Collaborative Research: Experimental Study of Mineral-Fluid Fractionation of Non-Traditional Isotopes (Fe, Cu, Zn, S) with Implications for Seafloor Hydrothermal Systems

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Many empirical studies of hydrothermal vent systems on the seafloor and an increasing number of biogeochemical studies are being carried out to look at various mineralogical and biological processes using unconventional stable isotopes (i.e., those of heavy elements such as iron, zinc, copper, and sulfur). To allow quantitative and predictive results of these empirical studies, fractionation factors of these isotopes must be known. However, at present, no experimental work to derive these coefficients and parameters have been carried out. This research builds off a one-year proof-of-concept study to show that fractionation occurs in these systems in a systematic way. The new project examines the effects of temperature, fluid chemistry, and reaction rate on the fractionation of non-traditional stable isotopes (Fe, Cu, Zn, S) between sulfide minerals and fluids at elevated temperatures and pressures. The work will include phase separation experiments to assess the role of fluid chemistry on non-traditional stable isotope fractionation between vapor and brine. It will use isotope tracers in equilibrium experiments to look at reaction progress and to see how isotope systematics respond to reaction rates and mechanisms. Sulfur isotope exchange for homogeneous and heterogeneous systems will also be tested experimentally. Broader impacts of the work include building fundamental infrastructure for science via the development of kinetic and fractionation factors that are essential for the development of theoretical models for predicting stabilities of minerals containing Fe, Cu, Zn, and S. Impacts also include the engagement of graduate and undergraduate students in state-of-the-art experimental studies of water-rock interaction and the involvement of an early career PI from an institution in an EPSCOR State (Louisiana).