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.

Open pit mining is contemplated, using equipment conventional to the industry.

The open pit area was divided into three geotechnical zones, with pit slope angles that range from 42–52º. Mining dilution, based on a cut-off grade of 0.2% CuT is assumed to be 2.3% for tonnes, and a contained copper loss of 4.6% will result.

Eight pit phases are planned. phase 1 targets the material with the highest grade in the central area, down to 920 masl. phases 2 and 3 are successive expansion to the north, down to 960 masl and 870 masl, respectively. phase 4 is an almost independent pit at the northern area of the deposit with an exit to the north and a connection with phase 3 for exiting to the primary crusher to the south. This phase will extend to the 890 masl. phase 5 is an expansion to the west of the main pit, to 830 masl. phases 6 and 7 are final expansions to the south and west, respectively to 890 masl and 830 masl. phase 8 corresponds to the final expansion of the north pit, to 880 masl.

A road width of 30 m was selected to accommodate trucks up to 190 t. NCL used a 10% road gradient which is common in the industry for this type of truck. The 2020 PEA mine plan is designed with 10 m benches stacked to 20 m (i.e. double benching) for the geotechnical Zone 1 (East wall). Mining costs are based on blasting 10 m benches for every material type. Additional 20 m wide safety berms were included in the design when the slope height exceeds 150 m, in accordance with geotechnical recommendations.

The mine plan was tailored toward a copper cathode production rate of 40,000 t/y. An initial pre-stripping period of 4.0 Mt would be required to expose sufficient mineralised material to start commercial production in Year 1. The mineralised material mined during pre-stripping will be stockpiled in the stockpile area and will make up part of the Year 1 plant production. The total stockpiled for later re-handling during Year 1 will amount to 139 kt, plus 32 kt of low-grade material. The pre-stripping period will be approximately three months. Three separate mining rates will be used during commercial production. An initial three-year period will mine at a rate of 14.5 Mt/y. This will be followed by a two-year period that will mine at a rate of 18.54 Mt/y, which will meet the initial plant throughput capacity of 5.4 Mt/y. To meet the second plant throughput capacity rate of 9.0 Mt/y a total mining rate of 23.5 Mt/y is required for the remainder of the mine life.

Two waste rock storage facilities area (WRSFs), will be located to the west (WSFN) and south (WSFS) of the pit. A ROM pad area was designed in a flat valley, located in between the WRSFs, where the ROM leach process will take place. The leaching of this low-grade material is planned in 10 m lifts. The mine plan assumes that 42.3 Mt are placed in the facility. The life of mine (LOM) plan stockpiles low-grade material for later re-handling at the end of the LOM to the primary crusher for crush leaching. The low-grade stockpile was designed at the toe of the WSFS and will accommodate 1.3 Mt.

The drilling equipment will consist of diesel units capable of drilling 7.9” diameter holes in all material types.

The major equipment was selected based on the mine production schedule, nine months of pre-production and approximately 12 years of commercial mining operations. The pre-production period will include an initial pioneering period estimated at six months for preparing initial roads and bench openings and storage material facilities, followed by a pre-stripping period estimated to be three months long. The total material mined during pre-stripping will be 4 Mt. Re-handling of material will be required in Year 1 for material mined during pre-stripping to meet the plant feed requirements. The mining operation will use 22 m3 hydraulic excavators, 23 m3 front-end-loaders and trucks with a capacity of 150 t. This type of equipment can achieve the required productivity for an annual total material movement of 23.5 Mt. The fleet will be complemented with drill rigs for material delineation. Auxiliary equipment will include track dozers, wheel dozers, motor graders and a water truck. The mine fleet will also include the necessary equipment to re-handle the material from the stockpiles to the primary crusher. This operation will be carried out using a front-end loader and the same 150 t trucks used in the open pit.

Crushing Plant and Stockpile Reclaim
The comminution circuit will consist of a three-stage crushing plant. A single primary crusher (Sandvik CS660, or equivalent) will be used, which is sized to be amenable for crushing the mineralization at the required throughput for phase 2 of the production plan. No upgrade of primary crusher is required at the end of phase 1.

Secondary crushing duty will be performed by cone crushers (Sandvik CH870i, or equivalent) in a secondary crushing plant sized for phase 1 of the production plan. An expansion of this crushing stage will be required, with addition of a cone crusher and auxiliaries, to treat the higher throughput of phase 2.

Two cone crushers of the same type used for secondary crushing duty will be used for tertiary crushing, and an additional third cone crusher will be required for phase 2 tonnages. The circuit is designed to process the corresponding throughput for each phase of the mine plan and will generate a crushing product of P90 < 12.7 mm (1/2 inch).

A rock breaker will be available for dealing with oversized mineralization that requires mechanical breakage to enter the crusher gape. A dust suppression system based on process water will be included to mitigate dust emissions.

Sizing was performed with vendor support and crushing plant simulators, based on the projected “average” hardness of mineralization throughout the LOM. A utilization rate of 75% was assumed for the crushing plant.

A dome-enclosed stockpile for tertiary crusher final product is included in the design and will allow for approximately six hours of continuous feed to the crushed mineralized material leaching facilities at nominal throughput, based on phase 2 tonnage. For phase 1, the stockpile will have capacity for approximately 10 hours of continuous feed to the heap leaching facility. Approximately 9,000 t of live capacity will be available in the stockpile, corresponding to 36,000 t of total capacity including dead volume. The dome structure and the dust suppression system will contribute to the overall control of all dust emissions from the stockpile area.

Feeders beneath the stockpile will reclaim the crushed material and supply feed to the agglomeration area. Reclaim and material handling downstream from the stockpile assumes 70% utilization to allow for the material handling downtime caused by the necessary relocation of the multiple portable conveyors (“grasshoppers”) used to stack the crushed material onto the heap leach pad.

The Marimaca Project will operate a conventional salt acid leaching process consisting of a comminution circuit, crushed mineralized material heap leach (HL) and ROM leach facilities, and SX and EW plants to produce Grade-A copper cathodes. All leaching will be performed using seawater-based process solutions, with sulphuric acid and salt addition to both acidleach the copper oxide mineralization and chloride-leach the sulphide copper mineralization sent to leaching.

Water devoid of chloride for SX/EW requirements will be provided by a dedicated reverse osmosis (RO) plant. The brine RO plant reject stream will be recovered as process water, hence providing additional chloride to the process and making full use of all available water to meet process needs.

The SX plant has been designed to operate with high levels of chloride present in the pregnant leach solution (PLS) and includes two organic washing stages that will allow for a low and manageable transfer of ch ........