High-precision Measurement for the Concentration and Isotopic Composition of Rhenium and Osmium in Micro-amount of Geological Samples

This paper presents the methods for determinations of Os content and measurement of Os isotopic ratios of geological samples by a new thermal ionization mass spectrometer(TIMS,IsoProbe-T) and determination of Re content by Neptune Multi-collector Inductively Coupled Plasma Mass Spectrometer(MC-ICPMS).Samples were digested using Carius tube method.The Savillex Teflonware distillation and micro-distillation methods were used for Os separation and anion exchange method for Re separation.Measurement of Os isotopic ratios by IsoProbe-T mass spectrometer provides advantages of high sensitivity and high precision.When Os standard solution(containing 0.2 ng Os) is measured,the signal intensity of 192Os16O-3 can reach to 100 mV and last for about 20 minutes with precision of better than 0.1%RSD for 187Os/188Os.By combination of the Re-Os chemical separation procedure presented in this study with high-precision TIMS determination,PGE standard reference peridotite(WPR-1) has been analyzed with satisfactory results.