Experimental Calibration of Mineral-Fluid Fractionation of Non-Traditional Isotopes (Fe, Cu, 33-S): Implications for Mass Transfer in Seafloor Hydrothermal Systems

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Recent advances in analytical geochemistry have demonstrated that stable isotopes of iron and sulfur can provide clues to the physical and chemical conditions deep in the earth that are responsible for the chemistry of hydrothermal vent fluids and that help to control the chemistry of seawater. Until now, how these isotopes partition between minerals and fluids at different temperatures and oxidation-reduction conditions has been speculated upon but not experimentally verified. This research involves controlled laboratory experiments at temperatures from 300 to 450 Celsius and a pressure of 500 bars to determine fractionation of non-traditional stable isotopes (Fe, Cu, S) between minerals and fluids. Experiments are designed to examine the effect of fluid chemistry on the rates and processes of isotope exchange and determine the kinetic rates of formation of pyrite and chalcopyrite, two important sulfide minerals that precipitate from hydrothermal vent waters. Results of the research will be used to interpret iron, copper, and sulfur isotope ratios in terms of mineral formation mechanisms and to constrain conditions of interaction between minerals and fluids in subseafloor hydrothermal systems. Broader impacts of the work include training undergraduate students and enhancing science infrastructure with the development of new experimental approaches that can be used for research outside the fields of geochemistry and ocean sciences.