Zn/Cd ratios and cadmium isotope evidence for the classification of lead-zinc deposits.
Zn/Cd ratios and cadmium isotope evidence for the classification of lead-zinc deposits.
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DOI：
10.1038/srep25273
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发表时间：
2016-04-28
影响因子：
4.6
通讯作者：
Fu S
中科院分区：
文献类型：
--
作者：
Wen H;Zhu C;Zhang Y;Cloquet C;Fan H;Fu S
铅锌矿床往往很难分类，因为缺乏明确的标准。近年来，新的工具，如镉和锌同位素，已被用来更好地了解成矿过程和铅锌矿床分类。本文研究了9个铅锌矿床中闪锌矿的Cd含量、Cd同位素系统学和Zn/Cd比值，斑岩），低温系统（例如，密西西比河谷型[MVT]）和呼气系统（例如，沉积喷流[SEDEX]）。我们的研究结果表明，在高温系统分馏的证据很少。在低温系统中，镉的浓度是最高的，但也是高度可变的，结果与较高的分馏镉在低温下。低温体系的δ114/110 Cd值富集较重的同位素（平均值为0.32 ± 0.31‰）。结果表明，大气中Cd的δ114/110 Cd值最低，为0.12 ± 0.50‰;因此，我们得出结论，不同的成矿系统导致不同的特征镉浓度和馏分水平和低温过程导致最显着的分馏镉。因此，Cd的分布和同位素研究可以更好地理解成矿作用的地球化学和铅锌矿床的分类。
Lead-zinc deposits are often difficult to classify because clear criteria are lacking. In recent years, new tools, such as Cd and Zn isotopes, have been used to better understand the ore-formation processes and to classify Pb-Zn deposits. Herein, we investigate Cd concentrations, Cd isotope systematics and Zn/Cd ratios in sphalerite from nine Pb-Zn deposits divided into high-temperature systems (e.g., porphyry), low-temperature systems (e.g., Mississippi Valley type [MVT]) and exhalative systems (e.g., sedimentary exhalative [SEDEX]). Our results showed little evidence of fractionation in the high-temperature systems. In the low-temperature systems, Cd concentrations were the highest, but were also highly variable, a result consistent with the higher fractionation of Cd at low temperatures. The δ114/110Cd values in low-temperature systems were enriched in heavier isotopes (mean of 0.32 ± 0.31‰). Exhalative systems had the lowest Cd concentrations, with a mean δ114/110Cd value of 0.12 ± 0.50‰. We thus conclude that different ore-formation systems result in different characteristic Cd concentrations and fraction levels and that low-temperature processes lead to the most significant fractionation of Cd. Therefore, Cd distribution and isotopic studies can support better understanding of the geochemistry of ore-formation processes and the classification of Pb-Zn deposits.