Twin Creeks Mine

Producer in Humboldt county in Nevada, United States with commodities Gold, Silver, Lead, Zinc, Arsenic, Mercury, Antimony, Barium-Barite
Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Ore body information
  14. Controls for ore emplacement
  15. Economic information about the deposit and operations
  16. Mining district
  17. Land status
  18. Ownership information
  19. Bibliographic references
  20. General comments
  21. Reporter information

Geologic information

Identification information

Deposit ID 10310333
MRDS ID M242950
Record type Site
Current site name Twin Creeks Mine
Alternate or previous names Chimney Creek Mine, Rabbit Creek Mine, Mega pit (the merged pit), DZ Zone, Main, Chert Zone, HGO Zone, Jackrabbit Zone, LGO Zone, Sage, Section 8, Snowshoe Zone, South Layback, Section 30, South Oxide, Upper Sill Zone, West Pit, SWS Zone
Related records 10047577

Comments on the site identification

  • The Twin Creeks Mine was formed in 1987 from the merging of the pits of the Chimney Creek mine and the Rabbit Creek mine. All pertinent material from earlier records M242950, M042791, W700409, and W700381 for those two mines has been incorporated into this record along with other new material.

Geographic coordinates

Geographic coordinates: -117.15096, 41.28322 (WGS84)
Elevation 1590
Relative position The Twin Creeks Mine is located about 40 miles NE of Winnemucca.\n\n

Site location context

Political divisions (FIPS codes)

Humboldt(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Dry Hills North(quadrangle 1:24,000 scale)

Osgood Mountains(quadrangle 1:100,000 scale)

McDermitt(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Middle Humboldt(hydrologic unit)

Humboldt(hydrologic accounting unit)

Black Rock Desert-Humboldt(hydrologic subregion)

Great Basin(hydrologic region)

Geographic areas

Country State County
United States Nevada Humboldt

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 039N 042E 12, 13 24 Nevada
Mount Diablo 039N 043E 05 06 07 08, 18, 19, 30 Nevada

Comments on the location information

  • The Twin Creeks Mine is located about 6 miles northeast of the Getchell Mine in the Dry Hills off the northeast flank of the Osgood Mountains.

Commodities

Commodity Importance
Gold Primary
Silver Primary
Lead Tertiary
Zinc Critical Tertiary
Arsenic Critical Tertiary
Mercury Tertiary
Antimony Critical Tertiary
Barium-Barite Critical Tertiary

Comments on the commodity information

  • Ore Materials: gold
  • Gangue Materials: albite, chlorite, kaolinite, sericite, calcite, amphibole, quartz, pyrite, augite, epidote, limonite, leucoxene, K-feldspar, tourmaline, fluorite, barite, organic carbon, goethite

Materials information

Materials Type of material
Gold Ore
Albite Gangue
Chlorite Gangue
Kaolinite Gangue
Sericite Gangue
Calcite Gangue
Amphibole Gangue
Quartz Gangue
Pyrite Gangue
Augite Gangue
Epidote Gangue
Limonite Gangue
Leucoxene Gangue
Feldspar Gangue
Tourmaline Gangue
Fluorite Gangue
Barite Gangue
Goethite Gangue

Alteration

  • (Local) Decalcification, silicification, dolomitization, argillization, and minor sericitization of sediments. Albitization and propylitization of basalt. Decalcification increased porosity, allowing introduction of mineralizing fluids. Silica was introduced in several stages in the HGO orebody. Dolomitization accompanied one of the silicification stages. Argillization is important in the LGO orebody. Hydrothermal alteration formed sericite, kaolinite, dickite, alunite, natroalunite. A zone of phyllic alteration, 50 m wide around feeder zone, contains ore-grade mineralization. Carbonate dissolution zones; two generations of silicification (jasperoid); propylitic alteration of basalts.

Mineral occurrence model information

Model code 173
USGS model code 26a.1
Deposit model name Sediment-hosted Au
Mark3 model number 17

Host and associated rocks

  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Shale
    Rock type qualifier interlayered calcareous
    Rock unit name Valmy and Comus Formations
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Siltstone
    Rock unit name Valmy and Comus Formations
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Sedimentary Rock > Chemical Sediment > Chert
    Rock unit name Valmy and Comus Formations
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Mafic Volcanic Rock
    Rock unit name Valmy and Comus Formations
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Sedimentary Rock > Carbonate > Limestone
    Rock type qualifier carbonaceous
    Rock unit name Etchart Limestone
    Stratigraphic age (youngest) Early Permian
    Stratigraphic age (oldest) Middle Pennsylvanian
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Pyroclastic Rock > Tuff
    Rock type qualifier basaltic hydroclastic
    Stratigraphic age (youngest) Ordovician
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt
    Rock type qualifier basalt
    Stratigraphic age (youngest) Ordovician
  • Host or associated Associated
    Rock type Sedimentary Rock > Mixed Clastic/Volcanic Rock
    Rock type qualifier volcaniclastic
    Stratigraphic age (youngest) Ordovician
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt
    Rock type qualifier basaltic sills
    Stratigraphic age (youngest) Ordovician
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt
    Rock type qualifier lava flows
    Stratigraphic age (youngest) Ordovician
  • Host or associated Associated
    Rock type Plutonic Rock > Ultramafic Intrusive Rock
    Rock type qualifier ultramafic (iherzolite) sills
    Stratigraphic age (youngest) Ordovician

Nearby scientific data

(1) -117.15096, 41.28322

Economic information

Geologic structures

Type of structure Local
Structure description The Conelea overturned anticline dominates the structural picture of the early Rabbit Creek Mine area. The fold axis strikes N20-30W, dips 20-30 degrees southwest, and plunges 5 degrees northwest. The Conelea Anticline is offset by three NE-striking faults; the northernmost of the three (DZ fault) has about 2000 ft. of dextral offset. The DZ fault is interpreted as a Riedel "R" shear associated with an inferred major N-S basement suture with right lateral offset, the "Rabbit Suture". Low angle unconformity developed in the Gough's Canyon Formation. The Chimney Creek deposit occurs along a northeasterly range front lineament that is probably an extension of the Getchell Fault. Host rocks strike NE, dip 21-32 NW.
Type of structure Regional
Structure description Leviathan allochthon. Antler orogenic belt. major, deep seated, N-S structural zone (suture) 40 km (25 miles) long, known as the Getchell high-angle fault system bounds the eastern flank of the Osgood Mountains. N-S trending belt of gold mineralization that is at least 5.6 km (3.5 miles) long and 300 m (1000 ft) to 450m (1500ft) wide. Roberts Mountain Thrust (below) and the Golconda Thrust (above), intruded by the mid-Cretaceous Osgood Mt. granodiorite and related trachyandesite dikes.

Ore body information

  • General form tabular to irregular

Controls for ore emplacement

  • The "Rabbit Suture" is considered a first order control. The DZ fault was probably a feeder fault. Favorable calcareous lithologies within NW- trending overturned anticline are stratigraphic controls. Bedding in the lower member of the Etchart Limestone. Complex tectonics, stratigraphy and alteration.

Comments on the geologic information

  • The original Rabbit Creek Gold Deposit was concealed under a thick series of coalescing alluvial fans forming a pediment of the Osgood Mountains. The ore body occurs in Paleozoic sedimentary rocks which are completely covered by quaternary sand, gravel and clay. The Paleozoic rocks deposited in a eugeosynclinal environment were extensively deformed during three pre-Tertiary tectonic events. Thrusting during the Antler and Sonoma orogenies brought Western facies deep water units over or interleaved them with Eastern facies, shallow water units in a complex assemblage. Thrusts are generally N-NE striking. Paleozoic units are tilted and folded, often isoclinally, and steeply dipping. During the basin and range extension mafic and felsic dikes were intruded. High angle faults played a primary role in localizing the flow of hydrothermal systems responsible for the deposition of gold. Host rocks are black, carbonaceous, calcareous shales, siltstones, cherts, interbedded basaltic hydroclastic tuffs, and coeval basalts and volcaniclastics. Concordant sills and lava flow of high-titanium basalts of tholeiitic-to-alkalic composition.
    The Chimney Creek Deposit is stratigraphically and tectonally complex. The deposit is sandwiched between the mid-Paleozoic Roberts Mountain Thrust and the Permo-Triassic Golconda Thrust. Alteration and mineralization re channeled into the thick bedded lower member of the Etchart Limestone along high angle fault feeder zones in the Gough's Canyon Formation and spread out laterally along bedding to form a conformable sediment-hosted gold-silver deposit above a disconformable structurally controlled volcanic-hosted feeder zone. Mineralization occurs exclusively in the Gough's Canyon Formation and the lower members of the Etchart Limestone. The highest Au-Ag grades are coincident with the most severe carbonate dissolution zones in the etchart formation. Gold grade drops off slightly with increasing distance from the projected feeder pipes. Au-bearing bedded jasperoids form tabular bodies from 30-50m thick extending at least 600 m outward from the center of the chimney creek. Alteration is pervasive and extensive inside and below the orebody. Etchart Formation, 850 m thick, consists of siliciclastic carbonate shallow water sequence ( rich in silicate mineral detritus), pebbly litharenite, siltstone, sandy dolomite and dolomite. Metamorphosed d altered basalts, ranging from greenschists retaining igneous textures to intensely hydrothermally altered rocks. Dacite dikes are related to the Osgood Mountains granodiorite and cut altered rocks and are themselves altered.

Economic information about the deposit and operations

Operation type Surface
Development status Producer
Commodity type Both
Significant Yes
Discovery year 1985
Discoverer Gold Fields Mining Corp./ Santa Fe Pacific Gold
Year of first production 1986
Year of last production 2006
Production years 1987-present

Mining district

District name Potosi District

Land status

Ownership category Private
Area name Winnemucca BLM Administrative District
Ownership category BLM Administrative Area

Ownership information

  • Type Owner-Operator
    Owner Newmont Gold Co.
    Year 2006

Comments on the workings information

  • Twin Creeks is developed as a large open pit mine by the Mega-pit with the Sage layback at the north end and the Section 30 layback at the south end, plus the Vista pit to the north. Two mills (Pinon and Sage), heap leach facilities, waste rock dumps, ore stockpiles.

Comments on other economic factors

  • From 1987 to 1996, 3,346,538 troy ounces of gold and more than 150,780 troy ounces of silver were produced from 108,531,000 short tons of ore. The remaining resource as of 1996 was 305,449,000
    short tons of ore grading 0.06 opt gold. In mid-1996, gold reserves at Twin Creeks stood at 10.5 million ounces.
    In 2002 the reported proven and probable reserves for Twin Creeks Mine were: 47.6 million tons of ore grading 0.081 ounces of gold per ton plus measured and mineralized material: 55 million tons grading 0.057 ounces of gold per ton, as well as inferred mineralized material of 1.8 million tons grading 0.046 opt Au ounces of gold per ton.
    Twin Creeks Mine production from 1993 through 2002 was 6,614,829 ounces of gold and 1,794,678 ounces of silver.

Comments on development

  • The Chimney Creek deposit was discovered in 1985 by Gold Fields Mining Corp., after which Santa Fe Pacific geologists reviewed the railroad grant sections in the adjacent Rabbit Creek area. They identified and drilled a strong N-S photolineament between the Chimney Creek to Rabbit Creek deposits and the third round of drilling in January 1987 dicovered the Rabbit Creek orebody. Prestripping commenced March 1989, mill and heap leach construction began in August 1989, and initial production began August 1990 utilizing oxide ores with an output of 200,000 ounces of gold per year. In 1993, Santa Fe Pacific Gold Company's Chimney Creek Mine and Rabbit Creek Mine merged into one "mega pit" which since that time has been called the Twin Creeks Mine.
    In 1997, Newmont Gold Company acquired the property as part of its takeover of Santa Fe Pacific. Since the merger of the two mines, Twin Creeks' production has averaged about a half million ounces of gold per year. Production decreased temporarily due to an incident in late 1994 in which about 3 million tons of overburden slid into the Twin Creeks pit covering ore that was scheduled to be mined in 1995.
    In mid-1996, gold reserves at Twin Creeks stood at 10.5 million ounces. Santa Fe Pacific increased its exploration budget to drill test extensions south of the main pit, as well as sulfide mineralization around the Vista Pit and two underground targets. In early 1997, the mine began a sulfide expansion project which included construction of two 4,000 tpd autoclave circuits, which was expected to increase Twin Creeks' annual production by about 100,000 ounces of gold. SFPG also invested $30 million in its shovel and haulage fleet, including the addition of a new electric shovel with a 56-cubic yard bucket, the largest of its kind in the industry.
    In 1996, deep exploration targets (to 3,000-feet) were drilled below the Vista and Mega pits. Santa Fe?s efforts to expand gold resources at the Twin Creeks mine during 1996 focused on three areas: the Galena vein, Zone 40, and Section 30 South Mega pit.
    Newmont acquired Santa Fe Pacific Gold Corporation in 1997, adding Twin Creeks, Lone Tree and several satellite deposits near Winnemucca to its portfolio. The Sage layback was broadly drilled by Santa Fe Pacific Gold in the mid-1990s. Infill drilling and a new model by Newmont in late 2002 were successful in adding high-grade ounces and reducing layback costs by $50 per ounce. Sage was added to Twin Creeks? reserves in 2003. The Sage ore body is a northern extension of the existing Twin Creeks Mega pit, and occurs in the overturned fold axis of a NW-trending anticline at depths of 600 to 1200 feet. The carbonaceous and sulfide ore will be processed through the Sage autoclave

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit The original gently dipping mineralized zone containing significant gold values was found in an area about 1600 by 800 feet covered by 60m to 165 m of alluvium. It consisted of a gold-bearing tabular jasperoid body 30-50 m thick extending at least 600 m outward from the center of Chimney Creek. Seven other nearby gold mineralized zones were soon recognized. These zones were first developed as the separate Rabbit Creek and Chimney Creek open pit mines, later merged into a single ?Mega-pit?. In the Section 30 South Mega pit area, mill-grade oxide mineralization was found in both limbs of a large fold, with mineralization extending more than 1,500 feet south of the limit of the Mega pit as currently planned. All three target areas were drilled extensively in 1996 and1997, and Santa Fe Pacific Gold intersected "high-grade" in some of their drilling below the Twin Creeks pit. The Galena vein underground target is relatively high-grade (0.25-0.40 opt) mineralization within a northeast-southwest trending fault zone in the greenstones immediately beneath the Vista deposit north of the Mega pit. The target extended along strike for over 1,000 feet and about 500 feet down the structure, averaging about 10-15 feet wide, open along strike and at depth. The Zone 40 target is a fold-controlled zone of high-grade (about 0.5 opt) refractory mineralization at the bottom of the Mega pit.
The Sage ore body is a northern extension of the existing Twin Creeks Mega pit, and occurs in the overturned fold axis of a NW-trending anticline at depths of 600 to 1200 feet. The carbonaceous and sulfide ore will be processed through the Sage autoclave.
Most gold values are found in calcareous shales in the Ordovician sequence and in limestones in the Etchart Formation, although not all layers contain the same amount of gold. Strongest gold mineralization is not adjacent to faults but the form and distribution of mineralization suggests that gold-bearing solutions gained access to favorable layers along faults. In the Ordovician sequence, gold values are highest in shales that have undergone maximum dissolution of carbonate minerals. Petrographic study shows that some gold is associated with adularia, but deposit-scale comparisons do not show a consistent relation between K/Al ratios and gold values. The distribution of antimony is similar to that of gold, whereas mercury is more concentrated than gold, and arsenic is more widely dispersed than gold. The relation between gold, iron, and sulfide sulfur values shows that mineralization is concentrated in rocks that have gained sulfur, but not iron, to form gold-bearing arsenian pyrite. Thus, these rocks have undergone sulfidation rather than pyritization. The iron that underwent sulfidation came largely from preore, diagenetic(?) ferroan dolomite and was released into solution by decarbonation, a common form of alteration associated with Carlin-type deposits. It appears tha wall-rock iron content and decarbonation processes which liberate this iron are the most important factors controlling formation of this Carlin-type gold deposit.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-DEC-2006 LaPointe, D.D. Nevada Bureau of Mines and Geology
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.

Authoritative Nevada resources

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