SIMS ANALYSIS OF SULFIDE MINERALS FOR PT AND AU - METHODOLOGY AND RELATIVE SENSITIVITY FACTORS (RSF)

Relative sensitivity factors (RSF) were determined for Au-197 and Pt-1 98 some common sulfide minerals using a CAMECA IMS-4f ion microprobe, Sulfides implanted with Au-197 and Pt-198 were sputtered using a Cs+ p rimary beam, and negative secondary ions were measured. Mass interfere nces were eliminated by operating in a high-mass-resolution mode (m/De lta m = 2,000), giving rise to average minimum detection-levels rangin g from 0.013 to 0.223 ppmw. The RSF values for Au-197 are 3.84 x 10(18 ) cm(-3) +/- 9.7% (monoclinic pyrrhotite), 2.67 x 10(19) cm(-3) +/- 12 .0% (pyrite), 3.69 x 10(18) cm(-3) +/- 29.2% (chalcopyrite), and for P t-198, 1.35 x 10(19) cm(-3) +/- 7.4% (chalcopyrite), 1.51 x 10(19) cm( -3) +/- 12.32 (monoclinic pyrrhotite), and 9.21 x 10(18) cm(-3) +/- 38 .1% (pentlandite). In all cases, the reference matrix mass used for th e RSF calculations was Fe-56. The higher Au-197 RSF values for pyrite, compared to chalcopyrite and pyrrhotite, are attributed, in part, to a larger quantity of electronegative species in pyrite, which tends to inhibit the amount of Au- emitted.