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Eagle Mine, Marquette Co., Michigan, USA

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Latitude & Longitude (WGS84): 46° 44' 53'' North , 87° 52' 53'' West
Latitude & Longitude (decimal): 46.74811,-87.88146
GeoHash:G#: f039bnnxt
Owned/operated by:Lundin Mining 
Locality type:Mine
Köppen climate type:Dfb : Warm-summer humid continental climate

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.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

12 valid minerals.

Rock Types Recorded

Note: this is a very new system on mindat.org and data is currently VERY limited. Please bear with us while we work towards adding this information!

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

1600 - 2500 Ma

ID: 3185010
Paleoproterozoic sedimentary and volcanic rocks

Age: Proterozoic (1600 - 2500 Ma)

Stratigraphic Name: Marquette Range Supergroup

Comments: Penokean Orogen

Lithology: Bimodal volcanic rocks; shale,quartz arenite,dolomite,quartzite,conglomerate,greywacke,siltstone,iron formation; turbidite

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

1600 - 2500 Ma

ID: 2783631
Baraga Group; Michigamme Formation; Gray to black slate

Age: Proterozoic (1600 - 2500 Ma)

Stratigraphic Name: Michigamme Formation

Description: Strongly cleaved. Represents lower stratigraphic part of formation

Comments: Continental margin assemblage (north of Niagara Fault)

Lithology: Major:{slate}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Ware, Andrew, Cherry, Jon, and Ding, Xin (2008), Geology of the Eagle Project: Proceedings of the Institute on Lake Superior Geology: volume 54, Part 2 - Field Trip Guidebook: 87-114.
Xin Ding, Edward M. Ripley and Chusi Li (2012) PGE geochemistry of the Eagle Ni–Cu–(PGE) deposit, Upper Michigan: constraints on ore genesis in a dynamic magma conduit. Mineralium Deposita: 47: 89-104.
Ding, Xin, Ripley, Edward M., Li, C., Geochemical and stable isotope studies of hydrothermal alteration associated with the Eagle deposit, northern Michigan: Proceedings of the Institute on Lake Superior Geology, volume 54, Part 1 – Program and Abstracts: 14-15.

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