高压水热流体中黄铁矿在差应力作用下活化溶解行为的原位电化学研究

Pyrite is widespread in hydrothermal systems with large scale reserve, its dissolution in hydrothermal fluids is a crucial geochemical process involving the geochemical cycling of Fe and S, alteration of redox state and pH in ore-forming hydrothermal fluids, and precipitation of some ore-forming metals. Differential stress presents almost everywhere in the interior of the earth, observation of pyrite texture in ore deposits and samples after simulation experiments has demonstrated that differential stress plays an important role in the dissolution of pyrite. However, limited by experimental techniques, current studies on this issue can neither quantify the influence of differential stress in the dissolution of pyrite, nor reveal how differential stress affect pyrite dissolution. In this project, we will study the influence of differential stress on pyrite dissolution with the aid of a high temperature high pressure electrochemical measurement system coupled with a uniaxial stress testing machine. Through the measurements of open circuit potential, linear polarization plots, Tafel plots, electrochemical impedance spectroscopy and Mott-Schottky plots at different differential stress and temperature, we can gain information about how thermodynamic stability, dissolution rate and surface state parameters respond to the changes in different differential stress and temperature, the function mechanism of differential stress will also be discussed by experimental data analysis. The research in this project will help us in estimating the tendency and scale of pyrite dissolution in hydrothermal fluids, furthermore, it can provide reference for the research of pressure solution of other electroconductive minerals.

黄铁矿在热液系统中分布广且储量大，它在热液中的活化溶解关系到Fe、S元素的活化迁移、热液氧化还原状态及pH值的改变、相关金属元素沉淀等一系列地球化学过程。地球内部差应力无处不在，对矿床中黄铁矿组构的观察及模拟实验已证实差应力是造成黄铁矿活化溶解的重要因素。然而由于实验技术的限制，现阶段的研究既无法量化差应力在黄铁矿活化溶解过程中所发挥的作用，也未能揭示其作用途径和微观机制。本项目中拟应用叠加了单轴应力试验机的高压水热三电极电化学实验平台，测量不同温度、差应力条件下黄铁矿的开路单位、线性极化曲线、Tafel曲线、电化学阻抗谱及Mott-Schottky曲线，获得不同温度下黄铁矿热力学稳定性、溶解速率及表面状态参数对差应力的量化响应，并推测差应力的作用途径及机制。本项目的开展不仅有助于我们正确评估黄铁矿在热液系统中发生活化溶解的趋势及规模，还可以为其它导电性矿物压溶作用的研究提供参考。