Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI52A10SW00003

Record: MDI52A10SW00003

General

Commodities

Primary Commodities: Silver

Secondary Commodities: Nickel, Cobalt, Lead, Fluorite, Barite, Zinc, Gold

Location

Township or Area: Macgregor

Latitude: 48° 31' 22.31"    Longitude: -88° 59' 8.53"

UTM Zone: 16    Easting: 353382   Northing: 5376321    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52A10SW, 52A11SE

Point Location Description: AMIS No. 2 Shaft location

Location Method: Conversion from MDI

Access Description: The 3A mine site may be reached via Lakeshore Drive. A gravel road, described in 1978 as “poor”, opposite the Silver Harbour Drive, proceeds north from Lakeshore Drive. The 3A mine is located 0.5 km north of Lakeshore Drive along this road.

Exploration History

1870: Vein discovered by A. Cyrette and another miner. Winter 1871-2: test pit sunk to 5.5 m. Winter 1872-73: 3A Company became incorporated. Two shafts were developed: No. 1 (west) shaft to depth of 23.5 m and No. 2 (main) shaft to 30 m. 1873-74: development continued on all 3 shafts. No. 2 (main) shaft sunk to 45.7 m, with drifting at the 8 m level. Further development had been discontinued by the summer of 1874, for which there was reported 91.5 m of levels and 30.5 m of cross-cutting. 1888: Some surface blasting of vein by A. Andrews. 1911: 61 m of drifting and cross-cutting was reported on the first level by Stewart and Skene. 1922: new exploratory shaft, near No. 1 shaft, sunk to depth of 13.5 m by Nipigon Prospecting Company. No assessment reports were found on file.

Geology

Province: Southern

Formation Group: Animikie Group

Geological Age: Paleoproterozoic  

Lithology

Lithology Comments

Apr 24, 2018 (Therese Pettigrew) - The general geology at lot 3A of MacGregor Township consists of an Archean assemblage of volcanic and plutonic rocks that unconformably underlie southern Proterozoic rocks of the Animikie Group. The Archean rocks consist mainly of massive to pillowed mafic flows with some intercalated volcanoclastic material. To the north, and increasingly to the west, a coarse-grained reddish, porphyritic granite is present. South of the lot, and along the shore of Lake Superior, Animikie rocks of the Lower Gunflint formation are encountered. Chert, carbonate, and shale beds are present, along with a thin Keweenawan sill. The host rock at the 3A mine site is a Keweenawan pillowed andesite. The flow unit is dark green, fine-grained and well foliated. Cleavage strikes 75 degrees azimuth and dips vertically. A fault zone, up to 0.6 m wide, is hosted by the andesite flow. Within this zone of weakness, the composite vein system, striking 60 to 83 degrees and dipping vertically to 60 degrees north, is found (Tanton, 1931).

Mineralization

Mineralization Comments

Apr 24, 2018 (Therese Pettigrew) - Mineralization is confined to a composite vein system within a NE-trending and steeply dipping fault zone hosted by foliated andesitic flows. The vein, up to 0.6 m wide, has been traced along the entire width of Lot 3A and has also been found in Lots 1A, 2A, and 4A of MacGregor Township. The andesite in contact with the vein has been altered, producing a thin enveloping zone of talcose and serpentine schist. Gangue mineralogy of the vein consists of milky white, fine-grained quartz, calcite, amethyst, and barite. Mineralization within the vein is localized and erratic. Localized aggregations of sphalerite, galena, pyrite, marcasite, and chalcopyrite occur along with native silver and argentite/acanthite. Assays have also indicated the presence of nickel, cobalt and gold. The silver was found both native and as argentite, and was associated with minerals containing cobalt, and this argentiferous material was concentrated in parts of the vein in large and small patches (Tanton, 1931). Silver values decrease with depth (Sergiades, 1968). Niccolite is also reported to occur within the vein. J.M. Floyd reported assays of $17.80 Au and $301.45 Ag. A sample assayed 1465.7 opt Ag, 0.014% Co, and 25% Ni (McKellar, 1874). With the occurrence of the mineralization in a faulted metavolcanic, and the presence of Co and Ni minerals, the 3A deposit is more like an Island-type silver deposit, rather than a Mainland-type deposit.

Mineral Record Details

References

Mono - Silver cobalt calcite vein deposits of Ontario

Publication Number: MDC010 Page: 66  Date: 1968

Author: Sergiades A.O.

Publisher Name: Ontario Dept. of Mines

Location:

Publication - Fort William and Port Arthur, and Thunder Cape Map-area, Thunder Bay District, Ontario; Geological Survey of Canada, Memoir 167

Publication Number: GSC Memoir 167 Page: 158  Date: 1931

Author: Tanton, T.L.

Publisher Name: Geological Survey of Canada

Location: https://doi.org/10.4095/100799

Publication - Mining on the North Shore, Lake Superior, p. 16-19

Publication Number: Pamphlet Date: 1874

Author: McKellar, P.

Publisher Name: Toronto

Location: RGP Files, Thunder Bay Office

Report an Error

We are continuously updating our assessment file / technical report information. If you notice errors in the data, please contact us.

Terms of Use

Please review our Terms of Use agreement for this data product.

Ministry Contact Information

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