type: Host Rock
Age Young: Cretaceous

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Erythrite
Ore: Millerite
Ore: Niccolite
Ore: Galena
Ore: Chalcopyrite
Ore: Sphalerite
Ore: Arsenopyrite
Ore: Pyrite
Gangue: Quartz
Gangue: Ankerite
Gangue: Talc

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Comments

Comment (Geology): LOCAL GEOLOGY The Pine Tree-Josephine deposit is situated in the Mother Lode Belt of gold mineralization of the Sierra Nevada. The deposit is along the Melones Fault Zone, which in this area juxtaposes metasedimentary rocks of the Jurassic Mariposa Formation on the southwest (footwall) with Jurassic metavolcanic rocks on the northeast (hanging wall). In the immediate area of the deposit, within the fault zone, is a complex of serpentinite, metagabbro, metadiorite, phyllite, and ankerite schist, with lesser amounts of metavolcanic and epiclastic rocks. Some of these rocks are hydrothermally altered. The zone is about 500-2,000 feet wide in the Pine Tree-Josephine area. Within the Melones Fault Zone here at the deposit is a much narrower fault zone (averaging 125 feet wide) found in the mine workings, which is termed by Bowen and Gray (1957) and McAllister and Barabas (1990) the "Mother Lode fault zone." This zone is along the footwall of the broader Melones Fault Zone. The main ore deposit consists of two main veins (Pine Tree and Josephine) with intervening low-grade mineralized schists termed the ?Intervein carbonate ore body?. Julihn and Horton (1940) reported at least two generations of quartz veining, the later one containing sufficient gold to make milling ore. McAllister and Barabas (1990) recognized three stages of quartz deposition. McAllister and Barabas (1990) summarized the geology of the deposit as follows: "Gold is found along a 3,000 foot section of the Early Cretaceous Mother Lode fault zone. In this area the Mother Lode fault zone is along the footwall of the older, more ductilely deformed Melones fault zone. Two subparallel, mineralized vein systems, the Pine Tree and Josephine veins, comprise the hanging wall and footwall, respectively, of the Mother Lode fault zone in the mines. These fracture zones strike N. 30o-35o W., dip 55o-60o NE., and are generally 70-150 feet apart. Both north of the Pine Tree mine and at the south end of the Josephine mine, the Pine Tree and Josephine structures converge to form a single vein, which continues along the footwall of the Melones fault zone. Gold in the Pine Tree-Josephine mine is in the largest of four elongate, lens-shaped bodies of altered rock, which extend along 15,000 feet of the Melones fault zone. In the Pine Tree-Josephine mine rocks between the Pine Tree and Josephine veins are altered. Alteration extends more than several hundred feet into the hanging wall of the Mother Lode fault zone. The dominant altered rock type is ankerite schist developed from the serpentinite and greenstone in the Melones fault zone. Ankerite-quartz schist derived from serpentinite contains mariposite, pyrite, and in places talc, relict chromite, and serpentine. Ankerite-quartz schist developed from greenstone is finer grained and weakly foliated; sericite, chlorite, and pyrite are usually present.

Comment (Workings): Workings were developed along a 3,000-foot section of vein system from the Pine Tree Mine on the north end to the Josephine Mine on the south end. Because of the relationship of the steep topography to the structural orientation of the ore body, much of the work on the veins was accomplished through adits rather than shafts, although one shaft was developed to an inclined depth of about 1,150 feet in the Pine Tree. The Pine Tree workings aggregate over 8 miles, whereas those of the Josephine total about 7,700 feet. The two mines are connected by a single raise.

Comment (Economic Factors): Clark (1970) reported a production value in excess of $4 million for the Pine Tree-Josephine Mine. From McAllister and Barabas (1990): The greatest production from the Pine Tree-Josephine was between 1933 and 1944, when the Pacific Mining Company produced 71,000 oz. of gold worth about $2.5 million, or more than half of the cumulative production for the two mines, which is estimated to be in excess of $4 million. In 1988, Northgate Exploration Ltd., ABM Gold's parent company, announced open pit-mineable reserves of 9.5 million tons with an average grade of 0.065 opt gold. McAllister and Barabas (1990) calculated that a minimum of about 117,000 ounces of gold were produced between 1860 and 1944.

Comment (Geology): REGIONAL GEOLOGY The Pine Tree-Josephine Mine is within the Sierra Nevada Mountains, where bedrock consists of northerly trending tectonostratigraphic belts of metamorphosed sedimentary and volcanic rocks and associated intrusive rocks that range in age from Paleozoic to Mesozoic. 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 and are characterized by extensive faulting, shearing, and folding (Earhart, 1988). From El Dorado County southward into Mariposa County, lode gold deposits occur in three distinct belts - the West Belt, the Mother Lode Belt, and the East Belt. The Mother Lode Belt is responsible for most of the gold produced. However, there has also been substantial gold production from the West Belt and East Belt. The West Belt in Mariposa County consists of widely scattered gold deposits located west of the Mother Lode vein system, which represents the Mother Lode Belt. Gold occurs in irregular quartz veins and stringers in schist, slate, granitic rocks, altered mafic rocks, and as gray ore in greenstone. The West Belt is cut by the northwest-trending Bear Mountains Fault Zone, which separates an assemblage of metavolcanic and metasedimentary rocks of Jurassic age on the southwest from a more disrupted and diverse assemblage of metavolcanic, metasedimentary, plutonic, ultramafic, and melange rocks on the northeast. The metavolcanic rocks consist generally of volcanic and volcanic-sedimentary rocks of island-arc affinity. These rocks are mostly mafic to intermediate in composition and include flows, breccias, and a variety of layered pyroclastic rocks. Some silicic rocks are present also. Various formation names assigned to the metavolcanic assemblages include Gopher Ridge, Copper Hill, Logtown Ridge, and Penon Blanco. The metasedimentary rocks are dominantly distal turbidites and hemipelagic sequences of black slate. Assigned formation names include Mariposa, Salt Spring Slate, and Merced Falls Slate. The northwest-trending Mother Lode Belt traverses western Mariposa County and is associated with the Melones Fault Zone. The rocks of this belt are typically metavolcanic, metasedimentary, and ultramafic, some of which have been hydrothermally altered to assemblages as described below. Mother Lode Belt mineralization is characterized by steeply dipping gold-bearing quartz veins and bodies of mineralized country rock adjacent to veins. Mother Lode veins are characteristically enclosed in Mariposa Formation slate with associated greenstone. The Mother Lode belt 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, limonite, talc, chromium-bearing mica, and sericite. Stringer veins are commonly found in both adjacent footwall and hanging walls. Mother Lode ores are generally low- to moderate-grade (1/3 ounce of gold or less per ton), but ore bodies can be large. Ore shoots are generally short, 200-300 feet being the average stope length. However, they persist at depth, some having been mined to several thousand feet (Clark and Lydon, 1962). Ore shoots are commonly localized at bulges in veins, shear zones, vein intersections, or near abrupt changes in strike or dip.

Comment (Commodity): Commodity Info: Copper and silver were also recovered from this mine. Nickel content of the concentrates ranged from 0.35 to 1.35 percent. During mining in the 1930?s-1940?s, millheads averaged about 0.152 ounces gold, while tailings averaged 0.0228 ounces for a recovery rate of 85%.

Comment (Commodity): Ore Materials: Native gold, auriferous sulfides (pyrite, arsenopyrite). Also minor chalcopyrite, sphalerite, galena, niccolite, millerite, erythrite, danaite are present.

Comment (Commodity): Gangue Materials: Quartz, ankerite, talc

Comment (Geology): REGIONAL GEOLOGY (continued) Wall rocks have invariably been hydrothermally altered, having been partially to completely converted to ankerite, sericite, quartz, pyrite, arsenopyrite, chlorite, and albite with traces of rutile and leucoxene (Knopf, 1929). The mineralization is generally adjacent to the veins in ground that has been fractured and contains small stringers and lenses of quartz. Locally, greenstone bodies adjacent to the quartz veins contain enough disseminated auriferous pyrite in large enough bodies to constitute what has been called "gray ore.? Altered slate wall rock commonly contains pyrite, arsenopyrite, quartz, chlorite, and sericite with or without ankerite (Zimmerman, 1983). Large bodies of mineralized schist also form low-grade ore bodies throughout the Mother Lode. This ore consists of amphibolite schist that has been subjected to the same processes of alteration, replacement, and deposition that formed the greenstone gray ores. The altered schist consists mainly of ankerite, sericite, chlorite, quartz, and albite. Gold is associated with the pyrite and other sulfides that are present. Pyrite comprises about 8 percent of the rock. The average grade of mineralized schist is about 0.1 oz per ton. The Melones Fault Zone separates the Mother Lode Belt from the East Belt. The East Belt is dominantly argillite, phyllite and phyllonite, chert, and metavolcanic rocks of Paleozoic-Mesozoic age. Carbonate rocks (marble) are also present locally. The phyllite and phyllonite are dark to silvery gray. The chert is mostly thin-bedded with phyllite partings. The Upper Paleozoic-Lower Mesozoic metasedimentary and metavolcanic rocks of the East Belt have been assigned to the Calaveras Complex by most investigators (Earhart, 1988). The Lower Paleozoic metamorphic rocks farther east have been assigned to the Shoo Fly Complex. More recently, some geologists have reinterpreted certain assemblages along and immediately east of the Melones Fault Zone as separate Jurassic units (Schweickert and others, 1999). The metamorphic complexes are intruded in places by Mesozoic plutonic rocks. Lode deposits of the East Belt consist of many individual gold-bearing quartz veins enclosed in metamorphic rocks of possible Jurassic age, metamorphic rocks of the Calaveras Complex, metamorphic rocks of the Shoo Fly complex, or in granitic rocks. Most of the veins trend northward and dip steeply. An east-west set of intersecting faults may be a controlling factor in controlling deposition of ore. Ore deposits of the East Belt are smaller and narrower than those of the Mother Lode, but commonly are more chemically complex, and richer in grade. Gold is generally associated with appreciable amounts of pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, and arsenopyrite.

Comment (Identification): The Pine Tree and Josephine mines are among the most notable in the Mother Lode, not only because of their production, but also their long and colorful history. Originally separate mines, they were eventually merged into a single property.

Comment (Development): March 7, 2003 Goldrea has entered into an agreement to purchase approximately 3,350 acres (part of the Rancho Las Mariposa Land Grant) located 15 miles north of Mariposa, California. The property has all surface and mineral rights incorporated in the title and contains the Pine Tree-Josephine Gold Deposits. The Pine Tree-Josephine covers a 4 km segment of the Mother Lode. Though not in accordance with current CIM resource/reserve definitions, open pit geologic resource reserves were calculated in 1988 as 826,965 ounces of gold at a 0.025 opt gold cutoff grading 0.084 opt/gold and in 1986 as 963,780 ounces of gold at a 0.030 opt gold cutoff grading 0.065 opt gold. Underground geologic resource reserve estimates in 1989 resulting in 838,000 ounces at a 0.07 opt gold cutoff grading 0.116 opt gold. The company has the right to carry out a 45 day due diligence which will include reviewing resource and feasibility studies; assessing any potential environmental liability; assessing the potential to increase resource along strike and down-dip from the existing resources; amd reviewing all metallurgical studies carried out over the previous years; and examining the potential for exploration of two small high-grade vein type targets east of the Pine Tree/Josephine Zone.? As of 2007, this property was no longer listed under Goldrea Resources, Ltd. Ore was originally processed at Benton Mills (now Bagby) along the nearby Merced River at the bottom of the canyon to the north; later milling was done on-site. Concentrates were shipped to the smelter at Selby. Tailings were disposed of both on-site and along the bank of the Merced River. Amalgamation processes were used at this mine.

Comment (Deposit): The Pine Tree-Josephine Mine consists of a low-sulfide quartz-vein complex typical of those formed in greenstone-slate-serpentinite wall rock along the southern Melones Fault Zone. The main ore deposit consists of two main veins (Pine Tree and Josephine) with intervening low-grade mineralized schists termed the ?Intervein carbonate ore body?. The veins strike N30-35W, dip 55-60NE, and are generally 70-150 feet apart (McAllister and Barabas,1990). The main ore minerals are native gold, pyrite, and arsenopyrite. High grade ores of the Pine Tree and Josephine veins were associated with narrow ribbon quartz veins, containing tetrahedrite and pyrite, localized along the margins of lenticular bodies of barren or low-grade, milky white, "bull" quartz. McAllister and Barabas (1990) reported that nearly all the gold in this deposit is present in the Mother Lode fault zone portion of the Melones Fault Zone. The zone is characterized by laterally and vertically extensive quartz veins, associated irregular stockworks of quartz veins, fault breccia, hydrothermally altered rocks, and gold.

Comment (Development): The Pine Tree Mine was the more productive part of the deposit. After discovery in 1849, the two mines were operated fairly continuously over the next 25 years or so. Little mining took place from 1875 to 1900, but sustained, successful mining took place from 1900 to about 1915. After another period of inactivity, the most productive period of operation was between 1933 and 1944, after which the mine closed because of World War II. In 1984-86, ABM Gold Corporation's subsidiary, Goldenbell Resources Inc., explored the Pine Tree-Josephine ore zone and other nearby zones. In 1988, Northgate Exploration Limited acquired ABM, and determined that the Pine Tree-Josephine property was economically marginal (McAllister and Barabas, 1990). Regarding relatively recent activity at the deposit, the following is quoted directly from the InfoMine (2007) website (www.infomine.com): ?April 21, 2003 Goldrea Resources has negotiated an extension of its agreement with A.J. Land Company until May 21, with regard to the Pine Tree/Josephine Mine in California. The company has received the draft due diligence report with regard to the property recommending that Goldrea acquires the property if recently passed mining and reclamation regulations for open pit metallic mines in California are acceptable to explore and develop the mine. Goldrea says it will investigate the impact of the new California regulations and will also investigate the possibility of mining the open pit resources by underground methods. April 14, 2003 Goldrea has reported that further to its press release dated March 24, regarding due diligence work on the Pine Tree/Josephine Mine, the company will be examining the impact of the recent California regulation, adopted April 10, requiring mining companies to refill new open-pit metal mines and flatten mine waste piles back to nearly the natural landscape. The company said this new law could severely hamper the economics of the Pine-Tree/Josephine mines open pit deposit. The company expects to have a draft of the Policy 43-101 due diligence report within the week. March 24, 2003 Goldrea Resources has commenced a due diligence study on the Pine Tree/Josephine gold resource north of Mariposa, California. Particular emphasis will be placed on the open pit and underground resource reserves and the potential for additional ounces to a depth of 5,300 feet. Current underground resources only include the first 800 feet beneath the open pittable resource as reported by Goldenbell Mining in a summary report dated June 1991. The open pittable resources are open in all directions. The company will also investigate the prior metallurgical testing, permitting process and any environmental liability. The purchase of this land package as reported in early March is subject to regulatory approvals and a positive due diligence.

Comment (Geology): LOCAL GEOLOGY (continued) Most of the ore was mined from two large quartz veins, irregular vein stockworks in the wall rock, and from intervening, altered greenstone. High grade ores of the Pine Tree and Josephine veins were associated with narrow ribbon quartz veins, containing tetrahedrite and pyrite, localized along the margins of lenticular bodies of barren or low-grade, milky white, "bull" quartz. In the Pine Tree mine, several ore shoots in the Pine Tree vein were exploited from the surface to depths of at least 1,500 feet. In the Josephine mine, both the Pine Tree and Josephine veins were explored to depths of 700-800 feet, but nearly all the mining took place within the upper 300-400 feet. High gold grades in both veins, within a hundred feet of the surface, were 1.2-2.5 ounces per ton (opt) gold, and may have been due to secondary enrichment. Deeper than 400 feet in both mines the gold grades were in the range of 0.3 to 0.4 opt. A grade of about 0.2 opt gold was maintained to the deepest part of the Pine Tree vein. About 150,000 tons of ankeritized greenstone, with quartz vein stockworks, abundant pyrite, and gold grades of about 0.15 opt, were mined in the central part of the combined Pine Tree-Josephine mine in the 1930's and 1940's. Mineralized and ankeritized greenstone, called gray ore, and mariposite-ankerite schist compose a significant portion of the current ore potential." McAllister and Barabas (1990) also concluded from fluid-inclusion studies of the quartz veins that hydrothermal fluids from which the gold was deposited were rich in CO2 and that there is a close association of amounts of pressurized gases trapped in the inclusions and gold grade. They observed that hydrothermal alteration, which was largely carbonate in nature, extended well into the hanging wall of the fault zone, but not far into the slate of the Mariposa Formation of the footwall. Kistler and others (1983) reported a potassium-argon age of about 108 million years from a sample of mariposite obtained at the nearby Mary Harrison Mine, which is about 7 miles northwest of the Pine Tree-Josephine. They concluded that formation of gold-bearing quartz-mariposite veins along the Mother Lode Belt between Sonora and the Mary Harrison took place during the Early Cretaceous between approximately 127 and 108 Ma.

Comment (Location): Location selected for latitude and longitude is the Pine Tree Mine adit symbol near BM 1964 symbol on the USGS 7.5-minute Bear Valley quadrangle.

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References

Reference (Deposit): Bowen, O.E., Jr. and Gray, C.H., Jr., 1957, Mines and mineral resources of Mariposa County, California: California Journal of Mines and Geology, v. 53, nos. 1-2, p. 35-343.

Reference (Deposit): Castello, W.O., 1921, Mariposa County: California State Mining Bureau, 17th Annual Report of the State Mineralogist, p. 86-143.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Division of Mines and Geology Bulletin 193, p. 29.

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. 72-73.

Reference (Deposit): Earhart, R.L., 1988, Geologic setting of gold occurrences in the Big Canyon area, El Dorado County, California: U.S. Geological Survey Professional Paper 1576, 13 p.

Reference (Deposit): Evans, J.R. and Bowen, O.E., 1977, Geology of the southern Mother Lode, Tuolumne and Mariposa counties, California: California Division of Mines and Geology Map Sheet 36, scale 1:24,000.

Reference (Deposit): Julihn, C.E., and Horton, F.W., 1940, Mineral industries survey of the United States - Mines of the southern Mother Lode Region, Part II - Tuolumne and Mariposa counties: U.S. Bureau of Mines Bulletin 424, 179 p.

Reference (Deposit): Kistler, R.W., Dodge, F.C.W. and Silberman, M.L., 1983, Isotopic studies of mariposite-bearing rocks from the south-central Mother Lode, California: California Geology, v. 36, no. 9, p. 201-203.

Reference (Deposit): Knopf, A., 1929, The Mother Lode system of California: U. S. Geological Survey Professional Paper 157, 88 p.

Reference (Deposit): Koschmann, A.H., and Bergendahl, M.H., 1968, Principal gold-producing districts of the United States: U. S. Geological Survey Professional Paper 610, 283 p.

Reference (Deposit): Landefeld, L.A., 1990, The geology of the Mother Lode gold belt, Foothills metamorphic belt, Sierra Nevada, California, in Landefeld, L.A. and Snow, G.G., editors, Yosemite and the Mother Lode gold belt: Geology, tectonics, and the evolution of hydrothermal fluids in the Sierra Nevada of California: American Association of Petroleum Geologists, Pacific Section, Guidebook 68, p. 117-124.

Reference (Deposit): Logan, C.A., 1935, Mother Lode gold belt of California: California Division of Mines Bulletin 108, 240 p.

Reference (Deposit): Bateman, P.C. and Krauskopf, K.B., Geologic map of the El Portal Quadrange, west-central Sierra Nevada, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-1998, scale 1:62,500.

Reference (Deposit): Moore, L., 1968, Gold resources of the Mother Lode Belt, El Dorado, Amador, Calaveras, Tuolumne, and Mariposa counties, California: U.S. Bureau of Mines Technical Progress Report 5, p. 1-22.

Reference (Deposit): McAllister, C.A. and Barabas, A.H., 1990, Geology, ore deposits, and modern mining history of the Pine Tree-Josephine properties, Bagby District, southern Mother Lode, California, in Landefeld, L.A. and Snow, G.G., editors, Yosemite and the Mother Lode gold belt: Geology, tectonics, and the evolution of hydrothermal fluids in the Sierra Nevada of California: American Association of Petroleum Geologists, Pacific Section, Guidebook 68, p. 125-145.

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): Strand, R.G., 1967, Mariposa Sheet: California Division of Mines and Geology Geologic Map of California, scale 1:250,000.

Reference (Deposit): Wagner, D.L., Bortugno, E.J., and McJunkin, R.D., 1990, Geologic map of the San Francisco-San Jose Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 5A, scale 1:250,000.

Reference (Deposit): Zimmerman, J.E., 1983, The geology and structural evolution of a portion of the Mother Lode Belt, Amador County, California: Unpublished M.S. thesis, University of Arizona, 138 p.

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California Gold

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