Dramatic increase in uranium exploration in Québec
By Serge Perreault, M.Sc., P. Geo.
Assistant to the Director General
Géologie Québec directorate
The mining community's interest in uranium has risen dramatically in Québec, after 22 years of relative inactivity. This keen interest in uranium is directly related to its spot market price, which reached a peak of US$72 per pound at the end of January 2007. As a result, exploration expenditures for uranium, which were only in the tens of thousands of dollars in 2000, rose from $1.36 million and $4.3 million in 2004 and 2005, respectively, to $16 million in 2006 (data from Natural Resources Canada and preliminary actual ISQ data for 2006). These expenditures were distributed over roughly 40 projects, mainly located in the Grenville Province (in the Témiscamingue area (Kipawa), in the Outaouais Region (Fort-Coulonge), in the Laurentides Region (Mont-Laurier), in the Côte-Nord Region (Baie-Johan-Beetz – Aguanish), in the sedimentary basin of the Monts Otish (northeast of Chibougamau) and in the eastern portion of Nunavik (in the Core Zone) and the metasedimentary rocks of the Torngat Orogen (Lake Harbour Group).
|Two sectors have attracted the attention of the mineral exploration community in 2006 because of the results obtained and the opening of new exploration territories: the Monts Otish basin and the Core Zone area in Nunavik.
The Monts Otish basin, Québec's Athabasca ?
The uranium potential of the Monts Otish Paleoproterozoic sedimentary basin is often compared to the Athabasca Mesoproterozoic sedimentary basin in Saskatchewan (the Athabasca basin accounts for one-third of world supply). There are several uranium showings typical of unconformity-related uranium deposits (e.g. Camie River and Beaver Lake) in the Monts Otish basin. The Otish Supergroup is characterized by fluvial deposits at the base (Indicator Group) and marginal basin deposits near the top (Genest, 1989). The Indicator Group is composed of sub-arkosic to arkosic sandstones. These rocks are cut by dikes and sills of Paleoproterozoic gabbro.
In 2006, several companies were active in the Monts Otish area, including Cameco (the world's largest low-cost uranium producer, with a 20% market share) and junior Strateco Resources Inc. The promising results obtained by Strateco Resources on the Matoush property (A.A. Matoush showing) highlight the potential of vein-type mineralization associated with a shear zone in sedimentary rocks.
According to Strateco Resources Inc. and previous work carried out by Uranerz Exploration and Mining in 1984, the active channel facies in the sandstone of the Indicator Group is favourable for the emplacement of uranium mineralization. The unit is cut by a post-deposit fault and by gabbro sills that played an important part in mobilizing and concentrating uranium along the fault, which makes the property more interesting. The best recent intersections obtained in drilling are:
- 2.1% U3O8 over 12.4 m including an intersection grading 4.7% U3O8 over 3.3 m (hole MT-06-30, December 22 press release by Strateco Resources).
- 1.01% U3O8 over 14.1 m including 2.01% U3O8 over 5.2 m (hole MT-06-4, December 22 press release by Strateco Resources).
The company traced the Matoush structure (fault) over a strike length of 8 km; it has been tested by drilling over nearly 730 metres. Strateco Resources Inc. also mentioned that the true width of the mineralized intervals had not yet been determined.
The Matoush uranium showing differs from the unconformity-related uranium deposit model. Instead, it is similar to uranium-bearing veins associated with shear zones, except that the mineralized zone lies above the unconformity in the sandstone units and not in basement rock as it does at Rabbit Lake or Beaverlodge in northern Saskatchewan (production of more than 25,000 metric tons of U from 1950 to 1982).
The Core Zone of the Nouveau-Québec and Torngat orogens, a new Rössing?
The Core Zone represents new territory for uranium exploration. It attracted attention following the discovery of zones of anomalous uranium values in lake-bottom sediments collected by the MRNF in 1997. In addition, new uranium showings discovered there in 2006 suggest that this area could become a uranium metallogenic province.
The Core Zone (formerly known as the Churchill Province or Rae Province ) forms the basement of the eastern portion of Nunavik. It is wedged between the Paleoproterozoic volcanosedimentary and magmatic rocks of the Nouveau-Québec Orogen (Labrador Trough), to the west, and the Torngat Orogen, to the east, at the Québec–Labrador border. All of these rocks have been affected by the deformation and metamorphism episodes of the Trans-Hudson Orogen (~1.85 to 1.75 Ga). The Core Zone is mainly composed of Archean to Mesoproterozoic tonalitic gneiss, granitoids and mafic intrusions. The Core Zone is divided into several lithotectonic domains, separated by wide deformation corridors; Wardle et al., 2002). Veins and dikes of syn- to late-Hudsonian granitic pegmatite cut across the Archean basement of the Core Zone and the rocks of the Nouveau-Québec and Torngat orogens.
Between the formation of the Archean basement and its exposure on surface (about 2.5 billion years (Ga), the formation of Paleoproterozoic volcanosedimentary sequences (~ 2.1 to 1.85 Ga) and the final emplacement of the last granitic magmas in the form of pegmatites (about 1.75 Ga), more than 750 million years elapsed during which uranium could be mobilized and transported in the course of episodes of erosion, deformation and metamorphism, then deposited and concentrated in the form of mineralization in sedimentary rocks, granites and pegmatites or in structural traps. Accordingly, the huge area covered by the eastern portion of Nunavik, east of the Labrador Trough, is fertile ground for various types of uranium mineralization including:
- mineralization associated with Rössing-type (Namibia) granitic intrusives (production of 3,711 metric tons at an average grade of 330 ppm U in 2005, representing 7.7% of global production; Rössing Mine Plc) and Madawaska-type (Ontario) granitic intrusives (total production of 4.54 mt at 0.0997% U3O8 and 4,295,281 kg U from 1957 to 1982; Alexander, 1982);
- mineralization associated with uranium veins related to major Beaverlodge-type shear zones;
- mineralization associated with unconformity-related uranium or with Athabasca-type sedimentary rocks in the Lake Harbour and Hutte Sauvage groups.
However, it is very likely that the primary uranium mineralization potentially present in the Lake Harbour and Hutte Sauvage groups was remobilized into units or structures favourable for uranium accumulation following the metamorphism and deformation of the Trans-Hudson Orogen.
Lake Harbour Group
The Lake Harbour Group (2.1 to 1.9 Ga) is a volcanosedimentary sequence of the Torngat Orogen. It is composed of quartzofeldspathic, aluminous and graphitic paragneiss, of sequences of calcitic and dolomitic marbles and calcsilicate rocks, and of quartzite and mafic volcanic rocks. These rocks are cut by the Nuvilik mafic suite and by granitoids and pegmatites.
The Lake Harbour Group (2.1 to 1.9 Ga) is a volcanosedimentary sequence of the Torngat Orogen. It is composed of quartzofeldspathic, aluminous and graphitic paragneiss, of sequences of calcitic and dolomitic marbles and calcsilicate rocks, and of quartzite and mafic volcanic rocks. These rocks are cut by the Nuvilik mafic suite and by granitoids and pegmatites. Since the last two years, the junior mining company URANOR explore this area.
The gneissic basement of the Core Zone
The Rae North uranium property, held by the Azimut Exploration Inc. and Northwestern Mineral Ventures Inc. joint venture, is located south and southeast of the village of Kangiqsualujjuaq, at the mouth of the Rivière George, on the east coast of Ungava Bay. The basement of the property is composed of tonalitic and granitic gneiss and of Late Archean granite and pegmatite intrusions. There are also several tectonic outliers of the supracrustal rocks of the Lake Harbour Group and of the Nuvulialuk mafic suite (Verpaelst et al., 1999).
The main mineralized zone is located in a strongly anomalous radiometric zone (from 2,000 to 30,000 counts per second), which is about five kilometres long. Uranium anomalies have been detected in the lake-bottom sediments and preliminary analysis of the helicopter-borne radiometric survey identified 14 anomalies more than one kilometre long, including 7 that are over three kilometres in length. Uranium mineralization has been observed in pegmatites, granites and gneisses. Uraninite has been observed and analyzed by electron microprobe in samples from two sites. Analysis of twenty-two samples revealed grades over 0.05% U3O8 (500 ppm) from 10 different uranium showings in the Rae-1 Zone of the Rae North property. Fourteen samples returned values higher than 0.1% U3O8 (or 1000 ppm); the best values obtained were 0.59%, 0.57%, 0.46%, 0.3% and 0.22% U3O8.
Further south, on the Rivière George property consisting of seven claim blocks distributed between the Rivière George and the Québec–Labrador border, in the area of lakes Brisson and Mistinibi, Freewest Resources Canada discovered four uranium showings. These occurrences of uranium mineralization are located within granitic pegmatite dykes that cut across the gneissic basement of the Core Zone. The mineralized zone is 700 metres wide and nearly 2.6 km long. The best values obtained were 0.384 and use 0.132% U3O8, in grab samples from the Stewart Lake Trend in Block 1. The grades from grab samples of bedrock and erratic blocks range from 100 to 1000 ppm. On the Abigail showing, analysis of a sample from a two-metre-wide granitic pegmatite dyke returned a grade of 0.369% U3O8.
Databases for exploration
There are still huge areas where little exploration for uranium has been done because of a lack of radiometric and geological data. The geochemical survey of lake-bottom sediments conducted in 1997 in Nunavik, by the MRNF and five private sector partners, brought to light significant zones anomalous for uranium along and east of the Rivière George and in the area at the border between Québec and Labrador, between the 54th and 58th parallels. The Géologie Québec directorate published a special-edition map, updated in January 2007, entitled “Uranium in the secondary environment and uranium mineralization". The map highlights the geochemistry of lake-bottom and stream sediments and known mineralization from the SIGÉOM database.
ALEXANDER, R.L., 1982, Geology of Madawaska Mines Limited, Bancroft , Ontario , in Uranium deposits of Canada , CIM special volume 33, p. 61-69.
GENEST, S., 1989, Histoire géologique du bassin d’Otish, du Protérozoïque inférieur, Québec, thèse de doctorat non publiée, Université de Montréal.
VERPAELST, P , BRISEBOIS, D., PERREAULT, S., SHARMA, K.N.M., DAVID, J., 2000, Géologie de la région de la rivière Koroc (24 I) et d’une partie de la région d’Hébron (14 L), Ministère des Ressources naturelles et de la Faune, RG 99-08, 62 pages.
WARDLE, R. J., JAMES, B., SCOTT, D. J., HALL, J., 2002, The Southeastern Churchill Province: synthesis of a Paleoproterozoic transpressional orogen, Canadian Journal of Earth Sciences; volume 39, No. 5, pages 639-663.
Additional suggested reading on the types of uranium deposits in Canada and around the world:
Geology of Canadian Mineral Deposit Types , edited by O.R. Eckstrand, W.D. Sinclair and R.I. Thorpe, Geological Survey of Canada, Geology of Canada, No. 8, 1995. See sections 1.1, 1.2, 7, 8.1, 12, 13, 14, 21 and 22 on uranium deposits.
Dahlkamp, F.J., 1993, Uranium ore deposits, Springer-Verlag, New-York Berlin Heidelberg; 460 pages.
Van der Leeden, J., Bélanger, M., Danis, D., Girard, R., Martelin, J., 1990, Lithotectonic domains in the high-grade terrain east of the Labrador Trough (Quebec), in the Early Proterozoic Trans-Hudson Orogen of North America, Lewry, J.F. and Stauffer, M.R., Geological Association of Canada, Special Paper 37, pages 371-386.