Experimentally determined mineral-melt partition coefficients for Sc, Y and REE for olivine, orthopyroxene, pigeonite, magnetite and ilmenite

摘要: Our current lack of understanding the partitioning behavior Sc, Y and REE (rare-earth elements) can be attributed directly to a sufficiently large or chemically diverse experimental data set. To address this problem, we conducted series experiments using several different natural composition lavas, doped with elements interest, as starting compositions. Microprobe analyses orthopyroxene, pigeonite, olivine, magnetite, ilmenite co-existing glasses in charges were used calculate expressions that describe function variety system parameters. Using represent mineral-melt reactions (versus element ratio distribution coefficients) it is possible terms express low-Ca pyroxene-melt are independent both pyroxene melt composition. Compositional variations suggest Sc substitution olivine involves either paired Al or, more commonly, vacancies. The dependent on temperature. experimentally determined olivine-melt Ds (partition similar to, but slightly higher than those reported by McKay (1986) support their conclusions olivines strongly LREE depleted. mineral/melt partition coefficients for magnetite range from 0.003 La 0.02 Lu. Ilmenite 0.007 0.029 These values two orders magnitude lower many published phenocryst/matrix separation techniques.