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

分析地球化学的最新进展表明，铁和硫的稳定同位素可以提供地球深处的物理和化学条件的线索，这些条件负责热液喷口流体的化学作用，并有助于控制海水的化学作用。到目前为止，这些同位素在不同温度和氧化还原条件下如何在矿物和流体之间分配一直是推测的，但没有得到实验验证。这项研究包括在300至450摄氏度和500bar压力下进行的受控实验室实验，以确定矿物和流体之间非传统稳定同位素(铁、铜、S)的分馏。实验旨在研究流体化学对同位素交换速率和过程的影响，并确定黄铁矿和黄铜矿的形成动力学速率，这两种矿物是从热液喷口水中沉淀出来的两种重要硫化物矿物。研究结果将被用来从矿物形成机制的角度解释铁、铜和硫的同位素比值，并限制海底热液系统中矿物和流体之间的相互作用条件。这项工作的更广泛影响包括培训本科生和通过开发可用于地球化学和海洋科学领域以外的研究的新实验方法来加强科学基础设施。

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.