The Milk River Ridge-Whiskey Gap area has seen both historic and recent exploration for sandstone-hosted uranium deposits. Within the past two years mineral exploration industry reports have stated that selected well waters in the Milk River Ridge-Whiskey Gap region produced water samples with highly elevated concentrations of radon and, to a lesser extent, uranium. For example, Hartley (2005) reported 26 water well samples from the area produced: (a) radon concentrations averaging 32.6 bequerels per litre (Bq/L), with some samples having radon concentrations up to 185 Bq/L, and (b) uranium concentrations averaging 8.4 parts per billion (ppb), with some samples having uranium concentrations up to 30 ppb. However, although Hartley (2005) provided detailed information about the radon and uranium concentrations in each sample, there were no location data provided for each sample.
As a result, AGS conducted a preliminary program of water well sampling in June 2006 that resulted in the collection of 20 water samples from 19 sites distributed about the Milk River Ridge-Whiskey Gap area. The water samples collected by the AGS were analyzed at the Saskatchewan Research Council for radon, uranium and a suite of 24 other elements. Results from these 20 water samples include: (a) radon contents ranging from 7 up to 222 Bq/L (189 to 5994 picoCuries/litre), (b) uranium contents ranging from 0.2 up to 160 ppb, and (c) some other elements having, in places, elevated concentrations, including arsenic (up to 140 ppb), iron (up to 2.1 parts per million or ppm), manganese (up to 0.5 ppm), molybdenum (up to 420 ppb), selenium (up to 7.1 ppb), sulphate (up to 670 ppm), vanadium (up to 14 ppb) and zinc (up to 56 ppb).
Prior hydrogeological mapping by Tokarsky (1974b) indicated there is a down-dip west-flowing 'tongue' of meteoric water that occurs in the Blood Reserve Formation and immediately adjacent strata just east of and beneath the Milk River Ridge-Whiskey Gap area. As well, AGS field examinations during June 2006 found outcrops of Blood Reserve sandstone further east along the Milk River ridge that exhibit both oxidization and reduction alteration colours. The author suggests these are important observations with respect to possible uranium genesis in this region. That is, the geological and hydrogeological setting that exists at the Milk River Ridge-Whiskey Gap area is positive for the formation of sandstone-type uranium deposits because it is similar to those that existed and are believed to have formed important sandstone-type uranium deposits in Wyoming, the Colorado Plateau, New Mexico and south Texas.
Future exploration in the Milk River Ridge-Whiskey Gap region should consider an exploratory drilling methodology or pattern similar to that used successfully in several sandstone-type uranium districts in the USA. This methodology comprises (1) initially a wide spaced drill pattern (holes from 2 to 10 km apart), (2) followed by more closed spaced drilling (holes from a few hundred metres to 1 or 2 kilometres apart) and (3) finally closed spaced drilling (holes tens of metres to a few hundred metres apart) in selected areas intended to find and define uraniferous zones.
Finally, regardless of whether important concentrations of uranium exist at surface, in the subcrop or in the subsurface at the Milk River Ridge-Whiskey Gap area in southern Alberta, the hydrogeological setting consisting of a westerly downward flowing tongue of groundwater beneath the Milk River Ridge may explain why there exist locally anomalous uranium, radon and some other elements in groundwater in places along the flanks of the Milk River Ridge and why the Blood Reserve Formation is oxidized in this area.
Olson, R.A. and Anderson, S.D.A. (2007): Preliminary water well sampling to assess the uranium potential in the Whiskey Gap area of southern Alberta (NTS 82H/2, 3); Alberta Energy and Utilities Board, EUB/AGS Earth Sciences Report 2007-08, 41 p.