Gadolinium: Distribution between Aqueous and Silicate Phases
Robert L. Cullers 1,
L. Gordon Medaris Jr. 1, and
Larry A. Haskin 2
1 Department of Geology, University of Wisconsin, Madison 53706
2 Department of Chemistry, University of Wisconsin, Madison
Studies of the partition of trivalent gadolinium between aqueous and silicate phases have been made at temperatures from 800° to 900°C and at pressures from 500 to 1000 bars. Constant values for the distribution coefficients for forsterite, enstatite, and diopside were obtained over a concentration range from 0.6 part per billion to 4 parts per thousand in the solid phases. Ratios of silicate crystal-aqueous phase distribution coefficients to silicate melt-aqueous phase distribution coefficients are close to the values for silicate crystal-silicate melt distribution coefficients estimated from natural systems. The free ion activity of trivalent gadolinium in the silicate melts appears to be less than one-hundredth of its value for aqueous phases of the same concentration.
