McEwen Copper Inc. holds a 100% interest in the Los Azules copper project in San Juan.
McEwen Mining owns 47.7% of McEwen Copper which owns 100% of Los Azules.
October 16, 2023 - After closing the Nuton LLC investment, also announced today, McEwen Copper will have 30,937,615 common shares outstanding, and its shareholders are McEwen Mining Inc. 47.7%, Stellantis 19.4%, Nuton 14.5%, Rob McEwen 12.9%, Victor Smogon Group 3.2%, and other shareholders 2.3%.
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Summary:
Los Azules is located within the Central Chile segment (400 km-long) of the Miocene-early Pliocene porphyry copper belt (6,000 km-long) of the north and Central Andes.
In many respects the Los Azules deposit is a classic Andean-style porphyry copper deposit. In the bedrock below a thick surface cover of scree and valley fill, a barren leached zone overlies a zone of secondary or supergene enrichment of variable copper grades and thickness. Primary or hypogene mineralization extends to at least 1,000 m below the present surface. Circulation of meteoric ground water near surface leached primary sulfides (mainly pyrite and chalcopyrite) from the host rocks over the past several million years and the leached copper was redeposited below the water table in a sub-horizontal zone of supergene enrichment as secondary chalcocite and covellite. Hypogene bornite appears at deeper levels together with chalcopyrite. Gold, silver, and molybdenum are present in trace amounts, but copper is by far the most important economic constituent at Los Azules.
Starting at the boundary between the barren leached zone and the supergene mineralization, secondary enrichment mineralization gradually transitions to predominately hypogene mineralization at depth.
Sillitoe (2014) examined about 9,000 m (approximately 25% at the time) of the available drill core and proposed a revised geologic interpretation for Los Azules.
Sillitoe’s interpretive model has features in common with the giant Río Blanco-Los Bronces and Los Pelambres deposits in Chile; both are part of the same Miocene-Pliocene porphyry copper belt as Los Azules. Vázquez (2015) subsequently relogged 44,000 m from 98 drill holes representing essentially all the drill core available at that time. Vázquez confirmed Sillitoe’s interpretation, and he also refined the temporal sequence and spatial distribution of distinct phases of alteration and mineralization.
Triassic volcanic country rocks (VOLCS) at Los Azules are intruded by a pre-mineral multi-phase, calc alkaline quartz diorite pluton dated at 10.6 Mya to 10.7 Mya (Zurcher, 2008b). The pluton is elongated in an NNW direction and is at least 7 km in north-south extent and at least 2.5 km wide . The pluton comprises numerous compositionally and texturally distinct phases, of which equigranularity, fine- to medium grained diorite, monzodiorite and quartz diorite appear to be the most abundant within the mineralized zone. However, there are also phases such as felsic as quartz monzonite, and some of the quartz diorites are porphyritic.
There are a series of small hydrothermal-magmatic type breccia bodies (MAG-HBX) generated by the release of over pressured magmatic fluid. Vázquez interpreted these breccias to be approximately coeval with the inter-mineral dikes because breccia clasts of porphyry were observed with type-A early veinlets of quartz and early hypogene mineralization. The breccia bodies are controlled by high angle pre-mineral faults as they generally trend NNW and dip steeply to the east, but they are discontinuous and relatively small compared to the total mineralized volume of Los Azules. There are two main sectors where these breccia bodies occur. The first is located west of the early mineralized porphyry dike between coordinates 6,558,600 N and 6,559,900 N as bodies of no more than 20 m to 30 m wide and up to 500 m long. The second domain occurs in the northern sector of the system between coordinates 6,559,800 N and 6,560,900 N (Figure 7.13) where the breccia bodies appear to have the form of pipes.
The Los Azules hydrothermal alteration system is at least 5 km long and 4 km wide and is elongated in an NNW direction along a major structural corridor. The system disappears below volcanic cover to the north, so the ultimate extent is unknown. The altered zone surrounds the Los Azules deposit, which is approximately 4 km long by 2.5 km wide. The limits of the mineralization along strike and at depth have not been entirely constrained by drilling.
Recent geological studies have resulted in an updated geologic model (Mortimer, 2022) that shares many features with other well-known Andean porphyry copper deposits. These studies have defined the temporal sequence and spatial distribution of the following distinct alteration phases and mineralization zones.
• Intrusion of pre-mineral dioritic stock or pluton.
• Pervasive chlorite-magnetite alteration accompanied by chalcopyrite mineralization in the upper levels of the pluton grading into potassic alteration with chalcopyrite and bornite mineralization at depth.
• Intrusion of early mineralized porphyry dike phase and formation of magmatic- hydrothermal breccia bodies.
• Intrusion of later “inter-mineral” phase porphyry dikes and formation of magmatic- hydrothermal breccia bodies.
• Late sericite alteration accompanied by pyrite and chalcopyrite.
• Formation of erratic quartz veins containing base and precious metals.
• Supergene enrichment.
The mineralized system disappears below volcanic cover to the north; therefore, the ultimate extent is unknown. Los Azules has been geologically mapped over many years. The entire area comprising the Los Azules deposit is covered by thick talus or valley fill, so none of the mineralized materials are exposed in outcrop, although some near-surface exposures have been exposed in trenching at the crest of the La Ballena ridge that defines the long axis of the deposit. Consequently, the interpretation of the structures and intrusive bodies is based almost entirely upon drill hole data.
Hypogene minerals include chalcopyrite and to a lesser extent, bornite. However, chalcopyrite is the most important copper mineral in the upper levels of the deposit, while hypogene bornite appears at deeper levels together with chalcopyrite. Copper sulfides rarely exceed 2% to 3% of rock volume. Intervals of 0.1% to 0.35% copper are common in the hypogene mineralization.
Circulation of meteoric ground water leached the primary sulfides (pyrite and chalcopyrite) from the host rocks over the past several million years, and the leached copper was redeposited below the water table in a sub-horizontal zone, or blanket, of supergene enrichment as secondary chalcocite and covellite. The intensity of secondary enrichment diminishes with depth, except along major structures where it may extend to great depth.
Los Azules can be described as a typical copper porphyry deposit, with large tonnages of disseminated copper minerals with the usual succession of leached, supergene, and hypogene mineralization.
Overall, modelling shows that Los Azules is a large structurally controlled porphyry deposit, open towards the west, northwest and at depth. The extensive supergene enriched zone has developed down structures that transition into primary sulfide mineralization. Modelling shows multiple bornite centers within the primary zone highlighting exploration potential at depth and along the currently modelled structures.