What Lies Beneath – Exploring deeper with surface geochemistry

Basic CMYKMany mineral deposits that lie near the earth’s surface are either being mined or are depleted. To look deeper, the challenge for mineral explorers is to develop new exploration techniques to image mineral deposits at depths beyond the capability of our current geophysical and geochemical technologies.

The Athabasca Basin of northern Saskatchewan, is an ancient sandstone basin that hosts high-grade uranium deposits at and below the unconformity between the sandstone and older crystalline basement rocks (Figure 1). These uranium deposits account for about 20 per cent of the world’s primary uranium production with the highest ore grades in the world. Uravan Minerals Inc. (Uravan) realizes that to find the next generation of “greenfields” uranium deposits in the Athabasca Basin, there is the need to innovate beyond the current exploration techniques.

The high cost of drilling in frontier exploration areas, particularly the under-explored deeper Athabasca Basin, requires improved drill-hole vectoring to target uranium-bearing bedrock sources. The subtle signatures expressed by deep-penetrating geophysical signatures need additional remote sensing methods to narrow the exploration window.

To accomplish this task, Uravan partnered with the Queens Facility for Isotope Research (QFIR), at Queen’s University in Ontario. QFIR is a state-of-the-art research facility housing some of the most technologically advanced analytical equipment in Canada. Under the direction of Dr. Kurt Kyser, the QFIR research team and Dr. Colin Dunn, an independent specialist in biogeochemistry, are working with Uravan’s technical group to develop new exploration technologies using applied research.

Conceptually, the “MODEL” adopts the premise that fluids associated with uranium deposits, either in basement rocks or the overlying sandstone, produce significant alteration halos (Figure 2).  The rationale is that elements associated with these alteration zones, and the ore deposit itself, are mobilized and migrate to the surface environment (soils and trees) where they are trapped in a variety of media which can be analyzed for their geochemical signatures.

In 2009 and 2013, Uravan and QFIR in collaboration with Cameco Corporation and Areva Resources Canada Inc. conducted multifaceted surface geochemical studies over two known high-grade uranium deposits in the Athabasca Basin – the Cigar West and Centennial deposits. The results of these studies identified specific deposit-sourced elements and isotopic compositions that have been trapped on surfaces of the clay mineral fraction of certain soil horizons, and within the wood of tree trunks. These findings support the concept of vertical migration of elements, metal ions, and unique isotopic compositions to the surface environment from the Cigar West and Centennial deposits at depths of 450 metres and 800 metres, respectively. The next step for Uravan was to apply this cumulative knowledge with a drill program on its Stewardson property, a “greenfields” prospect in the deeper part of the Athabasca Basin.

The Stewardson property is located on the Virgin River structural trend within the south-central portion of the Athabasca Basin (Figure 3). The exploration program is a joint effort between Uravan and Cameco. Uravan owns 100 per cent of the Stewardson property and Cameco is earning an interest, with Uravan being the operator.
In 2011 and 2013, several remote sensing surveys, consisting of surface geochemical surveys and airborne and surface EM geophysical surveys, were conducted over the Stewardson property. These surveys identified potential bedrock sources of uranium mineralization along a highly anomalous northeast-southwest trending EM conductive corridor (E-Conductor) that is coincident with a significant anomalous surface geochemical signature (Figure 4). Of particular interest are the radiogenic lead (Pb) isotopic ratios (207Pb/206Pb) in the clay-size fraction of the soils and in cored tree wood. These anomalous surface geochemical signatures, when superimposed on the E-Conductor and other interpreted geophysical features and structural patterns, highlight the most probable location of potential uranium mineralization along the trace of the E-Conductor.

Based on these compelling surface anomalies, Cameco approved Uravan’s 2014 budget to drill two 1,400 metre diamond drill-holes designed to test the uranium-bearing potential of the E-Conductor (Figure 5).  Larry Lahusen, CEO for Uravan comments, “I believe the E-Conductor represents a significant conductive ‘bright spot’ that correlates amazingly well with surface geochemical anomalies; which is a key requirement in Uravan’s exploration strategy for vectoring to uranium deposits under cover. We are now starting to recognize what a mineralized conductor looks like geochemically, when compared to the many barren or blind conductors that transect the Athabasca Basin. The E-Conductor correlates well with anomalous surface geochemical patterns that have defined a unique drilling opportunity and a potential ‘game changer’ for uranium exploration.”

At the time of writing, SL14-001 is being drilled at the Stewardson property, representing the next chapter for testing Uravan’s innovative exploration strategy.

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