Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001849

Record: MDI000000001849

General

Commodities

Primary Commodities: Diamond

Location

Township or Area: Oskabukuta Lake Area

Latitude: 48° 36' 11.13"    Longitude: -85° 28' 16.24"

UTM Zone: 16    Easting: 612706   Northing: 5384463    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 42C11SW

Point Location Description: Bulk sample location

Location Method: Based on Assessment

Access Description: The White River diamond occurrence is located 14 km west of the community of White River. Access to the site is obtained by travelling approximately 40 km along a network of logging roads from White River.

Exploration History

2008-2011: Prospecting, sampling, assays by B. Radul. 2012-2015: Rio Tinto conducted prospecting, airborne magnetic, ground magnetic, geological and geochemical surveys, assays, geochronology, and a mini-bulk sample.

Assessment Work on File

Geology

Province: Superior

Subprovince: Abitibi

Terrane: Wawa-Abitibi

Geological Age: Archean   Geochronological Age: 1945.3 +/- 1.9 Ma   Geochron. Age Ref.: AFRI 2.56539

Geology Comments

Aug 28, 2017 (Therese Pettigrew) - The Oskabukuta rocks are hosted by post tectonic gneissic to foliated granites of the Pukaskwa Complex (2.719-2.688 Ga) which intrude the nearby Schreiber-Hemlo and White River-Dayohessarah greenstone belts. These rocks are overlain unconformably by terrestrial and marine epiclastic sediments which are derived from the underlying volcanics and tonalities. There are more than 20 diabase dyke swarms present in the Superior Craton of varying age which range from 2.450 Ga (Matachewan gabbro swarm) to 1.03 Ga (Pukaskwa dyke swarm) in age, and range 1 – 30 meters in width (Percival et al., 2006). The most prevalent in the project area are the Matachewan dyke swarm (strike 285° – 330°) and the Marathon dyke swarm (strike 330° - 010°). A series of NE-oriented dyke swarms occur at the end of the Kapuskasing even and before the Mid-Continent Rift (1.11 –1.09 Ga). Accretion of the Grenville Superterrane on to the Superior Craton resulted in the sudden abate of Rift magmatism (1.10-0.98 Ga) (AFRI 2.56539).

Lithology

Lithology Comments

Aug 28, 2017 (Therese Pettigrew) - The property dominantly consists of post-arc granites of the Pukaskwa Complex (2.719-2.688 Ga) and deformed metasediments probably related to rocks of the Schreiber-Hemlo greenstone belt (2.90-2.68 Ga). These rocks are cut by diabase and gabbroic dykes, and several phases of lamprophyric rocks. Most of these intrusive rocks are starkly more magnetic than the host rock granites and are mapped by airborne and ground magnetic surveys. One dyke in particular, which has been called Rabbit Foot, shows macrocrystic textures, contains mantle derived micro-xenoliths of garnet peridotite and can contain up to 50 percent of altered country rock xenoliths. Airborne surveys show the Rabbit Foot rabbit showing as a dyke-like magnetic high feature striking approximately 320° and is in similar orientation to the strike of the regional Matachewan-Hearst diabase dyke swarm (2450 Ma). The Rabbit Foot feature is traced magnetically for over 9 km and in outcrop for 900 m. A ground survey provided enhanced resolution over the magnetic lineament and delineated two parallel dykes that merge at the south east portion of the grid (AFRI 2.56539).

Mineralization

Mineralization Comments

Aug 28, 2017 (Therese Pettigrew) - The Rabbit Foot dyke is 2 to 10 meters in width, contains abundant macrocrystic olivine (2 mm to 2 cm), rare garnet, ilmenite, chromite and chrome diopside macrocrysts, set in an olivine-phlogopite-clinopyroxene-carbonate-oxide (spinel-magnetite-perovskite) groundmass. Pyrite is common (0.1-0.3 pct). The rock can contain a significant proportion of altered crustal xenoliths, and in order of decreasing abundance include: various granitoids, metasediments, autoclasts, pyroxenites, and garnet-lherzolite. Granitoid xenoliths often show intense disequilibrium textures and are commonly rimmed by chlorite+/-clinopyroxene+/-sulphide reaction rim. Residual heavy mineral concentrate from a 2014 mini-bulk sample were picked with a special effort to select indicator minerals proportionately. Results of the proportionate picking include; 126 pyrope garnet, 21 eclogitic garnet, 120 chrome diopside, 155 olivine, 57 possible orthopyroxene, and 79 chromite/ilmenite grains. Four samples weighing a total of 133 kg were collected from the Rabbit Foot dyke and analysed for microdiamonds. A total of 172 microdiamonds were found, ranging from 0.106 to 0.85 mm, with most (85) being between 0.106-0.15 mm in size. Noteworthy diamond mineralization is confined to the xenolithic and macrocrystic melnoite (AFRI 2.56539).

Mineral Record Details

References

Map - Manitouwadge-Wawa sheet, geological compilation series, Algoma, Cochrane, Sudbury and Thunder Bay districts

Publication Number: M2220 Scale: 1:253,440    Date: 1972

Author: Milne V.G., Giblin P.E., Bennett G., Thurston P.C., Wolfe W.J., Giguere J.F., Leahy E.J., Rupert R.J.

Publisher Name: Ontario Division of Mines

Map - Precambrian Geology Compilation Series - White River Sheet

Publication Number: M2666 Scale: 1:250,000    Date: 2001

Author: Santaguida F.

Publisher Name: Ontario Geological Survey

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