Birch Lake

Prospect in St. Louis county in Minnesota, United States with commodities Copper, Nickel, Cobalt, Platinum, Palladium, Rhodium, Silver, Gold, Titanium

Geologic information

Identification information

Deposit ID 10072944
MRDS ID W018675
Record type Site
Current site name Birch Lake

Geographic coordinates

Geographic coordinates: -91.81794, 47.75027 (WGS84)
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Geographic areas

Country State County
United States Minnesota St. Louis
United States Minnesota Lake

Public Land Survey System information

Meridian Township Range Section Fraction State
4th Principal 061N;061N 012W;011W 25,35,36;07,18,19 Minnesota

Comments on the location information

  • The deposit is between 1,600 and 2,800 feet below the surface in an area about one mile east of the inactive Dunka iron mine and six miles east of Babbitt, Minnesota. It lies along the county line between Lake and St. Louis Counties. Though limits of the deposit are not yet known, it may extend into parts of Sections 19, 30 and 31, T61N R11W and Sections 24, 25 and 36, T61N R12W. A part of the deposit appears to lie below Birch Lake, a 15- to 30-foot-deep reservoir which holds water for Minnesota Power's Kawishiwi Hydroelectric Station.

Commodities

Commodity Importance
Copper Primary
Nickel Primary
Cobalt Secondary
Platinum Primary
Palladium Primary
Rhodium Secondary
Silver Tertiary
Gold Tertiary
Titanium Secondary

Comments on the commodity information

  • A VARIETY OF PGE MINERALS HAVE BEEN IDENTIFIED AT BIRCH LAKE. PGE MINERALIZATION IS KNOWN TO OCCUR ONLY ALONG THE WESTERN CONTACT OF THE 1.1 GA DULUTH COMPLEX. PB, CU, AND AG ARE REPORTED TO OCCUR WITH THE PD. A RU-SULFIDE MINERAL HAS BEEN OBSERVED. SEE DAHLBERG AND GLADEN (1987) FOR OTHER ANALYTICAL DATA FOR PGE IN OXIDE ZONES

Materials information

Materials Type of material
Bornite Ore
Chalcopyrite Ore
Pentlandite Ore
Pyrite Ore
Pyrrhotite Ore
Apatite Gangue
Biotite Gangue
Mica Gangue
Olivine Gangue
Plagioclase Gangue
Pyroxene Gangue

Alteration

  • (Local) Ultramafic Rocks Have Been Serpentinized

Analytical data

Result 30 FT ZONE AVERAGES GREATER THAN 2 PPM PT+PD
Result ONE 5 FT INTERVAL OF ONE CORE IN THE LOWER SECTION AVERAGES 7.443 PPM PT+PD, PT:PD=1. IN SECOND DRILL HOLE PD>PT. LOWER OXIDE SECTION AVERAGES 1.7 PPM PT+PD
Result UPPER OXIDE SECTION AVERAGES 547 PPB PT+PD

Mineral occurrence model information

Model code 9
USGS model code 5a
Deposit model name Duluth Cu-Ni-PGE

Host and associated rocks

  • Host or associated Associated
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Argillite
    Rock unit name Virginia Formation
    Stratigraphic age (youngest) Paleoproterozoic
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Gabbro > Troctolite
    Rock unit name South Kawishiwi Intrusion
    Stratigraphic age (youngest) Mesoproterozoic
  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Granite
    Rock unit name Giants Ridge Batholith
    Stratigraphic age (youngest) Archean
  • Host or associated Associated
    Rock type Sedimentary Rock > Chemical Sediment > Iron Formation
    Rock unit name Biwabik Iron Formation
    Stratigraphic age (youngest) Paleoproterozoic

Nearby scientific data

(1) -91.81794, 47.75027

Geologic structures

Type Description Terms
Local Several Ne-Trending Normal Faults Parallel The Midcontinent Rift System Near The Margin. These Faults Formed During The Opening Of The Rift And Controlled Emplacement Of The Troctolitic And Late Intrusions.
Local Brecciation

Ore body information

  • General form TABULAR, DISSEMINATED
    Strike N20E
    Dip 25SE
    Thickness 120M
    Depth to top 2M
    Length 12000M

Controls for ore emplacement

  • Sulfides Segregated In Basal Troctolites Sub-Parallel To Lower Contacts. Faults And Folds Were Responsible For Localizing Sulfide Mineralization As Well As For Providing Conduits For Later Syn- To Post-Magmatic Hydrothermal Fluids.

Comments on the geologic information

  • THE DULUTH COMPLEX IS A LARGE, COMPOSITE THOLEIITIC MAFIC INTRUSION THAT WAS EMPLACED INTO COMAGMATIC FLOOD BASALTS ALONG A PORTION OF THE MIDDLE PROTEROZOIC (1.1 GA, KEWEENAWAN) MIDCONTINENT RIFT SYSTEM. IN THE SOUTH KAWISHIWI INTRUSION, SULFIDES FORM A DISCREET ZONE UNDERLYING SULFIDE-FREE ROCKS. MOST SULFIDES OCCUR INTERSTITIALLY BETWEEN EUHEDRAL OLIVINE OR PLAGIOCLASE OR ARE INCLUDED IN THE RIMS OF SILICATES. THE SULFIDES FORMED AFTER MOST SILICATES HAD ACCUMULATED. BIWABIK AND VIRGINIA FORMATIONS OVERLIE OLDER GRANITE. DULUTH GABBROS EMPLACED IN RIFT-RELATED VOIDS AND GRABENS. TROCTOLITIC LAST GABBROS FORM BASAL CONTACT. OXIDE CUMULATES PRESENT IN THIS DEPOSIT ARE THOUGHT TO BE ASSOCIATED WITH ASSIMILATED BLOCKS OF BIWABIK FORMATION.
  • SULFIDES ORIGINATED AS INTERCUMULATE IN LITHIFYING TROCTOLITE WHEN SULFUR WAS INTRODUCED INTO LIQUID FRACTION CREATING IMMISCIBLE SULFIDE AND SILICATE LIQUIDS. HIGHER DENSITY OF SULFIDE AND BASAL INTRODUCTION OF SULFUR CREATED BASAL LOCALIZATION. VARIATION IN SULFUR SOURCE, PATHWAYS, AND FAULTING CREATED LOCAL VARIATION AND HIGHER HORIZONS

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic
Deposit size Large
Significant Yes
Discovery year 1967
Discoverer Duval Corp.
Discovery method Ore-Mineral In Place

Mining district

District name Western Margin Duluth Complex

Ownership information

  • Type Operator
    Owner Duval Corp
    First year 1984
  • Type Owner
    Owner State Of Minnesota

Comments on the ownership information

  • In the late 1960s and early 1970s, the Duval Corporation drilled approximately seven holes near the Birch Lake Reservoir while searching for copper-nickel mineralization. The samples showed lean Cu-Ni values of no economic interest and Duval abandoned their search. The Minnesota Department of Natural Resources (MDNR) reanalyzed some of Duval's cores in 1985. This work identified a seven-foot thick section with commercially significant amounts of Pt and Pd, as well as Cu and Ni. Lehmann Exploration Management (LEM), Minneapolis, is managing the exploration program for the Beaver Bay Joint Venture (BBJV), a Minnesota enterprise comprised of three privately owned upper Midwest corporations: North Central Mineral Ventures (NCMV) and Powell Production Company, both headquartered in Minnesota, and Connor Management Inc., based in Wisconsin

Reserves and resources

  • Type In-situ
    Estimate year 2005
    Total resources 4,400,000,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Copper 0.66 wt-pct Copper Major 2005
    Nickel 0.2 wt-pct Nickel Major 2005

Comments on the reserve resource information

  • ALONG THE WESTERN MARGIN OF THE DULUTH COMPLEX, THE CU-NI SULFIDE RESOURCES ARE ESTIMATED AT 4.4 BILLION TONS OF 0.66 PERCENT CU WITH A CU:NI RATIO OF 3.3:1 (HAUCK AND OTHERS, 1997).

Workings at the site

  • Type of workings Surface
    Area 1920HA
    Overall length 10972.8M
    Overall width 1600M

Comments on development

  • Based on recent (2001) drilling, the following scenario has been proposed: the orebody would be reached by a main vertical shaft located same distance south of Birch Lake reservoir. The relatively thin bed of mineralized rock, more than 1,600 to 2500 feet below the surface, would probably be mined by a highly mechanized method known as room and pillar mining. The ore could be drilled, blasted and crushed underground, then hoisted to a processing plant on the surface. There it would be ground to a fine sand and "froth flotation," would be used to separate the mineralized grains from the barren "tailings." the product would be a sulfide concentrate, with an upgraded PGM content.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS W018675

Bibliographic references

  • Commodity

    BONNICHSEN, BILL, 1974, COPPER AND NICKEL RESOURCES IN THE DULUTH COMPLEX, NORTHEASTERN MINNESOTA: MINNESOTA GEOLOGICAL SURVEY INFORMATION CIRCULAR 10, 24 P

  • Geology

    MORTON, PENELOPE, AND HAUCK, S.A., 1987, PGE, AU AND AG CONTENTS OF CU-NI SULFIDES FOUND AT THE BASE OF THE DULUTH COMPLEX, NORTHEASTERN MINNESOTA: NATURAL RESOURCES RESEARCH INSTITUTE TECHNICAL REPORT NRRI/GMIN-TR-87-04, 81 P.

  • Geology

    DAHLBERG, E.H., 1989, LITHOCHEMISTRY OF THE PLATINIFEROUS OXIDE-ULTRAMAFIC ASSOCIATION OF THE BASAL ZONE DULUTH COMPLEX, BIRCH LAKE-DUVAL AREA, IN MOREY, G.B., ED., WORKSHOP ON THE APPLICABILITY OF GOLD AND PLATINUM-GROUP-ELEMENT MODELS IN MINNESOTA: MINNESOTA GEOLOGICAL SURVEY INFORMATION CIRCULAR 30, P. 49-50.

  • Geology

    DAHLBERG, E.H., AND GLADEN, 1987, COMPARISON OF OXIDE CUMULATES IN THE BIRCH LAKE AREA OF THE DULUTH COMPLEX WITH PGE DEPOSITS [ABS.]: GEOLOGICAL SOCIETY OF AMERICA ABSTRACTS WITH PROGRAMS, V. 19, NO. 4, P. 195.

  • Deposit

    PAGE, N. J, 1986, DESCRIPTIVE MODEL OF DULUTH CU-NI-PGE, IN COX, D.P. AND SINGER, D.A., MINERAL DEPOSIT MODELS: U.S. GEOLOGICAL SURVEY BULLETIN 1693, P. 16.

  • Geology

    HAUCK, S.A., SEVERSON, M.J., ZANKO, L., BARNES, S-J., MORTON, P., ALMINAS, H., FOORD, E.E., AND DAHLBERG, E.H., 1997, AN OVERVIEW OF THE GEOLOGY AND OXIDE, SULFIDE AND PLATINUM-GROUP ELEMENT MINERALIZATION ALONG THE WESTERN AND NORTHERN CONTACTS OF THE DULUTH COMPLEX: GEOLOGICAL SOCIETY OF AMERICA SPECIAL PAPER, V. 312, PP. 137-185.

  • Geology

    FOOSE, M.P., 1985, THE SETTING AND DISTRIBUTION OF COPPER-NICKEL SULFIDES IN THE SOUTH KAWISHIWI INTRUSION, DULUTH COMPLEX, MINNESTOA, IN KRAFT, KATHLEEN, ED., U.S. GEOLOGICAL SURVEY RESEARCH ON MINERAL RESOURCES--1985, PROGRAM AND ABSTRACTS: U.S. GEOLOGICAL SURVEY CIRCULAR 949, P. 12-13.

  • Geology

    HAUCK, S.A., SEVERSON, M.J., ALAPIETI, T., KAUKONEN, R., RIPLEY, E., AND GOLDBERG, S., 1995, ORIGIN OF PGE-CR MINERALIZATION, BIRCH LAKE, SOUTH KAWISHIWI INTRUSION, DULUTH COMPLEX, MINNESOTA, GEOCHEMICAL AND ISOTOPIC DATA, IN PETROLOGY AND METALLOGENY OF VOLCANIC AND INTRUSIVE ROCKS OF THE MIDCONTINENT RIFT SYSTEM, INTERNATIONAL FIELD CONFERENCE AND SYMPOSIUM, PROCEEDINGS: INTERNATIONAL GEOLOGICAL CORRELATION PROGRAM, UNIVERSITY OF MINNESOTA DULUTH, CONTINUING EDUCATION AND EXTENSION, P. 63-64.

General comments

Subject category Comment text
Deposit 30 FT ZONE AVERAGES GREATER THAN 2 PPM PT+PD; ONE 5 FT INTERVAL OF ONE CORE IN THE LOWER SECTION AVERAGES 7.443 PPM PT+PD, PT:PD=1. IN SECOND DRILL HOLE PD>PT. LOWER OXIDE SECTION AVERAGES 1.7 PPM PT+PD; UPPER OXIDE SECTION AVERAGES 547 PPB PT+PD (DAHLBERG, 1989).
Deposit FAULTS AND FOLDS WERE RESPONSIBLE FOR LOCALIZING SULFIDE MINERALIZATION AS WELL AS FOR PROVIDING CONDUITS FOR LATER SYN- TO POST-MAGMATIC HYDROTHERMAL FLUIDS. SULFIDES SEGREGATED IN BASAL TROCTOLITES SUB-PARALLEL TO LOWER CONTACTS. SEVERAL NE-TRENDING NORMAL FAULTS PARALLEL THE MIDCONTINENT RIFT SYSTAM NEAR THE MARGIN. THESE FAULTS FORMED DURING THE OPENING OF THE RIFT AND CONTROLLED EMPLACEMENT OF THE TROCTOLITIC AND LATE INTRUSIONS.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JAN-1984 no name U.S. Geological Survey
Updater 01-JAN-1991 Peterson, J.A. U.S. Geological Survey
Reporter 01-JAN-1996 Sutphin, D.M. (Cannon, W.F.) U.S. Geological Survey
Updater 01-MAR-1997 Sutphin, D.M. U.S. Geological Survey
Editor 01-MAY-1997 Mason Jr., G.T. U.S. Geological Survey
Editor 01-DEC-2003 Woodruff, Laurel G. U.S. Geological Survey Work done in Filemaker
Editor 25-FEB-2005 Woodruff, L.G. U.S. Geological Survey