Overview
The Goldstrike Complex is located on the Carlin Trend, the most prolific gold mining district in the Western Hemisphere, about 60 kilometres northwest of Elko, Nevada, USA.
The Goldstrike operations consist of the Betze-Post open pit mine and the Meikle and Rodeo underground mines which are located just north of the Betze-Post pit, along the same mineralized trend.
The Betze-Post pit is a truck-and-shovel operation using large electric shovels. Meikle is a high-grade ore body which is mined by transverse longhole stoping, underhand drift and fill mining methods. Rodeo is a further extension of the mineralization found at Goldstrike and is a trackless operation, using two different underground mining methods: long-hole open stoping and drift-and-fill. The Goldstrike Property consists of two processing facilities: (1) an autoclave circuit, which is used to treat the property?s non-carbonaceous sulfide (refractory) ore; and (2) the roaster, used for treating carbonaceous ore (not suitable for autoclaving). These facilities treat ores from both the surface and underground operations.
In 2009, the Goldstrike Property produced 1.36 million ounces of gold at total cash costs of $464 per ounce1. Goldstrike?s estimated proven and probable mineral reserves as of December 31, 2009 were 12.2 million ounces of gold
Location
The 9,921-acre (4,000 ha) Goldstrike property is split into two main listings, the Betze-Post Mine and the Meikle Mine (separately listed). The Betze-Post mine includes the Screamer zone, North Betze, and West Betze areas. The separately listed Meikle mine includes the Rodeo and Griffin deposits.
The properties are located in the Carlin Trend, the most prolific gold mining district in the Western Hemisphere, about 60 kilometres northwest of Elko, Nevada, USA.
Geology
The mine formerly consisted of 3 deposits (Post, Goldstrike and Betze), the mine was expanded to include the Deep Post reserves, by extending the Betze Pit to encompass the Deep Post reserve. The Deep Post orebody, of high grade gold in sulphide ore, crosses the boundary between American Barrick and Newmont Gold Co, and each will share in the cost of mining. Other area where mineralization has been identified on the property include; Screamer, and Deep Star."
The area consists of folded and faulted Paleozoic sedimentary rocks, which were intruded by the diorite and granodiorite Goldstrike stock of the Jurassic Age. Mesozoic folding and thrust faults form important structural traps for the mineralization in the Betze-Post pit. Tertiary faulting developed ranges and basins, which were subsequently filled with volcanics and sediments during Tertiary time. Gold mineralization occured at the onset of Tertiary volcanism, approximately 39 million years ago. High-angle normal faults in Vinni, Popovich, and Roberts Mountain formations served as conduits for gold-bearing hydrothermal fluids produced by volcanic activity.
Mining & Operations
The open pit mine is a truck-and-shovel operation. It has two sulphide ore zones (the Betze and Deep Post deposits). More than 6,500 drill holes have been completed within and around the Betze-Post deposit.
Drill spacing through the Betze, West Betze and Screamer deposits is approximately 53 meters and at Post is 46 meters. Drill spacing in the North Screamer and West Barrel deposits is approximately 30 meters. Almost all of the total drill hole footage has been sampled on 1.5-meter intervals and assayed for gold.
The Meikle mine, located 1.6 kilometers north of the open pit, is a high-grade ore body. It incorporates the Main Meikle, Meikle Extension, South Meikle and Griffin underground zones.
Processing
Goldstrike has two processing facilities: an autoclave installation, which treats non-carbonaceous sulphide (refractory) ore; and a roaster to treat carbonaceous ore, because its active carbon content responds poorly to autoclaving.
The combined design capacity of these two facilities is approximately 33,000 to 35,000 tons per day. These process facilities treat the ore from both the Goldstrike Open Pit and Goldstrike Underground mines.
The Pressure Oxidation plant (part of the Autoclave Facility) consists of six autoclaves that process slurry and the oxygen plant (operated by Air Liquide) that provides the oxygen for the autoclaves. All of the six autoclaves have five internal compartments with critical temperature control.
The process is supplied with steam in the first two compartments, then the exothermic reaction due to the sulphides in the ore maintains heat in subsequent compartments.
Heat recovery from the slurry exiting the autoclaves is accomplished by using staged pressure flashing. Steam heats the slurry before it enters the autoclaves. The heat exchange is done in a direct-contact countercurrent inside splash towers.
The roaster uses a dry grinding process and Freeport McMoran roaster technology to handle 12 million ounces of carbonaceous ores. The plant also has a dry grinding circuit, a carbon-in-leach (CIL) circuit, gas scrubbers, and a stand-alone low-pressure oxygen plant.
