Regional exploration for channel and playa uranium deposits in Western Australia using groundwater R.R.P. Noble ⇑ , D.J. Gray, N. Reid CSIRO Earth Science and Resource Engineering, CRC Deep Exploration Targeting, PO Box 1130, Bentley, Western Australia 6102, Australia article info Article history: Received 17 December 2010 Accepted 15 June 2011 Available online 29 June 2011 Editorial handling by C. Reimann abstract Shallow calcrete aquifers in the central north of the Yilgarn Craton in Western Australia are the host to numerous secondary carnotite U deposits. Sampling and analysis of approximately 1400 shallow aquifer groundwaters were conducted to test if U mineralisation of this type may be found using a >5 km sample spacing. Results show this can be achieved. All the economic deposits and most of the minor deposits and occurrences are associated with groundwater that has carnotite (KUO 2 VO 4 ) approaching or exceeding saturated conditions. Soluble U concentrations alone identified the largest deposit (Yeelirrie) and several smaller deposits, but this parameter was not as successful as the mineral saturation indices. Palaeodra- inage distribution and thickness of cover combined with surface drainage and catchment boundaries pro- vided background information of U primary sources and for areas with the highest exploration potential for channel and playa U deposits. Granites in the SE of the study area are less prospective with regard to secondary U deposits. Groundwater geochemistry in conjunction with palaeodrainage mapping may greatly improve exploration through cover where radiometric geophysics is not effective. The study of regional, shallow groundwater for U shows multiple benefits for mineral exploration, the economy and potable water quality. Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction Uranium is important for energy supplies, and further discover- ies are critical for the predicted increase in future energy demand (Macfarlane and Miller, 2007). Previously, regional radiometric surveys have been successful at targeting surficial deposits, but a few metres of sediment cover (>2 m) may block this signal. Groundwater chemistry can be successfully used as a regional tar- geting tool in these terrains (Cameron et al., 1980; Gamble, 1984; Mann and Deutscher, 1978) and was widely employed by explora- tion companies in the 1970s and 1980s. More systematic regional exploration will be necessary, however, if more near-surface U ore deposits are to be found, particularly in areas of covered terrain such as in Australia. Surficial U deposits are hosted in calcrete and associated sedi- ments in palaeodrainage channels and playas in the northern Yil- garn Craton in Western Australia (Butt et al., 1977; Cameron, 1990). The largest known deposit is Yeelirrie (52,500 t U 3 O 8 at 0.15% grade), which has higher reserves than all other known deposits in the region combined, at higher grades and higher cut- off values (Table 1). These deposits are shallow and potentially rel- atively easy to mine, hence there has been renewed interest in exploration for this type of deposit. Groundwater interacts with mineralised rocks and may display a geochemical signature with a much greater size than other sam- pling media (Cameron, 1978; Giblin and Dickson, 1992; Gray and Noble, 2006a; Leybourne and Cameron, 2006; Taufen, 1997). These groundwater geochemical anomalies may reduce the required dril- ling density needed to explore regionally, an important consider- ation for cost-effective exploration in covered terrains. Uranium is generally soluble in groundwater and surface water and has shown geochemical haloes around U mineralisation (Mann and Deutscher, 1978; Cameron, 1980; Langmuir and Chatham, 1980; Rose and Wright, 1980; Peuraniemi and Aario, 1991). Other hydrogeochemical investigations for U exploration have looked at various styles of deposits including sandstone-hosted deposits in the USA. (Langmuir and Chatham, 1980; Rose and Wright, 1980), glacial till/peat in Finland (Peuraniemi and Aario, 1991) and unconformity deposits in Canada (Cameron, 1980). Aus- tralian secondary deposits in calcrete have also been subject to hydrogeochemical studies. Mann and Deutscher (1978) provided a comprehensive study of a single catchment hosting the Dawson Well–Hinkler Well–Centipede deposits, adjacent to the Yeelirrie catchment, Heath et al. (1984) studied the Lake Austin deposit, Gamble (1984) studied groundwater near the Lake Raeside depos- its and, Cameron et al. (1980) and Cameron (1984) published a summary of water chemistry from a large region sampled around Yeelirrie as part of exploration by Western Mining Corporation. Most showed some degree of success, particularly with oxidised 0883-2927/$ - see front matter Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2011.06.027 ⇑ Corresponding author. Fax: +61 8 6436 8559. E-mail address: ryan.noble@csiro.au (R.R.P. Noble). Applied Geochemistry 26 (2011) 1956–1974 Contents lists available at ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem