EGU21-3318, updated on 03 Mar 2021
https://doi.org/10.5194/egusphere-egu21-3318
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The effect of the trisulfur radical ion on molybdenum transport by hydrothermal fluids

Maria A. Kokh1,2, Clement Laskar2, and Gleb S. Pokrovski2
Maria A. Kokh et al.
  • 1Institut für Geowissenschaften, Universität Potsdam, 14476 Potsdam, Germany
  • 2Experimental Geosciences Group (GeoExp), Géosciences Environnement Toulouse (GET), Université de Toulouse, CNRS, IRD, F-31400 Toulouse, France

Knowledge of molybdenum (Mo) speciation under hydrothermal conditions is a key for understanding the formation of porphyry deposits which are the primary source of Mo. Existing experimental and theoretical studies have revealed a complex speciation, solubility and partitioning behavior of Mo in fluid-vapor-melt systems, depending on conditions, with the (hydrogen)molybdate (HMoO4-, MoO42-) ions and their ion pairs with alkalis in S and Cl-poor fluids [1-3], mixed oxy-chloride species in strongly acidic saline fluids [4, 5], and (hydrogen)sulfide complexes (especially, MoS42-) in reduced H2S-bearing fluids and vapors [6-8]. However, these available data yet remain discrepant and are unable to account for the observed massive transport of Mo in porphyry-related fluids revealed by fluid inclusion analyses demonstrating 100s ppm of Mo (e.g., [9]). A potential missing ligand for Mo may be the recently discovered trisulfur radical ion (S3•-), which is predicted to be abundant in sulfate-sulfide rich acidic-to-neutral porphyry-like fluids [10]. We performed exploratory experiments of MoS2 solubility in model sulfate-sulfide-S3•--bearing aqueous solutions at 300°C and 450 bar. We demonstrate that Mo can be efficiently transported by S3•--bearing fluids at concentrations ranging from several 10s ppm to 100s ppm, depending on the fluid pH and redox, whereas the available data on OH-Cl-S complexes cited above predict negligibly small (<100 ppb) Mo concentrations at our conditions. Work is in progress to extend the experiments to wider T-P-composition range of porphyry fluids and to quantitatively assess the role of S3•- in Mo transport by geological fluids.

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How to cite: Kokh, M. A., Laskar, C., and Pokrovski, G. S.: The effect of the trisulfur radical ion on molybdenum transport by hydrothermal fluids, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3318, https://doi.org/10.5194/egusphere-egu21-3318, 2021.

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