Underestimation of uranium mineralisation by gamma probes at the surficial carbonate associated uranium deposits of the Wiluna Project: unrelated to secular disequilibrium.

There is a discrepancy between U3O8 values derived from geochemical analysis of drill core samples and those derived from de-convolved gamma probe data at the Wiluna uranium Project in Western Australia. Using linear regression to create trend lines through the correlated data results in a relationship that would suggest that on average, U3O8 from geochemistry is up to 65% greater than U3O8 from the equivalent composited gamma data. Closed-can disequilibrium analysis on selected samples suggests that whilst positive disequilibrium may be contributing to the observed difference in some samples, the relationship is poor and does not account for the magnitude of the difference observed. The difference extends into block model comparisons across all of the Wiluna Project's resources. Testing shows that the geochemical analytical technique being used is not responsible. It is thought that the gamma probes are having difficulty measuring all of the radiation being emitted from uranium mineralisation within the particular geological setting of the Wiluna Project. Electrical logs and gamma gamma density data do not show any definitive relationship to the magnitude of the underestimation by the gamma probe, a reasonable correlation between this underestimation and sodium values derived from geochemical analysis may suggest a clay and/or groundwater salinity link.
There is a discrepancy between U3O8 values derived from geochemical analysis of drill core samples and those derived from de-convolved gamma probe data at the Wiluna uranium Project in Western Australia. Using linear regression to create trend lines through the correlated data results in a relationship that would suggest that on average, U3O8 from geochemistry is up to 65% greater than U3O8 from the equivalent composited gamma data. Closed-can disequilibrium analysis on selected samples suggests that whilst positive disequilibrium may be contributing to the observed difference in some samples, the relationship is poor and does not account for the magnitude of the difference observed. The difference extends into block model comparisons across all of the Wiluna Project's resources. Testing shows that the geochemical analytical technique being used is not responsible. It is thought that the gamma probes are having difficulty measuring all of the radiation being emitted from uranium mineralisation within the particular geological setting of the Wiluna Project. Electrical logs and gamma gamma density data do not show any definitive relationship to the magnitude of the underestimation by the gamma probe, a reasonable correlation between this underestimation and sodium values derived from geochemical analysis may suggest a clay and/or groundwater salinity link.