The Turquoise Ridge property is located about 70 kilometres northeast of Winnemucca, Nevada, USA. Barrick is the operator and 75% owner of the mine with Newmont owning the remaining 25%.
Turquoise Ridge uses underhand cut-and-fill mining methods due to the relatively low rock quality in the ore zones. Ore is transported to Newmont?s Twin Creeks mill for processing. The refractory gold ore is treated by pressure oxidation technology and gold is recovered using conventional carbon-in-leach technology.
In 2009, Turquoise Ridge?s production totaled 177koz ounces of gold at total cash costs of $570 per ounce1. Proven and probable mineral reserves as of December 31, 2009 is estimated at 5.47moz of gold.
The Turquoise Ridge property is located in the Potosi Mining District, about 70 kilometres northeast of Winnemucca, Nevada, USA, on the eastern flank of the Osgood Mountains.
Gold mineralization is hosted in Comus Formation and Preble Formation rocks, granodiorite dikes and granodiorite. The mineralization occurs as a series of discrete zones developed along the N-S trending Getchell Fault and with the NE trending Turquoise Ridge Fault. Intensity of gold mineralization is related to structural complexity and the location of rocks chemically receptive to mineralization.
Refractory sulfide gold deposits are found at depth along the Getchell Fault and in sedimentary units near the Getchell Fault. Oxidized gold deposits are also associated with the Getchell and Turquoise Ridge Fault zones and with other locations on the Getchell Property, typically occurring as discrete zones at depths shallower than the sulfide mineralization. Additional oxide and sulfide gold mineralization is found in an area known as Section 13 which is located approximately 3 miles northeast of the mill site.
Operations on the Getchell Property include a pressure oxidation "autoclave" mill facility, a heap leach facility and two underground mines, the "Turquoise Ridge" mine and the "Getchell Underground" mine.
The "Northwest Ore Zones" are located in the foot wall to the north and west of the current Getchell Underground workings."
Mining & Operations
Operations consist of the two underground mines, Turquoise Ridge and Getchell. Recent infrastructure upgrades include a 2,800 tpd material handling system, a 3,5600 gpm dewatering system, a water treatment facility, improved ventilation, larger underground shop, mobile equipment, and a backfill crusher. The target mining rate is 1,250 tpd.
Weak rock-mass conditions were the most important engineering and safety consideration. The danger is reduced by limiting open ground, ground control standards, and backfill.
The Turquoise Ridge mine is accessed by two existing shafts. All mining in Turquoise Ridge and N Zone use underhand cut-and-fill mining due to the relatively low rock quality. It has been safe and effective over 8,000 feet of topcut development. Topcuts have been used in four major ore zones.
The Getchell mine is accessed from two open pit portals. Getchell underground has a short mine life based on current proven reserves. The mine's life will probably be extended due to the lower processing costs of the joint venture, additional exploration drilling, and engineering analysis. Mining methods are longhole stoping and drift-and-fill stoping.
A surface quarry and crusher which makes aggregate for cemented backfill is run by an outside contractor.
Fresh water is provided by two wells in the Kelly Valley east of the project site. Mine water is treated in a water treatment plant, then recycled or discharged to the rapid infiltration basins. Electrical power averaging 7.0 mega watts is purchased from Sierra Pacific Power Company.
Ore is transported to the Sage Mill at Twin Creeks for processing. Twin Creeks is scheduled to process up to 1,800 tonnes per day of ore. Gold is recovered using a combination of pressure oxidation and carbon-in-leach ("CIL") technology.
The process consists of grinding, pressure oxidation, cyanide leaching, CIL, carbon stripping, zinc precipitation and refining.
Targets are steady state levels of 1200 to 1300 tpd in 2006, with dilution below 5% at 60% of cut-off grade, dewatering activities are scheduled at least six months ahead of production, and no incidental ore is scheduled