Bingham Mining District, Salt Lake County, Utah, USAi

Regional Level Types
Bingham Mining District	Mining District (Active)
Salt Lake County	County
Utah	State
USA	Country

The Bingham (West Mountain) mining district is located 22 mi southwest of Salt Lake City in southwest Salt Lake County. Bingham is the oldest and largest district in Utah and hosts a giant porphyry Cu-Au-Mo deposit. The Bingham Canyon open pit porphyry Cu-Au-Mo mine is the largest mine in the U.S. and the Bingham district is the largest Cu, Mo, Au, Ag, Pb, and Zn producer in Utah. The district’s total historical metal production at modern metal prices is valued at approximately $174 billion and the Bingham Canyon mine is still in production.
The Bingham district forms a lynchpin in the Bingham-Park City mineral belt in the Basin and Range Province. The district is centered on a giant, high-K, calc-alkaline, porphyry Cu-Mo-Au-Ag deposit (USGS Model 17). This deposit is associated with a small, composite monzonite stock dated at about 38 Ma. This stock intrudes a thick, intercalated sequence of Pennsylvanian- Permian marine quartz sandstones and limestones. A 400- to 1000-ft-wide quartz monzonite porphyry dike and a swarm of narrower, east-northeast-trending dikes cut the north flank of the early monzonite stock. The hypogene porphyry mineralization is concentrically zoned around the quartz monzonite porphyry dike from a deep, inner, low-sulfide core through progressively overlapping hypogene molybdenite, bornite-chalcocite, chalcopyrite, and pyrite zones. The inverted cup-shaped Cu shell is largely coincident with potassic alteration and garnet Cu-Au skarns (USGS Model 18a). The surrounding pyrite halo is spatially associated with propylitically-altered rocks. Each of three major phases of porphyry intrusion is followed by cycles of fracturing, alteration, veining, and metal deposition. This cyclic vein formation resulted in complex vein relationships partly constrained by age dates and crosscutting relations. The quartz monzonite porphyry dike and younger dikes are spatially coincident with the highest grades of Cu and Au in the orebody (Porter and others, 2012). The exposed quartz monzonite porphyry stock is too small to have provided the fluids and metals for the district, necessitating a connection to a far larger magma chamber at depth.
The outermost fringe of the pyrite halo is overprinted by the inner margin of a 3000-ft-wide, intermediate-sulfidation, sphalerite- galena ±tetrahedrite manto-vein zone where alteration is largely confined to the immediate vein walls (USGS Model 19a). The outer perimeter of the Pb-Zn veins locally contains rhodochrosite and/or barite. The Barneys Canyon and Melco distal disseminated Au deposits (USGS Model 19c) lie 4 mi north-northeast of the center of the district and outside Bingham’s megascopically recognizable sulfide and alteration system, but on the outer fringe of a weak As-Au geochemical halo (Babcock and others, 1995).

In 1848, Erastus Bingham and his two sons were the first to discover mineralization in Bingham Canyon. Because the Church of Jesus Christ of Latter-Day Saints (L.D.S. church), of which they were members, discouraged mining, the location was forgotten until 1863, when Colonel P.E. Conner of the U.S. Army stationed at Fort Douglas in Salt Lake City and others rediscovered the silver-rich lead ore while picnicking in the area. On September 17, 1863, George Ogilvie (a logger who first reported the find), Colonel Conner, and 23 others staked the Jordan claim in Bingham Canyon (Eldredge and Wilkerson, 1990). This claim was the first in the district and the first recorded in Utah. In 1863, the West Mountain mining district was officially organized. In 1864, placer gold was discovered near the mouth of Bingham Canyon by a group of California miners. With this discovery, gold became the first mineral mined in the district. Placer mining recovered approximately 72,600 ounces of gold. The largest gold nugget (over 7 ounces) ever found in Utah was in Bingham Canyon. By the early 1870s, placer mining was declining because the deposit was almost played out.

Beginning in 1870, mining began on the silver-rich oxidized lead ores at the Highland Boy, Jordan, Last Chance, Brooklin, and Yosemite mines (the Jordan, Last Chance, and Brooklin mines have since been consumed by the present-day Bingham Canyon open-pit mine). By the late 1880s, most of the shallow silver-rich ore bodies had been exhausted, and between 1890 and 1900 many of the mining properties were consolidated. Extensive underground mining of the silver, lead, gold, and copper ores began at mines that included the Lark, U.S., Butterfield Group, Highland Boy, and Carr Fork. Underground mining continued until 1971 when the Lark and U.S. mines closed.

In 1885, native copper found growing in organic rich portions of upper Bingham Creek led to the discovery that the creek water contained copper in solution. A small operation began to produce metallic copper by running creek water over scrap iron, where the copper in solution would precipitate onto the iron. In 1897, Enos Wall noticed copper carbonate mineralization on both sides of Bingham Canyon and scattered copper mineralization in monzonite in several abandoned mining tunnels. He subsequently staked a number of claims, known as the Wall Group (subsequently acquired by the Utah Copper Company). About the same time, Samuel Newhouse, who developed and sold the Highland Boy mine, also was aware of scattered copper mineralization and acquired property southwest of the Wall Group for the Boston Consolidated Mining Company.

The Boston Consolidated and Utah Copper companies began to mine copper ore in the early 1900s. Both companies started steam-shovel stripping or open-pit mining in 1906. Utah Copper shipped the first ore in 1907, and Boston Consolidated shipped ore in 1908. Over the next several years, Utah Copper and Boston Consolidated properties were the leading producers of copper in the district. In 1910, Utah Copper merged with Boston Consolidated for 310,000 Utah Copper shares valued at nearly $19 million. In 1936, Kennecott Utah Copper Corporation acquired the mine from the Utah Copper Company. During World War II, Kennecott supplied one-third of the total amount of copper used by the allied forces. In 1978, Kennecott Utah Copper was sold to Standard Oil Company, a subsidiary of British Petroleum. British Petroleum sold its interests to the Rio Tinto Zinc Corporation in 1987. In the 1980s, copper became uneconomical to mine due to high labor, haulage, smelting, and refining costs. Over the next several years, Kennecott spent $2 billion modernizing its operations and facilities. As a result, the mine is now one of the most efficient in the world. At present (2005), the Bingham Canyon mine is more than a half-mile deep and about 2.5 miles across from rim to rim.

The Barneys Canyon and Melco gold deposits, located north of the Bingham Canyon mine, were initially found in 1878, but the significance was unrecognized. Sampling was conducted in 1968-69 at an old mine dump in Barneys Canyon that returned values of 0.10 to 0.20 ounces of gold per ton. Drilling on the Barneys Canyon deposit began in 1985 and the deposit was discovered on the third hole. In 1986, drilling began on the Melco deposit and the ore body was discovered on the first hole. Mining began at Barneys Canyon and Melco deposits in 1989 and continued until late 2001.