GEOCHEMISTRY OF SOILS OVERLYING THE COLES HILL URANIUM PROPERTY

A geochemical survey of soils was conducted at the Coles Hill uranium property. Sampling consisted of 25 auger holes along three east-west transects, one across the northern area of mineralization, one over the southern mineralization, and one between the two areas. The survey measured the concentrations of 42 major and trace elements and eight radioisotopes in the soil A and C horizons. Concentrations were examined along transects and were compared to concentrations from regional data collected as part of a national-scale soil geochemical study. Element associations and trends were examined using compositional data analysis, including variation matrices, cluster analysis, and principal component analysis.

Multivariate analyses of soil geochemical data show differences in composition between soils horizons and between Coles Hill and regional reference soils. With these different groupings, signatures of different parent rock types can also be seen, including separation between elements associated with felsic minerals and redox-sensitive elements. Concentrations of elements associated with the uranium decay chain (U, Th, Pb, Bi) were elevated in some Coles Hill soils relative to regional reference soils. In reference soils, U is closely associated with Th, whereas in Coles Hill soils, U is more strongly correlated with V, La, and Ce, suggesting different parent minerals and/or weathering processes at Coles Hill compared to the regional soils. Examination of metals and radionuclides along east-west transects shows elevated levels of U and U-progeny radioisotopes immediately over the ore mineralization relative to soils adjacent to the mineralization. The results of this study can further be used to assess geochemical processes involved in the weathering of Coles Hill and may provide geochemical pathfinders (e.g. V, La, Ce, Ra) that indicate potential locations of similar shallow uranium mineralization.