Copper Basin Mine, Battle Mountain Mining District, Lander County, Nevada, USAi

Regional Level Types
Copper Basin Mine	Mine
Battle Mountain Mining District	Mining District
Lander County	County
Nevada	State
USA	Country

Sec 32 T32N R44E.

Porphyry copper-gold deposit. Many claims and mines.
Structure: North-south-trending fractures exert minor control on mineralization. Low angle NNE-and NNW-trending-faults have been important in localizing supergene ore bodies. Major deformation of the Paleozoic rocks occurred during the Mississippian Antler and Late Permian -Early Triassic Sonoma orogenies before the intrusive and mineralization events occurred.

Alteration: Strong-potassic, silicic, sericitic, propylitic, pyretic alteration of host granodiorite to quartz monzonite porphyry

Commodity: Ore Materials: chalcocite, chalcopyrite, sphalerite, galena, gold , silver locally, molybdenite bismuthinite; malachite, azurite, turquoise in oxidized zones, Gangue Materials: arsenopyrite, pyrite, pyrrhotite, marcasite, garnet, tremolite, epidote

Deposit: Two main types of mineralization occur on the property. Ore grade mineralization is localized along contacts of the Cambrian sediments with altered granodiorite and also occurs in a series of high-angle north-northeast trending silicified structures. The ore minerals in both types are pyrite, galena, sphalerite and lesser amounts of chalcopyrite, marcasite and stibnite. Silicification also occurs within the fault zones and immediately adjacent to skarn units. The historically mined copper orebody consisted of replacement and fracture fillings in hypogene ore, but the dominant type of ore is secondarily-enriched. Ore is hosted by contact metamorphosed rocks (sandstone, siltstone, limestone, calcareous shale) of the Harmony Formation, Battle Formation and Antler Peak Formation, although most ore is confined to the Harmony Formation. The deposits in the Copper Basin area all occur within the Harmony Formation. The gold-copper and gold mineralization have developed due to metamorphic and metasomatic processes resulting from the emplacement of the late-Cretaceous monzonite porphyry. Later mid-Oligocene igneous activity may have produced a gold-only phase of mineralization (Schmidt et al., 1988) (Table 8.1). North-south elongate bodies that tend to be conformable with bedding occur as calcic-skarns and silica-pyrite bodies. The skarns occur as garnet and garnet-pyroxene-amphibole assemblages with varying degrees of retrograde alteration (Schmidt, 1988). Porphyry copper deposits in the copper zone surrounding a central molybdenum zone underwent supergene enrichment to create the Contention, Carissa, Copper Queen, Widow, and Sweet Marie copper deposits. The Copper Basin area has produced considerable amounts of copper, gold, and silver from supergene-enriched porphyry copper, skarn, replacement, and distal disseminated deposits, all of which are hosted in calcareous rocks of the Late Cambrian Harmony Formation and/or Middle Pennsylvanian Battle Formation. The proximity of the Late Cretaceous Buckingham stockwork molybdenum system, the early Oligocene Paiute Canyon Mo-Cu porphyry system, and other Tertiary dikes and stocks in the area makes it difficult to establish with certainty a direct relationship between deposits and mineral systems from which they were derived. Gold skarn ore at the Surprise Mine and distal disseminated silver-gold ore associated with silica-pyrite alteration at the Empire Mine may be related genetically to the Late Cretaceous Buckingham stockwork molybdenum system. There is some suggestion, however, that there was a subsequent low-temperature epithermal overprint in some of the ores in the Empire Mine. Gold-silver skarn at the Labrador Mine apparently is associated with late Eocene or early Oligocene porphyritic leucogranite of the Paiute Canyon porphyry Mo-Cu system. The Paiute Canyon system consists of four 38- to 39-Ma intrusive bodies aligned along a N 40? W trend and emplaced into the Harmony

Deposit type: Porphyry Cu, skarn-related

Development: The ICBM/Copper Basin project is located in the northern part of the Battle Mountain Mining District near the northwest limit of the Battle Mountain-Eureka Trend. The Battle Mountain district has been the source of base and precious metal production since the late 1800s. In the 1960s Duval Corporation developed and began mining several porphyry-skarn copper-gold deposits located at Copper Canyon in the southern part of the district and the Copper Basin located in the northern part of the district. Continued exploration in the 1970s and 1980s led to the discovery of gold-silver, skarn-replacement deposits that are spatially related to the copper-gold deposits. Battle Mountain Gold Company was spun off from Duval Corporation to develop these deposits (Tomboy, Minnie, Fortitude in the Copper Canyon area; Surprise, Labrador, and Bailey Day in the Copper Basin area). Battle Mountain Gold (now Newmont Mining Corporation) has had continued exploration success and has developed and mined other deposits (Midas, Reona, Phoenix) primarily in the southern Copper Canyon porphyry system within the Battle Mountain district. A total gold resource (including past production and current reserves) of approximately 9 million ounces has been discovered in the Battle Mountain mining district. The reserve/resource at the Phoenix deposit stands (2002) at approximately 6 million ounces at a grade of 0.034 opt Au. The area encompassed by Duval's Copper Basin open pit deposit was earlier the site of several mines, including the Copper King, Sweet Marie, Contention, Carissa, Copper Queen area and Blue Gem Turquoise, (and nearby Surprise, Labrador, and Bailey Day Mines covered in a separate MRDS record). It was acquired by Copper Canyon Mining Co. in 1916 and worked intermittently by various lessees until takeover by Duval in the early 1960s. Later it was operated by Battle Mountain Gold Co. for a number of years. Copper-gold-silver ore from the Copper Basin pit was mainly produced from a secondarily-enriched orebody, which was placed on dumps with the copper-laden waters treated at a nearby leach plant. From 1977 until the 1990s, copper production was curtailed due to a depressed copper market, and for a time gold was the only commodity being produced. Much of the property was recently acquired by Newmont Gold as it ramped up development of its Phoenix Project. In 2004, the ICBM 65 claims were owned by LAC Minerals (USA) Inc which was bought by Barrick Gold. The Copper Basin claim group had 3 owners: Battle Mountain Gold Company owned 42 of the claims, Union Pacific Mining Corporation owned 46, and the remaining 42 claims were owned by Rocky Mountain Energy Corporation (RMEC).

Geology: Siliceous clastic rocks of the Cambrian Harmony Formation underlie the Copper Basin area that forms part of the upper plate of the Roberts Mountains allochthon, emplaced during the Antler Orogeny, Devonian-early Mississippian (Roberts, 1964). The Roberts Mountains allochthon is comprised of several thrust slices and is represented in the Copper Basin area by at least two members. The sole fault, the Roberts Mountains thrust, is not exposed beneath the Ordovician Valmy Formation. The upper member, the DeWitt thrust, juxtaposes Cambrian Harmony Formation on top of the Ordovician Valmy Formation. The nearest outcrop of Valmy Formation lies two miles to the west. There is a possibility that a third thrust member is present between the Harmony and Valmy Formations, but deep drilling would be required to determine this relationship. Within the immediate property boundaries the Cambrian Harmony is the principal rock formation and consists of feldspathic and micaceous, locally calcareous sandstone and interbedded shale. The Harmony has been intruded locally by diabasic to granitic dikes and sills. While locally folded, regionally the Harmony Formation forms a north-striking easterly dipping homoclinal sequence. Where rocks are proximal to the various intrusives, they are metamorphosed to quartzite, hornfels and skarns. The Harmony has been intruded by at least seven episodes of igneous intrusion. The earliest, a Devonian and/or Ordovician age diabase, is found in the southwest portion of the project near the site of the Buckingham camp. The next earliest is the Cretaceous monzogranitic porphyry and is the principal host rock of a stockwork molybdenite resource. The molybdenite mineralization is thought to be genetically related to these monzogranitic stocks. The other intrusives are Tertiary monzogranite, granodiorite, and leucogranite dikes, sills, and stocks.

Ore(s): A fracture set trending N70 degrees west is a dominant ore control

Other Databases

Link to USGS MRDS:	10310327

Other Regions, Features and Areas containing this locality

References