Eagle Mine, Marquette County, Michigan, USAi

Regional Level Types
Eagle Mine	Mine
Marquette County	County
Michigan	State
USA	Country

The Eagle Ni-Cu-PGE deposit occurs in olivine-rich melagabbro, melatroctolite, and feldspathic peridotite units that were emplaced during the early stage of development of the Midcontinent Rift. Mineralization is characterized by the presence of two semi-massive sulfide zones in olivine-rich rocks that are linked by a zone of massive sulfides. Pyrrhotite, pentlandite, and chalcopyrite comprise the bulk of the sulfide mineral assemblage. Possibly formed in a magma conduit.

The Eagle deposit is a high-grade magmatic sulphide deposit containing nickel and copper mineralization and minor amounts of cobalt, precious and platinum group metals (PGMs).
The economic minerals associated with this deposit are predominately pentlandite and chalcopyrite.

Three distinct types of sulphide mineralization occur at the Eagle deposit. They are described as disseminated, semi-massive and massive sulphide. Massive sulphide is generally over 90% pyrrhotite-pentlandite-chalcopyrite. Semi-massive, or matrix ore, is 30% or greater net textured sulphide. Disseminated mineralization is generally uneconomic. The semi-massive and massive sulphides occur in separate zones called the Massive Sulphide, Semi-massive East, and Semi-massive West zones.

Eagle is a relatively shallow underground mine with access gained via a surface ramp that also serves as the route for waste, ore and backfill haulage. The mine employs transverse bench-and-fill stoping with mining in an up-dip primary secondary sequence. Backfilling is undertaken using cemented and uncemented rockfill. Two ventilation shafts are in place, with the downcast shaft also equipped for emergency egress. Ore from the mine is stored in a covered coarse ore stockpile facility prior to transport by road 105 km to the Humboldt mill site.

From a second covered coarse ore storage facility, the ore is processed using a conventional crush, grind and differential flotation process to produce separate nickel and copper concentrates. Tailings from the plant are deposited sub-aqueously in the adjacent former Humboldt iron ore open pit.

Nickel and copper concentrates are stored in a covered concentrate building on site prior to being transported via rail car direct to smelter facilities within North America or to ports for shipment overseas.

Mineral Reserves at Eagle are sufficient until 2024.

Both the mine and mill operate under a number of local, state and federal permits. First commercial concentrate production was achieved in the fourth quarter of 2014.

Other Regions, Features and Areas containing this locality

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