氧逸度是指研究体系中有效的氧分压，它可以表征地质过程中的氧化还原条件。氧逸度调控主要通过氧逸度缓冲技术来实现，该技术将贵金属管（Pt，Ag-Pd，Au）制成反应腔，利用H2在Pt或Ag-Pd中扩散来控制反应腔内的氢逸度/氧逸度。受限于低温条件下H2在Pt或Ag-Pd合金里的扩散速率很低，现有的氧逸度缓冲技术只适用于400℃以上的热液实验。扩散实验表明，熔融毛细硅管是很好的低温H2半透膜，低温条件下（＜400℃）H2对熔融毛细硅管有很高的扩散速率。本研究基于熔融毛细硅管技术和激光拉曼定量方法，利用冷封式高压釜实验平台，开发一套完整、有效的低温氧逸度控制技术。主要的研究工作包括：(1)完成低温氧逸度缓冲技术的基本物理设计；(2)确定扩散平衡和化学平衡所需的时间；(3)测定含水样品的氢分压值并计算对应的氧逸度值；(4)利用氧逸度缓冲及测量技术对低温条件下受氧化还原条件制约的地质过程开展研究工作。

Oxygen fugacity (ƒO2) refers to the effective oxygen partial pressure and it defines redox state of a given geological process. The oxygen buffer technique is routinely adopted to control or measure the ƒO2 in experimental studies. This technique controlled ƒO2 by superimposing defined hydrogen fugacity (ƒH2) on studied sample in an enclosed capsule made of Pt or Ag-Pd alloys, which also served as H2 semi-permeable membranes. However, this technique is only suitable for hydrothermal experiments 400℃, because of low permeability of these metal membranes to H2 at lower temperatures. Previous diffusion experiments show that the fused silica capillary tube is a very good low temperature (< 400℃) H2 semi-permeable membrane. This study will apply the fused silica capillary H2 membrane and quantitative Raman spectroscopic analysis method to the cold-sealed pressure vessel experimental platform, in order to develop a complete set of effective low-temperature redox control technology. The main research work will include: (1) Complete the basic physical design of redox buffer technology; (2) Determine the time required for osmotic equilibrium and chemical equilibrium; (3) Determine quantitatively the hydrogen partial pressure (hydrogen fugacity) and calculate the corresponding oxygen fugacity in samples containing water; and (4) Study the natural geological processes related to redox conditions at low temperatures by applying the redox buffer and measurement techniques established in this study.