Re-Os同位素稀释N-TIMS测定计算方法

N-TIMS measurement and calculation method for Re-Os isotopes

为了更好地实现Re-Os同位素实验室之间数据比对,本实验室在了解国内外部分实验室的数据处理方法的基础上,提出了本实验室的N-TIMS Re、Os同位素计算方法。本文所涉及到的Re、Os同位素计算方法包括氧同位素干扰校正、Re同位素比值和含量计算、Os同位素测定质量分馏校正方法、三峰法和全峰法Os同位素比值和含量计算、测定结果的不确定度、Isoplot作图基本参数介绍和相关系数Rho的计算。对于辉钼矿和普通Os信号弱(^(187)Os/^(188)Os>2000)的样品适合采用三峰法计算Os同位素比值,普通Os信号强(^(187)Os/^(188)Os<2000)的样品应该采用全峰法计算同位素比值。在全峰法计算中,按照指数分馏规律以迭代计算方式校正Os同位素比值的质量分馏,采用5iso方法进行样品中Os和稀释剂中Os的摩尔比(N_(5iso)/S)_(Os)的计算。

For better comparing the data from different Re-Os isotope laboratories, the new calculation method for N-TIMS Re-Os determination is proposed with referencing to the data processing methods used by several laboratories at home and abroad. The new calculation involves the oxygen isotope interference correction for Re and Os, the isotope ratio and content calculations for Re, the mass fractionation correction for Os isotope, the isotope ratio and content calculations using the threepeaks method or all-peaks method for Os, the uncertainty evaluations, and the calculation of Isoplot input data including the correlation in the uncertainties （Rho）. The Os isotope ratio and content calculations using the three-peaks method are applicable to molybdenite and some other samples with weak common Os signals （187Os/188Os 〉 2000）, and the all-peaks method is applicable to the samples with intense common Os signals （187Os/188Os 〈 2000）. The latter employs the iterative calculation to correct the Os isotope mass fractionation according to the index law, and then the 5ios method is used to calculate the ratio between Os in the sample and that in the spike （（N5iso/S）Os）.