کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6436948 | 1637621 | 2013 | 9 صفحه PDF | دانلود رایگان |
- Ab-initio molecular dynamics (MD) simulations of Au-S3â complexing
- Family of linear complexes as a function of S speciation and pH
- The affinity of the S3â ion for Au+ is similar to that of HSâ (300 °C, 0.5-2 MPa).
- The stability of S3â will increase Au mobility and modify Au solubility gradients.
Recent Raman spectroscopic studies suggest that S3â is an important sulfur species in magmatic hydrothermal and metamorphic fluids at P > 0.5 GPa 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 S3â ion, and suggested some possible Cu-S3 complexes in the ideal gas phase and in aqueous solution. We investigated the complexation of Au and S3â 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 2 GPa to investigate the competition among the S3â, HSâ, H2S(aq), OHâ and H2O ligands for Au+, aiming at evaluating the significance of the 'exotic' S3â ligand for Au metallogenesis. The results indicate that, in contrast to results of static calculations that show a symmetric Au-S3 complex with bidentate structure, Au+ forms linear complexes with S3â. The stoichiometry of these complexes depends on pH and fluid composition (e.g., Au(H2O)S3(aq); Au(HS)S3â; Au(OH)S3â; Au(S3)2â). The S3â and bisulfide (HSâ) 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.
Journal: Chemical Geology - Volume 347, 6 June 2013, Pages 34-42