The Pascua-Lama gold-silver property straddles the Cordillera de Los Andes which represents the Chilean-Argentine border. The majority of the ore deposit lies in the Region III of Chile, some 150 km southeast of the town of Vallenar. The Lama part of the property covers the Argentinean extension of the mineralized system and is located in 300 km northeast of the provincial capital city of San Juan. Pascua Lama is 10 km from Barrick?s Veladero mine in Argentina.
The gold-silver deposit was discovered in 1977 by St. Joe and CMSA. Barrick acquired the project in 1994.
The entire project is encompassed by a defined 'Protocol Area' that allows free passage of persons involved with the project across the border between the two countries. It will also benefit from existing infrastructure, processing, staffing, and community development programs at Barrick's Veladero mine located within ten kilometers.
Production is expected to commence in the first quarter of 2013 after a three year preproduction period at an estimated tag price of $2.3-$2.4B. The project is expected to achieve full production in 2015 at a rate of 45,000t/d of ore.
The life of mine average annual production is estimated at 600,000-700,000 ounces of gold and 20-25 million ounces of silver at total cash costs of $200-$250 per ounce.
Silver credits are important components of the cost structure and the mine is expected to produce an average 30Moz/year over the first 10 years. Over the life of mine production is expected to total 14 Moz gold and 494 Moz silver.
Plant feed is initially at a rate of 33 ktpd and expands to 44 ktpd (16 Mt/yr) from year 4 when refractory ore is also scheduled in the plant feed.
The process design includes crushing, an overland conveyor, dry grinding, CCD washing and neutralization followed by cyanidation and treatment in a Merrill-Crowe plant and refinery. Tailings will be contained in a facility near the plant.
The current plan is for 21 plus year mine life plus 3 years of processing stockpiles.
Chile and Argentina are two South American countries that share the southern part of the continent and are separated by the glaciated peaks of the Andes, which represent the world's longest exposed mountain range.
In Chile access to the project area is from the city of Vallenar, III Region. Secondary roads C-485 to Alto del Carmen and C-489 from Alto del Carmen to El Corral, Tres Quebradas and El Toro have a total length of about 150 km. In Argentina, it will utilize the 380km road that is currently used by the Veladero Project - Conconta.
The topography on the property is steep and rugged, and is characterized by high sierras ? 4300 m to 5250 m asl - and deep valleys. Overburden consists of scree and colluvium - primarily gravel, sand, silt and clay. Vegetation is sparse.
The area is considered to have a sub-arid, sub-polar, mountain climate. During winter months, extreme weather may create a challenging operating environment. Winter conditions can be severe, with intense winds, blowing snow, and extreme cold, and can adversely affect mine access and operations. Rocks and gravel airborne by strong gusty winds are a common hazard in mine operations and on access roads
Highest annual temperatures occur from December through February, when maximum daytime temperatures generally range between 10 and 22°C, with lows between 5° and -5°C. Winter months from June through August have daytime highs generally between -10° and 10°C, and nighttime lows of -10° to -30°C. Mean annual precipitation is estimated to be approximately 200mm at 4,400m elevation, with most of the precipitation arriving as snow.
Public infrastructure is absent in the mine area and there is no permanent habitation in the area; Vallenar is the nearest city.
The Pascua-Lama deposit is situated at the crest of the high cordillera on the northern edge of a major mineralized trend known as the El Indio belt. It is positioned near the center of a northerly trending graben that contains nearly the entire Tertiary volcanic sequence that is distributed along the spine of the cordillera in Chile and Argentina. Locally, the Pascua-Lama area has been the center of repeated intrusive and volcanic activity.
Approximately 75% of the ore body is located on the Chilean side of the border; 25% in Argentina.
The gold, silver, and copper mineralization and alteration assemblages at Pascua-Lama are associated with a structurally controlled acid sulfate hydrothermal system hosted by intrusive and volcanic rock sequences of Upper Paleozoic and Middle Tertiary age. Alteration and mineralization is of the high-sulfidation, epithermal type. Throughout the Pascua-Lama district, the alteration and mineralization appear to have been strongly controlled by structure. This control is most evident along the Esperanza, Pedro and Quebrada de Pascua fault systems.
The breccias, which host much of the gold-silver mineralization, occur at the intersections of three or more fault sets. In total, at least 14 major centers of mineralization and a number of smaller centers have been recognized, of which Brecha Central is the most significant. The deposit comprises the Pascua, Esperanza, El Morro and Penelope orebodies.
Gold occurs primarily as native metal at Pascua-Lama, but it also is found in very minor amounts in gold telluride inclusions within enargite. Silver mineralization overprint the gold distribution but over a much broader lateral area.
The principal metal commodities are gold and silver - copper is by-product.
As of December 31, 2009 the mineral deposit has proven and probable reserves of 17.8 million ounces of gold and 718 million ounces of silver.
Mining & Operations
The project is planned as an open pit operation that will mine the Pascua, Esperanza, El Morro and Penelope ore bodies.
The bulk of mining is based on the use of electric rope shovels of 54 m3 capacity, loading 320 t trucks. Ore and associated selective waste mining is with 30 m3 hydraulic excavators and support and stockpile rehandle is with 25 m3 front-end loaders. Mining rate is of 300,000 tpd.
Ore will be transported by trucks to a primary crushing plant; a 4.7 km long conveyor system transfers ore from primary crusher underground to a covered ore stockpile.
The mine production schedule is over 21 production years followed by three years of stockpile reclaim. Peak mine capacity is 126.6 Mt/yr. In addition a total of 60.1 Mt of ore is sent to a long-term stockpile and treated at the end of the mine life. A total of 1,504 Mt of waste rock will be produced during the life of the mine.
Mining commences in 2011 with pre-stripping. The first ore is produced in late 2012. The production phase commences in 2013.
The average ore plus waste mining rate is 66.0 Mt/y, comprising 18.3Mt/y of ore and 48.8Mt/y of waste. The average overall strip ratio is 2.71:1, exclusive of the pre-production period. The average overall strip ratio inclusive of the pre-production period is 2.88:1.
Due to the ARD capacity of the ore significant quantities of lime would be required to neutralize solutions resulted from washing of the ground ore. A limestone deposit was identified at 40 km by road from Pascua Lama and a quarry, limestone and lime production facility would be constructed at that location.
The Pascua ores are very complex ranging from highly oxidized ore where the gold and silver can be recovered by conventional cyanide leaching, to highly refractory ore. The distribution between non-refractory and refractory ore types is 71 percent and 29 percent respectively.
Non-refractory ore is subjected to cyanide leach and the pregnant solution is recovered from a counter current decantation circuit and treated in conventional Merrill Crowe circuit to produce a gold-silver dore.
The refractory ore is subjected to flotation to produce a gold-silver rich but low-grade (12%) copper concentrate. Flotation tailings are then subjected to a cyanide leach for further precious metals recovery.
Most of the Pascua ores contain water soluble sulphates that need to be removed prior to leach or flotation. This is accomplished in a wash circuit where the soluble salts are removed in a wash CCD circuit and then precipitated with lime.
The Pascua Lama concentrate could be viewed as a complex precious metals concentrate with significant copper credits. It also contains high levels of arsenic and mercury.
During years 1 to 3, the processing facility is designed to process 33,000 tpd of non-refractory ore assaying 2.2 g/t of gold and 80 g/t of silver in a circuit consisting of primary crushing, secondary crushing, drying grinding, ore washing, pre-aeration, leaching, CCD thickening for pregnant solution recovery, cyanide destruction, Merrill-Crowe precipitation mercury retorting and smelting.
According to the mine plan, the treatment of refractory ore starts in Year 4, and the plant capacity is increased. On that basis, the process plant is expanded to process 45,000 tpd starting in year 4 (30,000 tpd non-refractory and 15,000 tpd refractory).
Equipment planned to be used include: a 1,370 mm x 1 880 mm gyratory crusher, a 1,220 mm wide downhill belt conveyor, a 6,600 mm diameter x 16,250 mm EGL double rotator grinding mill, thickeners, 160 m3 rougher flotation tanks, 17,700 mm diameter x 18,600 mm high leach tanks, clarifiers, mercury retorts, two diesel-fired 1 m3 liquid volume reverberatory furnaces and cyanide destruction circuits.
The tailings disposal facility is located east of the processing plant in the Rio Turbio valley, at an elevation of 3,900 m above sea level. In order to accommodate the life of mine production the tailings facility would need to accommodate 420 Mt waste.
Water rights have been approved in both countries and they cover the project?s needs.
The Pascua-Lama project will buy power from a public utility by connecting to a 170 km long 220kV aerial transmission line.