The Cerro Casale gold–copper deposit is located in the Aldebarán sub-district of the Maricunga Volcanic Belt in northern Chile. The Maricunga belt is made up of a series of coalescing composite, Miocene andesitic to rhyolitic volcanic centres that extend for 200 km along the western crest of the Andes. Reverse faults parallel to the axis of the Andes have uplifted hypabyssal intrusive rocks beneath the extrusive volcanics, exposing porphyry-hosted gold-copper deposits in the Aldebarán area. In addition to Cerro Casale, the Aldebarán property is host to several, less-explored, satellite deposits including Zona de Vetas, Eva, Cerro Roman, Estrella, Anfiteatro, Jotabeche, and Romancito Sur.

At Cerro Casale, gold–copper mineralization occurs in quartz–sulphide and quartz–magnetite–specularite veinlet stockworks developed in the dioritic to granodioritic intrusives and in adjacent volcanic wall rocks. Stockworks are most common in two dioritic intrusive phases, particularly where intrusive and hydrothermal breccias are developed. Mineralization has been encountered to at least 1,450 m vertically and 850 m along strike. The strike of mineralization follows west–northwest fault and fracture zones, and is open at depth along this strike. The main zone of mineralization pinches and swells from 250 m to 700 m along strike, and down dip steeply to the southwest. The highest grade mineralization is coincident with well-developed quartzsulphide stockworks in strongly potassic-altered intrusive rocks.

Oxidation resulting from weathering and/or high oxygen activity in the last phase of hydrothermal alteration overprints sulphide mineralization in the upper portion of the Cerro Casale deposit. Copper oxides are not common. Oxidation locally extends deeply along fault zones or within steeply-dipping breccia bodies.

Cerro Casale is considered to be an example of a gold–copper porphyry system based on the following:

- Hosted in a Mesozoic orogenic belt;

- Gold–copper mineralization at Cerro Casale formed during emplacement of multiple phases of diorite and granodiorite intrusions into a coeval sequence of intermediate to felsic volcanic rocks;

- Mineralization appears to be most closely related to strong potassic to phyllic alteration of the latest phases of intermediate to felsic intrusives and associated intrusive and hydrothermal breccias;

- Mineralization is focused in well-developed quartz–sulphide stockworks; veins, crackle and breccia zones are also present;

- Large tonnage but low grade.

Open pit mining will be carried out with haul trucks and a combination of electric shovels, hydraulic excavators, and large front-end loaders. All rock will require drilling for sampling and blasting purposes.

Mine design and production schedules were developed for a nominal mining rate of 225 Mt/a, smoothed for truck requirements. Mine production and processing facilities will operate 24 h/d, 7 d/wk, 365 d/a.

The optimized Cerro Casale final pit limit was divided into a sequence of nine pit phases of decreasing profitability in order to facilitate an efficient mining schedule and realize the highest project NPV. The last two of these phases were split into east and west sub-phases in order to defer waste mining and keep the peak mining rate as low as possible.

Considerable pre-stripping will be required to access the deeper, more profitable sulphide ore in the early stages of production. The primary crusher is located 500 m south of the ultimate pit limit, although a 2 km haul road is required out of the Stage 1 pit around the east side of Cerro Casale. Waste dumps and low-grade stockpiles are located within 500 m of the pit entrance.

All mining will be carried out on 16 m benches, with final pit wall berms at 32 m intervals. The overall wall slope angles vary from 34° to 47°. Haulage ramps are designed to a maximum grade of 10% and to a width of 40 m.

Approximately 2,231 Mt of waste will be mined over the 20 year life of the proposed mining operation. Of this total, approximately 170 Mt of waste rock were scheduled for tailings dam construction over the mine life. It is proposed to mine waste rock by a conventional truck and shovel operation using 360 t end-dump trucks. The average peak waste dump production rate is about 475,000 t/d.

The initial production fleet will consist of:
- Fifty-five 360 t trucks (increasing to 57 between 2022 and 2023);
- Five 1,200 t class electric shovels;
- Two 700 t class hydraulic shovels;
- Two 40 m3 rubber-tired loaders.

All rock will require drilling for sampling and blasting purposes. A fleet of seventeen 200 mm diesel-powered blasthole drills will perform this function for ore. Three 311 mm electric-drive blasthole drills (increasing to nine between 2016 and 2021) will be required for waste.

The proposed Project consists of a large open pit with a strip ratio of 2:1, a process plant of 160,000 t/d, and an heap leach operation of 100,000 t/d production throughput. The Project is planned to generate 16.8 Moz of payable gold, 4,832 Mlb of payable copper and 36.5 Moz of payable silver in three saleable products: copper concentrate, gold doré, and SART copper concentrate.

Sulphide ore will be processed in a 160,000 t/d flotation plant facility designed to recover a copper/gold flotation concentrate, followed by dewatering and then dispatch via pipeline to a filtration plant adjacent to a port facility. Filtered concentrate will be loaded into sea-going vessels and shipped to smelters overseas. Additional gold metal will be recovered by submitting the flotation cleaner tailings to a cyanide leaching stage.

Oxide ore will be processed through a run-of-mine (ROM) heap leach facility. The leach solution is treated in a carbon-in-column (CIC) circuit for recove ........