Abstract:

Abstract:  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 to reveal the kinetic mechanism of watermineral and waterrock interaction at the extreme conditions. 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. 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. 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. Kinetic experiments of minerals (albite, quartz, diopside, actinolite, etc.) and rock (basalts, syenite) in aqueous solutions were performed by using fluid through apparatus at temperatures of 20 to 435  ℃ and pressures of 23 to 35 MPa. We found that the dissolution rates exhibit a fluctuation during crossing the critical state of water. The dissolution rates of silicate minerals in water increase with increasing temperature until reaching the critical state of water. Then they decrease with continued increasing temperature. The dissolution rate reaches a maximum value in the critical region (300400  ℃). The fluctuation of dissolution rates are affected by the variation of water properties. As the deep metalbearing supercritical fluids rise up, they will have an opportunity to pass through the LV immiscibility region. We performed a series of experiments of LV immiscibility region of metalbearing fluids, and found Au, Cu, Sn, W, and Zn could be partitioned in liquid and vapor phases in the subcritical states of the fluids. Experiments demonstrated 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 drive a fluctuation of dissolution rates of silicate minerals in water. In addition, both vapor and liquid phases could carry metals up to the Earth surface as the fluids were separated into liquid and vapor phases in the LV immiscibility field.

Key words:

Key words: ultrahigh pressure and high temperature in Earth interior; critical state; fluid nature; molecular spectroscopy; kinetics; metal transport by vapor