Josemaria is located in the San Juan Province of Argentina, approximately 9 km east of the Chile-Argentina border. The project topography is mountainous with broad, flatbottomed valleys and moderately steep slopes ranging in elevation from approximately 4,000 to 4,900 m above sea level. Access to site is to be from the city of San Juan, a major mining centre, along public two-lane paved roads and a project-developed and maintained gravel road. The project has ready access to water, grid power, as well as transportation and logistics infrastructure wholly within San Juan province.
The Josemaria project is to be developed as a large-scale open pit mining operation. As currently envisaged, over 1 billion tonnes of ore will be mined at average diluted head grades of approximately 0.30% copper, 0.22 g/t gold and a strip ratio of 0.98 over a 19-year mine life.
The project is to employ conventional truck and shovel open-pit mining with conventional primary crushing, grinding and flotation at an estimated average processing rate of 152,000 t/d. Facilities on site include crushing, grinding, flotation, concentrate and tailings thickening, concentrate filtration, storage and loadout. To maximize productivity, efficiency and safety in a high-altitude environment, functions will be autonomously operated as much as possible.
Run-of-mine material will be delivered from the open pit to two gyratory crushers with crushed ore transported via an overland conveyor to a coarse ore stockpile. Material will be reclaimed from the coarse ore stockpile and conveyed to three SAG mill/ball mill circuits. Conventional copper rougher flotation, followed by concentrate re-grinding and copper cleaner flotation, will result in the production of a copper concentrate with a copper grade of 26% to 32% copper and payable precious metals. The gold-rich copper concentrate is to be transported by truck to San Juan, where it will be loaded onto rail and taken to the port at Rosario for export to international customers.
Geologic and Exploration Overview
Josemaria is classified as a porphyry copper-gold system. The deposit area presently measures approximately 1,500 m north-south by 1,000 m east-west and 600 to 700 m vertically from surface, within a larger alteration footprint of up to 4 km north-south by 2 km east-west. The deposit remains open to the south, beneath a thickening cover of post mineral volcanic rocks and also at depth.
Mineral zones are defined by the relative abundance of chalcopyrite, pyrite and chalcocite, as well as the mode of occurrence of chalcocite (hypogene or supergene) and level of oxidation. Chalcopyrite and pyrite are disseminated through the potassic and overprinting chlorite-sericite zones, with minor bornite. Sulphide mineralization in the upper advanced argillic and sericitic domains includes a hypogene-enriched high-sulphidation assemblage of chalcocite with covellite, tennantite, and minor enargite, resulting in some of the highest hypogene grades in the deposit.
Twelve drilling campaigns have been carried out at the deposit since its discovery in 2003/2004 field season. The first hole drilled encountered 280 metres grading 0.61% copper and 0.51 g/t gold. Drilling to March 2022 totaled nearly 96,800 m in 228 drill holes, of which 48 holes are reverse circulation holes and 180 holes are core holes, including 14 condemnation holes and 15 geotechnical holes. Lundin Mining believes there is significant potential to further increase value over the longer-term leveraging its copper-focused exploration expertise. Exploration potential in a highly prospective and emerging district, combined with the large Mineral Resource base, position Josemaria as the center of gravity for future development and expansion.