New Mexico Geological Society Annual Spring Meeting — Abstracts

Tellurium is a critical mineral of increasing importance in green energy technologies. Numerical simulations using previous thermodynamic data predict up to ~0.1 ppm in epithermal vapor with H₂Te(g) as the dominant vapor species [1]. However, fluid inclusion studies show up to hundreds of ppm Te in vapor inclusions from epithermal ore deposits [2]. In this study, we measured experimentally the solubility of tellurium in hydrothermal vapors to determine the hydrated tellurium speciation in water vapor. Hydration is the effect of water vapor molecules binding to a metal, greatly increasing its solubility [3]. Experiments were conducted in batch-type Ti Parr reactors at 250°C and a range of water vapor pressures (P_H2O) using several different oxygen buffers (e.g., MoO₂-MoO₃, WO₂-WO₃ and Ni-NiO). Kinetic experiments were conducted between 1-25 days at 250°C and 20 bar and at different redox conditions. At oxidizing conditions, equilibrium conditions were reached after ~10 days with 1.33 ±0.01 ppm dissolved Te, whereas in N₂-degassed experiments equilibrium was reached after ~22 days with 0.669 ±0.004 ppm dissolved Te, indicating slower reaction kinetics and reduced solubility at lower redox conditions. Experiments at 250°C and logfO₂ of -24 (MoO₂-MoO₃ buffer), show increasing Te solubility with increasing P_H2O ranging from 1-3 ppm between 15-25 bar to 12.27±0.01 ppm Te at 35 bar. The MoO₂-MoO₃ buffered experiments overlap in concentrations with results from the kinetic series at oxidizing conditions. Experiments at 250°C and logfO₂ of -39.37 (WO₂-WO₃ buffer), show an increase in Te solubility between 15-35 bar from 14.51 ppm up to 15.45±0.01 ppm. Previous experimental work has shown enhanced solubility of TeO₂ in water vapor due to the formation of TeO₂*xH₂O with x = 1 and 2 [1,4-5], whereas in this study Te shows higher hydration numbers similar to other metals [3]. Our results demonstrate the significant role of P_H2O on Tesolubility in low density fluids as wellas a strong redox control based on results from the WO₂-WO₃ buffered experiment. The experimental data generated can be applied in thermodynamic models to discern tellurium mobility in hydrothermal systems.

References:

1. [1] Grundler et al., (2013) Geochim. et Cosmochim. Acta120, 298–325.
2. [2] Wallier et al., (2006) Economic Geology101, 923–954.
3. [3] Hurtig et al., (2021) Economic Geology 116, 1599-1624.
4. [4] Glemser et al., (1964) Z. anorg. allg. Chem. 329, 51-55.
5. [5] Glemser et al., (1966) Omagiu Raluca Ripan, Editura Acedemiei Republici Socialiste Romania,Bucarest, 253-262.