Geochemistry of Critical and Precious Metal Deposits

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My research program focuses on understanding intrusion-related critical metal (notably tantalum, niobium and rare earth elements) and precious metal (gold and platinum group element) deposits. The critical metals have a bright future because they are used in components in many high-tech devices, speciality alloys etc.. The precious metals are currently the strongest sector in the Canadian mining industry. The long term objectives of my research are to develop models for the genesis and exploration of these ore deposit types by better understanding the fundamental magmatic and hydrothermal processes that are responsible for concentrating metals. Initial ore deposits models are generated complimentary studies funded from industry and NSERC CRD grants. These models are then tested by Discovery grant research, which focuses on placing constraints on models and testing hypotheses through experimental work. Precious metal deposit research will include a study of pyrite mineral chemistry because gold commonly occurs as inclusions in this mineral and there is an overall strong correlation between pyrite abundance and gold concentration at many deposits. Pyrite has been the subject of numerous recent studies, but the solubility limits of gold in pyrite remain controversial. Diffusion experiments will be conducted to determine true gold solubilities (as opposed to nanonuggets) in pyrite. It is well known that gold solubility in pyrite is strongly dependent on arsenic content, hence experiments will be conducted on both arsenic-free pyrite and arsenic-bearing systems. It is also well known that the chemistry of native gold is variable. In order to evaluate whether these compositions are primary or re-equilibrated, diffusivities need to be known. A series of experiments will determine the diffusivity of iron, copper, nickel and cobalt in native gold and the significance of the variation of gold chemistry in natural deposits will be modeled. Tourmaline is a common accessory mineral in gold deposits and this mineral in other environments can contain wt% levels of copper and silver. Experiments will be conducted to determine the effects of temperature, redox conditions, tourmaline composition and fluid composition on copper-silver-gold partitioning and the results will be applied to using tourmaline as an indicator mineral. The second area of research focuses on critical metals. One of the most important unresolved problem in rare metal deposits is the importance of metasomatism. The most abundant ore minerals of critical metals contain bivalent cations as primary constituents. New experiments will evaluate bivalent cation metasomatism in pegmatite melts for critical metal mineralization by interacting calcium-manganese-iron-rich fluids with tantalum- and niobium-rich melts to simulate metasomatism.