Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI52A04SE00019

Record: MDI52A04SE00019

General

Commodities

Primary Commodities: Copper, Nickel

Secondary Commodities: Palladium

Location

Township or Area: Crooks

Latitude: 48° 2' 45.47"    Longitude: -89° 32' 39.57"

UTM Zone: 16    Easting: 310380   Northing: 5324541    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52A04SE

Point Location Description: Map in AFRI 52A03SW2005

Location Method: Conversion from MDI

Exploration History

1957: SP geophysical survey and trenching was conducted by T.W. Page. 1965: Ker Addison Mines Ltd. conducted an EM survey and drilled 4 DDH totalling 226.8 m. 1969: I.C Christopher drilled 1 DDH totalling 30.8 m. 1995: R.L.Viitala conducted line-cutting, VLF and magnetometer geophysical surveys, prospecting and sampling. 2001: McVicar Minerals Ltd. conducted prospecting and sampling.

Assessment Work on File

Geology

Province: Southern

Formation Group: Animikie Group

Geological Age: Paleoproterozoic  

Geology Comments

Feb 28, 2018 (Therese Pettigrew) - The Mesoproterozoic geology of the Lake Superior region was formed during the development of the Midcontinent Rift (MCR), also known as the Keweenawan Rift, starting about 1110 Ma. The rift originated when a mantle plume arrived at the base of the lithosphere under the central part of what is now the North American continent. The rifting process involved the thinning, extension and subsidence of the overlying crust, accompanied by the production and eruption of a remarkable volume mafic magma. Geophysical modeling of aeromagnetic, gravity and seismic data show the rift to be composed of a deep (-30 km) asymmetric basin, infilled with a lower sequence of volcanic rocks, locally as much as 20 km thick and occupying a volume of over 2 million km2 , and a upper sequence of fluvial sedimentary rocks. The rifting and associated magmatic activity occurred over a relatively short period of approximately 22 million years from 1108-1186 Ma. Typical stratigraphy along the MCR consists of eroded Archean basement rocks, unconformably overlain by Paleoproterozoic sediments of the Animikie Group, ca. 1.8 Ma. It is believed that these rocks were deposited in an elongate depression that bordered an island arc or an orogenic belt. On the northern flank, they drape unconformable on the Archean "basement" rocks and thicken to the south, reaching several kilometres of thickness. The lower part of the Animikie Group is this area is referred as the Gunflint Formation. The Midcontinent Rift (MCR) consists of three major components: 1) a thick edifice of subaerial flood basalt lava flows; 2) local concentrations of intrusive rocks; and 3) an upper sequence of sedimentary rocks. The MCR volcanic sequence is composed predominately of flood basalts, with lesser intermediate to felsic rocks (andesitic and rhyolitic flows). The earliest lava flows erupted under seawater, but soon accumulated to a thickness that allowed them to erupt on dry land or subaerially. MCR intrusions are well-represented on the north shore of Lake Superior, where they are host to a number of nickel-copper, PGE, and Fe-Ti-oxide occurrences (AFRI 52A03SW2008).

Lithology

Lithology Comments

Feb 28, 2018 (Therese Pettigrew) - The property is underlain by early Proterozoic sediments of the Animikie Group. The Animikie Group is comprised of the Gunflint and Rove formations of which only the latter has been mapped in the project area. Three middle Proterozoic magmatic events are recorded. Earlier intrusions are recognized by their reversed magnetic polarity and generally take the form of thick sheets and sills whose geometry is strongly controlled by the subhorizontal bedding of the country rock. The younger intrusions having normal polarity generally occur as dykes or irregular-shaped differentiated bodies. The first phase is represented by fine to coarse-grained, ophitic to intergranular quartz diabase/gabbro referred to as the Logan Sills, emplaced conformable with the Early Proterozoic Gunflint and Rove Formations. Coarse-grained, intergranular gabbro, locally rich in granophyric mesostasis, is common in the interior of the thicker sills. These sills are cut by a series of linear east-northeast to northeast-trending olivine diabase and northwest-trending quartz diabase dykes called Arrow River dykes. The youngest intrusions in the area tend to be more irregular shaped and internally zoned. One of these is the Crystal Lake gabbro and its projected eastern extension, the Mount Mollie dyke that crosses the property. The dyke is described as composed of gabbroic, dioritic, and granophyric rocks. Gabbroic rocks along the margins of the dyke commonly have modal layering and sulfide mineralization similar to that in the Crystal Lake gabbro (AFRI 52A03SW2008).

Mineralization

Mineralization Comments

Feb 28, 2018 (Therese Pettigrew) - The main showing is situated along the south edge of an olivine diabase dike, carrying disseminated to massive copper-nickel sulphide mineralization in a fracture zone, up to 10.7 m in width and extending for a distance of at least 30.5 m along the dike. The copper-nickel sulphide mineralization is in the form of massive to disseminated nickeliferous pyrrhotite with minor chalcopyrite. A grab sample taken by J. Geul of well-mineralized material yielded 0.70 percent Cu and 0.35 percent Ni (Geul, 1973). This occurrence is typical of the diabase dyke zones in the area. It occurs 400 m south of the Little Pine River, in a rock cut on Highway 61. From the rock cut, going eastward, this mineralized zone has been observed in pits and in the Little Pine River bed over a distance of 1 km. From the rock cut going west, this zone has been observed in a number of pits along a length of approximately 1 km. The most important sulphide zones associated with the diabase dykes occur on the south side of the dykes at an approximate distance of 10 m from the contacts with the surrounding sedimentary rocks. The 3 m wide sulphide zones appear to occur along the entire length of the dykes and are an inherent part of their composition. The sulphide zone is layered vertically and parallel to the geological contact. The layering is defined by a series of vertical fractures and by rhythmic variations in the concentration of the sulphides. The sulphide content varies, generally between 3-15%. Zones of massive sulphides do occur, usually as pods. Pyrrhotite is the main constituent of the mineralized zones; it occurs as fine disseminated grains and also as large shiny flakes substituting biotite. Chalcopyrite grains are occasionally visible (AFRI 52A03SW2005).

Mineral Record Details

References

Mono - Copper, nickel, lead and zinc deposits of Ontario

Publication Number: MDC012 Scale:     Date: 1969

Author: Shklanka R.

Publisher Name: Ontario Dept. of Mines

Location:

MonoMap - Geology of Crooks Township, Jarvis and Prince locations, and offshore islands, District of Thunder Bay

Publication Number: R102 Scale:     Date: 1973

Author: Geul J.J.C.

Publisher Name: Ontario Division of Mines

Location:

Book - RES. GEOL. MIN. DEP. FILE TB

Publication Number: N/A Scale:     Date: 1996

Author:

Publisher Name:

Location:

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