碳酸盐岩Sr同位素比值的选择性溶解及测定技术

THE SELECTIVE DISSOLUTION AND DETERMINATION TECHNIQUE FOR Sr ISOTOPIC RATIOS IN CARBONATE ROCKS

传统的碳酸盐岩的Sr同位素比值测定由于采用盐酸溶样 ,虽然具有溶解迅速的优点 ,但同时也使非碳酸盐组分被溶解而往往导致测定值偏高 ,同时也增加了Sr分离与纯化的难度。因此 ,我们考虑用弱酸来溶解碳酸盐岩矿样 ,以改进传统方法的不足。实验中采用醋酸作为溶解介质 ,对比了不同浓度的醋酸的溶解效果 ,对较难溶解的白云岩样品作了弱酸溶解实验 ,同时比较了 2 .5mol/L盐酸和 4mol/L醋酸溶样后的测定结果和测定精度。实验结果表明碳酸盐岩Sr同位素的选择性测定技术可以使溶解对象局限于样品中的目标组分———碳酸盐岩 ,防止样品中的非碳酸盐岩组分的溶解 ,避免过多的杂质进入溶解液 ,使碳酸盐岩中的微量元素———Sr(通常含量在 10 4 — 10 5范围内 )的同位素比值测定趋于准确和可靠 ,同时也减少了杂质元素的干扰 ,便于Sr的分离与纯化。

This paper presents an experimental method used to determine the ratios of strontium (Sr) isotopes in carbonate rocks. The traditional method often gives the ratio greater than its true value. The selective determination technique for Sr isotopes in carbonate minerals is a new method using weak acid. HAc is used to dissolve samples in experiment, and its dissolving ability is limited, so only cabonate can be dissolved while non_carbonate cannot be dissolved. The research includes: selecting the best data on concentration, temperature and time of dissolving medium (HAc); comparing the effects by 2.5 mol/L HCl and 4 mol/L HAc. The experiment indicates the selective determination techniques can prevent non_carbonate from being dissolved, and prevent so many impurities from entering into the solution, so the purity of Sr is raised, so accurate ratio of Sr in carbonate minerals can be obtained. The method is available and reliable.