Complexation of gold in S3--rich hydrothermal fluids: Evidence from ab-initio molecular dynamics simulations
Complexation of gold in S3--rich hydrothermal fluids: Evidence from ab-initio molecular dynamics simulations
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DOI：
10.1016/j.chemgeo.2013.03.019
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发表时间：
2013-06
期刊：
影响因子：
3.9
通讯作者：
Y. Mei;D. Sherman;Weihua Liu;J. Brugger
中科院分区：
文献类型：
--
作者：
Y. Mei;D. Sherman;Weihua Liu;J. Brugger
最近的拉曼光谱研究表明，S3−是岩浆热液和变质流体中重要的硫种，温度为0.5GPa，温度为250°C，可能是金属输运的重要配体（Pokrovski和Dubrovinsky， 2011）。基于静态密度泛函理论计算，Tossell（2012）证实了S3−离子的稳定性，并提出了理想气相和水溶液中可能存在的cu - s3配合物。我们通过从头算分子动力学（MD）模拟研究了Au和S3−在水溶液中的络合作用。我们在300°C、0.5和2GPa的水溶液中进行了从头算MD模拟，研究了S3−、HS−、H2S（aq）、OH−和H2O配体对Au+的竞争，旨在评估“外来”S3−配体对Au成矿的意义。结果表明，与静态计算结果相反，Au+与S3−形成线性配合物，而Au+与S3−形成对称的双齿结构。这些配合物的化学计量取决于pH值和流体组成(例如Au(H2O)S3(aq)；非盟(HS) S3−;非盟(OH) S3−;非盟(S3) 2−)。S3 -和二硫化物（HS -）离子是具有相似强度的Au+配体；这证实了Pokrovski和Dubrovinsky（2011）的假设，即这种“外来”配体可能在岩浆和变质环境中促进金的流动性方面发挥重要作用。
Recent Raman spectroscopic studies suggest that S3−is an important sulfur species in magmatic hydrothermal and metamorphic fluids at P>0.5GPa and T>250°C, and may be an important ligand for metal transport (Pokrovski and Dubrovinsky, 2011). Based on static Density Functional Theory calculations, Tossell (2012) confirmed the stability of the S3−ion, and suggested some possible Cu–S3complexes in the ideal gas phase and in aqueous solution. We investigated the complexation of Au and S3−in aqueous fluids by ab-initio molecular dynamics (MD) simulations. We performed ab-initio MD simulations in aqueous solution at 300°C, 0.5 and 2GPa to investigate the competition among the S3−, HS−, H2S(aq), OH−and H2O ligands for Au+, aiming at evaluating the significance of the ‘exotic’ S3−ligand for Au metallogenesis. The results indicate that, in contrast to results of static calculations that show a symmetric Au–S3complex with bidentate structure, Au+forms linear complexes with S3−. The stoichiometry of these complexes depends on pH and fluid composition (e.g., Au(H2O)S3(aq); Au(HS)S3−; Au(OH)S3−; Au(S3)2−). The S3−and bisulfide (HS−) ions are ligands of similar strength for Au+; this confirms Pokrovski and Dubrovinsky's (2011) assumption that such ‘exotic’ ligands may play a major role in promoting Au mobility in magmatic and metamorphic environments.