The relevance of the work is caused by the fact that the study of the coefficients of REE+Y distribution between the mineralsconcen trators of these elements and between minerals and sulfate fluids in various alkaline and weakly acidic systems makes it possible to ob tain the missing parameters necessary for modeling crystallization and ore formation within the carbonatite oremagmatic systems. To determine the mechanisms of concentrating ore components, the most important is the identification of the main and minor minerals concentrators of rare elements. The main aim of the study is to estimate the distribution coefficients of lanthanides +Y between REEbearing minerals and between these minerals and the hydrothermal fluid in equilibrium with them in weakly acidic and weakly alkaline conditions at the temperature of 500-100 °C and pressure of 2000-125 bar. The methods: the thermodynamic modeling of monazite and calcite interaction with hydrothermal fluids using the HCh software com puter code (developer Yu.V. Shvarov); minimization of Gibbs free energy of the system (Gibbs program) together with UNITHERM ther modynamic database were used to determine the equilibrium state in the program algorithm. The results. It is shown that the coefficients of REE+Y distribution between minerals are mostly independent on the acidalkaline mine ral formation environment. The acidityalkalinity of fluids has a noticeable effect only on distribution of REE between fluorite and fluo rapatite. The main influence on REE fractionation is exerted by temperature and the parameters associated with it. Only for the mona zite/REEfluorite pair, the decrease in temperature promotes the increase in values of the distribution coefficients, i. e. the entry of REE into monazite. In pairs monazite/REEfluorapatite, xenotime/REEfluorapatite, and in acidic conditions in the REEfluorite/REEfluora patite pair, decrease in temperature is accompanied by decrease in the distribution coefficients and facilitates some enrichment of fluo rapatite with rare earths. Kd mineral/fluid for monazite, xenotime and REEfluorite is above one and this means that when the equilibri um fluid is cooled, REE+Y predominantly concentrates in these minerals.
|Журнал||Известия Томского политехнического университета. Инжиниринг георесурсов|
|Состояние||Опубликовано - 1 янв 2018|