Coefficients of distribution of REE+Y between minerals and cooling rich sulfate fluid (thermodynamic modeling)
The relevance of the work is caused by the fact that the study of the coefficients of REE+Y distribution between the minerals-concentrators of these elements and between minerals and sulfate fluids in various alkaline and weakly acidic systems makes it possible to obtain the missing parameters neces...
| Main Authors: | , |
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| Format: | Article |
| Language: | Russian |
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Tomsk Polytechnic University
2018-11-01
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| Series: | Известия Томского политехнического университета: Инжиниринг георесурсов |
| Subjects: | |
| Online Access: | http://izvestiya.tpu.ru/archive/article/view/2100 |
| Summary: | The relevance of the work is caused by the fact that the study of the coefficients of REE+Y distribution between the minerals-concentrators of these elements and between minerals and sulfate fluids in various alkaline and weakly acidic systems makes it possible to obtain the missing parameters necessary for modeling crystallization and ore formation within the carbonatite ore-magmatic 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 REE-bearing 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: thethermodynamic modeling of monazite and calcite interaction with hydrothermal fluids using the HCh software computer 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 coefficients of REE+Y distribution between minerals are mostly independent on the acid-alkaline mineral formation environment. The acidity-alkalinity of fluids has a noticeable effect only on distribution of REE between fluorite and fluorapatite. The main influence on REE fractionation is exerted by temperature and the parameters associated with it. Only for the monazite/REE-fluorite 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/REE-fluorapatite, xenotime/REE-fluorapatite, and in acidic conditions in the REE-fluorite/REEfluorapatite 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 REE-fluorite is above one and this means that when the equilibrium fluid is cooled, REE+Y predominantly concentrates in these minerals. |
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| ISSN: | 2500-1019 2413-1830 |