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| Alamo Dorado mine in the Sierra Madre Mexico |
Alamo Dorado mine is mining production for gold and silver, this mining method with open pit mine. Alamo Dorado mine in the Sierra Madre mountain range in Sonora, approximately 40 kilometers southeast of the town of Alamos, in the Sierra Madre Occidental and approximately 320 km from the state capital of Hermosillo in the Mexican state.
Alamo Dorado mine is owned by Pan American Silver Corp and acquired Alamo Dorado project in February 2003, and upon completion of the acquisition of Minera Corner Bay. On April 1, 2007 the Alamo Dorado mine began commercial production, after the construction of the mine and the mine has since become the company’s largest silver- producing mine.
Mineralisation And Ore Deposit In Alamo Dorado mine
The Alamo Dorado mine complex comprises the contiguous 509 ha Alamo Ocho and the 4 865 ha Alamo Dorado concessions, five exploration concessions covering 6 014 ha and surface rights covering 763.64 ha.
The silver-gold mineralization at Alamo Dorado is predominantly fracture- controlled and associated with moderate to intense pervasive silification. About 50 percent of the silver mineralization is in strongly fractured rhyodacites and about 30 and 10 percent in the rhyolites and dacites, respectively. The main silver mineral at Alamo Dorado appears to be chlorargyrite which is a silver mineral derived from a silver chloride complex occurring along with the quartz - pyrite minerals filling the fractures. The gold mineralization occurs as free, micron-size particles and/or in the crystal lattices of micro-crystalline pyrite.
The rocks hosting mineralisation at the Alamo Dorado mine comprise a sequence of deformed, steeply dipping, Mesozoic-aged marine rocks that contain minor intercalated siliceous exhalite mineral and pillow basalt.Mineralisation and alteration at Alamo Dorado are controlled by an early cryptic structural zone that has since been transposed and kink folded by the regional ductile deformation events.
The Laramide orogeny event probably caused at least the first phase of deformation, which resulted in the development of a strong planar fabric and the metamorphism of the sediments to greenschist facies.Deformation of the rocks at Alamo Dorado was episodic and occurred before, during and twice after the mineralising events. The metamorphosed marine sedimentary rocks were intruded by several dykes and granodiorite stocks.
Silver and gold mineralisation may have been associated with the emplacement of the diorite feldspar porphyry dyke and/or first phase granodiorite stock, both of which display hydrothermal alternation and contain silver mineralisation.
Ore zones are typically localized in structures, but may occur in permeable lithologies. They are typically centred on structurally controlled hydrothermal conduits. Vein systems can be laterally extensive but ore shoots have relatively restricted vertical extent. Through-going, branching, bifurcating, anastamosing and intersecting fracture systems are commonly mineralized. Hanging-wall fractures in mineralized structures are especially favourable for higher grade mineralization.
Deposits can be strongly zoned along strike and vertically. Zoning typically comprises a base metal poor, Au-Ag-rich top to a relatively Ag-rich base metal bearing lower zone. Ag/Au ratios are typically high in these deposits. Alteration is marked by extensive silicification due to multiple generations of quartz. Sericite-illite-kaolinite assemblages flank the silicified zones. Propylitic alteration dominates at depth and peripherally.
Pan American Silver Corp estimates that mineral resources at Alamo Dorado, as at December 31, 2013, are as follows:
Deposits can be strongly zoned along strike and vertically. Zoning typically comprises a base metal poor, Au-Ag-rich top to a relatively Ag-rich base metal bearing lower zone. Ag/Au ratios are typically high in these deposits. Alteration is marked by extensive silicification due to multiple generations of quartz. Sericite-illite-kaolinite assemblages flank the silicified zones. Propylitic alteration dominates at depth and peripherally.
Pan American Silver Corp estimates that mineral resources at Alamo Dorado, as at December 31, 2013, are as follows:
| Resource Category | Tonnes (Mt) | Grams of Silver per tonne | Grams of Gold per tonne |
|---|---|---|---|
| Measured | 1.2 | 50 | 0.23 |
| Indicated | 1.0 | 79 | 0.39 |
| Inferred | 0.0 | 41 | 0.65 |
Pan American Silver Corp estimates that the Proven and Probable mineral reserves for the Alamo Dorado mine, as at December 31, 2014, are as follows:
| Reserve Category | Tonnes (Mt) | Grams of Silver per tonne | Grams of Gold per tonne |
|---|---|---|---|
| Proven | 2.8 | 60 | 0.25 |
| Probable | 0.6 | 84 | 0.61 |
| TOTAL | 3.4 | 64 | 0.31 |
Mineral reserve estimates in Alamo Dorado mine are based on a number of assumptions that include metallurgical, taxation and economic parameters. Increasing costs or increasing taxation could have a negative impact on the estimation of mineral reserves.
Mining Method And Ore Processing In Alamo Dorado mine
The Alamo Dorado mine is open pit mining uses a 7.5 m3 hydraulic shovel, a 6.5 m3 front end loader and six 53 t mechanical rock trucks for principal earthmoving. open pit mining equipment narrows to 12 cubic meter front-end loaders and 90-tonne haulage trucks. Support equipment in Alamo Dorado mine include tracked dozer, rubber-tired dozer, water truck for road watering, and a backhoe.
Primary production equipment of this size and capability dictate haul road characteristics and mine bench design. Haul roads are designed at widths of 30 meters including berms for all ex-pit haulroads and at 23 meters including berms for all in-pit haulroads. These widths are narrowed to 15-meter minimum for mining the uppermost benches in a new development or the lowest few benches in a phase or ultimate pit development.
Ore from the Alamo Dorado mine deposit is treated by conventional crushing and semiautogenous-/ball-mill grinding to 74 µm , Mineral ore is inserted into SAG (Semi Autogenous Grinding) to make smaller. mineral rocks . To make very fine particles less than one-fifth of the diameter of one millimeter, the ore is put into the Ball Mills which look like huge steel drums rotating, adding water to do to make the mineral ore become a pulp.
Mineral slurry seed then through cyanide leaching stage, followed by thickening, leach residue filtration and direct electrowinning to produce a cathode sludge. This is followed by AVR cyanide recovery and recirculation, thus reducing the mine's environmental impact and future reclamation costs. Leach residue washing with AVR product solutions, dry stack tailings and conventional silver and gold doré bar production from melting of the cathode sludge. The mine's tailings treatment process recovers approximately 97.5% of the sodium cyanide. The nominal design treatment rate is 4 000 t/d of ore on a 24-hour-a-day schedule.
The current Alamo Dorado mine has entered the final stages of mining operations. As expected, in 2014, the mine’s silver production declined from 5.08 million ounces to 3.47 million ounces due to the planned processing of lower silver grade ores, combined with lower silver recoveries. Increased throughput rates helped to partially offset lower silver grades. 2014 gold production of 17,560 ounces was similar to 2013 production due to higher average gold grades.
As anticipated, Alamo Dorado mine will continue along a declining production profile as it enters the final year of open pit mining. Although anticipated throughput of 1.7 million tonnes is expected to remain relatively consistent with 2014 levels, a larger percent of ore processed will be sourced from the lower-grade ores and stockpiles.
2015 silver production is expected to be between 2.95 million and 3.20 million ounces, a decline of at least 8% from 2014 production. Similarly, 2015 gold production is also anticipated to decrease from 2014 levels to between 15,500 and 16,600 ounces
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| Mining operation in open pit Alamo Dorado mine |
Primary production equipment of this size and capability dictate haul road characteristics and mine bench design. Haul roads are designed at widths of 30 meters including berms for all ex-pit haulroads and at 23 meters including berms for all in-pit haulroads. These widths are narrowed to 15-meter minimum for mining the uppermost benches in a new development or the lowest few benches in a phase or ultimate pit development.
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| Plant ore processing in Alamo Dorado mine |
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| Conveyor for mineral ore in Alamo Dorado mine |
Ore from the Alamo Dorado mine deposit is treated by conventional crushing and semiautogenous-/ball-mill grinding to 74 µm , Mineral ore is inserted into SAG (Semi Autogenous Grinding) to make smaller. mineral rocks . To make very fine particles less than one-fifth of the diameter of one millimeter, the ore is put into the Ball Mills which look like huge steel drums rotating, adding water to do to make the mineral ore become a pulp.
Mineral slurry seed then through cyanide leaching stage, followed by thickening, leach residue filtration and direct electrowinning to produce a cathode sludge. This is followed by AVR cyanide recovery and recirculation, thus reducing the mine's environmental impact and future reclamation costs. Leach residue washing with AVR product solutions, dry stack tailings and conventional silver and gold doré bar production from melting of the cathode sludge. The mine's tailings treatment process recovers approximately 97.5% of the sodium cyanide. The nominal design treatment rate is 4 000 t/d of ore on a 24-hour-a-day schedule.
The current Alamo Dorado mine has entered the final stages of mining operations. As expected, in 2014, the mine’s silver production declined from 5.08 million ounces to 3.47 million ounces due to the planned processing of lower silver grade ores, combined with lower silver recoveries. Increased throughput rates helped to partially offset lower silver grades. 2014 gold production of 17,560 ounces was similar to 2013 production due to higher average gold grades.
As anticipated, Alamo Dorado mine will continue along a declining production profile as it enters the final year of open pit mining. Although anticipated throughput of 1.7 million tonnes is expected to remain relatively consistent with 2014 levels, a larger percent of ore processed will be sourced from the lower-grade ores and stockpiles.
2015 silver production is expected to be between 2.95 million and 3.20 million ounces, a decline of at least 8% from 2014 production. Similarly, 2015 gold production is also anticipated to decrease from 2014 levels to between 15,500 and 16,600 ounces
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