The relevance of the work is caused by appearance of thermodynamic data on heavy REE phosphates, bastnesite and parizite, as well as experimental data on stability of lanthanides sulfate complexes and yttrium fluorine complexes in solutions. This circumstance makes it necessary to evaluate the behavior of REE+Y according to the updated thermodynamic database UNITHERM under the conditions of oxidized hydrothermal fluids of complicated chloride-sulfate-bicarbonate composition, which is characteristic for alkaline magmatic complexes. The main aim of the study is to determine the stable associations of minerals of macro-And microsystem, and the composition of equilibrium hydrothermal fluids containing rare earth elements in weakly acidic and weakly alkaline conditions at 500-100 °C at a pressure of 2000-125 bar. The methods: Thermodynamic modeling of monazite and calcite interaction with hydrothermal fluids using the HCh software compu-Ter code (developer Yu.V. Shvarov). Minimization of Gibbs free energy of the system (Gibbs program) together with UNITHERM thermodynamic database were used to determine the equilibrium state in the program algorithm. The results. It is shown that the initial monazite and calcite solid phases alter to REE-fluorite, REE-fluorapatite and xenotime under the action of hydrothermal fluid and in the weakly acid conditions anhydrite and at 100 °C native sulfur are formed. In weakly alkaline con- ditions there is partially non-reacted calcite, and at high temperatures soda (500 and 400 °C) is formed, while at 100 °C nahcolite is detected. Owing to high sulfate sulfur concentration the nardite appears to be stable in both versions with respect to acidity-Alkalinity. REE distribution in the fluid is discussed.
|Number of pages||9|
|Journal||Известия Томского политехнического университета. Инжиниринг георесурсов|
|Publication status||Published - 2017|
- Oxidized fluid
- Thermodynamic modeling