Torrecillas is a high-grade gold project being developed by Australian mining company Minera Gold, in the Chala district of Arequipa, Southern Peru.
Minera Gold, formerly known as Mundo Minerals, acquired the underground mining project from Sociedad Minera Surex in 2007.
Successful trial mining at Torrecillas continued from 2009 until 2014, the year in which commercial production began with Minera Gold’s acquisition of San Santiago processing plant.
In 2014, trial mining was also underway at three high-grade narrow veins named Tessie, Rebeca and Ady, at the project site. Full-scale mining at these veins is expected to start in 2015.
Ore trucking from Torrecillas to the San Santiago plant commenced in July 2014 and the first gold was poured in August. Gold production during the quarter ending September 2014 stood at 454oz.
Ore from Torrecillas was being processed by a third party operator prior to the commissioning of the San Santiago plant. The mine produced 4,234oz of gold and generated $5.37m sales in 2013.
Torrecillas geology and reserves
Minera Yanacocha operates a complex of five gold mines and two processing facilities.
Minera Gold’s 100%-owned Torrecillas gold project is located within a 13,000ha concession package in the gold-rich Nazca-Ocoña geological belt in Southern Peru. Minera Gold is also developing the Tumi gold project, near the Torrecillas project area, which comprises of a multitude of narrow vein, high-grade mineralised structures.
Most of the mineralisation at Torrecillas occurs in narrow high-grade pyritic and locally siliceous fault-related veins. Torrecillas vein, which is currently in commercial production, is one of the 23 known veins in the larger Torrecillas concession block.
As of December 2013, the Torrecillas vein was estimated to contain 124,000t of measured and indicated resources at an average grade of 16.1g/t Au, containing 66,100oz of gold.
Gold mining and processing at Torrecillas
Cut and fill short hole mining method is employed at the underground mine. Ore is mined in horizontal slices and then filled with unconsolidated waste rock.
The mined ore is transported by trucks to the San Santiago processing plant located in Otapara, which is located approximately 185km away from the mine site. The 350 tonnes per day (tpd) capacity processing plant, acquired by Minera Gold for $5.5m in September 2014, comprises of a carbon-in-pulp circuit (CIP) for treating gold.
It also houses two copper circuits to treat both oxide and sulphide copper materials.
Until March 2014, Minera Titán del Peru (MTP) purchased ore from Torrecillas under an annual marketing agreement and processed it at a plant located in Chala, Peru. MTP applied normal carbon-in-leach procedures to produce gold.
Gold streaming agreement for Torrecillas mine
Minera Gold entered into a $5m gold streaming deal with SilverStream in April 2014, according to which the latter will purchase 10% of the monthly gold production during the life of the Torrecillas mine.
SilverStream also signed a $4.4m worth binding financing agreement with Minera Gold in August 2014, for the acquisition of the San Santiago processing plant.
Associated infrastructure facilities for Torrecillas mine
The gold mine is accessed via a 45km access road, which is designed to carry trucks weighing up to 50t. Electricity required for the mining operations is met through on-site diesel generators.
Workers are accommodated at a 300-person accommodation camp located at the project site.
Consultants involved with the Peruvian gold mine development
In August 2011, Ausenco was engaged by Minera to conduct a metallurgical review of the MTP plant. BMGS Perth (BMGS) prepared the technical report on the Torrecillas gold project in 2012.