Comparative analysis of sulfides for gold using SXRF and SIMS

Sulfides may be analyzed for gold using Secondary Ion Mass Spectrometry (SI MS) and Synchrotron X-Ray Fluorescence (SXRF); we have compared the two met hods with respect to instrumental requirements, time, analysis volume, and detection limits. A limitation in this comparison is the inhomogeneous dist ribution of Au within arsenopyrite, as demonstrated using SIMS imaging for samples from the Sb Bento deposit, Brazil. Analysis of the same grains of a rsenopyrite produces good agreement between the two techniques; discrepanci es are attributable to slight shifts in analysis locations between the two techniques or the different volumes being analyzed. Whereas SIMS has imagin g capability and sub-ppm detection limits, quantitation is difficult. SXRF spectra are relatively simple, and quantitative analysis is not as matrix-d ependent as with SIMS. The detection level for Au in arsenopyrite by SXRF i s limited by the background from AsK alpha to about 50 ppm, but will be red uced to about 15 ppm using more intense synchrotron sources.