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The Sibley Basin (also referred to as the Nipigon Embayment) of northwest Ontario is a late Proterozoic (Helikian age) sedimentary basin that shows significant geological parallels with the Athabasca Basin of Saskatchewan. These similarities have long been recognised before, but led only to a very modest amount of exploration for uranium in the late 1970s and early 1980s. Overall, the Sibley Basin is the least explored of all the Helikian-age sedimentary basins in Canada. It is also the most accessible, with an extensive network of logging roads.
The first phase of diamond drilling on the company's Voltaire Lake property in the Sibley basin, 150 kilometres north of Thunder Bay, Ontario have been completed. Drill holes have intersected massive sulphides including chalcopyrite in unmapped basement rocks that are buried under a cover of Sibley sediments and a diabase sill. The basement geology that has been revealed contains environments that are favourable for gold, volcanogenic massive sulphide (VMS) and nickel-copper PGE mineralization.
Five diamond drill holes totalling 1,203 metres were drilled to test a group of conductors defined by a VTEM(r) airborne magnetic and electromagnetic survey carried out over the 73,000 acre Voltaire Lake property in the summer of 2007. Samples from these three drill holes have been split and sent for assay.
Similarities between the Athabasca and Sibley basins are:
- Both are unmetamorphosed, continental sedimentary basins.
- Both basins are of Helikian age (Athabasca Formation 1,800 my, Sibley Group 1,600 my)
- Both basins have well developed regolith (deep weathering) of basement rocks at the unconformity where they overlie older rocks.
- Both basins overlie basement rocks with high background uranium contents and/or zones of uranium enrichment. In the Sibley basin, the Quetico Group metasediments, and particulalrly the intrusive granites in the Quetico subprovince are conspicuously enriched in uranium.
- Both basins have been intruded by Helikian-age mafic magmatic activity (diabase dykes and sills in the Athabasca Basin; the Nipigon sills in the Nipigon Basin)
- The basement rocks under both basins contain chemical traps (such as graphitic units) that are capable of reacting with uranium-bearing groundwater to precipitate and concentrate uranium mineralization.
- Both basins contain high grade uranium mineralization in basement rocks close to the basal unconformity.
The most favourable part of the Nipigon Basin for uranium is the southern part of the basin between Lake Nipigon and Lake Superior. In this area, Sibley Group sediments overlie uranium-rich metasediments and granitic intrusives of the Quetico subprovince. At the northern margin of the Quetico rocks the basement rocks change to metavolcanics and metasediments of the Beardmore-Geraldton greenstone belt within the Wabigoon subprovince, containing abundant graphitic units, sulphide zones and iron formations, all of which represent potential chemical traps for uranium.
| COMPARISON BETWEEN ATHABASCA AND SIBLEY BASINS |
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ATHABASCA |
SIBLEY |
| Mid-Proterozoic (Helikian) continental sedimentary basin |
Yes |
Yes |
| Uranium-enriched basement source rocks |
Yes |
Yes |
| Regolith developed at basement unconformity |
Yes |
Yes |
| Chemical traps in basement rocks (graphite, sulphides) |
Yes |
Yes |
| Post-basin faults (fluid channels, structural traps) |
Yes |
Yes |
| Pitchblende veins in exposed basement |
Yes |
Yes |
| Unconformity-type uranium deposits |
Yes |
(to be found ) |
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