The Cerro Negro gold-silver mineral property is located in the Santa Cruz province of Southern Argentina.
Gold mineralization was first discovered in 1992 by Roberto Schupback, an Argentine prospector. The project changed hands several times in subsequent years. In 2004, Andean Resources acquired Oroplata S.A., a local company that at that time held title to the mineral deposit. In 2010, Andean Resources became a wholly owned subsidiary of Goldcorp. In December 2010 the province of Santa Cruz approved the EIA for the development of the project.
The low sulphidation mineral resource consist of three free milling non-refractory mineral deposits with a combined reserve of 7.1 M t at 9.03 g/t Au and 89.70 g/t Ag.
The proposed type of mining is underground and surface operations that would process 675,000 tpa in the first years and 895,000 tpa in subsequent years. Over a mine life of 9 years a total of 1.96 Moz of gold and 17.69 Moz silver would be produced. Precious metal can be recovered from the ore using conventional cyanide leach techniques. Tailings would be stored in an adjacent large shallow valley.
The estimated construction and pre-production expenditure for the project is US$274.9 M including a contingency allowance of $30.5 M.
Construction of the Eureka ramp commenced in 2010. Mine preparation is planned to start in Q1 2011, along with construction of the process plant. Mining activities will commence in Q1 2012 and ore commissioning of the plant is planned for Q1 2012. The process plant will be handed over at the end of Q2 2012.
Argentina (argentum = silver) is the second largest country in South America and the largest among Spanish speaking nations.
Evidence of humans in Argentina is 11,000 years old; in the 15th century the Inca Empire conquered only the northwest part of the country; Europeans arrived in 1516 and established the Viceroyalty of Peru in 1542. The country declared independence from Spain in 1816.
The Santa Cruz province encompasses the well known region of Patagonia that stretches to the Magellan Strait. The province is bordered to the west by the Andes that feature numerous glaciers some of them constituting a touristic attraction ? e.g. Los Glaciares National Park.
Oil, gas and mineral resources provide most of the income for the province?s prosperous economy.
The Cerro Negro property is located 345 km by road southwest of the coastal city of Comodoro Rivadavia locate din the province of Chubut. The closest towns to the property are Las Heras and Perito Moreno. Local economy is based on oil industry, agriculture and tourism.
Elevations in the project area are no higher than 600 m asl.
The climate is semi-arid with short summers and heavy snow during the winter months of June to September. Water supply is uncertain in times of drought.
The Cerro Negro deposit is located near the western margin of the Desseado Massif, a 60,000 sq. km rigid crustal block that was once part of the Gondwana (from Sanskrit: the ?forest of the Gonds?) continent.
The deposit area is underlain by an Upper Jurassic volcanic to sub-volcanic sequence. The western part of the property contains a rhyolite dome complex that hosts the 151 million years old epithermal and hot-spring mineralization.
Veins are hosted by an andesite-dacite volcanic-subvolcanic complex in the core of the dome and by rhyodacitic ignimbrites on its margins. Vein systems at Vein Zone, Eureka, and Bajo Negro strike northwest to westnorthwest, but Vein Zone and Eureka also display east-trending segments.
The Eureka resource occurs over a strike length of about 1.5 km and it is typical of low sulphidation epithermal systems. There is a close association between fine-grained sulphides and high gold and silver grades.
The Bajo Negro gold mineralization occurs dominantly in a single vein with minor splits. The vein was defined over a strike length of 1.2 km and boasts an average width of 3.9 m over a known vertical extent of up to 300 m. It contains low silver grades and coarse pyrite
Vein Zone is a west-northwest-trending arcuate system of quartz veins, sheeted veins, and breccia zones, in which the veins have east, northwest, or north strikes and steep to sub-vertical dips to the north and northeast. Gold is associated with oxidized pyrite and manganese oxide.
As of 2010, total reserve was estimated at 7.1 M t at 9.03 g/t Au and 89.70 g/t Ag.
Mining & Operations
Exploitation at Eureka and Bajo Negro will be by underground mining methods.
Underground mining at Eureka West and Bajo Negro would employ open stoping method of bulk mining.
A transverse stoping method with backfill was selected to develop the Eureka vein to suit the orebody geometry and rock quality. A 3,892 m decline would connect the surface with the lowest level of the mine (-190 m). Levels would be spaced at 26 m vertical distance. Equipment to be used includes two boom jumbo drills; 2.7 m3 and 4.6 m3 LHD units; two 5.7 m3 front-end loaders, and seven 20 t and 28 t haul trucks, one motor grader; one water truck.
At Bajo Negro mining would be undertaken utilizing the equipment and personnel released from Eureka once that operation is finished. The mining would employ the same mining method and characteristics as at Eureka. Total estimated length of the decline would be 2,840 m (-280 m).
Mine refuges consist of a transportable, hermetically sealed, 20-person cabin. Escape shaftways consist of a set of metal stairs installed in the main raise that connect to every level of the mine.
Vein Zone will be an open pit mine that would use standard drilling, blasting, loading and hauling operations. Equipment to be utilized in open pit mining include diesel drills of 114.3 mm diameter (Atlas Copco Roc L8); 8.6 m3 front-end loaders (Cat 990); track dozers (Cat D9), motor graders (Cat 160) and 20 m3 water trucks.
Construction of the Eureka ramp commenced in 2010. Mine preparation is planned to start in Q1 2011, along with construction of the process plant. Mining activities will commence in Q1 2012.
The process plant is located in a shallow valley running northeast-southwest approximately 5 km north of the Bajo Negro and Vein Zone deposits.
Precious metal would be recovered from the ore using conventional cyanide leach techniques.
Major process operations are: primary crushing; 5.20 x 2.85 EGL SAG mill grinding; 4.5 x 6.97 EGL ball mill grinding; pre-leach thickening; leaching; counter-current decant solution washing; Merrill Crowe process; refinery incorporating mercury retort and smelting facilities; tailings filtration and disposal; fresh and reclaim water supply; reagent preparation and distribution.
The project has an installed maximum power demand of 12 MW that would be provided by connecting to a power grid.
Access would be by constructing a new access road connecting to Highway 39.
The process tailings will be stored in large shallow valley area with two earth fill embankments providing the necessary enclosure. This tailing storage facility (TSF) will have a geosynthetic liner to prevent seepage into the groundwater system. The potential final capacity of the TSF, subject to further expansions, is up to 10 Mt.
Water supply to the process plant and infrastructure will be provided from three water bores located in the valley adjoining the plant site. The water treatment plant will be located at the El Retiro accommodation camp.
Ore commissioning of the plant is planned for Q1 2012. The process plant will be handed over at the end of Q2 2012.