Nevada Gold Mines includes Carlin, Cortez, Turquoise Ridge, Phoenix and Long Canyon. Barrick is the operator of the joint venture and owns 61.5%, with Newmont Corporation owning the remaining 38.5%.
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Summary:
Phoenix is a skarn-hosted polymetallic massive sulfide replacement deposit.
Phoenix Complex deposits include Fortitude and Bonanza and Greater Phoenix. Combined deposit lengths are 16,000 ft long, deposit width is 3,900 ft, and the deposits have a thickness range from 200-550 ft.
Two major regional scale north–south-striking faults demark the Phoenix mineralization corridor. The west boundary is the Copper Canyon fault zone (also known as the Canyon fault) and to the east, is the Virgin fault zone. Numerous subsidiary faults are developed in the vicinity of these main faults.
Preferred host lithologies for gold mineralization are the Antler Peak Limestone and Battle Formation. Copper mineralization hosts include the Copper Canyon stock and Havallah sequence.
Mineralization
Gold mineralization is primarily hosted in pyrrhotite- and pyrite- bearing skarn consisting of pyroxene, epidote, and actinolite garnet.
Gold occurs as free gold grains and electrum. It can also occur as inclusions totally encapsulated by sulfide minerals. including pyrite, pyrrhotite, and to a lesser extent arsenopyrite. chalcopyrite, and sphalerite. Chalcopyrite is the most abundant hypogene copper- bearing mineral. The transition zone can include chalcocite and covellite. Oxide copper minerals can include chalcanthite, malachite, chrysocolla, azurite, and lesser cuprite. Silver minerals are dominantly electrum, hessite, and lesser argentite.
Gold mineralization occurs freely at gangue-gangue or at sulfide-gangue grain boundaries, and only rarely as inclusions within gangue minerals. Some inclusions were noted in quartz, pyroxene, epidote, and orthoclase. The remaining gold occurred as inclusions totally encapsulated by sulfide minerals including pyrite, pyrrhotite, and to a lesser extent arsenopyrite, chalcopyrite, and sphalerite. Silver minerals are dominantly electrum, hessite, and lesser argentite.
Copper oxide mineralization locally contains minor amounts of chalcanthite, malachite, chrysocolla, azurite, and lesser cuprite. Enriched copper mineralization typically has chalcopyrite + covellite present. Covellite locally rims chalcocite grains where the effects of oxidation are more advanced. In hypogene mineralization, chalcopyrite occurs as disseminations and bedded replacements with skarn and silicate minerals, and in conjunction with pyrite.
Alteration
Skarn alteration is hosted by all sedimentary rock units adjacent to the Copper Canyon granodiorite. In the Phoenix deposit, skarn hosted by the Antler Peak Limestone is zoned from a proximal garnet > pyroxene assemblage adjacent to the stock (with Cu> Au), to an intermediate assemblage of pyroxene > gamet distal to the stock (with Au > Cu). Skarn in the Greater Midas deposit is zoned from a proximal assemblage of pyroxene>garnet with strong retrograde alteration adjacent to the stock (with Cu> Au) that grades outward to a similar skarn assemblage with lesser retrograde alteration, and to distal assemblages containing actinolite with only minor pyroxene, and chlorite + biotite + clay, respectively (with Au > Cu).
Hydrothermal alteration is centered on the Copper Canyon stock, which has produced about 4,200 acres of hornfels and skarn. Skarn alteration is hosted by all sedimentary rock units adjacent to the Copper Canyon granodiorite, with the reactive calcareous protoliths of the Edna Mountain Formation, Antler Peak Limestone and Battle Formation hosting the bulk of the skarn alteration. Alteration of the Copper Canyon stock consists of quartz–sericite–pyrite argillic, or propylitic, alteration.