Comparison of Lam Icp MS and Micro-Pixe Results for Palladium and Rhodium in Selected Samples of Noril'sk and Talnakh Sulfides

Comparisons of PGE measurements by laser-ablation microprobe (LAM–ICP–MS) with micro-PIXE analyses on the same sulfide grains were made in order to assess data quality. Pyrrhotite, pentlandite and chalcopyrite from a few samples of dissemi-nated ores of the Noril’sk I intrusion and massive ore from the Talnakh deposit, Russia, were analyzed for Pd and Rh by micro-PIXE and for all PGE by LAM–ICP–MS. Micro-PIXE analyses employed focused proton beams of 8 15 m for grains in heavy-mineral separates and 15 20 m for grains in hand samples. These represent analyzed volumes of about 2,350 m3 in pyrrhotite and 5,900 m3 for Pd in pentlandite. LAM analyses were performed with a focused, 266-nm laser beam fired at 0.3 mJ/ pulse and 10 Hz, resulting in 35–40 m spots and analyzed volumes of about 85,000 m3. Fused pyrrhotite standards separately doped with Pd, Ru, and Rh were synthesized for LAM–ICP–MS, and calibrated against sintered pyrrhotite PGE standards of Ballhaus & Sylvester (2000). The level of Pd, Ru and Rh varies by ~4 to 9 % (1) in the fused pyrrhotite standards at a 50-m sampling scale. The LAM and micro-PIXE results for the natural sulfides are quite comparable, with the large majority of determinations falling within 33 % of each other for both Pd and Rh on the same spot. This agreement is considered encouraging for use of the LAM–ICP–MS for trace PGE analysis, considering the large differences in volumes analyzed, and in probable