Stephan Klemme, Michael Feldhaus, Vasily Potapkin, Max Wilke, Manuela Borchert, Marion Louvel, Anselm Loges, Arno Rohrbach, Petra Weitkamp, Edmund Welter, Maria A. Kokh, Christian Schmidt, Denis Testemale

• We present a new autoclave that enables in situ characterization of hydrothermal fluids at high pressures and high temperatures at synchrotron x-ray radiation sources. The autoclave has been specifically designed to enable x-ray absorption spectroscopy in fluids with applications to mineral solubility and element speciation analysis in hydrothermal fluids in complex compositions. However, other applications, such as Raman spectroscopy, in high-pressure fluids are also possible with the autoclave. First experiments were run at pressures between 100 and 600 bars and at temperatures between 25 degrees C and 550 degrees C, and preliminary results on scheelite dissolution in fluids of different compositions show that the autoclave is well suited to study the behavior of ore-forming metals at P-T conditions relevant to the Earth's crust.