Crandon Zn - Cu Deposit

Prospect in Forest county in Wisconsin, United States with commodities Zinc, Copper, Lead, Silver, Gold

Geologic information

Identification information

Deposit ID 10097436
MRDS ID W019008
Record type Site
Current site name Crandon Zn - Cu Deposit

Geographic coordinates

Point of reference Ore Body
Geographic coordinates: -88.91972, 45.48083 (WGS84)
(click for info)

Geographic areas

Country State County
United States Wisconsin Forest

Public Land Survey System information

Meridian Township Range Section Fraction State
35N 13E 30 SW Wisconsin


Commodity Importance
Zinc Primary
Copper Primary
Lead Secondary
Silver Tertiary
Gold Tertiary

Materials information

Materials Type of material
Pyrite Ore
Sphalerite Ore
Chalcopyrite Ore
Galena Ore
Silver Ore
Gold Ore
Quartz Gangue
Chlorite Gangue
Sericite Gangue
Dolomite Gangue


  • (Local) Intense Hydrothermal Alteration Is Present Stratigraphically Below The Massive Sulfides And Consists Of Silicification, Sericitization, Pyritization, And Minor Chloritization.

Mineral occurrence model information

Model code 186
USGS model code 28a
Deposit model name Massive sulfide, kuroko (Phanerozoic)
Mark3 model number 104

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Meta-Argillite
    Rock type qualifier Greenschist facies meteamorphism
    Rock unit name Crandon Unit
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Dacite
    Rock type qualifier Andestic to dacitic meta-volcanic rocks

Nearby scientific data

Ore Body (1) -88.91972, 45.48083

Geologic structures

Type of structure Local
Structure description Felsic Center Developed In Back-Arc Basin Facies Rocks

Ore body information

  • Name of the ore body Crandon
    General form LINEAR
    Depth to bottom 760M
    Depth to top 60M
    Width 100M
    Length 1600M

Comments on the ore body information

  • DeMatties, 1994 describes a 4200 ft long, 1800 ft deep, 100 ft thick, steeply dipping massive sulfide orebody, open at depth. Exxon's 1986 estimate was 42.9 million tons at 8.4% Zn, 0.60% Cu, 0.73% Pb, 1.80 oz/ton Ag, and 0.05 oz/ton Au. DeMatties describes the mineralization as sphalerite, galena, and chalcopyrite in syngenetic laminated and thinly bedded pyrite, interbedded pyritic and carbonaceous meta-argillites, pyritic metatuffs, metacherts, and dolomite. Dematties also points out that zinc distribution is not uniform, with some values as high as 25 percent, and that gold is strongly correlated with zinc.

Comments on the geologic information

  • The new model type for Crandon is Volcanogenic Massive Sulfide, felsic

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic
Deposit size Large
Significant No
Discovery year 1975
Discovery method Ore-Mineral In Place

Mining district

District name Crandon

Ownership information

  • Type Operator
    Owner Crandon Mining Co.
    Home office Wisconsin
    Year 1994
  • Type Owner
    Owner Exxon Minerals Co.
    Interest 50
    Home office Houston, Texas
    Year 1994
  • Type Owner
    Owner Rio Algom Ltd, Toronto Canada
    Interest 50
    Home office Canada
    Year 1994
  • Type Owner
    Owner the Mole Lake Sokaogon Chippewa and the Forest County Potawatomi Tribes
    Interest 100
    Year 2011
    First year 2003

Comments on the ownership information

  • Ownership passed from Exxon Coal and Minerals (the discoverer in 1975) to the Crandon Mining Company, which was a partnership between Exxon and Rio Algom Ltd. 9n 1994. January 1998 Rio Algom became sole owner and assigned ownership to Nicolet Minerals Company (a wholly owned subsidiary). In 2000 Billiton Acquired acquired Rio Algomand In 2001 Billiton merged with BHP.

Reserves and resources

  • Type In-situ
    Estimate year 1979
    Total resources 65,700,000
    Remarks From DeMatties (1994) Econ. Geol. Could not find later work on reserves/resources probably because of legal problems encountered by owners.
    Commodity Subtype Grade units Group Importance Year
    Zinc Zn 5.56 wt-pct Zinc Primary 1979
    Copper Cu 1.04 wt-pct Copper Primary 1979
    Silver Ag 48.9 g/mt Silver Tertiary 1979
    Gold Au 1.2 g/mt Gold Tertiary 1979
    Lead Pb 1.04 wt-pct Lead Secondary 1979

Comments on the reserve resource information

  • The resources occur in two zones, massive zone (Zn rich) and the stringer zone (predominantly Cu). The main zinc ore mineral in the deposit is sphalerite and composes the Crandon Formation itself. The main stringer ore mineral is chalcopyrite and is contained within footwall rocks underlying the Crandon Formation. The stringer ore occurs stratigraphically beneath the zinc mineralization. Estimated ore reserves and average metal content of the Crandon Ore Body Zinc Copper Lead Silver Gold Massive Ore 9.8% 0.4% 0.83% 1.20 oz/ton 0.043 oz/ton 30 Million mt ---------------------------------------------------------------------------------- Stringer Ore 0.96% 1.71% 0.05% 1.21 oz/ton 0.043 oz/ton 25 Million mt Source: Wisconsin Department of Natural Resources

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS W019008
U.S. Bureau of Mines Minerals Availability System MAS 0550410003

Bibliographic references

  • Age

    Schulz, K.J., Nicholson, S.W., and Van Schmus, W.R., 2008, Penokean massive sulfide deposits: age, geochemistry, and paleotectonic setting [abstract]: Institute on Lake Superior Geology, Proceedings volume 55, Part 1: Program and Abstracts, p. 76-77.

  • Deposit

    STAFF, 1977, NORTHERN MINER 1 - 6 - 77 P. 1, 6

  • Ownership

    Wisconsin Department of Natural Resources, 2009, Proposed Crandon Mine Information., Last updated 5/15/2009. Acquired 7/21/2010.

  • Deposit

    Dematties, T.A., 1994, Early Proterozoic Volcanogenic Massive Sulfide Deposits in Wisconsin: An Overview: Economic Geology, V.89

  • Reserve-Resource

    Wisconsin Department of Natural Resources, 2008, Geologic History of the Crandon Area,, last updated 10/17-2008, acquired 7/21/2010

  • Deposit


General comments

Subject category Comment text
Age The age of 1874+/- 4 my is inferred from the dating of several contemporaneous VMS deposits in the same magmatic province. (Schulz and others, 2008).

Reporter information

Type Date Name Affiliation Comment
Reporter 01-APR-77 Schruben, Paul G. U.S. Geological Survey
Updater 16-JAN-92 Beougher, Dee (Spanski, Gregory T.) U.S. Geological Survey
Updater 16-JUL-95 Nicholson, S.W. U.S. Geological Survey
Updater 01-MAR-97 Sutphin, David M. U.S. Geological Survey
Editor 01-MAY-97 Mason Jr., G.T. U.S. Geological Survey
Reporter 13-JUL-11 Lipin, Bruce U.S. Geological Survey