|Commodity||Silver, Zinc, Lead, Copper|
|Location||320 Km NE from Lima, Peru
Latitude: 11° 0' (North)
Longitude: 76° 25' (West)
|Owners||Pan American Silver Corp. - 99.93%|
|Operator||Pan American Silver S.A.C. Mina Quiruvilca|
|Production||2.769 Moz silver, 9.6 kt zinc, 4.9 kt lead, 1.3 kt copper (2011)|
|Deposit Type||Vein & manto type polymetallic deposit|
|Reserves & Resources||10.3 Mt @ 183 g/t (Dec 31, 2011, proven & probable reserves)|
|Mining Method||Overhand cut-and-fill & long hole mining|
|Processing Method||Three-stage-crushing, ball mill grinding and selective flotation of the ore to concentrates, followed by thickening and filtering of the concentrates.|
|Mine Life||To 2027|
|Mining Equipment||Jackleg and jumbo electro-hydraulic drills; 30HP 25"-36"slushers (15); 1.25, 2.5 or 3.5 m3 LHD scoop trams; electric locomotives|
|Processing equipment||Three-stage-crushing (jaw and Symons cone crushers), 12" X 16" and 8' X 8' ball mills, selective flotation circuit, 1.2 X 1.2 m Andritz 1500 filter press|
|Employees||Approx 208 permanent & 417 contractors (2006)|
|Contact Information||Suite Of. 301, Av. La Floresta 497
Edif. Parque Las Lomas
Last updated: May 28, 2012
The Huaron property consists of 252 concessions spanning over 63,822 ha and is located in the province of Pasco, one of three provinces forming the Pasco Department in the Central Highlands of Peru. It is situated 320 km northeast of Lima in the eastern flank of the Western Cordillera of the Andes at elevations of 4,250 m to 4,800 m above sea level.
Huaron is a primary silver mine that historically produced more than 220 million ounces of silver from 70 known veins since operations began in 1912. In April 1998, Huaron's production ceased after its underground workings were flooded due to an accident at a neighbouring mine.
Pan American acquired a majority interest in the Huaron mine in March 2000 and fast-tracked the project through feasibility, financing and construction to begin full-scale operation in April 2001 and subsequently acquired the remaining interest.
Huaron is an underground mine displaying both narrow and wide veins of silver-rich base metal sulphides, as well as replacement mineralization in conglomerate (mantos in limestones) and dissemination in sediments.
The mining method is overhand cut-and-fill using mill tailings as the backfill material.
The mill flowsheet consists of three-stage-crushing, ball mill grinding and selective flotation of the ore to concentrates, followed by thickening and filtering of the concentrates.
Based solely on proven and probable end of 2006 mineral reserves the mine life extends to 2019. The plan was based on providing average of 2,150 tpd of ore to the mill.
The Huaron mine is located in the Department of Pasco, Province of Pasco, District of Huayllay in central Peru, 320 kilometres northeast of Lima.
Peru is a Spanish speaking developing country that straddles the Andes and encompasses a strip of the Pacific coast to the west and a flat terrain covered by the Amazonian jungle to the east. It is approximately two-thirds the size of Mexico and it is the fourth most populous country in South America.
Access to the Huaron property is by a continuously maintained 285 km paved highway between Lima and Unish and a 35 km gravel road between Unish and the Huaron property, the latter was being upgraded by the Peruvian government.
The main lithology in the Huaron area is a sequence of continental redbeds consisting of interbedded sandstones, limestones, marls, conglomerates, breccias and cherts of Upper Cretaceous to Lower Tertiary age.
To the west of the mine, a series of andesites and dacites outcrop. A series of sub-vertical porphyritic quartz monzonite dykes, generally strike north-south and cut across the mine stratigraphy.
The mine is located within an anticline formed by east-west compressional forces. The axis of the anticline is approximately north-south striking and gently plunging to the north. There are two main fault systems: north-south striking thrust faults parallel to the axis of the anticline; and east-west striking tensional faults.
Huaron is a polymetallic deposit - hosting silver, lead, zinc and copper - consisting of mineralized structures probably related to Miocene monzonite dykes principally within, but not confined to the Huaron anticline. Mineralization is encountered in veins parallel to the main fault systems, in replacement bodies associated with the calcareous sections of the conglomerates and other favorable stratigraphic horizons, and as dissemination in the monzonitic intrusions at vein intersections.
The first pulse of mineralization was associated with the emplacement of intrusive bodies and the subsequent opening of structures, during which zinc, iron, tin, and tungsten minerals were deposited. This was followed by a copper, lead and silver rich stage, and finally by an antimony-silver phase associated with quartz. There is a definite mineral zoning at Huaron and the mine has been divided into seven separate zones.
The central core of the district has adularia-sericite alteration overprinted with strong silicification and epidote-pyrite. This core is surrounded by a zone containing epidote-pyrite-quartz that grades outwardly to a zone containing chlorite and magnetite. The mineralized structures are concentrated in the central core of the district but important structures continue into the outer zones.
Exploration is conducted using a combination of underground drilling and drifting. Generally, underground drill holes that intersect promising ore grade mineralization are followed up by drifting for mineral resource and mineral reserve definition.
The Huaron mine is located at an elevation between 4,250 and 4,650 m above sea level and mining activities extend over a 2 km by 2 km area. The processing plant and mine offices are located at the same elevation as the 500 level. The 250 level is 250 m below the 500 level and is the drainage level for the mine providing gravity drainage to a point further down a river valley.
Access to the mine is via three adits driven into the side of the mountain at levels 500, 420, and 250. The main haulage level is on Level 500 which is accessed via a rehabilitated 3 m by 3 m tracked. Electric locomotives are used for mine haulage on the 500 level. Ore from above the 500 level is either fed to that level via ore passes or taken out of the mine via other portals to be hauled to the mill stockpile with surface haul trucks. There are three existing shafts on the property, but these have not been used since the late 1980's. One of the shafts will be deepened to the 180 level and refurbished.
The mining method is overhand cut-and-fill using mill tailings as the backfill material. Starting with 2011, the long hole mining method was also implemented. During 2012, long hole mining of the Farallon, Tapada, Llacsacocha and Productora veins is expected to reach 35% of the total production from underground.
Mine was deepened to provide access to known northern vein extensions that have not been previously mined and a new conveyor-way ramp system was installed in 2006.
During 2010, the D shaft refurbishment was completed and the shaft was put into operation. In 2011, an electric locomotive haulage system was installed on the 250 level to connect the D shaft with the North zone and to continue to develop the 180 level.
Drilling is performed with jackleg and jumbo electro-hydraulic drills, drilling over head, 1.2 m cuts. The blasts are done with emulsion, gel dynamite explosives, and in some areas of the mine the company is permitted to use ANFO.
In general veins that are less than 1.8 m thick are mined with 15-30 hp slushers utilizing 25 to 36 inch buckets. For veins exceeding 1.8 m it is advantageous to muck with LHD scoop-trams of 1.25, 2.5 or 3.5 cubic meter capacity.
Prior to its acquisition by Pan American, approximately 22 million tonnes of silver-rich base metals sulphide ore were mined from the property.
The Huaron Mine operates a mill using froth induced flotation technology to produce silver in copper, lead, and zinc concentrates. The mill flowsheet consists of three-stage-crushing, ball mill grinding and selective flotation of the ore to concentrates, followed by thickening and filtering of the concentrates.
Oxidized material from above the 500 level is blended with fresh sulphide to produce acceptable recoveries through flotation. Over the long term, as mining progresses deeper, the amount of primary sulphide ore in the feed will increase.
The crushing plant consists of three-stage-crushing and uses jaw and Symons cone crushers.
The grinding circuit consists of a 12 ft diameter by 16 ft long primary ball mill operating in a closed circuit with one of an 8 ft diameter by 8 ft long secondary ball mill or an 8 ft diameter by 3 ft long secondary ball mill. The grinding circuit uses a D-20 hydrocyclone for classification.
Bulk flotation to produce a copper - lead concentrate is followed by copper and then zinc separation. Bulk flotation occurs in 3 stages: roughing, cleaning and scavenging.
The lead concentrate is thickened in a Dorr Oliver 26 ft diameter by 6 ft high thickener or an auxiliary 20 ft diameter by 8 ft high Dorr Oliver thickener. In the same way, the copper concentrate is thickened in a Denver 18 ft diameter by 8 ft thickener. The zinc concentrate goes to a 28 ft diameter by 10 ft Fima thickener and excess concentrate is sent to a Dorr Oliver 24 ft diameter by 8 ft thickener. A 1.2 m by 1.2 m Andritz 1500 filter press with 34 plates is used to obtain a 8 percent moisture content final concentrate.
Copper concentrates contain 25 percent copper, lead concentrates contain up to 45 percent lead, and zinc concentrates contain up to 47 percent zinc. Silver recovery is directly related to the silver head grade as well as copper and lead grades. The long term silver recovery in the life of mine plan is 80 percent.
Lead and zinc concentrates produced at the Huaron Mill are loaded and transported by road to the port at Callao near Lima. Copper concentrate with high silver grades is transported to the La Oroya smelter.
The tailings dam is constructed primarily of waste rock from the mine. Tailings from the processing plant are pumped to the Presa 5 tailing impoundment.
The continuous fresh water supply requirements for the Huaron concentrating plant average 91.7 liters per second. The water is gravity fed from the Llacsacocha Lake with an 8 inch diameter pipe and is directed to the mill, flotation, and other areas of the plant.
The primary source of power for the Huaron Mine is the Peruvian national power grid.
The concentrator plant processed 614,400 tonnes of ore in 2011, down from the 704,100 tonnes processed in 2010.
An EIA for the expansion of a tailings dam at Huaron mine was approved in 2011. The expansion will allow for another 12 years of production.
The Huaron Mine has operated for over 85 years, and significant historic environmental disturbances pre-dated Pan American's ownership. Studies have been designed and recommendations from these studies have been partially carried out to establish and implement closure strategies and options for remediation of historic disturbances. Remediation is ongoing during mine operations. Field investigations defined water sources and flows to establish accurate base line conditions and separate flows from the adjacent, but separately owned Chungar mine. Community meetings are held to improve communication and to initiate awareness training about environmental, health and safety issues.
The most significant environmental issues currently associated with the mine are relatively high metal concentrations in the waters discharged from the mine and localized areas of acid rock drainage from the mineâ€™s tailings deposit areas. Mine dewatering water is treated in a treatment plant to achieve compliance with discharge limits.
The current present value of closure expenditures at Huaron as at December 31, 2011 was estimated at $10.4 million.
As of December 31, 2006, the operation directly employed 625 full time employees - 208 permanent and 417 temporary - and indirectly employed 940 persons through agreements with Peruvian mining contractors. Employees commute to the property via company sponsored bussing, company vehicles, or privately owned vehicles.