Copper and gold concentrate
The Josemaria copper-gold project is a high-grade copper-gold porphyry project being developed by NGEx Resources in San Juan Province, Argentina.
The preliminary economic assessment (PEA) of the project was completed in January 2016, while the pre-feasibility study (PFS) was completed in November 2018.
The project is anticipated to produce more than 5.4 billion pounds of copper and 4.6 million ounces (Moz) of gold during its anticipated mine life of 20 years. It is expected to produce approximately 125,000t of copper, 230,000oz of gold, and 790,000oz of silver a year.
The Josemaria copper-gold project is located approximately 10km from Chilean border and 140km from Copiapo, Chile. The deposit remains open to the south and is hosted under a thick cover of post-mineral volcanic rocks.
The copper-gold mineralisation at the mine is hosted within a Miocene porphyry system, which is estimated to have formed approximately 24.7 million years ago. It features copper and gold mineralisation associated with the upper parts of the potassic alteration zone.
The project hosts chalcopyrite and pyrite plus minor bornite through the potassic zone, while quartz–magnetite and chalcopyrite veining is also identified within the main mineralised zone.
The probable reserves at Josemaria copper-gold project are estimated to be approximately one billion tonnes, grading 0.29% copper, 0.21 grams per tonne (gpt) of gold, and 0.92gpt of silver.
Contained copper, gold, and silver are estimated to be 6.5 billion pounds, 6.5Moz, and 28.8Moz respectively.
Conventional open-pit mining method, involving drilling and blasting followed by loading and hauling by autonomous trucks, will be employed at the Josemaria copper-gold project.
The processing plant is expected to treat ore at a nominal rate of 150,000tpd of sulphide ore to produce copper concentrate. Ore from the open-pit will undergo three stages of crushing, including primary, secondary, and tertiary. The tertiary crushing unit will employ high-pressure grind rolls (HPGR) to crush the ore.
The fine crushed product will be forwarded to the grinding unit, which comprises a cyclone cluster and a ball mill. Discharge from the ball mill will be sent to cyclone cluster, with the cyclone underflow flowing to the ball mills and overflow reporting to the rougher flotation section.
Conventional flotation process will include rougher scavenger flotation, regrinding, and three stages of cleaner flotation to produce a final copper concentrate. The concentrate will then be thickened with flocculant in a high-rate thickener and fed to the agitated copper filtration stock tank.
The final concentrates will be loaded onto concentrate trucks and transported to the port of Caldera in Chile for shipping to customers.
The project site will be connected to the Argentina Ruta Nacional 76 highway through a 57km-long access road, which will be upgraded.
Power required by the project is proposed to be supplied by a 250km-long, 220kV transmission line from the Guanizuil substation, which will be upgraded to facilitate the new interconnection.
Water for the mining operations is proposed to be collected from groundwater wells and nearby aquifers. The groundwater will be pumped from the wells and stored in an intermediate fresh water holding tank for supply to process facility, fire, camp water treatment, and other facilities.
Construction and operational staff will be accommodated at the accommodation camp, to be situated approximately 2.5km from the open-pit.
Tailings generated at the plant will be stored in a typical surface storage facility.
SRK Consulting (Canada) prepared the PFS of the project in Argentina. Other consultants who participated in PFS preparation included Ausenco Engineering, Knight Piésold, BGC Engineering, Merlin Geosciences, and Gino Zandonai.
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