Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001670

Record: MDI000000001670

General

Commodities

Primary Commodities: Iron

Location

Township or Area: Icarus Lake Area

Latitude: 48° 6' 41.62"    Longitude: -90° 44' 31.13"

UTM Zone: 15    Easting: 668070   Northing: 5331166    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52B02SE

Point Location Description: Sample location

Location Method: Field Visit with GPS

Access Description: The Gunflint Lake iron property is located 110 km southwest of Thunder Bay. Access is obtained by travelling 75 km along Highway 588 and Trout Bay Road (Trout Bay Road begins at the end of pavement) from the junction of Highway 593 to Gunflint Road and travelling south 12.5 km to the property along Gunflint Road.

Exploration History

Early 1900s: Patents granted for claims believed to have been staked in anticipation of mining opportunities opening up following completion of the Port Arthur, Duluth and Western Railroad. The railroad passed through the property, but it ultimately failed and was abandoned. 2012: Prospecting, sampling and assays by K. Buchanan.

Geology

Province: Southern

Geological Age: Paleoproterozoic  

Geology Comments

Mar 14, 2014 (Mark Puumala) - The following is an excerpt from OFR 6285. Outcrops on the Gunflint Lake Iron Property expose rocks that represent an essentially complete cross-section through the Gunflint Formation, from the basal unconformity with the underlying Archean Saganaga tonalite basement to the Sudbury impact layer that is found at the top of the formation. The basal unconformity strikes approximately east in the central portion of the property. The Gunflint Formation strata are nearly flat-lying, dipping at a shallow angle (10° or less) toward the south-southeast. Rocks interpreted to be parts of the Lower Cherty, Upper Cherty and Upper Slaty members (Wolff 1917; Broderick 1920), as well as the Sudbury impact layer (Addison et al. 2005) were observed in the field. The rocks immediately above the unconformity comprise nearly massive magnetite units, but grade upward into a sequence of interbedded magnetite and chert. Approximately midway between the unconformity and Gunflint Lake (a distance of approximately 550 m), magnetite-bearing grainstones (taconite), interpreted to be representative of the Upper Cherty member, are overlain by much finer-grained rocks of the Upper Slaty member. These rocks are in turn overlain by rocks of the Sudbury impact layer on the southern portion of the property, closer to the shoreline of Gunflint Lake (approximately 900 m south of the unconformity). Mesoproterozoic Logan diabase sills form prominent topographic highs in the southern portion of the property where they intrude Gunflint Formation rocks. They may be correlative with the Logan diabase sill identified by Jirsa and Fralick (2010) at the top of the Gunflint section immediately to the west of the property in Minnesota.

Lithology

Mineralization

Assay Samples

Mineral Record Details

Site Visit Information

Date: Sep 25, 2012

Geologist: Mark Puumala

Notes: The iron formation sample was collected from an outcrop located immediately south of the Saganaga tonalite. The outcrop exposes Gunflint iron formation consisting of approximately decimetre-scale layers of alternating massive magnetite and cherty grainstone. In places, the cherty grainstone layers are brecciated, with some fractures in-filled with magnetite. Bedding plane surfaces are uneven, ranging from flat-lying to having dips of up to 30°. This is likely attributable to the uneven unconformity surface that is present in this area.

References

Publication - Gunflint Iron - Bearing Formation, Ontario; Geological Survey of Canada, Summary Report (1924), Part C

Publication Number: Sum Rep 1924 C Date: 1925

Author: Gill, J.E.

Publisher Name: Geological Survey of Canada

Location: https://doi.org/10.4095/103167

Journal - Recent geologic developments on the Mesabi Iron Range, Minnesota.

Publication Number: v. 56 Date: 1917

Author: Wolff, J.F.

Publisher Name: IMME

Location: Thunder Bay RGP office

Mono - Report of Activities 2012, Resident Geologist Program, Thunder Bay South Regional Resident Geologist Report: Thunder Bay South District

Publication Number: OFR6285 Date: 2013

Author: Puumala M.A., Campbell D.A., Cundari R.M., Zurevinski S.E., Tuomi R.D., Lockwood H.C., Debicki R.L., Moses P., Brunelle M.R., Pelaia R.

Publisher Name: Ontario Geological Survey

Location:

Book - Geology of the Gunflint iron formation and the Sudbury impact layer, northeastern Minnesota; in Field Guide to the Geology of Precambrian Iron Formations in the Western Lake Superior Region, Minnesota and Wisconsin

Publication Number: 10-01 Date: 2010

Author: Jirsa, M. and Fralick, P.

Publisher Name: PRC

Location: Thunder Bay RGP office

Journal - Economic geology and stratigraphy in the Gunflint iron district, Minnesota

Publication Number: v. 15 Date: 1920

Author: Broderick, T.M.

Publisher Name: Econ. Geology

Location: Thunder Bay RGP office

Thesis - Stratigraphy of the Gunflint iron-bearing formation of Ontario.

Publication Number: Date: 1953

Author: Goodwin, A.M.

Publisher Name:

Location: Thunder Bay RGP office

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For detailed information regarding this mineral record please contact the Thunder Bay South Resident Geologist District Office