The Donlin mineralization model is a high-level, reduced intrusion-related vein system. The Lewis–ACMA part of the district is a low sulphidation, reduced intrusion related, epizonal system with both vein and disseminated mineral zones.

The Donlin gold deposits lie in the central Kuskokwim basin of southwestern Alaska, which contains a back-arc continental margin basin fill assemblage of the Upper Cretaceous Kuskokwim Group, and Late Cretaceous volcano-plutonic complexes. The Project area is underlain by a 5 mile (8.5 km) long x 1.5 mile (2.5 km) wide granite porphyry dike and sill swarm hosted by lithic sandstone, siltstone, and shale of the
Kuskokwim Group.

The deposits are hosted primarily in igneous rocks and are associated with an extensive Upper Cretaceous gold–arsenic–antimony–mercury hydrothermal system. The northeast, elongated, roughly 5,000 ft (1.5 km) wide x 10,000 ft (3 km) long cluster of gold deposits has an aggregate vertical range that exceeds 3,100 ft (945 m). These areas consist of the ACMA and 400 Zone, Aurora and Akivik mineralized areas (grouped as ACMA) and the Lewis, South Lewis, Vortex, Rochelieu and Queen mineralized areas (grouped as Lewis).

Gold occurs primarily in sulphide and quartz–carbonate–sulphide vein networks in igneous rocks and, to a much lesser extent, in sedimentary rocks. Broad disseminated sulphide zones formed in igneous rocks where vein zones are closely spaced. Submicroscopic gold, contained pr ........

Two pits are planned, one at Lewis (nine phases), the other at ACMA (six phases); the pits will partly coalesce toward the end of the mine life. The pits have similar mineralization characteristics, with ore-grade gold hosted in both intrusive and sedimentary rock units. The grade of the gold mineralization in ACMA is higher than in the Lewis area, and because of the higher grades, the ACMA pit will be the first developed.

The mine is proposed to be a year-round, conventional “truck and shovel” operation using both bulk and selective mining methods on 12 m and 6 m benches, respectively. Ramps in final walls have a design width of 131 ft (40 m) and a gradient of 10%. A nominal minimum mining width of 492 ft (150 m) was used for phase design. The mine plan assumes the ACMA pit will be backfilled.

Mining will use a conventional truck-and-shovel fleet. Large electric hydraulic shovels mining the full 40 ft (12 m) benches will be the primary loading equipment in zones of waste and steeply-dipping ore. The same primary shovels will be used on the 20 ft (6m) split benches, thereby avoiding the need for a mixed fleet of hydraulic shovels. All shovels will be equipped with GPS positioning to allow real-time updates of the digging face and delineation of the ore–waste contacts. Large front-end loaders (FELs) will be used as a backup to the shovels and to work on less-productive faces and muckpile cleanup. Large 400 st (360 t) capacity haul trucks will be used for ........

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The process is based on conventional technology. The concentrator, pressure oxidation, and cyanidation facilities will be at the forefront of technology for large, modern gold processing plants.

Mine haul trucks (with capacities to 380 st (345t)) will dump run-of-mine (ROM) open pit ore directly into dump hoppers ahead of a 60" x 89" gyratory crusher.

The overall grinding configuration will consist of an open-circuit SAG mill followed by the “mill-chemical-float-mill-chemical-float” (MCF2) circuit. The MCF2 circuit will entail a primary ball mill followed by primary rougher flotation; the tailings produced from primary flotation will be sent to a secondary ball mill, followed by a secondary rougher flotation. The two individual ball mills will operate in a closed circuit with their respective classification cyclones.

Donlin ore contains a mixture of intrusive and sedimentary rock containing sulphide mineralization. The optimum gold recovery will be a ........