| 富有机物流体中一些重要Ge同位素的平衡分馏参数 |
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| 引用本文： | 李雪芳,唐茂,刘耘.富有机物流体中一些重要Ge同位素的平衡分馏参数[J].地球化学,2009,38(3):299-306. |
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| 作者姓名： | 李雪芳 唐茂 刘耘 |
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| 作者单位： | 中国科学院,地球化学研究所,矿床地球化学国家莺点实验室,贵州,贵阳,550002 |
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| 摘 要： | 锗（Ge）同位素在地球化学领域有着潜在的应用意义，但是Ge同位素平衡分馏参数的缺乏，严重制约了其在相关研究中的应用。本研究提供了富有机物流体中物种Ge（OH）4、GeO（OH）3^-以及Ge的一些亲有机质络合物（Ge与邻苯二酚、柠檬酸以及草酸配合形成的络合物）之间的Ge同位素平衡分馏参数。用基于Urey模型（或称Bigeleisen-Mayer公式）理论，结合量子化学计算的方法，在B3LYP／6-311＋G（d，p）理论水平下计算了这些Ge同位素平衡分馏系数，其中，溶液效应用精确的“水滴法”来处理。预测这些基本分馏参数的误差约为±0．2‰。纯水溶液中，△Ge（OH）4-GeO（OH）3^-约为0．6‰，海水中稍小，约为0．3‰；而△Ge（OH）4-Ge-邻苯二酚、△Ge（OH）4-Ge-草酸、△Ge（OH）4-Ge-柠檬酸（c）和△Ge（OH）4-Ge柠檬酸（d）非常大，分别约为4．4‰、3．5‰、3．8‰和3．9‰。这些大的分馏或许可以用来示踪生物作用参与过程。结果表明，轻的Ge同位素将富集在富有机质的环境，如煤系、黑色页岩及一些缺氧的条件下，因此这些环境可能存在一个轻Ge同位素的“汇”。
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| 关 键 词： | Ge同位素 Ge(OH)4 GeO(OH)3- 有机物 Urey模型 量子化学计算 |
Some important Ge isotope equilibrium fractionation coefficients in organic-rich fluids |
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| LI Xue-fang,TANG Mao,LIU Yun.Some important Ge isotope equilibrium fractionation coefficients in organic-rich fluids[J].Geochimica,2009,38(3):299-306. |
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| Authors: | LI Xue-fang TANG Mao LIU Yun |
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| Institution: | ( State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China ) |
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| Abstract: | Germanium （Ge） isotope has a great potential that has not been well recognized in the field of geochemistry. Our ability to explore the unknown world for Ge isotope, however, has been severely limited by the lack of the basic isotope fractionation parameters. In this study, we provided some important Ge isotope equilibrium fractionation coefficients between the dominant Ge （OH）4, GeO（OH）3^- species in solutions and several Ge-bearing organic complexes （including Ge-catechol, Ge-oxalic acid, and Ge-citric acid） in organic-rich fluids, based on the Urey model （or Bigeleisen and Mayer equation） and the quantum chemistry calculations. The calculations were made using Gaussian03 at the B3LYP/6-311 ＋ G（d, p） level. Solvent effect was modeled using the ＂water droplet＂ method. The accuracy of the parameters are estimated to be around 0. 2%0. The △Ge（OH）4-GeO（OH）3^- is 0. 6‰ in pure water, and is slightly lower （about 0. 3‰） in sea water. In comparison, the △Ge（OH）4-Ge-catechol,△Ge（OH）4-Ge-oxalic acid, △Ge（OH）4-Ge-citric acid（c） and △Ge（OH）4-Ge-citric acid（d） are much larger, around 4. 4‰, 3.5‰, 3.7‰ and 3.9‰, respectively. The large fractionations might suggest a new way to distinguish the possible bio-interference process. Furthermore, our calculations indicated that light Ge isotopes should be enriched in organic-rich environments like the coal-bearing series and blank shale series formed under anoxic conditions, therefore such environments might represent a reservoir of light Ge isotopes. |
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| Keywords: | Ge(OH)4 GeO(OH)3- |
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