Distinguishing adularia haloes around low-sulfidation epithermal veins using portable X-ray fluorescence

This study combines pXRF and XRD for the detection of adularia within the low sulfidation Waihi Au-Ag deposit, New Zealand. The pXRF was used to analyse 300 samples from the Favona vein system, we use K/AI ratios as an indicator for adularia. The presence of adularia is known to indicate system permeability and occurs associated with mineralisation. Consequently, it is used as a vectoring tool, and understanding its association to vein systems is important. We compared the ratios of 60/300 samples to XRD analysed samples. We found that adularia was almost always present in a sample with a K/AI ratio of >0.4. This "magic ratio" was used to infer the presence of adularia in the samples unanalysed by XRD. Using this technique, the adularia halo was found to be much smaller than those presented in previous studies. There are clear adularia zones before and after vein intersections and a strong anomaly at similar to 100rin drill-hole depth in all 3 holes. Possibly marking the extent of fluid flow which leads to cooling. However, comparison of samples with known adularia concentrations to the XRD analyses shows that the XRD rarely picks up adularia in samples with <10%. Therefore, likely missing low adularia samples.