铷锶同位素年龄标准物质的研制

An Investigation on the Mineral Standard Reference Material for Rb-Sr Dating

本文报导了铷锶同位素年龄标准物质的研制结果。文中叙述了本标准物质的样品选择、采集、加工、均匀性检查、定值分析及对测定数据的统计学检验等内容。根据国内9个实验室的定值分析结果求出了本标准物质三项特征量值的最佳估计值和不确定度,提出了推荐值。文中还介绍了对本标准物质的国际验证数据和经过一年多对本标准物质稳定性检查的结果。

A mineral standard reference material, potassium feldspar, is established for the Rb-Sr dating and the trace rubidium and strontium determination. The sample is collected from a pegmatite in the Huangling granite of about 800 Ma in age. The sample is carefully selected and cleaned before and during the sample preparation. The sample is sieved to less than 200 mesh. After sufficiently stirring to make the sample homogeneous, the sample is split into units with about 10 grams in weight and stored in glass bottles with plastic covers. About 3×3n1/2 of the total amount of sample bottles are analysed to examine the homogeneity of Rb and Sr concentration and 87Sr/86Sr ratio in the samples. Based on the statistical estimate of analytical data, all the F values of Rb and Sr and 87Sr/86Sr are smaller than the respective critical F value and a good homogeneity of the sample is concluded. Based on the data duplicately measured by nine laboratories on the prepared material, the certificate values for three quantities of the sample are concluded as follows(95% confidence level). Rb-249.47±1.04 ppm, Sr-158.92±0.70 ppm; 87Sr/86Sr-0.75999±0.00020 ppm. The BMR of Australia and Geological Survey of Japan also provided duplicated data on one of the sample units and the results are in agreement with our data within analytical error.