Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI52F09NW00016

Record: MDI52F09NW00016

General

Commodities

Primary Commodities: Gold, Silver

Secondary Commodities: Copper

Location

Township or Area: Southworth

Latitude: 49° 40' 8.82"    Longitude: -92° 28' 12.78"

UTM Zone: 15    Easting: 538227.905   Northing: 5501977.338    UTM Datum: NAD83

Resident Geologist District: Kenora

NTS Grid: 52F09NW

Point Location Description: Mineral occurrence at surface symbol (Map, GDIF322)

Location Method: Field Visit

Access Description: The Niemi Occurrence is located in Concession III, lot 6, of Southworth Township and is approximately 3 km southeast of Dinorwic. The occurrence and main trench are situated in a swampy ditch on the north side of a concession road, about 1.2 km east of its intersection with Highway 17, approximately 2.3 km south of Dinorwic.

Exploration History

1956: Surface trenching, stripping, sampling, diamond drilling, and electromagnetic and self-potential geophysical surveys were conducted on the Niemi Property by Rio Canadian Explorations Limited.

Geology

Province: Superior

Subprovince: Wabigoon

Terrane: Western Wabigoon

Belt: Eagle-Wabigoon-Manitou

Geological Age: Precambrian  

Lithology

Lithology Comments

Aug 03, 2022 (Q Unknown) - The area around the occurrence is underlain by mafic metavolcanic flows intruded by gabbro stocks and a massive diabase dike. The metavolcanics are commonly sheared, chloritic, and intensely carbonatized.

Mineralization

Mineralization Comments

Aug 03, 2022 (Q Unknown) - The Niemi Occurrence consists of a 15 m wide shear zone striking 040°/50° SE for at least 75 m, in coarse-grained, intensely altered mafic rocks, with massive fine-grained mafic metavolcanic flows to the west. The strike of shearing changes abruptly to 070° - 078°/65° S about 30 m north of the main trench. The shear zone is crosscut by irregular wide stockworks of quartz-iron carbonate veins, hosting tourmaline, massive tetrahedrite, chalcopyrite, azurite, malachite and pyrite, with associated gold and silver mineralization. The country rock is intensely sheared, sericitic, chloritic, bleached, and variably altered by iron carbonate. Small (2 mm-4 mm) dark green clots of chlorite occur throughout the rock, as well as variable amounts of disseminated pyrite and acicular crystals of arsenopyrite. A dark green, chloritic, gabbro outcrop, with moderate calcium carbonate alteration occurs immediately north of the occurrence. The gabbro is similar to, but less altered than, the sheared, altered rock at the trench, and contains the same chlorite clots described above, suggesting that the rock at the trench is highly altered gabbro or a coarse-grained mafic flow. North of the occurrence, the sheared country rock is intensely brecciated with angular fragments embedded in mineralized quartz. The fragments are bleached and carbonatized with dark chlorite rims and apple-green cores, possibly due to the presence of fuchsite. They also contain dark green chlorite clots, coarse needles of arsenopyrite, and finely disseminated pyrite. Medium-grained, dark green, chloritic, pyritic, and carbonatized mafic metavolcanics occur immediately west of the Niemi Occurrence. The author has interpreted an approximate north-south contact between the metavolcanics and the gabbro. The main trench is approximately 15 m x 10 m and is located in a ditch north of the concession road. Three smaller, shallow trenches are situated towards the north end of the occurrence. All the trenches are full of water and mud. The main occurrence is fairly well stripped, however, exposure elsewhere is poor. Grab samples of the mineralized quartz taken from the main trench, by the author, assayed from 0.05 ounce gold per ton to 0.58 ounce silver per ton and were anomalous in arsenic, copper, and antimony with values as high as 1.55% arsenic, 1.13% copper and 1640 ppm antimony. Grab samples taken by Rio Canadian Explorations Limited assayed up to 0.45 ounce gold per ton and 2.8 ounces silver per ton, while a chip sample assayed 0.10 ounce gold per ton. (OFR5723, p.258,259)

Mineral Record Details

References

Mono - Gold deposits of Ontario, part 1, districts of Algoma, Cochrane, Kenora, Rainy River, and Thunder Bay

Publication Number: MDC013 Page: 239  Date: 1971

Author: Ferguson S.A., Groen H.A., Haynes R.

Publisher Name: Ontario Dept. of Mines and Northern Affairs

Location:

Mono - Gold deposits of the Kenora-Fort Frances area, districts of Kenora and Rainy River

Publication Number: MDC016 Page: 30  Date: 1976

Author: Beard R.C., Garratt G.L.

Publisher Name: Ontario Division of Mines

Location:

Compend - Report of activities, 1984, Regional and Resident Geologists

Publication Number: MP122 Page: 25-26  Date: 1985

Author: Kustra C.R.

Publisher Name: Ontario Geological Survey

Location:

Mono - Geology, gold mineralization and property visits in the area investigated by the Dryden-Ignace economic geologist, 1984-1987

Publication Number: OFR5723 Page: 258-259  Date: 1989

Author: Parker J.R.

Publisher Name: Ontario Geological Survey

Location:

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Ministry Contact Information

For detailed information regarding this mineral record please contact the Kenora Resident Geologist District Office