Abstract Strontium isotope stratigraphy (SIS) is widely used in geoscience as a chemo-stratigraphic tracer. In past SIS research, diverse sample dissolution methods have been developed and applied to bulk carbonate rocks to extract target Sr isotope signatures of primary carbonates, which are easily contaminated with Sr from extraneous phases. However, the accuracy of the various dissolution methods is debated because all carbonate materials in previous studies were collected directly from the field and did not undergo strict homogeneity examination before sample dissolution. To verify and evaluate the actual bias for carbonate in SIS research, in this study, we analysed a set of artificial carbonate mixed standard samples including carbonate certificate reference materials (CRMs) GBW03105a for limestone and JDo-1 for dolostone in addition to that for clay minerals, GBW03103. These samples were verified to be stable in their Sr concentrations and 87Sr/86Sr ratios and could be used as benchmarks to enable reasonable evaluation on the extraction method for carbonate materials. We conducted a subtle chemical leaching experiment with 12 steps on these samples after preleaching by ammonium acetate. Our results show that the acidic preleach is useful in diminishing the Sr contamination from the extraneous phases. Nevertheless, the Sr contamination from the clay mineral can not be completely removed by the chemical leaching method and it would be more substantial for carbonate samples with lower purity and relatively lower original 87Sr/86Sr. Our work suggests an optimised dissolution scheme for carbonate 87Sr/86Sr analysis: (1) an acidic preleach to dissolve about ~60% of the sample, (2) a further dissolution of ~20% of the sample to prepare for the 87Sr/86Sr analysis, (3) leaving at least 10% of the sample undissolved. A simplified dissolution protocol with advantage of rapid operational and relatively-high reliability was finally proposed for strontium isotope stratigraphy research, particularly for reconstruction of secular Sr isotope evolution curve.

中文翻译：

---

基于碳酸盐标准物质化学浸出的锶同位素地层溶解方法再评价与优化

摘要 锶同位素地层学（SIS）作为化学地层示踪剂被广泛应用于地球科学。在过去的 SIS 研究中，已经开发了多种样品溶解方法并将其应用于大块碳酸盐岩，以提取原生碳酸盐的目标 Sr 同位素特征，这些原始碳酸盐很容易被外来相中的 Sr 污染。然而，各种溶解方法的准确性存在争议，因为之前研究中的所有碳酸盐材料都是直接从现场收集的，并且在样品溶解前没有经过严格的均匀性检查。为了验证和评估 SIS 研究中碳酸盐的实际偏差，在本研究中，我们分析了一组人造碳酸盐混合标准样品，包括用于石灰石的碳酸盐证书参考材料 (CRM) GBW03105a 和用于白云岩的 JDo-1，以及用于粘土矿物的 GBW03103。这些样品经证实在其 Sr 浓度和 87Sr/86Sr 比率方面是稳定的，可用作基准，以便对碳酸盐材料的提取方法进行合理评估。在用醋酸铵预浸后，我们对这些样品进行了 12 个步骤的精细化学浸出实验。我们的结果表明，酸性预浸可用于减少来自外来相的 Sr 污染。尽管如此，粘土矿物中的 Sr 污染不能通过化学浸出法完全去除，对于纯度较低和原始 87Sr/86Sr 相对较低的碳酸盐样品，它会更严重。我们的工作提出了用于碳酸盐 87Sr/86Sr 分析的优化溶解方案：(1) 酸性预浸以溶解约 60% 的样品，(2) 进一步溶解约 20% 的样品以准备 87Sr/86Sr分析，(3) 留下至少 10% 的样品未溶解。最终提出了一种简化的溶出方案，该方案具有操作快速和可靠性较高的优点，用于锶同位素地层研究，特别是用于重建长期的 Sr 同位素演化曲线。(1) 酸性预浸以溶解约 60% 的样品，(2) 进一步溶解约 20% 的样品以准备 87Sr/86Sr 分析，(3) 留下至少 10% 的样品未溶解. 最终提出了一种简化的溶出方案，该方案具有操作快速和可靠性较高的优点，用于锶同位素地层研究，特别是用于重建长期的 Sr 同位素演化曲线。(1) 酸性预浸以溶解约 60% 的样品，(2) 进一步溶解约 20% 的样品以准备 87Sr/86Sr 分析，(3) 留下至少 10% 的样品未溶解. 最终提出了一种简化的溶出方案，该方案具有操作快速和可靠性较高的优点，用于锶同位素地层研究，特别是用于重建长期的 Sr 同位素演化曲线。