The role of sulfur in molybdenum transport in hydrothermal fluids: Insight from in situ synchrotron XAS experiments and molecular dynamics simulations

Stability and structure of platinum sulfide complexes in hydrothermal fluids

“…Furthermore, similar stoichiometries and structures were found in model hydrothermal fluids for Pt II Cl 4 2-, which may be the major Pt chloride complex in saline sulfur-free hydrothermal-magmatic fluids (Tagirov et al, 2019), as well as for the analogous Pd II (HS) 4 2predicted using FPMD to be the most stable among Pd II -HS complexes (Mei et al, 2015a), and for Pd II Cl 4 2shown to be stable in highly saline S-free solutions at moderate temperatures (Bazarkina et al, 2013;Tagirov et al, 2014). The formation of doubly charged chalcophile metal complexes, coordinated with S ligands was also demonstrated for Mo VI S 4 2- (Liu et al, 2020), and Pt II (HS) 2 (S 3 ) 2 2and Pt IV (HS) 3 (S 3 ) 2 2- (Pokrovski et al, 2021). The stability of such complexes, at least at temperatures below 350 °C in liquid-like density fluids, is in line both with the high chemical affinity of the metal for reduced sulfur and with the relatively high dielectric constant of aqueous solution at such temperatures (>10) stabilizing negatively charged species (e.g., Brimhall and Crerar, 1987).…”

Exploring Platinum Speciation with X-ray Absorption Spectroscopy under High-Energy Resolution Fluorescence Detection Mode

“…These results demonstrate the much larger influence of S 0 2 than σ 2 on the determination of coordination numbers, at least for EXAFS spectra with comparable signal-to-noise ratios at relatively low k values (<10 Å −1 , Figure 7). More generally, the necessity of the S 0 2 value correctly calibrated in the right mode may be particularly crucial when determining ligand coordination numbers in a mixture of aqueous complexes from EXAFS data, for example, in the case of Pd-O/Cl complexes [14] or Mo-O/S complexes [102]. Note that, an error of 0.2 in S 0 2 would lead to an error of 0.4 to 0.8 sulfur atoms for the average number of HS − ligands around Pt in an aqueous solution containing Pt(HS) 2 0 , Pt(HS) 3 − , and Pt(HS) 4 2− complexes, making it difficult to identify the major solubility-controlling complex [96].…”

Molybdenum Disorder in Hydrated Sedovite, Ideally U(MoO4)2·nH2O, a Microporous Nanocrystalline Mineral Characterized by Three-Dimensional Electron Diffraction, Density Functional Theory Computations, and Complexity Analysis

“…Uranyl molybdates are not so scarce in nature (e.g., Krivovichev and Plaśǐl 2013;Steciuk et al, 2019). However, except for some knowledge about the transport of Mo in hydrothermal fluids, 60 the knowledge on the mobility and behavior of Mo under the low temperature is missing. Therefore, a more extensive study of the behavior of Mo 6+ in natural conditions is necessary for understanding the formation of supergene U-deposits.…”