The Project is held 100% by Marimaca Copper. Marimaca Copper has four Chilean subsidiaries that have actual, or eventual, rights over various mining properties that make up the Project:
- Compañía Minera Cielo Azul Limitada (MCAL);
- Compañía Minera NewCo Marimaca (Newco Marimaca);
- Compañía Ivan SpA (Compañía Ivan);
- Minera Rayrock Limitada (Rayrock).
Summary:
Deposit Types
The Marimaca deposit appears to be a new deposit style and does not readily conform to any of the major published geological models.
The deposit occurs in a district that has a number of vein-style IOCG deposits, which have common features including regional metamorphism/metasomatism, Ca–Na alteration, the presence of magnetite and hematite, chalcopyrite as the major copper-bearing mineral, and an overall low sulphide content (Sillitoe, 2003; Richards and Mumin, 2013). The Marimaca deposit setting includes some of these elements.
However, Marimaca also has affinities with “manto-type” mineralization styles, although the monzodiorite mineralization host is unusual, since the known manto-type deposits are typically associated with volcanic piles. If the host rock issue is not taken into consideration, Marimaca is analogous to manto-type copper deposits such as Mantos Blancos (Chavez, 1983) or El Soldado (Boric et al., 2002). The critical role of structures, dykes, and alteration zoning is a common feature in these deposits. The deep and extensive development of supergene alteration and oxidation is similar to that seen at Mantos Blancos.
The sulphide and alteration mineralogy at Marimaca resemble those encountered within IOCG systems; however, the lack of iron oxides and gold and the occurrence of hypogene chalcocite and covellite are not common in IOCG deposits (Richards and Mumin, 2013). These features appear to be more frequent in the “manto-type” deposits. In alteration terms, Marimaca appears to be a hybrid of the manto-type and IOCG deposits.
Mineralization
The Marimaca deposit consists of a supergene copper blanket (oxides and enriched sulphides).
The oxide zone is exposed on surface, and has dimensions of about 1.4 km long, 400–600 m in width, and a thickness that ranges from 150–350 m. The shape of the oxide zone is controlled by the parallel fracture system and dikes, with the deeper zones of oxidation typically related to northwest-trending faults. However, the rhyodacitic dykes also have a role in the location of higher copper grade zones, in combination with feeders and veins.
Most of the copper oxides occur as fracture staining and infill within fracture-veins and veinlets. Minerals in the upper copper oxide zone are typically zoned, extending outwards from brochantite, atacamite, chrysocolla and finally wad-rich zones. The brochantite zone contains more than 60% of the brochantite and or atacamite and 30–35% of chrysocolla, and forms high-grade cores. The chrysocolla zone borders the brochantite zone, and typically has >60% chrysocolla. The wad zone is the outermost zone, with the lowest copper grades, and typically displays about 90% non-green copper oxides.
The oxide zone grades into a mixed zone of oxide and sulphide materials. Chalcocite and covellite can occur as both primary and secondary sulphides, forming fracture stains, sulphide coatings, and massive replacement in breccias or veins (bands).
At depth, the primary mineralization is chalcopyrite in association with pyrite. The primary zones are not well defined due to the lack of drill data at depth.
The oxide blanket is better preserved in the southern part of the deposit area. Towards the north and east, it has been partially eroded, resulting in most of the wad and chrysocolla capping being removed. Brochantite that has been altered to atacamite crops out and has a more irregular distribution that is interpreted to be related to the main feeders and veins. Chrysocolla is better preserved closest to the surface at Marimaca, and within some ridges to the north.