Abstract
The transportation of W in aqueous gas-phases at and above 500°C is examined using thermodynamic data. The transport of W is possible as fluoride and oxifluoride. The deposition of wolframite continues with decreasing temperature and pressure. The stabilities of wolframates in hydrothermal solutions are examined for temperatures up to 300°C with Eh-pH-diagrams, exchange reactions of wolframite with oxides, sulfides and dissolved ions. Fe 2WO 6 becomes stable against Fe 2O 3 + WO 3 above 126°C. At 300°C its range of stability begins at high pO 2 which is not realised in hydrothennal endogenous solutions. In consequence of the very low Gibbs energies of MgWO 4, CaWO 4 and BaWO 4, the minerals MgWO 4 and BaWO 4 should be more important than wolframite, if Mg and Ba coexist in solution together with W. Co and Ni also should be found as trace elements in wolframite, if Co and Ni were in solution in sufficiently high concentrations together with W.
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