上地幔超高压流体的金刚石压砧实验研究

Experimental Study on Supper-High Pressure Fluids in the Upper Mantle Using Diamond Anvil Cell

地球深部流体主要是NaCl-H2O溶液,越到地球深部,它赋存的温度、压力越高,性质状态也不断变化,反之,亦然。当NaCl-H2O流体进入和脱离(上升过程)超临界状态时,其性质会发生截然不同的变化,影响着各种地质过程。使用金刚石压砧在高温高压下原位观测流体的实验,用谱学方法,结合同步辐射光源技术,成为定量化研究地球深部高温超高压流体的有效方法。作者使用同步辐射光源的红外谱研究了10GPa下的NaCl-H2O溶液;在地球化学动力学实验室研究了3GPa,650℃下的NaCl-H2O溶液红外谱,此测量方法可以提供温度压力和体积等数据,能研究其状态。NaCl-H2O溶液红外谱表明水分子主要振动谱受压力和温度影响是不同的。压力增加促使水分子主要振动谱向低波数变化。但是温度增加的效应相反。常温高压下水被压缩,结晶向紧密堆积变化。高温高压下的水有气、液、固和超临界流体各相。水分子间的氢键在近临界态开始减弱,氢键网络被破坏。

The deep earth fluids compose mainly NaCl-H2O. The properties of the earth fluids are getting to change with their locations in the different depth, form low temperature and pressure in the shallow to high temperature and pressure in the deeper parts of the earth. Fluids of NaCl-H2O lie in the deeper parts always presented in a supercritical state of water. As the fluids rose from deeper parts to shallow, they would go through the critical state, and to a state of lower than the critical point of water due to decreasing temperatures and pressures. The best method for in situ observation of the deep earth fluids is to utilized a hydrothermal diamond anvil cell （HDAC）connected to different spectrometers, and by using Synchrotron radiation technique. Authors performed a study of Infrared spectra of NaCl-H2O solution at 10GPa by using diamond anvil cell and connected to Infrared spectrometer by using synchrotron radiation light source, and a study of infrared spectra of NaCl-H2O solutions by using HDAC connected to FT-IR microscope in the conditions of 3GPa650°. Our method about measurements of infrared spectrometer for NaCl-H2O at high temperatures and pressures provides the data of temperature, pressure and volume of the tested fluids, thus the equation is the state of the fluids can be figure out. The spectra of NaCl-H2O solutions indicated that the vibration frequencies of water molecules are affected by temperatures and pressures. Increase of pressures lead the vibration frequency of water molecules change to low wave numbers. In oppositely, increase of temperatures would derive their vibration frequencies to high wave numbers. In opposite of the effects on water （or crystals ）with respect to increasing temperature, increasing pressure at ambient temperature will lead to compress water molecules and crystals, tb.us the crustal will go to a crystal structure close accumulate. Water at high temperatures and pressures will behave V-L-S phases, the critical state, and a supercritical fluid phase. The hydrogen-bond of inter-water molecules will be weaken and broken as close to the critical state of water.