Creation of Experimental Data obtained at Extreme Conditions for Renewing Geo-Thermodynamic and Kinetics Database

Ronghua Zhang, Shumin Hu, & Xuetong Zhang

Open Research Laboratory of Geochemical Kinetics, Chinese Academy of Geological Sciences, Institute of Mineral Resources, Baiwangzhang road 26, Beijing 100037 China, zrhhsm@pku.edu.cn

High pressure study develops very rapidly. Particularly, In Situ observations and measurements at extreme conditions by using Diamond anvil cell (DAC) and apparatus with window lead to new scientific discoveries. Increase of pressure to ultra-high pressure drives the changes of structure, bonding, state of minerals and synthesized materials. Hydrothermal reaction at extreme conditions is one important project.

We created kinetic data of reaction rates of minerals (quartz, albite, diopside, hedenbergite, actinolite, zeolite, calcite, dolomite, Fe₃O₄, FeW₂O₄ etc) at T up to 450ºC. The dissolution of a multi-oxide in water may require the breaking of more than one metal-oxygen bond type. Different elements behave different release rates. Results show that metals (Na,Ca,Mg,Fe, Al) dissolve faster than Si from 20 to 300°C, but slower from 300 to 400°C. The silicate dissolution becomes nearly congruent at 300°C and the maximum release rate of Si often occurs at 300°C. Thus, dissolution rate of minerals can be simplified as

-r = k (( a_H⁺)^Zk/a_Mk^Zk+)^a

where k is the rate constant, and a is the order with respect to the hydrogen ion activity vs the activity of dissolved metal M_k.

Experiments indicate that water properties behave anomaly from sub-critical to super-critical states (density, dielectric constant etc) which affect kinetic behavior of minerals (or compounds). Thus, dissolution rates of multi-oxide silicates are different between <300°C and >300°C, because of differences in polarizability among the Ca-O_br, Mg-O_br, Al-O_br and Si-O_br bonds. And the Si-O_br bond is more easily hydrated at T >300°C.

Our laboratory examined properties of fluids and minerals at T from 25 to 1100 ºC and pressure of 3 GPa (30GPa). The spectrum data of the matters at high T&P(FT-IR, VUV, Raman, EXAFS, XRD, etc) are obtained. We organize new experimental data to database of Geo-chemical kinetics and Geo-thermodynamics for predict natural and industrial processes.

Keywords: Creation of experimental data, at extreme condition, critical state Geo-Thermodynamic and Kinetics Database.

Session 6. Earth and Environmental Data

Session 8 . Physical Science Data