Transport of post-transition metals in hydrothermal fluids: thermodynamics from first-principles

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Since the Bronze age, the metals Sn and Pb have been of crucial economic importance. In recent years, the neighbouring elements on the periodic table, Ga and, In have come into demand because of their use in electronic devices. Together, Sn, Pb, Ga and In are referred to as the post-transition metals. These elements have unusual electronic structures and their geochemical behaviour is different from metals such as Cu and Zn. To meet future demand, we will need to locate and assess new resources of these metals. Most ore deposits of metals are usually formed by hydrothermal fluids deep in the Earth's crust. Such fluids are able to extract trace metals from large volumes of rock and concentrate them into solutions. As the hot solutions cool, depressurise or react with minerals, they will subsequently precipitate dissolved metals as sulphide or oxide minerals and form ore deposits. However, the chemical processes by which this happens is usually a mystery. Experimental investigations of the chemistry of hydrothermal fluids at high temperatures and pressures are very difficult. However, we can gain a great deal of insight on what happens in hydrothermal fluids using computational simulations based on quantum mechanics. We can now determine how metals are complexed by dissolved ligands such as Cl-, HS- and derive equilibrium constants for these reactions entirely from first-principles. This opens the door to vast new insights on the chemistry and role of fluids in the Earth's crust. The work proposed here will apply these methods to the post-transition metal complexes with ligands such as Cl-, HS- and F to develop a thermodynamic model of mineral solubilities that can be used to understand how ore-deposits of these metals form.