Lupaka Gold gained ownership of the Invicta gold project in Huaura Province of north-west Peru by acquiring Andean American Gold in October 2012. The poly-metallic deposit primarily consists of gold, along with good amounts of copper, lead, silver and zinc.
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Environmental impact assessment permit for the project was obtained in December 2009 from the Ministry of Mines & Energy of the Government of Peru (MEM). In February 2015, MEM granted the certificate of mining (COM) permit for the project.
Underground mining at the project started in May 2015, while commercial operations are expected to begin by mid-2015.
Invicta project geology and mineralisation
The Invicta gold-silver-copper-lead-zinc deposit is made up of 46 concession and petition claims. The project mainly hosts mafic volcanic rocks of the Calipuy Group, overlying diorite, tonalite and granodiorite of the Paccho pluton. The pluton is an intrusive suite and is a part of the Huaura plutonic complex.
The deposit comprises quartz-pyrite-chalcopyrite-acanthitehematite bearing quartz veins, with the sulphide mineralogy comprising stringers and blebs of pyrite and chalcopyrite. The deposit also contains minor amounts of chalcocite, digenite, chalcopyrite and bornite.
The gold mineralisation occurs as free grains in fractured quartz and pyrite, and most of the mineralisation is hosted by volcanic mafic rocks of the Calipuy Group.
The mineralisation has been classified into three major zones, Atenea, Pucamina and Dany Fault. Majority of the mineralisation is contained in the Atenea vein. The deposit also comprises Ydalias and Zone 4, which contain a smaller amount of resources.
Invicta poly-metallic deposit reserves
As of April 2012, the measured and indicated resources at Invicta gold project were estimated to be 8.64Mt of ore grading 2.13g/t Au, 15.90g/t Ag, 0.43% Cu, 0.24% Pb, and 0.29% Zn. The mine is expected to contain 591,000oz of gold, 4.41 million ounce (Moz) of silver, 81.17 million pounds (Mlbs) of copper, 46.28Mlb of lead, and 54.59Mlb of zinc.
Mining and processing of ore at the Invicta gold project
Sub-level open-stoping mining method is proposed for the underground mine. Initial mining operation is expected to begin from Atenea Vein, the highest-grade gold and copper mineralisation at the deposit.
Underground drilling and blasting, mining for process testing, and underground safety and ventilation infrastructure facilities will be solely undertaken by the mining contractor.
The processing plant is expected to have a capacity of 300t of ore a day. Conventional ore processing methods will be used to recover two types of concentrates, namely copper concentrate, which contains most of the gold and some silver and lead, and a lead concentrate, which contains some silver and gold.
The La Arena gold-copper project, which is being developed by Rio Alto Mining, is located approximately 480km north-northwest of Lima, Peru.
The copper and lead concentrates will be separated by depressing lead minerals and floating copper minerals. Majority of the gold and half of silver will report to the copper concentrate, while some gold and the other half of silver will report to the lead concentrate.
Infrastructure facilities at the Peruvian gold project
Power required for the mine is proposed to be obtained from the Andahuasi substation through a new 29km-long, 66kV electrical transmission line. A new 66kV/10kV step-down transformer will be constructed at the terminus of the transmission line to supply power for the mine, process plant, and water well site. Two separate 10kV transmission lines will be constructed from the terminus to supply power to the mine transformer and the water pumping station.
Water required for the mining operations will be sourced from the Huaura River, which is located approximately 7.5km to the west of the property. Invicta obtained a water use permit for 40l/s for 12h/d from the Peruvian Ministry of Agriculture through the ATDR (Irrigation District Technical Administration Authority) in October 2009.
Contractors involved with the mine development
PLH SAC Mining Contractors was awarded the contract for the underground mining. The contract for processing the bulk samples from the Invicta mine was awarded to Procesadora Leslie Semanco (PLS).
Minera Lucero, a private haulage contractor, was contracted to transport the mined material to the toll processor, and to improve and upgrade the access roads.
Aminpro Mineral Processing was engaged to conduct metallurgical assessments, plant design, and evaluation of the process options at the Invicta gold project.
SVS Ingenieros, a subsidiary of SRK Global Consulting, provided the mine engineering and project management consulting services for the project.
