Abstract:

Abstract:  Recent ultrahigh pressure and high temperature experiments provide a new opportunity to gain an insight into the fluids,fluid and matter interactions in the extreme conditions of the deep Earth interior. Insitu observations of the matter under ultrahigh pressure and high temperature conditions as in the Earth interior by using diamond anvil cell connected to spectrometer and microscope, combined with synchrotron radiation technique, may obtain new data and message of their molecular structures and natures in atomic scale and in kinetics. The nature of Earth fluids would be changed by the variations of the temperatures and pressures of their locations. It is well known that the properties of water in the critical region may show anomalies in many of its physical properties. For example, the density or dielectric constant of water may drop with increasing temperature. The molecule structures of aqueous solutions (NaClH2O) at high temperatures and pressures(800 ℃,3 GPa) have been examined by insitu observation using diamond anvil cell connected to FTIR spectrometer combining with synchrotron radiation technique. The sharp and strong O—H stretching vibration at 330 ℃ near the critical point of water proves the break down of the hydrogen bonding network. Within and near the critical region, the rapid decrease in the dielectric constant and density of water results from the destruction of the hydrogen bond network of the water molecules. The O—H vibration frequency increases with temperature. Experiments demonstrate that the nature and the structure of the Earth fluids will change with depth. As passing through the critical state,the anomalous properties of fluids will be affected by the variations of water molecule vibrations and the break down of hydrogen bond network in the critical state.
Key words: ultrahigh pressure and high temperature in Earth interior; critical state; fluid nature; molecular spectroscopy