Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI52P12SW00005

Record: MDI52P12SW00005

General

Commodities

Primary Commodities: Gold

Location

Township or Area: Firstloon Lake Area

Latitude: 51° 34' 53.33"    Longitude: -89° 51' 57.12"

UTM Zone: 16    Easting: 301446   Northing: 5718383    UTM Datum: NAD83

Resident Geologist District: Thunder Bay North

NTS Grid: 52P12SW

Point Location Description: DDH Database.

Location Method: Conversion from MDI

Exploration History

Early 1970s: Airborne EM surveys and diamond drilling by Umex and Conwest Exploration. 1986-88: Ground geophysical surveys, geological mapping and diamond drilling by Umex. 1990-91: Diamond drilling by Major General Resources.

Assessment Work on File

Geology

Province: Superior

Subprovince: Uchi

Terrane: North Caribou

Domain: Uchi

Belt: Pickle Lake

Geological Age: Archean  

Geology Comments

Nov 14, 2006 (Mark Puumala) - The First Loon lake gold prospect is located at the northeast end of the Pickle Lake Greenstone Belt, within rocks identified by Young (2003) as being part of the >2860 Ma Pickle Crow Assemblage. The occurrences lie immediately northwest of an inferred angular unconformity that separates the Pickle Crow Assemblage rocks from the younger (<2744 Ma) Confederation Assemblage. Dyer (1991) indicates that the First Loon Lake area is underlain by several bands of chert-magnetite-sulphide iron formation interbedded with mafic and ultramafic metavolcanic rocks. The supracrustal rock sequence has been intruded by quartz-feldspar porphyry dikes, lamprophyre dikes and tonalite of the Croshaw Lake pluton. Drilling carried out by Umex and Major General Resources at this location targeted folded, sulphidized iron formation and axial planar deformation zones. Dyer (1991) indicates that the most favourable gold values correlate with higher sulphide concentrations, generally within 150 m of fold closures. Supracrustal rocks in the vicinity of First Loon Lake have been deformed by a large westerly-plunging s-fold. Two limbs of this fold were encountered in diamond drill hole FL-88-12 (Mullen 1988). A 55 m wide deformation zone characterized by extensive quartz veining was also encountered in drill hole FL-88-12. This deformation zone is parallel to the axial plane of the fold. Map P3057 (Stott et al. 1989) indicates that foliations in this area strike approximately east-west, and dip steeply to the south (approximately 80 degrees). Mineral lineations plunge moderately toward the southwest. Dyer (1991) indicates that a major structural discontinuity separates the s-folded sequence from a less deformed sequence to the southeast. This discontinuity may represent the boundary between rocks of the Pickle Crow (>2860 Ma) and Confederation (<2744 Ma) Assemblages. Rocks of the Pickle Crow Assemblage typically young toward the northwest. However, stratigraphic indicators reported by Young (2003) suggest that the metavolcanic rocks locally face toward the southeast in the vicinity of First Loon Lake, as would be expected from the geometry of the s-fold that has been mapped in this area. The south-facing rocks of the Confederation Assemblage that occur to the south of these occurrences are interpreted to overlie the Pickle Crow Assemblage above an angular unconformity.

Lithology

Mineralization

Mineralization Comments

Nov 14, 2006 (Mark Puumala) - Mineralized diamond drill holes at this prospect (FL-88-8, FL-88-11, FL-88-12 and FLL-91-15) encountered a number of lithologies, including altered komatiite, massive mafic metavolcanics, quartz porphyry and iron formation (Mullen 1988 and Dyer 1991). Gold mineralization generally occurs within sulphidic iron formation. The mineralized iron formation at FL-88-8 is reported by Mullen (1988) to consist of pyrrhotite (up to 50% over 1 m) with minor pyrite, magnetite and grunerite. Assay values reported from sulphidized iron formation intersections include 0.066 oz/ton Au over 6.4 m in FL-88-8, 0.053 oz/ton over 1.05 m in FLL-91-15, 0.02 oz/ton over 1.5 m in FL-88-11, and 0.03 oz/ton over 1.1 m from FL-88-12. A 55 m wide zone of extensive quartz veining that parallels the fold axial plane is reported by Mullen (1988) in drill hole FL-88-12. The veins were up to 60 cm wide and are mineralized with albite, chlorite, tourmaline, calcite, hematite, pyrrhotite and chalcopyrite. The best gold assay obtained from this zone was 0.02 oz/ton over 1.5 m.

Mineral Record Details

References

Map - Geological series, Precambrian geology, Pickle Lake area, eastern part

Publication Number: P3057 Scale: 1:50,000    Date: 1989

Author: Stott G.M., Brown G.H., Coleman V.J., Green G.M., Reilly B.A.

Publisher Name: Ontario Geological Survey

Location:

Mono - The Geology and Tectonic History of the Central Uchi Subprovince

Publication Number: OFR5952 Date: 1996

Author: Stott G.M.

Publisher Name: Ontario Geological Survey

Location:

Book - New Structural, Geochronological, and Geochemical Constraints on the Tectonic Assembly of the Archean Pickle Lake Greenstone Belt, Uchi Subprovince, Western Superior Province

Publication Number: MSc thesis Date: 2003

Author: Young, M.D.

Publisher Name: unpublished thesis, Queen's University, Kingston

Location: Thunder Bay RGP

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