Penn Mine

Past Producer in Calaveras county in California, United States with commodities Copper, Zinc, Lead, Gold, Silver

Sections on this page

Identification information
Geographic coordinates
Site location context
Geographic areas
Public Land Survey System information
Commodities
Materials information
Alteration
Mineral occurrence model information
Host and associated rocks
Nearby scientific data
Geologic structures
Ore body information
Controls for ore emplacement
Economic information about the deposit and operations
Mining district
Land status
Bibliographic references
General comments
Reporter information

Geologic information

Identification information

Deposit ID	10310664
Record type	Site
Current site name	Penn Mine
Alternate or previous names	Campo Seco

Comments on the site identification

The Penn Mine is located in the Campo Seco district of western Calaveras County, approximately 4.5 miles north of Valley Springs, and just south of the Mokelumne River. It was one of the principal producers of copper in the Foothill Copper Belt, and a significant source of zinc, lead, gold, and silver. The property consisted of a number of patented claims including the Campo Seco, Hecla, Satellite, Little Satellite, Constellation, West Constellation, Meteor Gold, Blue Jay, and Happy Jack claims. The Penn Mine operated intermittently between 1861 and 1952 and produced an estimated 973,784 tons of ore, which yielded 82,534,054 pounds of copper, 22,196,482 pounds of zinc, 1,225,798 pounds of lead, 67,773 ounces of gold, 2,150,304 ounces of silver.

Geographic coordinates

Geographic coordinates:	-120.8741, 38.23075 (WGS84)
Elevation	60
Location accuracy	100(meters)
Relative position	The Penn Mine is located 1 mile west of the community of Campo Seco

Site location context

Political divisions (FIPS codes)

Calaveras(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Valley Springs(quadrangle 1:24,000 scale)

San Andreas(quadrangle 1:100,000 scale)

Sacramento(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

San Joaquin(hydrologic accounting unit)

San Joaquin(hydrologic subregion)

California(hydrologic region)

Geographic areas

Country	State	County
United States	California	Calaveras

Public Land Survey System information

Meridian	Township	Range	Section	Fraction	State
Mount Diablo	004N	010E	3,4		California

Comments on the location information

Location selected for latitude and longitude is the Penn MIne shaft symbol on the USGS 7.5 minute Valley Springs quadrangle

Commodities

Commodity	Importance
Copper	Primary
Zinc Critical	Primary
Lead	Primary
Gold	Primary
Silver	Primary

Comments on the commodity information

Ore Materials: Zoned massive sulfide ores consisting of pyrite, sphalerite, bornite, and chalcopyrite; stringer ores of pyrite, chalcopyrite, bornite, calcite, and barite; disseminated pyrite, chalcopyrite, and sphalerite in altered wall rocks
Gangue Materials: Quartz, calcite, barite, schist, quartz porphyry

Materials information

Materials	Type of material
Pyrite	Ore
Sphalerite	Ore
Bornite	Ore
Chalcopyrite	Ore
Quartz	Gangue
Calcite	Gangue
Barite	Gangue
Schist	Gangue
Quartz	Gangue

Alteration

(Local) Sericitic and silicic alteration of wall rock metavolcanics to sericite and chlorite schist.

Mineral occurrence model information

Model code	184
USGS model code	28a
Deposit model name	Massive sulfide, kuroko
Mark3 model number	93

Host and associated rocks

Host or associated Host

Rock type Plutonic Rock > Porphyry

Rock type qualifier Felsic quartz

Rock unit name Gopher Ridge Volcanics

Stratigraphic age (youngest) Jurassic

Host or associated

Host

Rock type

Volcanic Rock (Aphanitic) > Pyroclastic Rock > Tuff

Rock type qualifier

rhyolitic

Rock unit name

Gopher Ridge Volcanics

Stratigraphic age (youngest)	Jurassic

Nearby scientific data

(1)	-120.8741, 38.23075	ListMap

Economic information

Geologic structures

Type of structure	Regional
Structure description	Bear River and Melones fault zones

Ore body information

General form Pod, lens

General form	Pod, lens

Controls for ore emplacement

Syn-volcanic exhalative Kuroko type

Comments on the geologic information

REGIONAL GEOLOGY

Rocks in the Sierra foothills consist of north trending tectonostratigraphic belts of metamorphosed sedimentary, volcanic, and intrusive rocks ranging in age from late Paleozoic to Mesozoic. These belts represent rock sequences, largely of island-arc affinity, that were accreted to the continent. They extend about 235 miles along the western side of the Sierra and 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).

Historically, three belts have been identified in the southern Sierran foothills based on lithologic differences and the nature of gold mineralization - the West Gold Belt, the Mother Lode Belt, and the East Gold Belt. The Mother Lode Belt is responsible for most of the gold produced. However, substantial gold has been produced from the East Belt, as well as gold, copper, and other base metals from rocks of the West Belt.

The West Belt consists of an eastern component composed of an ophiolitic melange and a Jurassic age western component composed of the Copper Hill Volcanics, the Salt Springs slate, and Gopher Ridge Volcanics. The Bear Mountains fault zone separates the melange from the Copper Hill Volcanics. The West Belt contains widely scattered gold deposits occurring in quartz veins and stringers in schist, slate, granitic rocks, altered mafic rocks, and as gray ore in greenstone. The West Belt also hosts the Foothill Copper-Zinc Belt and the massive sulfide deposits of the Penn Mine.

The Mother Lode Belt traverses western Calaveras County and consists of the upper Jurassic Logtown Ridge and Mariposa formations the Logtown Ridge Formation consists of about 6,500 feet of volcanic and volcanic-sedimentary rocks of island arc affinity. The overlying Mariposa Formation contains a distal turbidite, hemipelagic sequence of black slate, schist, amphibolite and chlorite schist, fine-grained tuffaceous rocks, and subvolcanic intrusive rocks. The thickness of the Mariposa Formation is estimated to be about 2,600 feet thick at the Consumnes River (Earhart, 1988).

Mother Lode mineralization is characterized by steeply dipping gold-bearing mesothermal quartz veins and bodies of mineralized country rock adjacent to veins. Mother Lode ores are generally low to moderate grade (1/3 ounce of gold or less per ton), but ore bodies can be large. 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. 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, and sericite.

The Melones Fault zone separates the Mother Lode Belt from the East Belt. The Eastern Belt is dominantly argillite, phyllite and phyllonite, chert, and metavolcanic rocks of Paleozoic-Mesozoic age. The phyllite and phyllonite are dark to silvery gray. The chert is mostly thin bedded with phyllite partings. The Paleozoic-Mesozoic metasedimentary and metavolcanic rocks of the Eastern Belt have been assigned to the Calaveras Complex by most investigators (Earhart, 1988). Older Paleozoic metamorphic rocks have been assigned to the Shoo Fly Complex. The metamorphic complexes have 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 usually associated with appreciable amounts of pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, and arsenopyrite.

LOCAL GEOLOGY

The Foothill Copper-Zinc Belt forms part of a complex lithotectonic belt of Jurassic age island arc metavolcanic, metasedimentary, and metaplutonic rocks. It lies west of, and roughly parallel to the Mother Lode gold belt. The ore deposits, which form lenticular bodies in the metavolcanic rocks, are primarily composed of massive pyrite and various amounts of chalcopyrite, sphalerite, gold and silver. Some deposits, however, contain small amounts of pyrrhotite, galena, tetrahedrite, or bornite.

Until the early 1970s, the massive sulfide deposits at the Penn Mine were thought to be epigenetic replacement deposits formed along shear zones (Heyl, et al, 1948; Clark and Lydon, 1962). The reinterpretation of massive sulfide deposits in Japan as being of volcanogenic origin rather than replacement deposits resulted in a reevaluation of many massive sulfide deposits in the western US. As a result, more recent studies of specific deposits, including those of the Penn Mine, have proposed a syngenetic origin of these deposits (Peterson, 1985). Kemp (1982) defined the island-arc setting in which the Foothill Copper-Zinc Belt deposits are situated. Schmidt (1978) defined the textural and structural attributes, stratigraphic framework, and the sulfide ore mineralogy at the Penn Mine and concluded these deposits are more indicative of Kuroko-type syngenetic volcanogenic sulfides.

Bedrock
Bedrock at the Penn Mine consists primarily of greenschist-facies metavolcanic rocks of the Gopher Ridge Volcanics that strike N 30? W and dip steeply to the east (generally greater than 70?). Despite the regional metamorphism and eastward tilting there is little evidence of major folding or faulting in the area (Peterson, 1985). The metavolcanic rocks have a weak to intense foliation paralleling the strike. Peterson (1985) subdivided the Gopher Ridge Volcanics at the Penn Mine into one intrusive and five volcanic sub-units based on prominent lithologic features: 1) felsic quartz porphyry intrusive unit, 2) siliceous tuff unit, 3) basalt unit, 4) mafic to intermediate tuff unit, 5) heterogeneous tuff unit, and 6) vent complex unit. Most of the copper-zinc ore bodies are intimately associated with sills and lense-like bodies of the felsic quartz porphyry unit which occur within the lower three volcanic units. Also associated with the ore bodies are large areas of sericitic and silicic alteration that produced a quartz sericite schist, and chloritic, hematitic, and pyritic alteration halos around the known ore bodies.

Ore Bodies and Genesis
Ore occurs in two distinct zones of mineralization; a Western ore zone lying to the east of quartz porphyry schist and along which Shaft Nos. 1, 2, 6 were sunk, and an Eastern ore zone just west of chloritic quartz porphyry, which was mined in shafts Nos. 3 and 4. Twelve separate ore bodies were differentiated during underground mining. Heyl et al (1948) provides numerous cross sections through many of the mine's more important ore bodies.
Schmidt (1978) identified several zoned ore types including massive ores, stringer ores and disseminated ores. The principal ore bodies consist of massive mixtures of sphalerite, pyrite, bornite, and chalcopyrite with minor gangue comprised of barite, quartz, calcite and/or mica schist, and rare to minor galena and tetrahedrite/tennantite. Quartz, selenite, and some native copper are also present (Clark and Lydon, 1962). Many of the massive ores are banded with alternating layers of chalcopyrite, pyrite, or sphalerite, whereas others are a fine-grained heterogeneous mixture of up to 60% sphalerite, 50% pyrite, and varying proportions (up to 30%) of copper and accessory minerals. Many of the banded ores show kinks, swirls, and folds indicative of post-deposition deformation (Schmidt, 1978). The ore bodies are lenticular in form, and the long axes plunge down dip or steeply to the north or south. Ore bodies showed pronounced elongation with length:breadth ratios ranging from 2:1 to 5L:1 and averaging 3:1 (Schmidt, 1978). They varied considerably in size, some having been mined along the pitch length of as much as 1000 feet (Heyl et al, 1948). Thickness of the ore bodies varies from 4 to 30 feet.

Stringer ores are of pyrite, chalcopyrite, sphalerite, bornite, calcite, barite, and quartz. Gangue of fine-medium-grained aggregates of quartz, calcite, and barite occur interstitial to stringer ores. Disseminated ores consist of disseminated pyrite, chalcopyrite, and sphalerite, and are associated with extensive wall-rock alteration (Schmidt, 1978). Fine-grained pyrite comprises between 1 to 10 percent of the rock.

Ore bodies display a strong asymmetric zonation both in mineralogy and mode of ore occurrence, which was not consistent with a replacement origin. A typical ore body in the Western ore zone consists of: 1) a hanging wall layer of massive to banded ore rich in sphalerite, barite, chalcopyrite, pyrite, and galena, and tetrahedrite-tennantite, with sphalerite-barite rich ore being more abundant towards the hanging wall, and copper minerals more abundant towards the footwall; 2) a zone of stringer ores with copper minerals (bornite and chalcopyrite), pyrite, quartz, and minor tetrahedrite; and 3) quartz-pyrite veinlets and disseminated pyrite mineralization with quartz porphyry or rhyolitcic tuffs. In the Eastern ore zone, the above sequence is reversed, occurring from footwall to hanging wall. The zoning was attributed to a syngenetic process where gravity would contribute to the asymmetry of both the ores and alteration effects (Schmidt, 1978).

Mineralized zones are conformable with the volcanic section. Ore bodies lie along bedding and schistosity planes rather than along fault planes or fractures zones as would be expected by a hydrothermal origin. The mineralized zones also exhibit stratigraphic selectivity, occurring only within or to one side of a felsic quartz porphyry. Ore bodies commonly occur at the contact of a felsic porphyry with more mafic rocks. The felsic quartz porphyry intrusive units and parts of the volcanic units are sericitically altered and silicified in the stratigraphic horizons of the ore deposits (Peterson, 1985).

Similar associations of ore, felsic rocks, and alteration are characteristic of Kuroko-type deposits massive sulfide deposits (Franklin et al, 1981). The fluids affecting the felsic quartz porphyry intrusive and responsible for the ore are thought to have had a common origin, with alteration occurring contemporaneously with deposition of the massive ore bodies. First the volcanic units were deposited in an island arc environment. Contemporaneous with or shortly after their deposition, felsic quartz porphyry bodies intruded the volcanic rocks along bedding planes to form a number of sills, the massive sulfide bodies were deposited, and the adjacent country rock was altered.

Economic information about the deposit and operations

Operation type	Surface-Underground
Development status	Past Producer
Commodity type	Metallic
Deposit size	Medium
Significant	Yes
Discovery year	1861

Mining district

District name	Campo Seco

Land status

Ownership category	Private
Area name	Calaveras County Planning Dept.

Comments on the workings information

The Penn Mine was developed by at least 20 shafts (six of which were numbered) several adits, and numerous open pits and cuts. The workings total about 55,000 feet, of which 42,000 feet are in drifts and crosscuts, and 13,000 feet in shafts and raises. Plate 15 of California Division of Mines Bulletin 144 (Heyl, et al, 1948) provides a detailed geologic map of the Penn Mine and shows all the working entries. Plates 14 and plates 16 to 24 in the same publication provide detailed maps of mine workings.

The principal working entries have been Shafts No. 2, 3, and 5. All are inclined to the northeast. Shaft No. 2 is 1000 feet with a winze to 1100 feet, Shaft No. 3 is 1400 feet, and Shaft No. 5 is 400 feet deep on the incline. Shafts No. 3 and 5 are connected on the 400-foot level and Shafts No. 2 and 3 via raises between the 1400-foot level of the Shaft No. 3 and the 1100-foot winze level of of Shaft No. 2. On the 1400-foot level in the Shaft No. 3 level, a northeast inclined winze extends to the 3400-foot level, the deepest portion of the mine. Copper and zinc mining done by the Penn Chemical Company in 1948-53 was in the Shafts No. 2 and 3 areas. The largest underground work done in 1955-1957 by the Standard Mining Corporation was on the 400-foot level in the area of Shaft No. 3.

There have been several mills and two smelters on the property at different times. The last mill, which was used to produce zinc and copper-lead concentrates during the period 1949-53, was erected by the Penn Chemical Company. It was equipped with a Pacific jaw crusher, vibrating screen, Symons cone crusher, Hardinage conical ball mill, Pan-American jig, Knudson bowl, and two flotation circuits; a copper circuit containing a conditioner tank and five Denver sub-A cells which yielded a copper-lead-gold silver concentrate, and a zinc circuit containing a conditioner tank and 12 Denver sub-A cells.

Comments on other economic factors

The Penn Mine operated intermittently between 1861 and 1952 and produced an estimated 973,784 tons of ore which yielded 82,534,054 pounds of copper, 22,196,482 pounds of zinc, 1,225798 pounds of lead, 67,773 ounces of gold, 2,150,304 ounces of silver

Comments on development

In the summer of 1861, three copper deposits were discovered near Campo Seco, and named the Campo Seco, Lancha Plana, and Copper Hill claims. During the initial years of development, these claims were operated independently but were later consolidated into the Penn Mine. From 1861 to 1867, the claims were very active, largely the result of increased copper prices resulting from the Civil War. In 1865, a smelter with an 8-ton Welsh-type furnace was erected on the property. The smelter yielded matte containing 35 percent copper. The ore smelted ranged from 6 to 10 percent copper. The properties were shut down around 1867 when the copper prices declined and mining costs increased.

From 1883 to 1886, the Lancha Plana claim (later renamed the Satellite claim) was being worked. An adit was driven to connect with the old shaft (Shaft No. 1). About 1000 tons of ore were shipped and dump material was leached. During this time, material from the dump of the Campo Seco Mine was treated by roasting and leaching at the Sunrise Placer Mining and Copper Reduction Works (Hanks, 1884). About 1886, the San Francisco Copper Company acquired the Satellite Mine. In 1887, the Penn Chemical Company acquired the Campo Seco claim, dewatered the mine and treated large quantities of ore by heap roasting and leaching (Irelan, 1888). Later this company purchased the Satellite and Hecla Mines, and adjoining properties that were merged into an operating unit known as the Penn Mine.

In 1899, a smelter was erected and operated continuously until 1919. It was equipped with a crushing and grinding plant, eight roasting furnaces, and a blast furnace. A high-grade matte containing 50 to 60 percent copper was produced, which was crushed and shipped to New York for refining. Gross returns from the smelter operations, including gold and silver, were valued at $7,362,562 (Heyl et al, 1948). The smelter was shut down and dismantled when the price of copper decreased after World War I. The Penn Mining Company continued underground development work until 1921, and the mine was kept dewatered until 1926 when it was sampled for the American Smelting and Refining Company (Clark and Lyndon, 1962).

In 1928, the mine was leased to the Mateo Mining Company, and shaft No. 2 was dewatered to the 700-foot level. Only a small amount of ore was mined. In 1937, another similar, short-lived project was undertaken by the Penn Copper and Zinc Company (Heyl, et al, 1948).

From November 1942 to February 1945, the mine was studied by the U.S. Geological Survey as part of a wartime investigation of the Foothill Copper Belt, and results were published in California Division of Mines Bulletin 144. Also in 1942, the U.S. Bureau of Mines sampled the slag dump and mine water, and the results were published in U.S. Bureau of Mines Report of Investigations 4224. In 1943, the Constellation claims were diamond drilled by the U.S. Bureau of Mines, but no material considered worthy of assaying was found (Heyl, et al, 1948).

From 1943 to 1946, the mine was operated on a major scale by the Eagle-Shawmut Mining Company. The ore was trucked 70 miles south to the Eagle-Shawmut mill near Chinese Camp, Tuolumne County. Zinc was not produced from the mine until WW II. Copper-lead and zinc concentrates were produced and shipped to a smelter in Tooele, Utah. In July 1946, the Shawmut Copper Mine Company was formed and operated the mine until October, 1947.
In 1948, a new company, the Penn Chemical Company, leased the property and commenced operations. The upper levels were dewatered and the mill was reconditioned. Zinc ore that had been bypassed in earlier operations was mined. Zinc and copper-lead concentrates and gold amalgam were produced. The operation continued through 1952, when the mine was closed down. Total recorded production was 973,784 tons of ore, which yielded 82,534,054 pounds of copper, 22,196,482 pounds of zinc, 1,225,798 pounds of lead, 67,773 ounces of gold, and 2,150,304 ounces of silver. In the summer of 1953, New Penn Mines, Inc. was organized and initiated an exploratory drilling program in the vicinity of Shaft No. 3. Some ore was found, but not enough to warrant reopening the mine.

In the Fall of 1955, the property was leased by the Standard Mining Corporation. Shaft 3 was dewatered to the 400-foot level. Some crosscutting was done to the east and a small amount of ore was mined. In 1958, the property was subleased to Kenneth Boyles of Valley Springs and later to P. R. and Henry Bradley. They suspended operations in 1959.

Reference information

Bibliographic references

Deposit

Aubury, L.E., 1908, Copper resources of California: California Mining Bureau Bulletin 50, p. 228-245.
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. 28-31.
Deposit

Franklin, J.M., Lydon, J.W., and Sangster, D.F., 1981, Volcanic-associated massive sulfide deposits: Economic Geology Seventy-fifth Anniversary Volume, p. 485-627.
Deposit

Hanks, H.G., 1884, Copperopolis, Campo Seco, Satellite, and Sunrise copper mines: California Mining Bureau Report 4, p. 148-151.
Deposit

Heyl, G.R., Cox, Manning, W., and Eric, J.H., 1948, Penn zinc-copper mine, Calaveras County, California: California Division of Mines Bulletin 144, p. 61-84.
Deposit

Hutchinson, R.W., 1973, Volcanogenic sulfide deposits and their metallogenic significance: Economic Geology, v. 68, p 1223-1246.
Deposit

Irelan, W.R., Jr., 1888, Calaveras County: California Mining Bureau Report 8, p. 121-157.
Deposit

Kemp, W. R., 1982, Petrochemical affiliations of volcanogenic massive sulfide deposits of the Foothill CU-Zn belt, Sierra Nevada, California: University of Nevada - Reno, unpublished Ph.D. thesis, 458 p.
Deposit

Lambert, I.B., and Sato, T., 1974, The Kuroko and associated ore deposits of Japan - A review of their features and metallogenesis: Economic Geology, v. 69, p. 1215-1236.
Deposit

Peterson, J. A., 1985, Geologic map of the Penn Mine, Calaveras County, California: U. S. Geological Survey Miscellaneous Field Studies Map MF-1797, 2 sheets.
Deposit

Peterson, J. A., 1985, Geochemical analyses of rock samples collected at the Penn Mine, Calaveras County, California: U. S. Geological Survey Open-File report 85-588, 17 p.
Deposit

Sato, T., 1971, Physiochemical environment of Kuroko mineralization at Uchinotai Deposit of Kosaka Mine, Akita Prefecture: Society of Mining Geol. of Japan Special Issue no. 2, p. 137-144.
Deposit

Schmidt, J.M., 1978, Volcanogenic massive sulfides at Campo Seco (Calaveras County), California: Stanford University, unpublished M.S. thesis, 104 p.
Deposit

Tucker, W.B., 1914, Calaveras County - Penn Copper Mine: California State Mining Bureau, 14th Annual Report of the State Mineralogist, p. 59-62.
Deposit

Wiebelt, F.J., and Ricker, S., 1948, Penn mine slag dump and mine water, Calaveras County, California: U.S. Bureau of Mines Report of Investigations 4224, 6 p.
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.

General comments

Subject category	Comment text
Deposit	The Penn Mine is one of many massive stratabound zinc-copper deposits within the Foothill Copper Belt, a group of massive sulfide deposits that extends over 200 miles along the western Sierra Nevada from Butte County in the north to Fresno County in the south. These deposits occur in a complex metamorphosed upper Jurassic basaltic to rhyolitic volcanic sequence that formed as part of a Jurassic island-arc sequence. Early papers attributed the mineralization to an epigenetic replacement origin, but more recent studies indicate the massive sulfide deposits more likely originated within a Kuroko syngenetic volcanic model. Intermediate composition pyroclastics comprise the bulk of the stratigraphic section which also includes pillow basalts and other mafic flows, fine-grained felsic to rhyolitic tuffs, and at least two quartz porphyry flows. The deposits exhibit uni-directional layering in the ore and host rock sequence and asymmetric zonation both in mineralogy and mode of ore occurrence, which is consistent with a syn-volcanic exhalative Kuroko-type ore deposit rather than a replacement deposit (Schmidt, 1978). Typical ore bodies consist of a sequence of massive to banded ore rich in sphalerite, barite, chalcopyrite, pyrite, and galena, and tetrahedrite-tennantite; 2) a zone of stringer ores with copper minerals (bornite and chalcopyrite), pyrite, quartz, and minor tetrahedrite; and 3) quartz-pyrite veinlets and disseminated pyrite mineralization within quartz porphyry or rhyolitcic tuffs.

Subject category

Comment text

Deposit

The Penn Mine is one of many massive stratabound zinc-copper deposits within the Foothill Copper Belt, a group of massive sulfide deposits that extends over 200 miles along the western Sierra Nevada from Butte County in the north to Fresno County in the south. These deposits occur in a complex metamorphosed upper Jurassic basaltic to rhyolitic volcanic sequence that formed as part of a Jurassic island-arc sequence. Early papers attributed the mineralization to an epigenetic replacement origin, but more recent studies indicate the massive sulfide deposits more likely originated within a Kuroko syngenetic volcanic model.

Intermediate composition pyroclastics comprise the bulk of the stratigraphic section which also includes pillow basalts and other mafic flows, fine-grained felsic to rhyolitic tuffs, and at least two quartz porphyry flows. The deposits exhibit uni-directional layering in the ore and host rock sequence and asymmetric zonation both in mineralogy and mode of ore occurrence, which is consistent with a syn-volcanic exhalative Kuroko-type ore deposit rather than a replacement deposit (Schmidt, 1978). Typical ore bodies consist of a sequence of massive to banded ore rich in sphalerite, barite, chalcopyrite, pyrite, and galena, and tetrahedrite-tennantite; 2) a zone of stringer ores with copper minerals (bornite and chalcopyrite), pyrite, quartz, and minor tetrahedrite; and 3) quartz-pyrite veinlets and disseminated pyrite mineralization within quartz porphyry or rhyolitcic tuffs.

Reporter information

Type	Date	Name	Affiliation	Comment
Reporter	17-APR-2006	Downey, Cameron (Higgins, Chris, T.)	California Geological Survey CGS (Formerly CDMG)
Editor	01-SEP-2007	Schruben, Paul G.	U.S. Geological Survey	Converted from S&A FileMaker format to Oracle. Edit checks on rocks, units, and ages with Geolex search, and other fields.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

External references

Wikidata: Q49439869 (Penn Mine)

Maps centered on this site

Authoritative California resources

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