Effective Leaching of Argillaceous and Dolomitic Carbonate Rocks for Strontium Isotope Stratigraphy
Effective Leaching of Argillaceous and Dolomitic Carbonate Rocks for Strontium Isotope Stratigraphy
复制标题
用于锶同位素地层学的泥质和白云质碳酸盐岩石的有效浸出
DOI：
10.1111/ggr.12531
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发表时间：
2023
影响因子：
3.8
通讯作者：
Chen X
中科院分区：
文献类型：
--
作者：
Chen X
从碳酸盐岩中提取原始海水锶同位素信号用于锶同位素地层学研究的方法很多。然而，由于不同的样品纯度和矿物学，关于最佳方法几乎没有共识。在这项研究中，我们采用了顺序浸出的岩石样品范围，以探讨锶同位素浸出系统的不太有利的泥质和灰岩样品。在乙酸铵（NH 4Ac）预洗去除约10%的碳酸盐部分后，随后的稀乙酸浸出（10-30%等分试样）显示出提取最低的、明显变化最小的海水87 Sr/86 Sr同位素比，沿着在大多数情况下具有最高Y/Ho比（大多数> 36）的海水样稀土元素（REE）加钇（Y）模式。随后的溶解步骤表现出显着升高的87 Sr/86 Sr同位素比值，Rb/Sr，Al/Ca和Mg/Ca比值，表明更大的贡献，从铝硅酸盐和白云石的浸出液。新的溶解方法，通过比较显着增加的可能性，获得主要海水87 Sr/86 Sr同位素比值从泥质和灰岩的其他既定程序失败。广泛应用这种方法可以提高海水锶同位素曲线的时间分辨率，特别是在高纯度石灰岩样品稀缺。
Various methods have been developed to extract a primary seawater Sr isotope signal from carbonate rocks for strontium isotope stratigraphy. However, there is little consensus around the best method due to variable sample purity and mineralogy. For this study, we applied sequential leaching to a range of rock samples in order to explore strontium isotope leaching systematics of less favoured argillaceous and dolomitic limestone samples. Following an ammonium acetate (NH4Ac) prewash that removed ~ 10% of the carbonate fraction, a subsequent dilute acetic acid leach (10–30% aliquot) was shown to extract the lowest, demonstrably least altered seawater87Sr/86Sr isotope ratios, along with in most cases seawater‐like rare earth element (REE) plus yttrium (Y) patterns with the highest Y/Ho ratios (mostly > 36). Subsequent dissolution steps exhibited significantly elevated87Sr/86Sr isotope ratios, Rb/Sr, Al/Ca and Mg/Ca ratios, indicating greater contributions from aluminosilicates and dolomite in the leachates. The new dissolution method by comparison significantly increases the likelihood of obtaining primary seawater87Sr/86Sr isotope ratios from argillaceous and dolomitic limestones where the other established procedures failed. Broad application of this approach could improve the temporal resolution of the seawater Sr isotope curve, especially where high purity limestone samples are scarce.