Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001132

Record: MDI000000001132

General

Commodities

Primary Commodities: Uranium

Location

Township or Area: Mikinak Lake Area

Latitude: 49° 20' 24.71"    Longitude: -88° 48' 1.37"

UTM Zone: 16    Easting: 369218   Northing: 5466834    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52H07SW

Point Location Description: Field visit confirmed with Google Earth

Location Method: Field Visit

Access Description: The property is situated NE of Black Sturgeon Lake, 8.5 km along a gravel road that heads north from the old Split Rapids dam site at the outlet of Black Sturgeon Lake.

Exploration History

1981: Occurrence was discovered by R. H. Sutcliffe while doing fieldwork for the Ontario Geological Survey. 1982: property was acquired by Uranerz Exploration and Mining Corp. Ltd., who conducted trenching, stripping, geological mapping, magnetometer and radiometric surveys. 2000: East West Resources optioned the property from K. Fenwick and conducted linecutting and a ground IP geophysical survey. 2004: New Shoshoni Ventures ltd. acquired the property, then entered into an agreement with Rampart Ventures Ltd. 2004-5: Rampart conducted airborne electromagnetic and magnetic surveys. 2005: Rampart drilled 8 DDH totalling 320.22 m. 2007: Rampart drilled 76 DDH totalling 12,011.38 m.

Assessment Work on File

Geology

Province: Superior

Subprovince: Quetico

Geological Age: Archean  

Lithology

Lithology Comments

Apr 21, 2016 (Therese Pettigrew) - The stripping exposed a conformable sequence of metagreywacke, meta-iron formation and amphibolite that has been intruded by pink, coarse grained, myrmekitic, radioactive pegmatite dikes. The sequence strikes 065 degrees and dips 65 degrees S. A small dioritic plug occurs in the central portion of the exposure. The sequence is faulted and fractured; radioactive shears form conjugate sets that cross-cut the exposure. Within the shears, the highest radioactivity, as determined with a McPhar gamma ray TV-l-spectrometer, is restricted to areas where the fracture systems cross the iron formation. True widths of the metagreywacke and amphibolite could not be determined; the iron formation has an exposed width of 8 m and a true width of approximately 7.3 m. The iron formation is characterized by recrystallized magnetite, amphibole, large reddish-brown garnets and traces of pyrite. The garnets occur as individual crystals up to 4 cm across as well as aggregates of smaller crystals. The rock unit is laminated, black to dark green in color and makes a good marker horizon. The metagreywacke is fine grained, massive, and buff to cream in color. The unit contains wispy inclusions or segregations of mafic minerals. The wacke might be partly volcanic in origin. The amphibolite is dark green, coarse grained, and massive. Amphibole crystals range up to 2 to 3 cm in length and constitute approximately 75% of the rock unit. The remaining 25% is made up of feldspar and quartz. The pegmatites are very coarse grained, and pink in color. The feldspars exhibit striking myrmekitic and graphic textures. The northeastern exposure is radioactive and is crisscrossed by small (less than 2 mm) veinlets of hematite. Veinlets strike 240 degrees and trend beyond the pegmatite-greywacke contacts. Y. Gariepy (Geologist, Uranerz Exploration and Mining Company Limited, personal communication, 1982) suggests that the pegmatites are the source of the uranium. The age of the uranium mineralization in the fracture systems was determined to be 1090 ± 25 Ma (V. Ruzicka, Geologist, Geological Survey of Canada, personal communication, 1983). The fracture systems form a conjugate set and are subparallel to the Black Sturgeon Fault System, which is Late Precambrian in age. The presence of uranopilite (identification by the Geoscience Laboratories, Ontario Geological Survey, Toronto, Ontario) and its usual association with gypsum imply that the mineralization might be associated with the Sibley Group, which does contain gypsum. On the other hand, the iron formation has a small sulfide component and the sulfur necessary for the formation of the uranopilite might originate from the iron formation (Scott, 1987).

Mineralization

Mineralization Comments

Mar 18, 2011 (J Scott) - Veins with pitchblende cross cutting iron formation. Up to 12% U

Apr 21, 2016 (Therese Pettigrew) - Fracture zones with very high radioactivity occur on the property. Pitchblende, pyrite, malachite, chalcopyrite and uranopilite occur in the veins. Silver was present in one sample. Brannerite occurs in pegmatites adjacent to the showings. The highest radioactivity is confined to fault and fracture zones, the widest of which is 40 cm across. In most cases the radioactivity, as detected by the McPhar TV-1 gamma ray spectrometer, was of f -scale or nearly of f -scale at most localities. The fracture zones consist of felted masses of hematite, magnetite, a greenish colored rock flour, calcite, pitchblende and uranopilite. Trenching by Uranerz Exploration and Mining Limited has revealed that the veins persist to at least a depth of 2 m, and, although still of high grade, remain narrow (Scott, 1987). The mineralization consists of a breccia-like vein occupying a fracture or micro-fault, filled with hematite, pitch blende and silicate minerals, and the wallrocks are magnetite-chert iron formation with several percent of sulphide minerals. On the assumption that it is unconformity-related, it may represent the root zones of a mineralized zone at or near the unconformity, which has been eroded away and lay an unknown distance above the present land surface. Alternatively, it may be "sub-unconformity" type uranium mineralization such as is found in the Rabbit Lake-Collins Bay-Eagle Point mining camp in Saskatchewan, or in the Kombolgie basin of northern Australia. Every hoIe in the 2005 drill program cut one or more uranium-bearing fractures or breccia veins, always in magnetite iron formation. The best results were 0.563% U3O8 across 0.3 metres in hole 9, 1.99% U3O8 across 0.3 metres in hole 12 and 0.120% U3O8 across 3.52 metres in hole 16, the last being an average across several individual uraniferous seams (AFRO 2.31947).

Mineral Record Details

References

Mono - Uranium occurrences of the Thunder Bay-Nipigon-Marathon area

Publication Number: OFR5634 Scale:     Date: 1987

Author: Scott J.F.

Publisher Name: Ontario Geological Survey

Location:

Article - 1981 report of the Thunder Bay Resident Geologist

Publication Number: MP101.004 Scale:     Date: 1997

Author: McIlwaine W.H., Fenwick K.G., Scott J.F., Mason J.K., Schnieders B.R., Kristjansson F.J., Speed A.A., Bourdages H.M.

Publisher Name: Ontario Geological Survey

Location:

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