Separating the twins: the hydrothermal geochemistry of Nb and Ta

Niobium (Nb) is recognized as one of the so-called ‘critical minerals’, with wide applications in superalloys and superconductors but limited supply chain. An understanding of the speciation and solubility of Nb in hydrothermal solutions is key in helping both Nb exploration and mineral processing. High-resolution X-ray absorption spectroscopy (XAS) can reveal fine features of the XANES spectra, thus help identifying important Nb aqueous complexes (with O, F and Cl) that are hard to identify using conventional XAS detection techniques. This study plans to measure the coordination structure and solubility of Nb in hydrothermal fluoride, chloride and carbonate solutions at up to 500 °C and 800 bar to better understand the transport and deposition properties of Nb and its fractionation from its geochemical twin tantalum (Ta) in hydrothermal systems. This will complement our recent experiment on hydrothermal speciation of Ta.