United States

United States

Barrick Goldstrike Mine

It is owned and operated by the world's largest gold mining company, & it is the largest gold mine in North America.
The Goldstrike Mine.
The Goldstrike Mine.

Location: Eureka County, Nevada, United States.
Products: Gold , Silver.
Ore Type: Epithermal gold deposite in carbonate or silicate sedimentary rocks.
Owner: Barrick Gold.
Ounces of gold produced in 2014 >> 902,000
Ounces of proven and probable gold reserves >> 9,614,000
Overview: The Goldstrike mine, one of the top five gold-producing mines in the world, is Barrick Gold’s largest producing mine. The mine consists of both the Betze-Post open-pit and the Meikle and Rodeo underground mines (the “Goldstrike Mine”). Barrick, which is also the biggest gold producer in the world, has operated the mine for over 20 years (since 1987). The mine is located on the Carlin Trend in north-central Nevada, USA, about 40 kilometers northwest of the city of Elko. In 2007, the Goldstrike operation produced 1.63 million ounces of gold at average total cash costs of $373 per ounce. The Goldstrike property comprises approximately 4,197 hectares of surface rights ownership and approximately 3,535 hectares of mineral rights ownership on the Carlin Trend, a prolific gold producing region of North America. The northwestsoutheast trend is an 80 km long, 8 km wide belt that contains more than 20 major gold deposits. The operation employs approximately 1,600 employees.

Geological settings & Mineralization : The Goldstrike mine complex (including the Betze-Post-Screamer and Meikle Rodeo deposits). 
Betze-Post Open Pit
After Barrick took over the operation, two sulphide ore zones were identified as the Betze and Deep Post deposits in 1987. Since it entered production in 1993, the Betze-Post pit has been a truck-and-shovel operation using large electric shovels. The Betze-Post ore zones extend for 1,829 meters northwest and average 183 to 244 meters in width and 122 to 183 meters in thickness. The Post oxide orebody occurs in the siliceous siltstones, mudstones, argillites and minor limestones of the Rodeo Creek Formation. The Betze and Post oxide deposits are hosted in sedimentary rocks of Silurian to Devonian age. The mineralization of the Betze-Post pit was captured by structural traps developed by Mesozoic folding and thrust faults. Volcanic and sedimentary rocks filled ranges and basins formed by Tertiary faulting. The Tertiary volcanism initialized gold mineralization approximately 39 million years ago.
In 2007, the open pit mine produced 1,215,000 ounces of gold from 136.9 million tons mined and 10.5 million tons processed. The average grade processed is 0.136 oz/ton with a recovery rate of 85.5%. The average total cash cost was $355 per ounce. The open pit mine has proven and probable reserves totaling 12.19 million ounces from 94.9 million tons grading 0.128 oz/ton. The mine is expected to sustain the current production level for approximately 8 years, based on existing reserves. Most of the open pit mine is subject to a net smelter return of up to 4% and a net profits interest of up to 6%. 

Meikle Rodeo deposits
The Meikle deposit occurs in hydrothermal and solution collapse breccias in the Bootstrap Limestone of the Roberts Mountains Formation. The gold at Goldstrike was carried into the various orebodies by hot hydrothermal fluids, and deposited with very fine pyrite and silica. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the Post Oxide deposit. In the deeper deposits – Betze, Rodeo and Meikle – the gold is still locked up with the iron sulphide and an additional processing step (autoclaving or roasting) is required to free the gold. Two haulage drifts connect the Meikle and Rodeo orebodies.
The drifts are accessed from two shafts and by a decline at the bottom of the open pit mine. In the year ended December 31, 2007, the underground mine produced 413,186 ounces of gold at an average total cash cost of $431 per ounce. Proven and probable reserves underground are estimated at 7.42 million tons at 0.364 oz/ton, containing 2.7 million ounces. The Goldstrike’s total (open pit and underground) proven and probable mineral reserves as of December 31, 2007 are estimated at 14.9 million ounces of gold. The underground mine, which originally produced at a rate of approximately 2,000 tons of ore per day, averaged 3,562 tons per day in 2007. Based on current reserves and production capacity, the expected mine life is 9 years. The maximum royalties payable on the Meikle deposit are a 4% net smelter return and a 5% net profits interest.

Mining Processing & operations: The Goldstrike complex consist of three distinct mines: the large Betze-Post open pit mine, and the Meikle and Rodeo underground mines. The ore from all three mines is milled and leached by the cyanide process. Carlin-type gold deposits host gold mainly as microscopically fine grains. Refractory non-carbonaceous sulphide ore is treated in an autoclave followed by a carbon-in-leach (CIL) cyanidation circuit. Carbonaceous ore, also refractory, is treated with a roaster followed by a CIL circuit. The two treatment facilities treat ores from both the open pit and underground mines. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion.
In 2008 the Betze-Post open-pit mine produced 1,281,450 oz (36,328 kg) of gold and 152,886 oz (4,334.2 kg) of silver, while the Meikle-Rodeo underground operations yielded 424,687 oz (12,039.7 kg) of gold and 51,438 oz (1,458.2 kg) of silver. This was 30% of the total 5,698,000 oz (161,500 kg) output of all gold mining operations in Nevada.
Non-carbonaceous sulphide (refractory) ore is treated at an autoclave and carbon-in-leach (CIL) cyanidization circuit. Carbonaceous ore is treated at the roaster and CIL circuit, since the active carbon content in carbonaceous ore responds poorly to autoclaving. The two facilities treat ores from both the open pit and underground mines and, when combined, have a design capacity of 33,000 to 35,000 tons per day. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion. A modified pressure leach technology was successfully tested last year and it will be used to process ores that would otherwise have been treated at the roaster facility, consequently extending the life of the autoclave. The property also has a 115 megawatt natural gas-fired power plant, providing a significant portion of the operation’s power requirements off-grid.

Golden Sunlight Mine 
Golden Sunlight Mine

Location: Jefferson County, Montana, United States.
Products: Gold.
Owner: Barrick Gold Corporation.
Ore Type: Breccia pipe.
Reserves: Golden Sunlight produced 86,000 ounces of gold in 2014 at all in sustaining costs of $1,181 per ounce1. Proven and probable mineral reserves as at December 31, 2014, were 127,000 ounces of gold2.
In 2015, gold production is expected to be 90,000-105,000 ounces at all-in sustaining costs of $1,000-$1,025 per ounce.

Geological setting & Mineralization
The Golden Sunlight gold-silver deposit is hosted by a breccia pipe that cuts sedimentary rocks of the Middle Proterozoic Belt Supergroup and sills of a Late Cretaceous rhyolite porphyry (Porter and Ripley, 1985; Foster, 1991a, 1991b). At depth, rhyolite porphyry forms the matrix for fragments of the pipe. Creation of the pipe appears to be related to emplacement of an underlying hypabyssal stock related to the sills. Crosscutting the breccia pipe are hydrothermally altered lamprophyre dikes that postdate the gold-silver ore; locally, these dikes may have created areas of high-grade ore in the breccia pipe near their margins. The timing of emplacement of various igneous rocks and the hydrothermal alteration related to mineralization at the deposit.

Gold and silver in the region was concentrated along northeast-striking, high-angle faults and shear zones, some of which cut the breccia pipe and along which lamprophyre dikes have been emplaced (Porter and Ripley, 1985). These structures are thought to be part of a regional, northeast-striking zone of crustal weakness that has been intermittently active from the Proterozoic to the present (Foster and Chadwick, 1990; Foster 1991a). Because some hydrothermally altered and mineralized lamprophyre dikes are preferentially emplaced along structures that cross-cut the breccia pipe, their relationship to mineralization of the breccia pipe has been ambiguous. Certainly their emplacement is later than that of the pipe, and the simplest interpretation is that lamprophyre emplacement postdates mineralization. But, because the northeast-striking shear zones, veins, and dikes contain high-grade ore in places, a mineralizing process was obviously continuing during emplacement of the lamprophyre bodies.
Geologic cross section of the Golden Sunlight breccia pipe.
Geologic cross section of the Golden Sunlight breccia pipe.
Mine Life
Since its beginnings in 1982, Golden Sunlight Mine has continued to add resources to extend the life of the mine. Currently, the Montana DEQ is conducting the environmental review necessary to grant permission for mining additional resources referred to as the North Area Pit and South Area Layback, which would extend the mine life into 2016. Additional exploration is ongoing north of the Mineral Hill pit site with drilling activity in the Bonnie/Microwave area. 2013 will bring its own mix of success and challenge, so it is important that we remain intently focused on continuous improvement. As we work to deliver safe and profitable gold production, we cannot lose sight of our long-range goals—community partnership, environmental stewardship and most importantly, the safety and health of our people. I thank everyone again for the warm reception and look forward to getting to know you better in the coming months.

Safety and Health
We made great strides in improving our safety record, an achievement we celebrated in March, when we received Barrick’s Excellence Award for Best Safety Performance. As of first quarter 2013, GSM has gone five and a half years, and 2.7 million employee hours, without a lost-time incident, and over a year without a medical aid treatment incident. We still have more work to do in order to achieve our goal of zero incidents. As with most things, safety starts and ends with leadership. I expect all of our employees to be leaders when it comes to ensuring safety and continuing to send all GSM employees and contractors home safe and healthy every day.

Golden Sunlight Mine was the recipient of the prestigious Bureau of Land Management (BLM) 2012 Mineral Environmental Award for our third-party ore processing and reclamation initiatives. Golden Sunlight Mine initiated the program to assist small miners to mill outside “ores” and to assist with legacy mine materials containing reasonable concentrations of precious metals. In presenting the award, the BLM stated: “The Golden Sunlight Mine has turned liabilities into environmental and economic benefit—greatly enhancing the quality of the environment, saving taxpayer dollars, and creating local jobs.”

Bingham Canyon (Kennecott) Copper Mine
It is the world's deepest man-made open pit excavation.
Bingham Canyon (Kennecott) Copper Mine
Bingham Canyon (Kennecott) Copper Mine

Location: Salt Lake County, Utah, United States.
Products: Copper.
Owner: Rio Tinto Group.
Ore Type : Porphyry copper deposit.
The history of the Mine:
Bingham Canyon was settled in 1848 by the Bingham brothers, Thomas and Sanford, who were ranchers with no mining experience. In 1863, soldiers stationed at Fort Douglas in Salt Lake City explored the canyon and discovered lead ore. Utah’s first mining district was created in the Bingham Canyon area that same year. In 1893, Daniel Jackling, a metallurgical engineer, and Robert Gemmell, a mining engineer, studied the deposit and recommended developing the ore body through a revolutionary open-pit mining method and processing the ore on a large, industrial scale. The miners and their families lived near Bingham Canyon in places called Highland Boy, Copper Heights, Copperfield, Carr Fork, Heaston Heights, Telegraph, Dinkeyville, Terrace Heights, Greek Camp and Frog Town. At one point, the population in the area approached 20,000 people. In 1903, the Utah Copper Company was formed to develop the mine, based on the recommendations of Mr. Jackling and Mr. Gemmell. In 1906, the first steam shovels began mining away the waste rock that covered the ore body. The ore was found in a part of the mountain that divided the main canyon.

Geology of the Mine:
Every deposit of ore in the world is unique. There are no two ore bodies that are alike. Geologic forces were at work in the Oquirrh Mountains between 260 and 320 million years ago (Late Paleozoic Period). About 30 to 40 million years ago, molten, metal-bearing rock deep within the earth’s crust began to push toward the surface and formed Bingham’s ore deposit. Volcanoes erupted above the evolving ore body. This particular ore body contains primarily copper, gold, silver and molybdenum.
Tiny grains of ore minerals, mostly copper and iron sulfides, are scattered within what is called “host rock.” Because there is far more host rock than there are minerals, it is known as a low-grade ore deposit. Because this is a low-grade deposit, a ton of ore contains only about 10.6 pounds of copper. For every ton of ore removed, about two tons of overburden must first be removed to gain access to the ore.

How big is the Bingham Canyon Mine?
Kennecott Utah Copper’s (KUC) Bingham Canyon Mine has produced more copper than any mine in history— about 18.1 million tons.
The mine is 2¾ miles across at the top and ¾ of a mile deep. You could stack two Sears Towers (now known as the Willis building), on top of each other and still not reach the top of the mine. The mine is so big it can be seen by space shuttle astronauts as they pass over the United States. By 2015, the mine will be more than 500 feet deeper than it is now. If you stretched out all the roads in the open-pit mine— some 500 miles of roadway — you’d have enough distance to reach from Salt Lake City to Denver. KUC mines about 55,000,000 tons of copper ore and 120,000,000 tons of overburden per year.

The mining process:
Bingham Canyon Mine This is where the mining process begins. Every day, Kennecott Utah Copper mines about 150,000 tons of copper ore and 330,000 tons of overburden. The ore containing copper, gold, silver and molybdenum is hauled and deposited in the in-pit crusher and sent to the Copperton Concentrator.

Copperton Concentrator From the mine, ore is transported on a five-mile conveyor and stockpiled at the Copperton Concentrator. There the ore is ground into fine particles. The smaller pieces are then combined with air, water and chemical reagents to separate the valuable minerals from the waste rock. The mineral bearing concentrate is then transported to the smelter through a pipeline.

Tailings: Are the leftover rock material that have had most of the valuable metals removed. Tailings are sent through a pipeline from the Copperton Concentrator to the tailings impoundment north of the town of Magna where they are stored.

Smelter: At the smelter, the copper concentrate is transformed into liquid copper through a flash smelting process. The copper matte is processed in the furnace to produce 98.6 percent blister copper. From there, the 720 pound copper plates, called anodes, are sent to the refinery.

Refinery:  At the refinery, anodes are lowered into electrolytic cells containing a stainless steel blank and acidic solution. For 10 days, an electric current is sent between the anode and the cathode, causing the copper ions to migrate to the steel sheet. The other impurities, including gold and silver, fall into the bottom of the cell and are recovered in the Precious Metals plant. This process forms a plate of 99.99% pure copper. The copper is separated from the steel sheet and sent to market.

El Chino Copper Mine

El Chino CopperMine

El Chino CopperMine

Location: Santa RitaNew MexicoUnited States.

Products: Copper Deposit.
Ore Type:  Porphyry copper deposit with adjacent copper skarn deposits.
Host rocks: The predominant oxide copper mineral is chrysocolla. Chalcocite is the most important secondary copper sulfide mineral, and chalcopyrite and molybdenite the dominant primary sulfides.

Geological setting: The Cobre Mountains are composed of Proterozoic metamorphic and igneous rocks covered by about 3800 to 4800 feet of Paleozoic to Mesozoic sedimentary rocks. Cretaceous diorite to quartz diorite sills subsequently intruded these older rocks. Shortly thereafter, mafic to intermediate composition dikes and other intrusive bodies were emplaced and 2000 feet of intermediate composition lavas and breccias were erupted onto the surface. Next, the large granodioritic plutons at Chino and at Hanover-Fierro to the north were intruded. The last stage of intrusive activity in this area was the emplacement of rhyolitic dikes. The multiple intrusions locally domed and folded the older Paleozoic and Cretaceous strata.

Mineralization: Porphyry copper deposit are low-grade (<0.8%) disseminated deposits of copper found in and around small intrusive bodies composed of porhyritic diorite, granodiorite, monzonite or quartz monzonite (McLemore, 2008). The small plutons (also called stocks) are often shallowly emplaced at depth within 1 to 6 km of the earth's surface. The copper occurs within breccia or in networks of fractures, both in the porphyritic intrusion and in the adjoining country rocks.

Twin Creeks Mine

Twin Creeks Mine

Location: Northern Nevada, United States.
Products: Gold.
Owner: Newmont.
Deposit size: Length  4    km
                        Width    1     km
                        Area      3     sq km

Deposit features: Beds or lenses
                                Dikes or sills

                                Fault zone
Deposit age geologic: Eocene
Intrusive rock:  Dacite porphyry
Ore bearing unit: Pennsylvanian–Permian Etchart Fm.; Ordovician                      Valmy Fm. and Comus Fm.
Ore bearing unit thickness: 3000 m
Tectonic setting: North-American craton rifted western margin, imbricate structure.
Alteration : Contact metamorphism (?) decarbonatization, oxidation & silicification (jasperoid)
Associated deposits: sediment-hosted Au
Discovery date: 1984
Operation types: Open pit, Crushing and milling & Heap leach.
Total tonnage:   223.4tonnes
Contained gold: 484 tonnes
Recovery:  Au 80%
Gold grade: 2.67 g/t
Reserves (December 31, 2014): 0.158M oz. gold

Twin Creeks Mine

Reference information
Bloomstein, E.I., Massingil, G.L., Parratt, R.L., and Peltonen, D.R., 1991, Discovery, geology, and mineralization of the Rabbit Creek gold deposit, Humboldt County, Nevada, in Raines, G.L., Lisle, R.E., Schafer, R.W., and Wilkinson, W.H., eds., Geology and ore deposits of the Great Basin, Symposium Proceedings: Reno, Geological Society of Nevada, p. 821–843.
Breit, F.J., Jr., Ressel, M.W., Anderson, S.D., and Muirhead, E.M.M., 2005, Geology and gold deposits of the Twin Creeks mine, Humboldt County, Nevada, in Rhoden, H.N., Steininger, R.C., and Vikre, P.G., eds., Symposium 2005—Window to the world: Reno, Nevada Geological Society, p. 431–451.
Briggs, D.F., 2006, Mining operations report, version 2005: Unpublished.
Groff, J.A., Heizler, M.T., McIntosh, W.C., and Norman, D.I., 1997, 40Ar/39Ar dating and mineral paragenesis for Carlin-type gold deposits along the Getchell Trend, Nevada—Evidence for Cretaceous and Tertiary gold mineralization: Economic Geology, v. 92, p. 601–622.
Hall, C.M., Kesler, S.E., Simon, G., and Fortuna J., 2000, Overlapping Cretaceous and Eocene alteration, Twin Creeks Carlin-type deposit, Nevada: Economic Geology, v. 95, p. 1739–1752.
Nevada Bureau of Mines and Geology, 2011, The Nevada mineral industry, 2010: Nevada Bureau of Mines and Geology Special Publication MI-2010, 151 p.
Newmont, 2012, Reserves and non-reserve mineralization: Annual Report of December 31, 2011, 8 p., last accessed May 8, 2012, at http://www.newmont.com/sites/default/files/u87/NEM_2011%20Attributable%20Reserves%20and%20NRM.PDF.
Osteberg, M.W., and Guilbert, J.M., 1991, Geology, wall-rock alteration, and new exploration techniques at the Chimney Creek sediment-hosted gold deposit, Humboldt County, Nevada, in Raines, G.L., Lisle, R.E., Schafer, R.W., and Wilkinson, W.H., eds., Geology and ore deposits of the Great Basin, Symposium Proceedings: Reno, Geological Society of Nevada, p. 805–819.
Simon, G., Kesler, S.E., and Chryssoulis, S., 1999, Geochemistry and textures of gold-bearing arsenian pyrite, Twin Creeks, Nevada—Implications for deposition of gold in Carlin-type deposits: Economic Geology, v. 94, p. 405–422.
Stenger, D.P., Kesler, S.E., Peltonen, D.R., and Tapper, C.J., 1998, Deposition of gold in Carlin-type deposits—The role of sulfidation and decarbonation at Twin Creeks, Nevada: Economic Geology, v. 93, p. 201–215.
Thoreson, R.F., Jones, M.E., Breit, F.J., Doyle-Kunkel, M.A., and Clarke, L.J., 2000, The geology and gold mineralization of the Twin Creeks gold deposits, Humboldt county, Nevada, in Crafford, A.E.J., ed., Geology and ore deposits—The Great Basin and beyond; Geology and ore deposits of the Getchell region, Humboldt County, Nevada: Geological Society of Nevada Symposium 2000, Field Trip 9, p. 85–111.
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