高温密闭溶样电感耦合等离子体质谱准确测定辉钼矿铼-锇地质年龄

Highly Precise Re-Os Dating of Molybdenite by ICP-MS with Carius Tube Sample Digestion

采用Carius管高温密闭溶样,电感耦合等离子体质谱(ICP MS)法对采自两个不同金属矿床的辉钼矿样品的Re Os同位素地质年龄进行了准确测定。所得出的Re Os年龄的平均值分别为14.26±0.19Ma和34.39±0.81Ma,相对标准偏差分别为1.3%(以2s计算,n=6)和2.4%(以2s计算,n=7)。采用国际通用的ISOPLOT软件按Model1模式对这两组样品分别进行处理,所得Re Os等时线年龄分别为14.32±0.46Ma和34.52±0.38Ma(均为95%置信水平)。同批次样品中所带的内部管理样JDC的Re Os年龄与国际先进实验室采用负离子热表面电离质谱测量所得的结果吻合也较好。说明在严格的质量体系保证及有效地降低实验室空白水平的前提下,ICP MS完全可以准确地测定辉钼矿的Re Os年龄。

ReOs age of two groups of molybdenite samples from two different areas were highly precise analyzed using the technique of Carius tube digestion and ICPMS determination. The average ReOs ages of the samples are 14.26±0.19 Ma and 34.39±0.81 Ma with the RSD are 1.3%(2s,n=6)and 2.4%(2s,n=7) respectively. The isochrone ages are 14.32±0.46 Ma(95% conf. limit)and 34.52±0.38 Ma(95% conf. limit)respectively when they are calculated with the ISO PLOT using the Model 1fit. The ReOs age of the monitoring sample JDC is also perfectly agree with the reference value. All results show that the highly precise and accurate ReOs age of molybdenite sample can be obtained using ICPMS when all the sample pretreatment steps are careful and strict controlled to effectively decrease the total blanks of Re and Os.