Castle Mountain Mine

Producer in San Bernardino county in California, United States with commodities Gold, Silver, Clay, Arsenic, Antimony, Mercury, Molybdenum, Beryllium, Copper

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
Ore body information
Controls for ore emplacement
Economic information about the deposit and operations
Mining district
Land status
Ownership information
Bibliographic references
General comments
Reporter information

Geologic information

Identification information

Deposit ID	10310700
Record type	District
Current site name	Castle Mountain Mine

Geographic coordinates

Geographic coordinates:	-115.10028, 35.28472 (WGS84)
Elevation	1350
Location accuracy	100(meters)
Relative position	15.95 air miles S 37.75? E of town of Nipton, CA; 16.3 air miles S 40.2? W of town of Searchlight, NV.

Site location context

Political divisions (FIPS codes)

San Bernardino(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Hart Peak(quadrangle 1:24,000 scale)

Ivanpah(quadrangle 1:100,000 scale)

Kingman(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Piute Wash(hydrologic unit)

Lower Colorado(hydrologic accounting unit)

Lower Colorado(hydrologic subregion)

Lower Colorado(hydrologic region)

Geographic areas

Country	State	County
United States	California	San Bernardino

Public Land Survey System information

Meridian	Township	Range	Section	Fraction	State
San Bernardino	014N	017E	24	NW1/4	California

Comments on the location information

Longitude and latitude represent the hilltop (elev. 4766 feet) ESE of the E end of the Hart Mine Road. Location is approx. 27 road miles from Searchlight, NV, via NV State Hwy 164 (west 7 mi, paved); Castle Mountain Mine (aka Walking Box Ranch) Road and Castle Mountain Mine/Hart Mine Road (southwest 20 mi, improved; main route traveled by mine employees).

Commodities

Commodity	Importance
Gold	Primary
Silver	Primary
Clay	Secondary
Arsenic Critical	Tertiary
Antimony Critical	Tertiary
Mercury	Tertiary
Molybdenum	Tertiary
Beryllium Critical	Tertiary
Copper	Tertiary

Comments on the commodity information

Ore Materials: Native gold, electrum, oxidized pyrite
Gangue Materials: Quartz, hematite, goethite, pyrite, adularia, sericite, illite, kaolinite, montmorillonite, leucoxene, rutile

Materials information

Materials	Type of material
Gold	Ore
Electrum	Ore
Pyrite	Ore
Quartz	Gangue
Hematite	Gangue
Goethite	Gangue
Pyrite	Gangue
Adularia	Gangue
Sericite	Gangue
Illite	Gangue
Kaolinite	Gangue
Montmorillonite	Gangue
Leucoxene	Gangue
Rutile	Gangue

Alteration

(Local) Silicic
Argillic

Mineral occurrence model information

Model code	104
USGS model code	25a
Deposit model name	Hot-spring Au-Ag
Mark3 model number	45

Host and associated rocks

Host or associated Host

Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite

Stratigraphic age (youngest) Miocene
Host or associated Host

Rock type Volcanic Rock (Aphanitic) > Pyroclastic Rock > Volcanic Breccia (Agglomerate)

Stratigraphic age (youngest) Miocene
Host or associated Associated

Rock type Metamorphic Rock > Gneiss

Stratigraphic age (youngest) Proterozoic
Host or associated Associated

Rock type Plutonic Rock > Granitoid > Granite

Stratigraphic age (youngest) Proterozoic
Host or associated Associated

Rock type Sedimentary Rock

Stratigraphic age (youngest) Miocene
Host or associated Associated

Rock type Volcanic Rock (Aphanitic)

Stratigraphic age (youngest) Miocene

Nearby scientific data

(1)	-115.10028, 35.28472	ListMap

Economic information

Ore body information

General form Lens (one ore body is roughly square in plan view; 150-425 m long, 150-250 m wide, 60-120 m thick)

General form	Lens (one ore body is roughly square in plan view; 150-425 m long, 150-250 m wide, 60-120 m thick)

Controls for ore emplacement

The primary physical controls for ore grade mineralization are high porosity and permeability in the host rocks and proximity to the sources of hydrothermal fluids.

Comments on the geologic information

INTRODUCTION

The Castle Mountains gold deposit is located in the Hart Mining District at an elevation of 4500 feet (1372 m) in the southern portion of the Castle Mountains in eastern San Bernardino County, California. The Castle Mountains are in the eastern Mojave Desert within the southern Basin and Range Province. They form a small range at the northern end of Lanfair Valley in eastern San Bernardino Co., California, and extend north into Nevada. The Castle Mountains are located near the western margin of the Colorado River extensional corridor, a major regional tectonic feature. The volcanotectonic evolution of the Castle Mountains and accompanying synvolcanic gold mineralization is believed to be associated with formation of the Colorado River extensional corridor. No regional low-angle normal (detachment) faults crop out in the Castle Mountains (or in the Piute Range to the south), although detachment faults are exposed to the west in the Kingston Range and to the east in the Black Mountains of Arizona. Local low-angle normal faults cut both the Miocene volcanic rocks and underlying gneiss in the northern part of the Hart Peak Quadrangle. East-dipping normal faults in the northeast Castle Mountains may be antithetic to a possible north-striking, low-angle normal fault or detachment surface in the Piute Valley. Structures in the Castle Mountains are temporally and spatially consistent with crustal extension in the region, but on a much smaller scale as compared to the highly extended Colorado River extensional terrane to the east (Linder, 1989; Capps and Moore, 1991, 1997; Nielson and Turner, 1999; Spencer, 1985).
ROCK UNITS (Linder, 1989; Capps and Moore, 1991, 1997; Nielson and Turner, 1999)

Proterozoic Basement:
The Castle Mountains are composed of a Proterozoic metamorphic and plutonic basement overlain by minor Paleozoic rocks and by Tertiary volcanic and sedimentary rocks. Proterozoic rocks are exposed in the northeastern Castle Mountains and to the northwest in the area bordering the New York Mountains. Granitoid rocks were also intersected in drill holes at a depth of 440 m (1444 feet) beneath the Jumbo South deposit at the southern end of the range. Rock types include both strongly and poorly foliated gneiss, leucocratic granitoids, pegmatitic and alaskitic rocks, amphibolite, and minor massive white and very-light-gray lenses of quartz. Possible protoliths are fine-grained rhyolitic volcanic rocks, pelites, and some basic rocks. The dominant metamorphic facies are amphibolite and lesser granulite. Pre-Miocene metamorphosed chloritic mylonite and cataclasite occur locally as discontinuous lenticular zones and pods. Some metamorphosed mylonitic zones follow compositional gneissic layering and contain minerals typical of upper amphibolite facies (sillimanite and K-feldspar). Other, lower grade, pre-Miocene, tectonized zones contain secondary calcite and quartz and are moderately to weakly hematitic (Linder, 1989; Capps and Moore, 1991, 1997).

Paleozoic Rocks:
A light- to medium-gray and light-reddish-gray, weakly dolomitic limestone is found in a minor outcrop in the northern Castle Mountains. The upper contact is with gneiss along a northeast-striking >10m (>33 feet) wide hematitic and chloritic fault zone; the lower contact with Proterozoic gneiss may be depositional. The limestone contains fossils that suggest a Lower Cambrian to Middle Devonian age (Capps and Moore, 1991, 1997).

Prevolcanic Miocene Sedimentary Rocks:

Discontinuous basal sedimentary rocks are light- and medium-greenish-gray and light-gray, poorly-sorted sedimentary conglomerates, coarse sandstone, and sedimentary breccia. These rocks crop out only in the northeastern Castle Mountains. A drill intercept beneath the Jumbo South deposit cut about 3.1 m (10 feet) of prevolcanic conglomerate at a depth of 438 m (1437 feet) overlying moderately weathered Proterozoic granitoid and underlying the basal rhyolite ash-flow tuff. Clasts are both subrounded and angular, and are derived from Proterozoic granitoid, pegmatitic rocks, and biotite gneiss. Clasts range in size up to 10 cm and usually occur in a coarse sand-size matrix (Capps and Moore, 1991, 1997).

Peach Springs Tuff:
The basal sedimentary units are overlain by the regionally extensive 18.5-Ma Peach Springs Tuff ("Castle Mountains Tuff" prior to correlation with the regionally extensive Peach Springs Tuff) and by younger Castle Mountains volcanic rocks. Locally, the basal conglomerate and overlying Peach Springs Tuff are thickest in the same areas, suggesting they both filled topographic lows (Capps and Moore, 1991, 1997).

Miocene Castle Mountains Volcanic Sequence (CMV):
The calc-alkaline CMV consists of rhyolitic domes, flows, and tuff, and lesser andesitic, latitic, and basaltic lava. The CMV includes all volcanic units above the Peach Springs Tuff and below the Piute Range volcanic rocks. These rocks were derived for the most part, if not entirely, from sources within the Castle Mountains (Linder, 1989; Capps and Moore, 1991, 1997).
ROCK UNITS (Linder, 1989; Capps and Moore, 1991, 1997; Nielson and Turner, 1999) (continued)

The CMV consists predominantly of rhyolitic rocks emplaced during three intrusive-extrusive episodes between <18.5 and 14 Ma. The CMV has been subdivided into three informal units on the basis of stratigraphic relations, composition, and isotopic ages by Capps and Moore (1991, 1996).

1) Rocks of Hart Peak (youngest; 15 to 14 Ma): a) Trachyandesite and trachydacite: intrusions and minor flows; b) Rhyolite: porphyritic rhyolite flows, plugs, and welded ash-flow tuff; pyroclastic-surge tuff; and volcaniclastic rock; c) Basalt: porphyritic to aphyric basalt and trachyandesite.
2) Rocks of Linder Peak (~15 Ma): rhyolite flow-dome complexes, abundant pyroclastic-surge tuff, and volcaniclastic rock.
3) Rocks of Jacks Well (oldest; <18.5 to 15.2 Ma): trachyandesite and basalt flows, minor rhyolite ash-flow tuff, and locally abundant lahar and sedimentary rock.

Tertiary Intrusive Rocks (Capps and Moore, 1997):
1. Rhyolite dikes: Rhyolite dikes, probably related to Linder Peak rhyolite, occur throughout the Castle Mountains but are most abundant in the northeastern Castle Mountains. Quartz-adularia veins locally cut the dikes.
2. Pyroclastic dikes and sills: Possible pyroclastic dikes and minor sills, 1 to 3 feet wide, cut Linder Peak rocks throughout the Castle Mountains. Clasts are Proterozoic metamorphic rocks and minor CMV rocks. A possible pyroclastic sill and baked zone occurs along the upper contact of the large diorite sill in the north-central Castle Mountains.
3. Andesite dikes and plugs: Fine-grained, unaltered andesite dikes and plugs occur throughout the Castle Mountains. The dikes are probably related to late Hart Peak or Piute Range volcanism.
4. Diorite sills and dikes: Dark-gray, medium-gray, and dark-brown, coarse- and medium-grained diorite dikes and sills occur in the north-central and northeastern Castle Mountains. The diorites locally intrude low-angle normal faults. The diorite is probably related to late Hart Peak volcanism.
ROCK UNITS (Linder, 1989; Capps and Moore, 1991, 1997; Nielson and Turner, 1999) (continued)

Tertiary Rocks Associated with areas of Mineralization and Alteration (Capps and Moore, 1997):

1. Quartz veins: Finely banded veins of quartz ? iron oxides, calcite, sericite, pyrite, clay minerals, and adularia occur throughout the Castle Mountains. Veins are common in the southern castle Mountains where they occupy N25?-35?-E-striking fractures and cavities formed by hydrothermal leaching within Linder Peak rhyolite. Quartz-after-calcite is common. Adjacent wall rock is commonly silicified and contains thin seams of clay and hydromica.
2. Hydrothermal breccia: Dikes, sills, pipes and small irregular bodies of silicified breccia and microbreccia are associated with gold mineralization. Most bodies are less than 1 foot wide, but dikes up to 800 feet long and 100 wide occur in the Jumbo South deposit. Intrusive breccia typically grades into mosaic fractured rock. Clasts include a wide range of Linder Peak rocks as well as Jacks Well and Proterozoic rocks, and quartz-calcite veins. Early breccia is distinguished by greater silicification, rounding, and sorting of clasts than in late breccia.

Post-CMV-Pre-Piute Range Conglomerate (Capps and Moore, 1991, 1997):
Light-gray, unconsolidated and unsorted conglomerate crops out extensively in the western Castle Mountains, where it overlies Hart Peak rocks, and in the eastern Castle Mountains and western Piute Range, where it underlies Piute Range volcanic rocks. The conglomerate is at least 98 feet thick in the western Castle Mountains and 150 to 300 feet thick in a paleocanyon that is exposed in the Jumbo South-Lesley Ann pit where it is overlain by up to 25 feet of arkose. Well-rounded clasts averaging 1 foot but ranging up to 10 feet in diameter reside in a matrix of medium to coarse sand. Clasts consist of regional Precambrian, Mesozoic, and Tertiary rock units; CMV clasts are present only in reworked upper portions of the conglomerate in the southern Castle Mountains (Capps and Moore, 1991, 1997).

Miocene Piute Range Volcanic Rocks (PRV):
The youngest PRV rocks in the Castle Mountains are 14- to 13-Ma trachyandesites, which crop out in a few small areas of the Castle Mountains and extensively in the Piute Range. These rocks are flat-lying to gently west-dipping and unconformable overlie more steeply tilted CMV, including altered Linder Peak rocks. Other PRV rocks that crop out in the Castle Mountains include rhyolite tuff; lahars, debris flows, mudflows, and epiclastic rocks; volcaniclastic rocks; dacite; trachyandesite flows, and agglomerate and volcanic breccia (Capps and Moore, 1991, 1997).

Tertiary and Quaternary deposits (Capps and Moore, 1997):
1. Carbonate deposits: Light-gray Tertiary limestone, < 30 feet thick, caps boulder conglomerate in Lanfair Valley and the valley between the Castle and New York Mountains, and overlies Hart Peak basalt in Lanfair Valley.
2. Unconsolidated deposits: Late Tertiary and Quaternary deposits include unconsolidated and calichified pediment and elevated terrace sediments and colluvium; dissected terraces, unconsolidated older stream sediments and flood deposits of gravel-poor sand and sandy gravel; and undifferentiated stream channel deposits of sand and gravel in modern channels Tertiary carbonate deposits (Capps and Moore, 1997):
Light-gray Tertiary limestone, < 30 feet thick, caps boulder conglomerate in Lanfair Valley and the valley between the Castle and New York Mountains, and overlies Hart Peak basalt in Lanfair Valley.
STRUCTURAL GEOLOGY (Linder, 1989; Capps and Moore, 1991, 1997; Nielson, 1998; Nielson and Turner, 1999; Spencer, 1985)

Miocene volcanism and structural trends of Miocene rocks and faults in the region have been attributed to Miocene continental extension. Regional-scale detachment faults are exposed in the Kingston Range to the west of the Castle Mountains, and detachment faults underlie the Black Mountains of Arizona to the east. No regional low-angle normal (detachment) faults crop out in the Castle Mountains (or in the Piute Range to the south), although detachment faults are exposed to the west in the Kingston Range and to the east in the Black Mountains of Arizona. Local low-angle normal faults cut both the Miocene volcanic rocks and underlying gneiss in the northern part of the Hart Peak Quadrangle. East-dipping normal faults in the northeast Castle Mountains may be antithetic to a possible north-striking, low-angle normal fault or detachment surface in the Piute Valley. High-angle northwest- to northeast-trending normal faults in the Castle Mountains are also attributed to Miocene crustal extension. Steep faults offset basement rocks at the boundary between the Castle Mountains and Piute Range to the south.

The Castle Mountains have a strong north-northeast trend as shown by the strike of rock units and numerous fractures and silicified zones. Dips are shallow and usually to the west. Structures of the Castle Mountains indicate four episodes of deformation. Proterozoic rocks show a strong crystalloblastic foliation that generally strikes northwest and dips moderately northeast. A probable Mesozoic northeast-striking fault displaces the Proterozoic rocks and a small outcrop of Paleozoic limestone. North-northeast-striking faults, fractures, hypabyssal dikes, and quartz-calcite veins indicate west-northwest extension between about 18.5 and 14 Ma. Subordinate Miocene northwest-striking structures may predate the Miocene northeast-striking structures. Faulting and fracturing occurred throughout the evolution of the Castle Mountains but ended by 14 Ma. The Peach Springs Tuff and rocks that comprise older rocks of the Castle Mountains volcanic sequence are variably tilted west. Westward-tilting of younger rocks of the Castle Mountains volcanic sequence is relatively minor (Capps and Moore, 1991, 1997).

One and one/half miles northwest of the Castle Mountains Mine, a series of arcuate, silicified, and mineralized fractures form a zone about 1500 feet wide and 7,000 feet long (Northwest Rim fracture zone). Linder (1989) suggested that these features may be rim fractures of a caldera about 3? miles in diameter that encloses the known mineralized area of the Hart Mining District at the southern end of the Castle Mountains. Alternatively, these features may be the ring fracture zone of a small intrusive body underlying the southern end of the Castle Mountains.

On the basis of their own work and the work of others, Nielson (1998) and Nielson and Turner (1999) present the following geologic observations and interpretations, among others:

1. Locally erupted volcanic sequences in the Hart Peak quadrangle, which covers the Castle Mountains, northern Piute Range, and Castle Peaks areas) all formed after deposition of the 18.5 Ma-Peach Springs Tuff.
2. All Miocene deposits older than 12.8 Ma are tilted (Turner and Glazner, cited in Nielson and Turner, 1999).
3. The timing of volcanic activity and deformation coincides with major episodes of extensional faulting in the nearby Black and El Dorado Mountains of Nevada and Arizona (Faulds and others, 1994, cited in Nielson and Turner, 1999).
STRUCTURAL GEOLOGY (Linder, 1989; Capps and Moore, 1991, 1997; Nielson, 1998; Nielson and Turner, 1999; Spencer, 1985) (continued)

4. The outcrop pattern that has been interpreted as an anticline in the Castle Mountains (Bingler and Bonham, 1973, Turner and Glazner, 1990, cited in Nielson and Turner, 1999) probably is not due to compressional folding, but more likely is an artifact of differential subsidence during volcanic eruptions that was driven by regional extensional faulting in the nearby El Dorado Mountains (Faulds and others, 1990, 1994, cited in Nielson and Turner, 1999).
5. The volcanic sequences of the Castle Mountains and Piute Range formed coevally, for the most part, in close proximity on an irregular topography.
6. Abrupt variation in thickness of rhyolite units in the Castle Mountains and Castle Peaks areas indicate that the rhyolite units accumulated in a half-graben that shoaled to the east.
7. Piute range faults with north to northeast strikes, and apparently steep dips down to the east, are members of a fault system that formed the western boundary of an eastern volcano-tectonic half-graben basin.
8. The volcanic rocks of the Castle Mountains and Piute Range were erupted in adjacent fault-bounded volcano-tectonic depressions. Piute Range lavas accumulated in an eastern basin (volcano-tectonic half-graben basin) coeval with eruption of Castle Mountains rhyolite ejecta and domes in the western basin (volcano-tectonic half-graben basin); edits in italics added by MRDS reporter).
MINERALIZATION (Linder, 1989; Capps and Moore, 1991, 1997)

Gold mineralization is widespread over an area of at least two square miles and has a vertical depth range of more than 1500 feet, as shown by drilling and by old mine workings. The Castle Mountains ore bodies can be classified as volcanic-hosted epithermal-type mineralization. Gold is the major metal present. Silver content is low and base metal sulfides are completely absent. The overall gold-to-silver ratio is about 1:2, but in the core of the deposits the ratio is reversed with a gold-to-silver ratio of 2:1. In general, the Castle mountains ore bodies are associated with brittle, permeable, well-fractured, brecciated rock units. Significant amounts of mineralization occur in all of the hydrothermally altered Tertiary rock units, but the rhyolite dome complexes and associated hydrothermal breccias are more likely to contain important amounts of ore than are the lithic tuffs. Known ore deposits are hosted by the Linder Peak member rhyolites, but gold mineralization is found in all lithologic units older than and including the basal Hart Peak member.

Typical ore rocks have intense silicification associated with fractures, breccias, and other open spaces, and are commonly stained by iron oxides, which locally form Liesegang bands. Gold occurs in quartz stockwork veins, matrix silicification, and with drusy quartz in cavities.

All ore reserves are in the oxidized zone, and only rare sulfide grains occur above the water table, which is at a depth of about 550 feet.

Most mineralization is very fine-grained and is not visible to the naked eye. Some coarse gold occurs in shallow underground workings, like the Oro Belle deposit, and minor amounts of visible gold occur in drill cuttings and cores.

Microprobe studies show that electrum and native gold are the only ore minerals, and electrum has a highly variable gold-silver ratio. Gold occurs as irregular grains, but some euhedral native gold is observed. Gold occurs within or attached to pseudomorphs of partially to completely oxidized pyrite interstitial to quartz grain boundaries. Gold is not seen with fresh pyrite and is rarely seen free in quartz. Trace chlorargyrite is the only silver mineral observed. Gold particles range from 1 to 2000 microns with an average of about 10 microns. Where fresh pyrite has been preserved in oxidized rhyolites, it is usually smaller than 10 microns or is encapsulated by silica.

Metallurgical tests show that the ore is amenable to treatment by conventional heap leaching methods, with gold recovery estimated at 65-70 percent.

Gangue minerals:
Gangue minerals with quartz include hematite, goethite, partially oxidized pyrite, and small amounts of fresh pyrite. Adularia occurs in some veins and in matrix silicification as intergrowths with quartz. Sericite, illite, kaolinite, and montmorillonite occur sometimes on vein margins or within voids. Leucoxene and rutile are less common gangue minerals.

Argillic alteration in the ore deposits is thought to be coeval with mineralization. Consistent K-Ar age dates on illite-sericite from various ore bodies indicate hydrothermal alteration and mineralization occurred at about the same time in all areas (14.17 ? 1.32 Ma to 14.9 ? 0.5 Ma). The K-Ar age dates on illite-sericite have good precision but may be younger than the actual age due to possible argon loss (Perry, 1974; Thompson and Hower, 1973; Stevens and Shillebeer, 1956; cited in Capps and Moore, 1991). The actual age of mineralization may be closer to the K-Ar date of 15.7 ? 0.6 Ma on adularia from the Jumbo South deposit, which compares with the 14.9 ? 0.5 Ma on illite-sericite from this same deposit. This alteration age suggests that mineralizing events in the Castle Mountains occurred about 15 million years ago in mid-Miocene time.
MINERALIZATION (Linder, 1989; Capps and Moore, 1991, 1997) (continued)

Mineralization controls:
The primary physical controls for ore grade mineralization are high porosity and permeability in the host rocks and proximity to the sources of hydrothermal fluids. Most reserves are in the relatively flat-lying, thick and laterally extensive Jumbo South and Lesley Ann deposits, which are adjacent to high-angle, silicified fracture zones thought to be conduits for ore-forming fluids.

Lithologic controls are more dependent on rock texture than rock type. Tuff beds, autobreccias, and hydrothermal breccias have permeable fragmental textures. Brittle rhyolite flows and intrusives exhibit intense fracturing and have cooling joints, vesicular zones, spherulitic vugs, and flow foliations. Mineralization occurs in secondary silica in all of these features.

Major fracture systems and intersections of fracture systems provided structural controls for mineralization. In the deposit area, north-northeast-striking, mineralized fracture zones are exposed in outcrop.

Mineral deposits (Linder, 1989; Capps and Moore, 1991, 1997):
The six ore deposits fit within a rectangular area 600 m by 1500 m (1 km2) on a north-northeast trend parallel to the major structural fabric of the Castle Mountains. The ore deposits have generally similar host rocks, alteration, chemistry, mode of gold occurrence, and gold:silver ratios. Silicification is common to all ore, and despite pervasive low intensity argillic alteration the best ore is low in clay content. Mineralization is associated with hematite and goethite after pyrite, but some broad barren zones are also high in iron oxides.

Ore deposits (6) (Capps and Moore, 1991)

Lesley Ann: 9,275,000 short tons proven reserves; 0.055 oz Au/ton; lenticular; plan view; N-S trend; 240 m long, 150 m wide, 120 m max. thickness; completely blind; buried under 45 to 90 m of Tertiary gravels;

Jumbo South: 8,585,000 short tons proven reserves; 0.041 oz Au/ton; lenticular plan view; N-NE trend; 300 m long, 150 m wide, 120 m max. thickness;

Oro Belle: 6,780,000 short tons probable reserves; 0.044 oz Au/ton; lenticular plan view; N-NE trend along silicified fracture zone with a steep SE dip; 300 m long, 250 m wide, 100 m max. thickness;

Southeast Extension: 7,108,900 short tons possible reserves; 0.034 oz Au/ton; lenticular plan view; N-NE trend, but the northern 1/3 trends N toward the Lesley Ann Deposit; 425 m long, 150 m wide, 60 m max. thickness;

Jumbo: 2,986,600 short tons possible reserves; 0.066 oz Au/ton; roughly square plan; 150 m long, 150 m wide, 120 m max. thickness;

Hart Tunnel: 3,376,000 short tons possible reserves; 0.055 oz Au/ton; slightly elongate on a N-NE trend; 210 m long, 180 m wide, 60 m thickness.

Mineable reserves in the six ore bodies had grades ranging from 0.034 to 0.066 oz Au/Ton; cut-off grade is 0.015 oz Au/ton.
MINERALIZATION (Linder, 1989; Capps and Moore, 1991, 1997) (continued)

Geochemistry (Capps and Moore, 1991):

An area of about 5 Km2, centered on the known ore deposits, is marked by anomalous gold in silt and soil samples. Anomalous amounts of silver, arsenic, antimony, mercury, and molybdenum mark the area of intense hydrothermal alteration, but are generally peripheral to the ore deposits. Gold is the only element, which consistently shows anomalies over the exposed mineralized rocks, including portions of the Oro Belle, Jumbo, and Jumbo South deposits. Arsenic anomalies occur near but not directly above the deposits.

Whole rock analyses show that the most consistent chemical signature of altered rhyolite is a high potassium to sodium ratio. Altered rhyolites also show significant enrichment in silica and potassium and depletion in sodium and aluminum. In whole rock samples, anomalous trace elements in both silicified and argillized rhyolite show erratic high values for arsenic, antimony, and mercury, and rare high values for molybdenum, beryllium, and copper.
OVERALL SUMMARY

Age of Mineralization: ~15 m.y. B.P, mid-Miocene

Host Rock Age: <18.5 to 14.6 m.y. B.P.

Associated Rock Types:
1. Proterozoic basement composed chiefly of strongly and poorly foliated gneiss, leucocratic granitoids, pegmatitic and alaskitic rocks, amphibolite, and minor massive white and very-light-gray lenses of quartz. Possible protoliths are fine-grained rhyolitic volcanic rocks, pelites, and some basic rocks. The dominant metamorphic facies are amphibolite and lesser granulite. Pre-Miocene metamorphosed chloritic mylonite and cataclasite occur locally as discontinuous lenticular zones and pods.
2. Prevolcanic Miocene Sedimentary Rocks: Basal conglomerate, coarse sandstone, and sedimentary breccia.
3. Peach Springs Tuff: 18.5-Ma Peach Springs Tuff.
4. Miocene Castle Mountains Volcanic Sequence (CMV): the calc-alkaline CMV consists predominantly of rhyolitic rocks emplaced during three intrusive-extrusive episodes between <18.5 and 14 Ma. The CMV consists of rhyolitic domes, flows, and tuff, and lesser andesitic, latitic, and basaltic lava. The CMV includes all volcanic units above the Peach Springs Tuff and below the Piute Range volcanic rocks. These rocks were derived chiefly, if not entirely from sources within the Castle Mountains.

Host Rock Unit: Chiefly (~15 Ma) rocks of the Linder Peak member of the Castle Mountains Volcanic Sequence (CMV) composed of rhyolite flow-dome complexes, abundant pyroclastic-surge tuff, and volcaniclastic rock.

Host rock also includes all hydrothermally altered Tertiary rock units (andesitic and rhyolitic flows, domes, and pyroclastic rocks) of the CMV.

The CMV has been subdivided into three informal units on the basis of stratigraphic relations, composition, and isotopic ages by Capps and Moore (1991, 1996).
1. Rocks of Hart Peak (15 to 14 Ma): a) trachyandesite and trachydacite intrusions and minor flows; b) rhyolite: porphyritic rhyolite flows, plugs, and welded ash-flow tuff; pyroclastic-surge tuff; and volcaniclastic rock; c) basalt: porphyritic to aphyric basalt and trachyandesite.
2. Rocks of Linder Peak (~15 Ma): rhyolite flow-dome complexes, abundant pyroclastic-surge tuff, and volcaniclastic rock.
3. Rocks of Jacks Well (<18.5 to 15.2 Ma): trachyandesite and basalt flows, minor rhyolite ash-flow tuff, and locally abundant lahar and sedimentary rock.

Host Rock Unit Age: <18.5 to 14 m.y. B.P.

Tectonic Setting:
The Castle Mountain Mine is located near the southern end of the Castle Mountains, which are located near the western margin of the Colorado River extensional corridor, a major regional tectonic feature. The volcanotectonic evolution of the Castle Mountains and accompanying synvolcanic gold mineralization is believed to be associated with formation of the Colorado River extensional corridor. No regional low-angle normal (detachment) faults crop out in the Castle Mountains (or in the Piute Range to the south), although detachment faults are exposed to the west in the Kingston Range and to the east in the Black Mountains of Arizona. Structures in the Castle Mountains are temporally and spatially consistent with crustal extension in the region, but on a much smaller scale as compared to the highly extended Colorado River extensional terrane to the east.
OVERALL SUMMARY (continurd)

Gold mineralization (~15 m.y. B.P.) occurs near centers of calc-alkaline volcanism and associated structures characterized by formation of chiefly rhyolitic flow-dome complexes and associated hydrothermal activity. A synvolcanic depression, or sag-caldera, formed during Linder Peak member volcanism in the southern Castle Mountains (Capps and Moore, 1991, 1997). The ore deposits of the southern Castle Mountains and the areas of most mineralization and alteration lie within the Linder Peak-member-age (~15 m.y. B.P.) sag-caldera. The Northwest Rim fracture zone, along which Hart Peak member sedimentary rocks are mineralized, may represent reactivation of the western edge of the sag-caldera during early Hart Peak member volcanism. Alternatively or in conjunction with formation of a sag-caldera: the volcanic rocks of the Castle Mountains and Piute Range were erupted in adjacent fault-bounded volcano-tectonic depressions (Nielson, 1998; Nielson and Turner, 1999). Piute Range lavas accumulated in an eastern volcano-tectonic half-graben basin coeval with eruption of Castle Mountains chiefly rhyolite ejecta and domes in the western volcano-tectonic half-graben basin.

Alteration: Silicification, argillization
Hydrothermal alteration occurs throughout the Castle Mountains but is most pervasive and intense in rhyolites of the Linder Peak member at the southern end of the range. Hydrothermal alteration occurs in older but not in the younger Hart Peak member rocks (youngest CMV rocks) or in the even younger Piute Range volcanic rocks. Most silicification is centered on the known ore deposits with a peripheral zone of argillic alteration that covers at least 5 km2. Many silicified areas are associated with north-northeast-striking fracture zones, fracture zone intersections, and permeable lithologic features. A separate silicified area occurs 2.8 km northwest of the ore deposits in an arcuate north-northeast-striking fracture zone (Northwest Rim fracture zone) 2.4 km long and 450 m wide.

Ore control:
The primary physical controls for ore grade mineralization are high porosity and permeability in the host rocks and proximity to the sources of hydrothermal fluids. Most reserves are in the relatively flat-lying, thick and laterally extensive Jumbo South and Lesley Ann deposits, which are adjacent to high-angle, silicified fracture zones thought to be conduits for ore-forming fluids.

Lithologic controls are more dependent on rock texture than rock type. Tuff beds, autobreccias, and hydrothermal breccias have permeable fragmental textures. Brittle rhyolite flows and intrusives exhibit intense fracturing and have cooling joints, vesicular zones, spherulitic vugs, and flow foliations. Mineralization occurs in secondary silica in all of these features.

Major fracture systems and intersections of fracture systems provided structural controls for mineralization. In the deposit area, north-northeast-striking, mineralized fracture zones are exposed in outcrop.

Depth of mineralization: Gold mineralization is widespread over an area of at least two square miles and has a vertical depth range of more than 1500 feet, as shown by drilling and by old mine workings.

Economic information about the deposit and operations

Operation type	Surface-Underground
Development status	Producer
Commodity type	Both
Deposit size	Medium
Significant	Yes
Discovery year	1907

Mining district

District name	Hart District

Land status

Ownership category	BLM Administrative Area
Area name	BLM Needles Field Office

Ownership information

Type Owner-Operator

Owner Viceroy Resource Corporation

Year 2007

Type	Owner-Operator
Owner	Viceroy Resource Corporation
Year	2007

Comments on the workings information

Workings Type:
1. Historic underground workings.
2. Modern open-pit workings; six ore deposits:

Description of Mine Workings:

1. Historic old workings consisted of short shafts, adits, or trenches; some had extensive underground workings and large waste dumps.

2. Modern open pits:
Lesley Ann: 9,275,000 short tons proven reserves; 0.055 oz Au/ton; lenticular; plan view; N-S trend; 240 m long, 150 m wide, 120 m max. thickness; completely blind; buried under 45 to 90 m of Tertiary gravels

Jumbo South: 8,585,000 short tons proven reserves; 0.041 oz Au/ton; lenticular plan view; N-NE trend; 300 m long, 150 m wide, 120 m max. thickness;

Oro Belle: 6,780,000 short tons probable reserves; 0.044 oz Au/ton; lenticularplan view; N-NE trend along silicified fracture zone with a steep SE dip; 300 m long, 250 m wide, 100 m max. thickness;

Southeast Extension: 7,108,900 short tons possible reserves; 0.034 oz Au/ton; lenticular plan view; N-NE trend, but the northern 1/3 trends N toward the Lesley Ann Deposit; 425 m long, 150 m wide, 60 m max. thickness;

Jumbo: 2,986,600 short tons possible reserves; 0.066 oz Au/ton; roughly square plan; 150 m long, 150 m wide, 120 m max. thickness;

Hart Tunnel: 3,376,000 short tons possible reserves; 0.055 oz Au/ton; slightly elongate on a N-NE trend; 210 m long, 180 m wide, 60 m thickness.

Comments on other economic factors

Production: 1,150,000 troy ounces (35.8 metric tons) of gold during modern mining operation (approximately 10 years).

Deposit Size: Reserves (proven + probable + possible) of over 38 million short tons of ore in six deposits (Hart Tunnel, Jumbo, Jumbo South, Lesley Ann, Oro Belle, and South Extension) totaling about two million ounces (62.2 metric tons) of gold in the ground.

The mine produced about 1,150,000 troy ounces (35.8 metric tons) of gold during its 10 years of operation.

Ore Grade: Historic mostly underground mining: First vein discovered in 1907 carried 11 oz Au/ton; one vein carried 500 oz Au/ton. Most ore averaged 1 to 2 oz Au/ton during historic early mining.
Modern open pit mining: Mineable reserves in the six ore bodies had grades ranging from 0.034 to 0.066 oz Au/ton; cut-off grade was 0.015 oz Au/ton.

Gold:silver ratio: Overall gold-to-silver ratio is about 1:2; in the core of the deposits the ratio is reversed with a gold-to-silver ratio of 2:1.

Comments on development

OVERVIEW

Gold was first discovered in the Castle Mountains in 1907 by James Hart and brothers, Bert and Clark Hitt. The original discovery was in high grade veins carrying as much as 500 oz Au/ton, but most of the ore contained 1 to 2 oz Au/ton. Production was not significant, despite extensive underground workings at the Oro Belle and Hart consolidated mines, and operations ceased within a few years. In 1933, the Big Chief mine (aka Valley View Mine) was opened with underground mining and a cyanide mill, but production was minor and the mine closed in 1942 (Linder, 1989; Capps and Moore, 1991).

The major gold deposits were discovered in 1986 by consulting geologist, Harold Linder. Viceroy Gold Corporation (subsidiary of Viceroy Resource Corporation), operator of the Castle Mountains Mine, announced pre-mine (1990) combined reserves of over 38 million short tons of ore in six deposits (Hart Tunnel, Jumbo, Jumbo South, Lesley Ann, Oro Belle, and South Extension) totaling about two million ounces (62.2 metric tons) of gold in the ground. In 1992, production began on a single open pit to mine the Jumbo South and Lesley Ann deposits with a combined ore grade of 0.048 oz Au/ton. Reserves for these deposits assume a cut-off grade of 0.015 oz Au/ton. Ore grades for the other four deposits varied between 0.044 and 0.046 oz Au/ton. Gold recovery varies between 65% and 70%. Mining ceased in May 2001; heap leaching of ore ceased in 2005. The mine produced about 1,150,000 troy ounces (35.8 metric tons) of gold during its 10 years of operation. Viceroy's holdings include over 2400 claims, which include most of the Castle Mountains (Linder, 1989; Capps and Moore, 1991, 1997; Kohler, 2002, 2006).

The district has also been mined for clay by other mining companies. Two open pit clay mines, each about 450 meters (1476 feet) in diameter, are located immediately west of the newly discovered gold deposits. A third clay pit with minor production is located southeast of the deposits. Clay production began in the 1920s; the most recent production, mid- to late-1980s, was sporadic and totaled about 10,000 tons annually (Capps and Moore, 1991).

HISTORIC MINING

1907: Gold was first discovered in Castle Mountains by James Hart and brothers, Bert and Clark Hitt. The original discovery was in high grade veins carrying as much as 500 oz Au/ton, but most of the ore contained 1 to 2 oz Au/ton. The town of Hart formed two months later and, at its peak had 400 tent and frame buildings, 6 saloons, a newspaper, but no churches or schools. In 1910, Hart had a population of 40. The boom was shot-lived; high-grade vein-gold proved very limited in exte4nt and did not continue at depth. Production was not significant, despite extensive underground workings at the Oro Belle and Hart consolidated mines, and operations ceased within a few years.

WWI: Efforts to reopen the mines were unsuccessful.

Early 1920s: Beginning of mining of large clay deposits (by other mining companies) immediately west of the gold deposits. The two clay pits are about 1500 feet in diameter; one has been mined to a depth of about 200 feet. Numerous old pits, excavations, and bulldozer trenches occur on the western side of the Castle Mountains, made by prospectors for other economic clay deposits.

1933-mid-1980s: In 1933, the Big Chief mine (aka Valley View Mine) was opened with underground mining and a cyanide mill, but production was minor and the mine closed in 1942. Large quantities of clay were shipped from the P.S. Hart Mine. The C-1 Clay Mine is marked by an open pit that now occupies much of the original townsite of Hart. Most clay was used for "sanitary ware" (toilets, lavatories). In the 1980s the clay was used to make tableware and floor and wall tile. Annual clay production reached about 10,000 tons depending on market demand.
HISTORIC MINING

1907: Gold was first discovered in Castle Mountains by James Hart and brothers, Bert and Clark Hitt. The original discovery was in high grade veins carrying as much as 500 oz Au/ton, but most of the ore contained 1 to 2 oz Au/ton. The town of Hart formed two months later and, at its peak had 400 tent and frame buildings, 6 saloons, a newspaper, but no churches or schools. In 1910, Hart had a population of 40. The boom was shot-lived; high-grade vein-gold proved very limited in exte4nt and did not continue at depth. Production was not significant, despite extensive underground workings at the Oro Belle and Hart consolidated mines, and operations ceased within a few years.

WWI: Efforts to reopen the mines were unsuccessful.

Early 1920s: Beginning of mining of large clay deposits (by other mining companies) immediately west of the gold deposits. The two clay pits are about 1500 feet in diameter; one has been mined to a depth of about 200 feet. Numerous old pits, excavations, and bulldozer trenches occur on the western side of the Castle Mountains, made by prospectors for other economic clay deposits.

1933-mid-1980s: In 1933, the Big Chief mine (aka Valley View Mine) was opened with underground mining and a cyanide mill, but production was minor and the mine closed in 1942. Large quantities of clay were shipped from the P.S. Hart Mine. The C-1 Clay Mine is marked by an open pit that now occupies much of the original townsite of Hart. Most clay was used for "sanitary ware" (toilets, lavatories). In the 1980s the clay was used to make tableware and floor and wall tile. Annual clay production reached about 10,000 tons depending on market demand.

1986-2005: Major gold deposits were discovered in 1986 by consulting geologist, Harold Linder. Viceroy Precious Metals, the original operator of the Castle Mountains Mine, announced pre-mine (1990) combined reserves of over 38 million short tons of ore in six deposits totaling about two million ounces of gold in the ground. In 1992, production began on a single open pit to mine the Jumbo South and Lesley Ann deposits. Mining ceased in May 2001, and heap leaching of ore ceased in 2005. The mine produced about 1,150,000 troy ounces (35.8 metric tons) of gold during its 10 years of operation.
MODERN MINING SINCE 1990?S

Year of Discovery: 1907: historic gold discovery; the major low-grade gold deposits were discovered in 1986.

Production Size: the mine produced about 1,150,000 troy ounces (35.8 metric tons) of gold during its 10 years of operation. Mining began in 1992 and ended in 2001; heap leaching was ongoing in 2005.

Owner: Viceroy Resource Corporation, Vancouver, British Columbia, Canada (Quest Capital Corporation, since December 2003) (75%); MK Gold Company, Boise, Idaho (25%). Other Viceroy entities assoc. with the Castle Mountain Mine: Viceroy Gold Corporation, Delaware (subsidiary of Viceroy Resource Corp.; Viceroy Precious Metals Corporation, Las Vegas, NV.

Development Status: Mining began in 1992 and ended in 2001; heap leaching and reclamation was ongoing in 2005.

Exploration and Development History:
1985 - 1990: Harold Linder, consulting geologist, examined the property for Viceroy Resource Corporation in June 1985, and recommended a major exploration program which he started in September 1985. In February 1986, Linder discovered the Jumbo South deposit and in September 1986, the Lesley Ann deposit, which is completely blind, and is covered by as much as 90 m of poorly consolidated gravels.

Viceroy completed over 130,500 m of drilling in 662 holes, including 3400 m of reverse circulation and 3500 m of diamond core drilling, to establish reserves and to conduct metallurgical testing. After initial discoveries, silt and grid soil geochemical surveys were conducted over an area of about 26 km2, and outcrop mapping of the main deposit area was conducted in 1987 by Rodney Watkins, consulting geologist.

Engineering studies were completed for a heap leach operation to mine the Jumbo South and Lesley Ann deposits with one open pit. The mine plan estimated ore production of 8,000 tons per day (2,800,000 short tons per year) in an open pit heap leach operation utilizing dilute cyanide solutions. The overall stripping ratio (waste overburden:ore) is 2.17:1; gold recovery was estimated at 65-70 percent; annual gold production was estimated at 110,000 ounces.

Ore is broken by blasting in closely spaced drill holes, loaded by electric shovels or front-end loaders onto haul trucks, and transported to the ore crusher. After three stages of crushing, the ore is reduced to a diameter of less than 3/8 inch. The ore is agglomerated with cement and water to increase percolation then conveyed to the leach pad.

After leaching, the concentrated gold-bearing cyanide solution is pumped through an electrolytic cell where the gold is deposited on steel wool. The gold-plated steel wool is melted in a furnace and poured into dore (gold-silver) bars at the mine site, and sold to a refinery for final processing.

Four additional ore bodies were discovered.

1990 - 1992: Viceroy announced pre-mine (1990) combined reserves of over 38 million short tons of ore in six deposits totaling about two million ounces of gold (62.2 metric tons) in the ground. In 1992, production began on a single open pit to mine the Jumbo South and Lesley Ann deposits.

1992 - 2001: Mining began in 1992 and ceased in 2001.

2001-- 2005: Heap leaching continued after cessation of mining in 2001, and ended in 2005. Reclamation was ongoing in 2005.
MINING AND PROCESSING METHODS

Recoveries: Metallurgical tests show that the ore is amenable to treatment by conventional heap leaching methods, with gold recovery at 65 to 70 percent.

Mining plans estimated ore production of 8,000 tons per day (2,800,000 tons per year) in an open pit heap leach operation utilizing dilute cyanide solutions. The overall stripping ratio (waste overburden:ore) is 2.17:1; gold recovery is estimated at 65-70 percent. Annual gold production was estimated at 110,000 ounces.

Ore is broken by blasting in closely spaced drill holes, loaded by electric shovels or front-end loaders onto haul trucks, and transported to the ore crusher. After three stages of crushing, the ore is reduced to a diameter of less than 3/8 inch. The ore is agglomerated with cement and water to increase percolation then conveyed to the leach pad.

After leaching, the concentrated gold-bearing cyanide solution is pumped through an electrolytic cell where the gold is deposited on steel wool. The gold-plated steel wool is melted in a furnace and poured into dore (gold-silver) bars at the mine site, and sold to a refinery for final processing.

RECLAMATION

Reclamation at the Castle Mountains project includes: 1) re-contouring of mined areas to blend with the surrounding terrain; 2) ongoing re-vegetation that entails stockpiling existing soils and relocating individual plant specimens (mainly barrel cacti and Joshua Trees) to an on-site nursery; 3) reclaiming existing disturbed areas created by mining operations during the past 75 years; and 4) construction of an information center featuring archaeological sites, historic sites, and mining techniques (both pioneering and modern) in the area of the Hart mining district.

Reference information

Bibliographic references

Deposit

Ausburn, K.E., 1991, Ore petrogenesis of Tertiary volcanic hosted epithermal gold mineralization at the Hart mining district, Castle Mountains, NE San Bernardino Co., California: Geological Society of Nevada, Great Basin Symposium, v. 2, p. 1147-1188.
Deposit

Bingler, E.C., and Bonham, H.F., 1973, Reconnaissance geologic map of the McCullough Range and adjacent areas, Clark County, Nevada: Nevada Bureau of Mines and Geology Map 45, scale 1:125,000.
Deposit

Buesch, D.C., 1993, Feldspar geochemistry of four Miocene ignimbrites in southeastern Calif. and western Ariz., in Sherrod, D.R., and Nielson, J.E., Tertiary Stratigraphy of Highly Extended Terranes, California, Arizona, and Nevada: U. S. Geological Survey Bulletin 2053 p. 55-69.
Deposit

Burchfiel, B.C., and Davis, G.A., 1977, Geology of the Sagamore Canyon-Slaughterhouse Spring area, New York Mountains, California: Geological Society of America Bulletin, v. 88, p. 1623-1640.
Deposit

Capps R.C., and Moore J., 1991, Geologic setting of mid-Miocene gold deposits in the Castle Mountains, San Bernardino County California and Clark County, Nevada: Geological Society of Nevada, Great Basin Symposium, v. 2, p. 1195-1219.
Deposit

Capps, R.C., 1993a, Volcano-tectonic evolution of the Castle Mountains: 22 to 14 Ma [abs.]: Geological Society of America Abstracts with Programs, Cordilleran-Rocky Mountain Sections meeting, v. 25, no. 5, p. 17-18.
Deposit

Capps, R.C., 1993b, Relative K/Ar ages of Tertiary magmatism and gold mineralization in the Hackberry Mountain - Lanfair Buttes - Castle Mountains area, California and Nevada [abs.]: Geological Society of America Abstracts with Programs, Cordilleran-Rocky Mountain Sections meeting, v. 25, no. 5, p. 18.
Deposit

Capps, R.C., 1996, Geologic setting of Miocene volcanogenic gold mineralization near the western margin of the Colorado River Extensional Corridor - Eastern Mojave Desert, California and Nevada [Ph.D. dissert.]: University of Georgia, Athens, 391 p.
Deposit

Capps, R.C., and Moore, J.A., 1997, Geologic map of the Castle Mountains, San Bernardino County, California and Clark County, Nevada: Nevada Bureau of Mines and Geology Online Documents, Map 108, scale 1:24,000; accompanying text: Castle Mountains geology and gold mineralization, San Bernardino County, California, and Clark County, Nevada, 20 pgs. Also available on the following website: http://www.nbmg.unr.edu/dox/m108text.pdf#search=%22capps%20and%20moore%20castle%20mountains%20geology%20and%20gold%20mineralization%22)
Deposit

Capps, R.C., and Moore, J.A., 1998, Castle Mountains Geology and Gold Mineralization, in Black Canyon of the Colorado River and Castle Mountains Gold Mine: South Coast Geological Society Guidebook 26, pgs. 149-169.
Deposit

Capps, R.C., Moore, J., and Mitchell, T.L., 1996, Geologic setting of Miocene gold mineralization in the Hackberry Mountain area, Getchel mining district, San Bernardino County, California: Proceedings of the Geological Society of Nevada Symposium, Geology and Ore Deposits of the American Cordillera, April 10-13, 1995, p. 871-890.
Deposit

Crowe, D.E., Mitchell, T.L., and Capps, R.C., 1996, Geology and stable isotope geochemistry of the Jumbo South - Lesley Ann Au deposit, California: Evidence for magmatic and meteoric fluid mixing, in Coyner, A.R., and Fahey, P.L., eds., Geology and Ore Deposits of the American Cordillera: Geological Society of Nevada Symposium Proceedings, Reno/Sparks, Nevada, April 1995, p. 891-907.
Deposit

Fiero, Bill, 1986, Geology of the Great Basin: University of Nevada Press,197 pgs.
Deposit

Hewett, D.F., 1956, Geology and mineral resources of the Ivanpah Quadrangle, California and Nevada: U. S. Geological Survey Professional Paper 275, 172 p.
Deposit

Kohler, Susan, 2002, California's non-fuel mineral production 2001: California Geological Survey web site, http://www.consrv.ca.gov/CGS/minerals/min_prod/non_fuel_2001.pdf
Deposit

Kohler, Susan, 2006, California non-fuel minerals 2005, in Mining Engineering, May 2006, pgs. 70-74.
Deposit

Linder, H., 1988, Geology of the Castle Mountains gold deposit in Faber, D.L. and Faber, M.L., eds., Geological Society of America Field Trip Guidebook: Cordilleran Section Meeting, Las Vegas, Nevada, p. 78-79.
Deposit

Linder, H., 1989a, Castle Mountains gold deposit, Hart mining district, San Bernardino County, California: California Geology, v. 42, no. 6, p. 134-144.
Deposit

Linder, H., 1989b, The Castle Mountains gold deposit, Hart district, San Bernardino County, California, in The California Desert Mineral Symposium (Compendium), U.S. Department of the Interior-Bureau of Land Management, p. 177-193.
Deposit

Longwell, C.R., Pampeyan, E.H., Bowyer, B., and Roberts, R.J., 1965, Geology and mineral deposits of Clark County, Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 218 p.
Deposit

Mariano, John, Helferty, M.G., and Gage, T.B., 1986, Bouguer and isostatic residual gravity maps of the Colorado River region, including the Kingman, Needles, Salton Sea, and El Centro quadrangles: U.S. Geological Survey Open-File Report 86-347, 7 sheets, scale 1:250.000.
Deposit

Medall, S.E., 1964, Geology of the Castle Mountains, California [M.S. thesis]: University of Southern California, 106 p.
Deposit

Miller, D.A., and Wooden, J.L., 1993, Geologic map of the New York Mountains area, California and Nevada: U.S. Geological Survey Open-File Report 93-198, 10 p.
Deposit

Miller, D.A., Frisken, J.G., Jachens, R.C., and McDonnell, J.R., Jr., 1986, Mineral resources of the Castle Peaks Wilderness Study Area, San Bernardino County, California: U.S. Geological Survey Bulletin 1713-C, 12p.
Deposit

Mitchell, T.L., 1994, The stable isotope geochemistry and geology of synvolcanic gold mineralization in the Jumbo South deposit, Castle Mountains, east Mojave, California - evidence for magmatic input [M.S. thesis]: University of Georgia, Athens, 150 p.
Deposit

Nielson, J.E. and Nakata, J.K., 1993, Tertiary stratigraphy and structure of the Piute Range, California and Nevada, in Sherrod, D.R., and Nielson, J.E., Tertiary Stratigraphy of Highly Extended Terranes, California, Arizona, and Nevada: U. S. Geological Survey Bulletin 2053, p. 51-53.
Deposit

Nielson, J.E., 1999, Geologic map of the East of Grotto Hills quadrangle, California: a digital database: U.S. Geological Survey Open-File Report 99-35, downloadable text 9 pgs.
Deposit

Nielson, J.E., Frisken, J.G., Jachens, R.C., and McDonnell, J.R., Jr., 1987, Mineral resources of the Fort Piute Wilderness Study Area, San Bernardino County, California: U.S. Geological Survey Bulletin 1713, 12 p.
Deposit

Nielson, J.E., Glazner, A.F. and Lux, D.R., 1988, Problems of dating the Peach Springs Tuff [abs.]: Geological Society of America Abstracts with Programs, Cordilleran Section, 84th Annual Meeting, p. 218.
Deposit

Nielson, J.E., Lux, D.R., Dalrymple, G.B., and Glazner, A. F., 1990, Age of the Peach Springs Tuff, Southeastern California and western Arizona: Journal of Geophysical Research, v. 95, No. B1, p. 571-580.
Deposit

Nielson, J.E., Turner, R.D., and Bedford, D.R., 1999, Geologic Map of the Hart Peak Quadrangle, California and Nevada: A Digital Database: U.S. Geological Survey Open-File Report 99-34. Online Links: < http://wrgis.wr.usgs.gov/open-file/of99-34/ >
Deposit

Nielson, J.E., Turner, R.D., and Glazner, A.F., 1993, Tertiary stratigraphy and structure of the Castle Mountains and Castle Peaks, California and Nevada, in Sherrod, D.R., and Nielson, J.E., Tertiary Stratigraphy of Highly Extended Terranes, California, Arizona, and Nevada: U. S. Geological Survey Bulletin 2053, p. 45-49.
Deposit

Portions of various unpublished reports, and information from various Internet websites, contained in CGS (formerly CDMG) Minefile Folder No. 322-5530.
Deposit

Potts, D.A., and Cline, J.S., 1992, Preliminary petrographic and fluid inclusion study of the Oro Belle and Lesley Ann deposits from the Castle Mountains gold deposit, Hart mining district, San Bernardino County, California: Fourth Biannual Pan-American Conference on Research on Fluid Inclusions, Program and Abstract, University of California, Riverside, p. 66.
Deposit

Reynolds, S. J., 1988, Geologic map of Arizona, in Jenney J.P. and Reynolds, S. J., 1989, Geologic evolution of Arizona: Arizona Geological Digest, v. 17, scale 1:1,000,000.
Deposit

Smith, E., Feuerbach, D.L., and Naumann, T.R.,1990, Mid-Miocene volcanic and plutonic rocks in the Lake Mead area of Nevada and Arizona; production of intermediate igneous rocks in an extensional environment, in Anderson, J.L., ed., The nature and origin of Cordilleran magmatism: Geological Society of America Memoir 174, p. 169-194.
Deposit

Spencer, J.E. and Reynolds, S.J., 1989, Middle Tertiary tectonics of Arizona and adjacent areas: in Geological Evolution of Arizona, Arizona Geological Society Digest 17, p. 539-574.
Deposit

Spencer, J.E., 1985, Miocene low-angle normal faulting and dike emplacement, Homer Mountain and surrounding areas, southeastern California and southernmost Nevada: Geological Society of America Bulletin, v. 96, p. 1140-1155.
Deposit

Turner, R. D. and Glazner, A.F. 1990, Miocene volcanism, folding, and faulting in the Castle Mountains, southern Nevada, and eastern California, in Wernicke, B. P., ed., Basin and range extensional tectonics near the latitude of Las Vegas, Nevada: Geological Society of America Memoir 176, p. 23-35.
Deposit

Turner, R.D., 1985, Miocene folding and faulting of an evolving volcanic center in the Castle Mountains, southeastern California and southern Nevada [M.S. thesis]: University of North Carolina, 56 p.
Deposit

Viceroy Resources Corporation, 1988 Annual Report
Deposit

Weber, M.E., and Smith, E.I., 1987, Structural and geochemical constraints on the reassembly of mid-Tertiary volcanoes in the Lake Mead area of southern Nevada: Geology, v. 15, p. 553-556.
Deposit

Wells, R.E., and Hillhouse, J.W., 1989, Paleomagnetism and tectonic rotation of the Lower Miocene Peach Springs Tuff: Colorado Plateau, Arizona to Barstow, California: Geological Society of America Bulletin, v. 101, p. 846-863.
Deposit

Williams, W.J.W, 1992, Hydrothermal alteration associated with volcanic-hosted Miocene gold mineralization of the Jumbo South deposit, Hart District, Castle Mountains, San Bernardino County, California [M.S. thesis]: University of California, Riverside, 322 p.
Deposit

Wohletz, K.H., and Sheridan M.F., 1979, A model of pyroclastic surge: in Chapin, C.E., and Elston, W.E., eds., Ash-flow tuffs: Geological Society of America Special Paper 180, p. 177-194.
Deposit

Wooden, J.L., Miller, D.M., and Elliot, G.S., 1986, Early Proterozoic geology of the northern New York Mountains, southeastern California [abs.]: Geological Society of America Abstracts with Programs, v. 18, no. 5, p. 424.
Deposit

Young, R.A., and Brennan, W.J., 1974, Peach Springs Tuff: its bearing on structural evolution of the Colorado Plateau and development of Cenozoic drainage in Mohave County, Arizona: Geological Society of America Bulletin, v. 85, no. 1, p. 83-90.

General comments

Subject category	Comment text
Deposit	The Castle Mountain deposit is associated with centers of mid-Miocene calc-alkaline volcanism and related structures, and hydrothermal activity that deposited gold and electrum in permeable, brittle, well-fractured, and brecciated host rocks of chiefly rhyolite flow-dome complexes and associated hydrothermally altered, silicified, and mineralized breccias. These mineralized rocks overlie pre-mineralization, Miocene age, rhyolitic ash-flow tuff, latitic to basaltic but mostly andesitic flows, and associated volcaniclastic sedimentary rocks, which, in turn, overlie a Miocene pre-volcanic sedimentary basal conglomerate and Proterozoic basement composed mostly of well-foliated gneiss, leucocratic granitoids, pegmatitic and alaskitic rocks, and amphibolite. Possible basement rock protoliths are fine-grained rhyolitic volcanic rocks, pelites, and some basic rocks. Gold mineralization is widespread over an area of at least two square miles and has a vertical depth range of more than 1500 feet, as shown by drilling and by old mine workings. The Castle Mountains ore bodies can be classified as volcanic-hosted epithermal-type mineralization. Gold is the major metal present. Silver content is low and base metal sulfides are completely absent. The overall gold-to-silver ratio is about 1:2, but in the core of the deposits the ratio is reversed with a gold-to-silver ratio of 2:1. In general, the Castle mountains ore bodies are associated with brittle, permeable, well-fractured, brecciated rock units. Significant amounts of mineralization occur in all of the hydrothermally altered Tertiary rock units, but the rhyolite dome complexes and associated hydrothermal breccias are more likely to contain important amounts of ore than are the lithic tuffs. Known ore deposits are hosted by the Linder Peak member rhyolites, but gold mineralization is found in all lithologic units older than and including the basal Hart Peak member. Typical ore rocks have intense silicification associated with fractures, breccias, and other open spaces, and are commonly stained by iron oxides, which locally form Liesegang bands. Gold occurs in quartz stockwork veins, matrix silicification, and with drusy quartz in cavities.

Subject category

Comment text

Deposit

The Castle Mountain deposit is associated with centers of mid-Miocene calc-alkaline volcanism and related structures, and hydrothermal activity that deposited gold and electrum in permeable, brittle, well-fractured, and brecciated host rocks of chiefly rhyolite flow-dome complexes and associated hydrothermally altered, silicified, and mineralized breccias. These mineralized rocks overlie pre-mineralization, Miocene age, rhyolitic ash-flow tuff, latitic to basaltic but mostly andesitic flows, and associated volcaniclastic sedimentary rocks, which, in turn, overlie a Miocene pre-volcanic sedimentary basal conglomerate and Proterozoic basement composed mostly of well-foliated gneiss, leucocratic granitoids, pegmatitic and alaskitic rocks, and amphibolite. Possible basement rock protoliths are fine-grained rhyolitic volcanic rocks, pelites, and some basic rocks.

Gold mineralization is widespread over an area of at least two square miles and has a vertical depth range of more than 1500 feet, as shown by drilling and by old mine workings. The Castle Mountains ore bodies can be classified as volcanic-hosted epithermal-type mineralization. Gold is the major metal present. Silver content is low and base metal sulfides are completely absent. The overall gold-to-silver ratio is about 1:2, but in the core of the deposits the ratio is reversed with a gold-to-silver ratio of 2:1. In general, the Castle mountains ore bodies are associated with brittle, permeable, well-fractured, brecciated rock units. Significant amounts of mineralization occur in all of the hydrothermally altered Tertiary rock units, but the rhyolite dome complexes and associated hydrothermal breccias are more likely to contain important amounts of ore than are the lithic tuffs. Known ore deposits are hosted by the Linder Peak member rhyolites, but gold mineralization is found in all lithologic units older than and including the basal Hart Peak member.

Typical ore rocks have intense silicification associated with fractures, breccias, and other open spaces, and are commonly stained by iron oxides, which locally form Liesegang bands. Gold occurs in quartz stockwork veins, matrix silicification, and with drusy quartz in cavities.

Reporter information

Type	Date	Name	Affiliation	Comment
Reporter	31-AUG-2006	Hill, Robert L.	California Geological Survey CGS (Formerly CDMG)
Editor	20-FEB-2008	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: Q137842036 (Castle Mountain Mine)

Maps centered on this site

Authoritative California resources

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