Insight into formation of hydrothermal ore deposits using a hydrothermal autoclave and X-ray absorption spectroscopy

Hydrothermal fluids play an important role during the formation of most economically explored ore deposits. While cycling through the crust these supercritical fluids efficiently dissolve and transport metals from the source rocks; metal-rich minerals precipitate on their way towards the Earth’s surface. In general, compositions of hydrothermal ore fluids are well known, e.g., by analyzing fluid inclusions in ore minerals. However, because sources and physiochemical characteristics of hydrothermal fluids vary widely, complexation and speciation of metals in the fluid and precipitation mechanisms of ore minerals are still matter of controversial debates. Conclusions on metal complexation and speciation in the fluids are usually based on analysis of quench experiments that do not consider the probably non-quenchable nature of hydrothermal metal complexes e.g., as previously reported for gold (Pokrovski et al., 2015). Thus, reliable information on metal complexation and speciation during ore deposit formation can only be obtained using in-situ data.

Here, we present an autoclave dedicated to in-situ characterization of hydrothermal fluids at high pressures and temperatures at Deutsches Elektronen-Synchrotron (Klemme et al., 2021). Besides discussing details of the experimental set-up we will also focus on results of two ongoing projects dedicated to formation of W and Sn hydrothermal ore deposits.

G. Pokrovski et al., PNAS 112 (44), 2015; Klemme et al., Rev Sci Instr, 92, 2021

Funding: Bundesministerium für Bildung und Forschung (BMBF) grant FKZ 05K16PMA, DESY Center for Molecular Water Science - Early Science Project.