Original paper

Uranium oxidation states in allanite, fergusonite and monazite of pegmatites from Finland

Ervanne, Heini

Abstract

Ion exchange was used to determine uranium oxidation states in Ce–allanites, fergusonite and monazite contained in Svecofennian granitic pegmatites from Finland. In allanites, uranium was partly oxidized; U(IV)/Utot range from 0.33 to 0.43. The minerals were metamictic. Fergusonite was found to be totally oxidized, giving 0.06 for the U(IV)/Utot. The low ratio is assumed to be due mainly to the hydration of fergusonite. Of the samples analysed, the fergusonite and one allanite were from the same pegmatite, but they gave a different degree of oxidation for uranium. This finding may reflect the greater stability of allanite as compared to fergusonite. The monazite was indirectly found to be in reduced form (U(IV)/Utot 0.93). The method applied probably dissolved only the soluble oxidized form of uranium.

Keywords

uraniumoxidation statesallanitefergusonitemonazitepegmatitemineralsfinland.