Summary:
The deposits that comprise the Nevada Operations are considered to be examples of Carlin-style carbonate-hosted disseminated gold–silver deposits and intrusion-related gold–copper–silver skarn deposits.
At Cortez, mineralization is sedimentary rock-hosted and consists of submicron to micrometer-sized gold particles and gold in solid solution in pyrite. Phoenix is a skarn-hosted polymetallic massive sulfide replacement deposit. Carlin, Turquoise Ridge, and Long Canyon are a sediment-hosted disseminated gold deposit.
Host rocks for Carlin-style deposits are most commonly thinly-bedded silty or argillaceous carbonaceous limestone or dolomite, commonly with carbonaceous shale. Although less mineralized, non-carbonate siliciclastic and rare metavolcanic rocks can locally host gold that reaches economic grades. Felsic plutons and dikes may also be mineralized at some deposits. Deposits typically have a tabular shape, are stratabound, localized at contacts between contrasting lithologies, but can also be discordant or breccia related. Mineralization consists primarily of micrometer-sized gold and sulfide grains disseminated in zones of siliciclastic and decarbonated calcareous rocks and are commonly associated with jasperoids. Major ore minerals include native gold, pyrite, arsenopyrite, stibnite, realgar, orpiment, cinnabar, fluorite, barite, and rare thallium minerals. Gangue minerals typically comprise fine-grained quartz, barite, clay minerals, carbonaceous matter, and late-stage calcite veins.
Host rocks for intrusion-related gold–copper–silver skarn deposits include sedimentary carbonates, calcareous clastic rocks, volcaniclastic rocks or (rarely) volcanic flows. They are commonly related to high to intermediate-level stocks, sills, and dykes of gabbro, diorite, quartz diorite, or granodiorite composition. Mineralization frequently displays strong stratigraphic and structural controls. Deposits can form along sill–dike intersections, sill–fault contacts, bedding–fault intersections, fold axes, and permeable faults or tension zones. Pyroxene-rich Au skarns typically contain a sulfide mineral assemblage comprising native gold ± pyrrhotite ± arsenopyrite ± chalcopyrite ± tellurides ± bismuthinite ± cobaltite ± native bismuth ± pyrite ± sphalerite ± maldonite. Garnet-rich Au skarns can contain native gold ± chalcopyrite ± pyrite ± arsenopyrite ± sphalerite ± magnetite ± hematite ± pyrrhotite ± galena ± tellurides ± bismuthinite.
Carlin Complex
Carlin Complex deposits include the following zones or area:
- South Arturo: South Arturo open pit, El Niño underground. Deposit length is about 1,970 ft, the deposit width is approximately 394 ft wide, and averages about 50 ft in thickness;
- Betze–Post: Deep Post, Post, Betze, North Betze, West Betze, Screamer North Screamer, and West Barrel. Deposit lengths range from 2,000–5,300 ft, deposit widths are 1,000–4,500 ft, and deposit thicknesses range from 80–250 ft;
- Meikle–Rodeo: East Banshee, West Banshee, Meikle, South Meikle, East Griffin, Extension, West Griffin, Rodeo, Barrel, West Rodeo, and North Post. Deposit lengths range from 1,500–3,100 ft, deposit widths are 200–2,300 ft, and deposit thicknesses range from 250–1,400 ft;
- North Carlin: Tri-Star/Genesis (Silverstar, Bobstar, Goldstar, and Payraise), Perry, Lantern/Green Lantern, Exodus. Deposit lengths range from 900–10,000 ft, deposit widths are 550–6,000 ft, and deposit thicknesses range from 30–550 ft;
- Carlin–Gold Quarry: Quarry Main, Deep West, Deep Sulfide Feeder, Chukar North, Chukar South, and Carlin. The Good Hope, Mac, Magpie, Southwest, Wedge areas do not have estimated mineral resources or mineral reserves. Deposit lengths range from 4,500–12,000 ft, deposit widths are 950–8500 ft, and deposit thicknesses range from 100–2000 ft;
- Leeville: West Leeville, Turf, and Four Corners. Deposit lengths range from 2,000–4,600 ft, deposit widths are 300–5,200 ft, and deposit thicknesses range from 30–300 ft;
- South Carlin: Pete Bajo, Fence, Full House. Deposit lengths range from 2,000–4,000 ft, deposit widths are 500–900 ft, and deposit thicknesses range from 10 to 60 ft;
- Emigrant: Emigrant. The deposit is 12,000 ft long, 3,300 ft wide, and has a thickness range from 10– 330 ft.
Cortez Complex
Cortez Complex deposits include the following deposits:
- Cortez NW Deep and Cortez Hills open pit and underground: combined deposit lengths are 6,800 ft, 4,000 ft wide, and deposit thicknesses range from 10–350 ft;
- Crossroads and Pipeline: deposit length is 11,000 ft, 3,400 ft wide, and deposit thicknesses range from 50–1,400 ft;
- Gold Acres: deposit length is 7,000 ft, 2,600 ft wide, and deposit thicknesses range from 25–600 ft;
- Goldrush: deposit length is 17,300 ft, 1,400 ft wide, and deposit thicknesses range from 10–350 ft;
- Robertson: combined deposit lengths are 7,500 ft, 3,000 ft wide, and deposit thicknesses range from 150–1,400 ft.
Long Canyon Complex
The Long Canyon complex consists of the Long Canyon deposit, which has a 13,000 ft strike length, is about 2,500 ft. wide, with mineralized zones varying in thickness from 20–250 ft.
Phoenix Complex
Phoenix Complex deposits include the following deposits:
- Fortitude, Bonanza and Greater Phoenix: combined deposit lengths are 16,000 ft long, 3,900 ft wide, and the deposits have a thickness range from 20–550 ft.
Turquoise Ridge Complex
Turquoise Ridge Complex deposits include the following deposits:
- Turquoise Ridge Surface (Mega, Vista), Turquoise Ridge Underground (North and South), Vista Underground: deposit lengths range from 2,600–4,593 ft, deposit widths range from 984–2,600 ft, and deposit thicknesses range from 10 ft–98 ft.