High-precise Determination of Osmium Isotopic Ratio in the Jinchuan Copper-Nickel Sulfide Ore Samples

The ratio of 187Os/188Os determination in copper-nickel-sulfide ore samples from Jinchuan, China was carried out in 4 laboratories, including AIRIE of Colorado state university USA and other 3 Chinese laboratories, using 2 separate 190Os spikes and 4 different chemical processes. ICP-MS, TRITON and MAT-262 instruments were used for the measurements. 56 samples were determined with the results of 0.3356±0.0018（n=12, 2s）, 0.3363±0.0008（n=6, 2s）, 0.3363±0.0010（n=18, 2s） and 0.3353±0.0034（n=20,2s） from 4 different laboratories respectively. The weighted average value for 56 data was calculated using ISOPLOT software with result of 0.33602±0.00022 (confidence 95%). The results from two TRITON instruments are in good agreement with higher precision than those from ICP-MS and MAT-262 instruments. Two different digestion techniques (alkali fusion and Carius tube dissolution) were also compared. The results show that Carius tube acid digestion technique is feasible for completely digestion of all Os-bearing mineral phases and is suitable for 187Os/188Os ratio determination in copper-nickel-sulfide ore samples from Jinchuan, China.