The ReOs isotope system can directly date sulphide formation, making it useful for ore deposit studies. Recent work has demonstrated that laser ablation inductively coupled tandem mass spectrometry (LA-ICP-MS/MS) can be used to effectively separate 187Re from 187Os during analysis by reacting Os with CH4 gas, allowing for in situ ReOs age determination of molybdenite. However, the age calculation often requires a significant interference correction of 187ReCH2+ on 187OsCH2+. Here, we demonstrate that N2O gas is a viable alternative reaction gas for in situ ReOs geochronology. In this new method, Os forms a tetra-oxide complex, while Re shows very low reactivity with the N2O reaction gas (∼0.15 %), reducing the isobaric interference correction requirement relative to the CH4 method. We compare results from both reaction gases across a range of molybdenite samples of different ages (spanning ca. 1700–300 Ma), demonstrating that the N2O method achieves greater precision and accuracy for young molybdenite samples (ca. 300 Ma) compared to CH4. In addition, we demonstrate that in situ ReOs is capable of dating high-Re pyrite (i.e., >10 ppm).

中文翻译：

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LA-ICP-Q-MS/MS Re[sbnd]Os 地质年代学：N2O 和 CH4 反应气体的比较


ReOs 同位素系统可以直接测定硫化物形成的年代，使其可用于矿床研究。最近的工作表明，激光烧蚀电感耦合串联质谱法 （LA-ICP-MS/MS） 可用于在分析过程中通过将 Os 与 CH4 气体反应来有效地分离 187Re 和 187O，从而允许原位测定辉钼矿的 ReOs 年龄。然而，年龄计算通常需要对 187OsCH2+ 进行 187ReCH2+ 的显著干扰校正。在这里，我们证明了 N2O 气体是原位 ReOs 地质年代学的可行替代反应气体。在这种新方法中，Os 形成四氧化物络合物，而 Re 与 N2O 反应气体的反应性非常低 （∼0.15 %），相对于 CH4 方法，降低了同量异位干涉校正要求。我们比较了一系列不同年龄（跨度约为 1700-300 马）的辉钼酸盐样品中两种反应气体的结果，表明与 CH4 相比，N2O 方法对年轻的辉钼酸盐样品（约 300 马）具有更高的精度和准确度。此外，我们证明原位 ReOs 能够测定高 Re 黄铁矿（即 >10 ppm）的年代。