The Riou Lake Project is located near the northern margin of the Athabasca Basin. Formerly comprised of three contiguous properties, it consists of 13 claims totaling 33,283 hectares (82,209 acres). Many favorable indicators of environments for world-class McArthur River and Cigar Lake style uranium deposits are apparent in the project area. Exploration is at early stages, and to date ground and airborne geophysical surveys, prospecting, lake sediment sampling and drilling in widely spaced diamond drill holes have been completed. Work has been performed principally since 1995 by Pioneer Metals Corporation and since 2002, UEX Corporation. Central parts of the project are 35 kilometres southwest of, and in winter accessible by road from, the town of Stony Rapids, which in turn is connected by road to southern Saskatchewan, and is linked to the Saskatchewan power grid.

Geological setting

The Riou Lake project is underlain by 250-800 metres of Proterozoic sandstone of the Athabasca Group that dips shallowly to the south. The sandstone unconformably overlies Archean-aged basement rocks of the Tantato Domain, which comprise metavolcanic units, graphite-bearing metasedimentary gneiss, mafic sills and granites that have been affected by amphibolite to granulite facies metamorphism. Extensive Archean mylonitic shear zones are developed in the region, including the Black Lake shear zone east of the project, which defines the boundary between the Tantato Domain and the Mudjatik Domain. Basement rocks trend mainly northeast, and are affected by tight, megascopic folds. Post-Athabasca faults also strike mainly to the northeast, and include the southerly dipping Riou Lake reverse fault system. It bends to east-west and southeast trends to the south of Riou Lake, conforming with folded basement lithologies. This structure is associated with an extensive upthrust block of basement and sandstone, indicating apparent reverse displacement of at least 170 metres. Other northeast-trending faults include the Platt Creek Shear Zone, which extends through the adjacent Black Lake Project northward into older syn-metamorphic shear zones. Northwest trending post-Athabasca faults are also developed near Riou Lake.

Surface exploration activities and results

The uranium exploration potential of the Riou Lake area was first recognized with the discovery of the Nisto and Fond du Lac uranium deposits along the northern rim of the Athabasca Basin prior to 1970. In 1978, Saskatchewan Mining and Development Corp. identified an east-west boulder train of uraniferous Athabasca sandstone boulders in northern parts of the project, similar to boulder trains that have led to the discovery of several uranium deposits in the region. The boulders, which contain grades of up to 11.3% U, could be sourced up ice direction to the east along the Platt Creek Fault on the Black Lake Project, since boulders have not been found to the east of this structure. In addition to the boulders in till, several areas of locally derived, radioactive sandstone boulders containing up to 21% P2O5, and highly anomalous uranium and rare earth element concentrations occur in central parts of the Riou Lake Project (e.g., W-Zone). Alignment of these apatite-rich zones along northwest-trending faults suggests a tectonic-hydrothermal association, possibly as distal alteration to uranium mineralization.

Sampling of lake sediments and waters in the former Serendipity Lakes Project and eastern Riou Lake Project has returned anomalous concentrations of uranium and pathfinder (e.g. Ni, Co, Cu) elements that are comparable to those near known uranium deposits in the Athabasca region such as Cluff Lake and Cigar Lake. Other radioactive waters include clusters of radioactive radon and uranium-bearing artesian springs that are developed in the former Serendipity Lakes Project and south of the Riou Lake Fault in the southwestern part of the Riou Lake Project. The spring chemistry is similar to that of basal brine connate waters at the base of the sandstone column at the McArthur River Deposit, and to springs that occur near the Shea Creek Deposits (Anne and Colette) south of Cluff Lake. These spring waters may reflect the upward migration of deep waters along faults, suggesting structural targets in areas where basinal waters may have tapped a radioactive source. Similar waters have been obtained from artesian flow out of drill holes on the Riou Lake Project and former Serendipity Lakes Project, including Riou Lake Project hole RLG-10, which intersected low-grade uranium mineralization at the unconformity.

Ground electromagnetic surveys

Ground EM surveys carried out over magnetically low areas underlain by metasedimentary basement lithologies beneath the Athabasca sandstone have identified several prospective, conductive graphitic units beneath (PM Conductor), and south of Riou Lake (KC Conductor), and on the adjacent Black Lake Project along the trace of the Platt Creek Shear Zone. Drilling has confirmed the presence of graphite in many of these. Graphite-rich lithologies host most of the major uranium deposits in the eastern Athabasca Basin due to their chemical nature as a reductant, and the common localization of faulting and consequent structural permeability along the units. South of Riou Lake, conductive graphitic units curve from southwest to northwest trends progressively to the east, mimicking map and fault patterns, and providing favorable structural sites at potential constrictional and dilational bends in associated faults. Subsequent drill testing of structurally favorable sites along these conductors has intersected narrow intervals of anomalous uranium mineralization at several locations, graphitic gneiss, and faults, including overthrust fault steps of the unconformity of up to 60 metres in the Riou Lake Fault system. Similarly, along the Platt Creek Fault system, bends and bifurcation points of the fault and hosting graphitic gneiss delineated by EM surveys form prospective structural sites at the up-ice potential source of the uranium-bearing boulder train which will be drill tested during upcoming exploration.

Diamond drilling results

A total of 37 drill holes totaling approximately 24,000 metres have been completed on the project on the basis of ground EM surveys over conductive graphite-rich basement, anomalous lake and spring geochemistry, interpreted faults, and boulder sampling survey results. Although drilling has been of a reconnaissance nature, and is widely spaced, several areas of anomalous alteration, low grade uranium mineralization and associated faulting have been intersected near the sub-Athabasca unconformity, which form principal target areas for follow up drilling:

Southeastern Riou Lake - PM conductor area: Three holes drilled in this area, holes RLG-D1, D10 and P2-H1 have intersected a broad area of bleaching, silicification and clay alteration in the Athabasca sandstone column that is comparable to the peripheral alteration halo to many uranium deposits. Within this area, hole RLG-D10 intersected alteration straddling the unconformity containing mineralization as sooty pitchblende in concentrations up to 3428 ppm U over 0.12 m. Faults in the upper parts of these holes probably form the northern strands of the Riou Lake fault system, and with the along strike continuation of the alteration, will be targeted where they intersect the unconformity in this prospective area.

Conductors south of Riou Lake: Drilling in this area has intersected graphitic gneiss in several drill holes within basement rocks (holes RLG-D8, D9, D14 and D20) that are locally associated with disseminated pitchblende mineralization over narrow intervals near the unconformity. Holes RLG-D7 and RLG-D11, both intersected a major southwest dipping fault that forms a southerly strand of the Riou Lake Fault system. A 60 metre wedge of basement is thrust over Athabasca sandstone in hole RLG-D7. Although no mineralization or significant alteration is here associated with the fault, the style and magnitude of faulting is similar to that associated with uranium deposits elsewhere in the Athabasca basin, and the area is only 1.5 kilometre south of the alteration zone intersected in holes RLG-D1 and D10. Further faults comprising the main strands of the Riou Lake Fault must lie to the north of this structure to explain the 110 metre drop in the unconformity between holes RLG-D7 and RLG-D10. Mineralization and alteration in hole RLG-D10 immediately to the north indicates that uraniferous hydrothermal activity has occurred in the local area, and follow up drilling is planned. A further 150 metre drop in the unconformity elevation between holes RLG-D8 and RLG-D14 suggests that another significant fault occurs to the south of the Riou Lake Fault.

Exploration program

The Riou Lake project contains many favorable indications of the presence of unconformity-type uranium deposits, including significant reverse faults, basement graphitic gneiss units, uraniferous boulders in till, alteration, and low-grade uranium mineralization locally developed near the unconformity. At the depths of >300 m to the unconformity on the project, the target must be large and high grade, and exploration here will be directed to the discovery of McArthur River and Cigar Lake type deposits, which occur at comparable depths. Both of these deposits are associated with chains of mineralization in pods at and below the unconformity that extend for up to 1 km along faulted graphitic gneiss units, and which have well developed enveloping alteration chimneys. Bends, steps, and bifurcation points of faults and conductive units are highly prospective, since these areas require accommodation by faults that may induce fracturing and enhanced structural permeability.

Follow up drilling on the Riou Lake Project will further test prospective structural sites on EM conductors, and areas of alteration and uranium mineralization previously intersected. The drilling of angled holes during this program, particularly over faults, will allow testing of a broader lateral area across the width of structural zones in the sandstone column than vertical drill holes, increasing the probability of crossing through the alteration chimney typically developed in sandstone above large uranium deposits. In addition to drilling, EM surveys are planned over central and eastern parts of the project where lake sediment uranium anomalies occur, and to infill areas where favorable structural sites and conductors are interpreted. Surface mapping of bedding orientations, fracture densities and orientations, alteration and selective geochemical sampling of structural features in outcrop over the trace of the Riou Lake Fault has been undertaken to identify potential surface manifestations of alteration and mineralization along the fault at depth.

Maps

Riou Lake 57 KB, approx. 12 seconds at 56.6Kbps

Riou Lake project: Exploration compilation on magnetic gradient map 93 KB, approx. 18 seconds at 56.6Kbps