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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Experimental study on the fractionation of yttrium from holmium during the coprecipitation with calcium carbonates in seawater solutions

CHENGLI QU, GANG LIU, YONGFANG ZHAO
Geochemical Journal, Vol. 43, No. 6, P. 403-414, 2009

ABSTRACT

The partitioning of Y and Ho between CaCO3 (calcite and aragonite respectively) and seawater was experimentally investigated at 25°C and 1 atm. Both Y and Ho were observed to be strongly partitioned into the overgrowths of calcite or aragonite. Their partition coefficients, DY and DHo, were determined to be ∼520-1400 and ∼700-1900 in calcite, ∼1200-2400 and ∼2400-4300 in aragonite, respectively. Y fractionates from Ho during the coprecipitation with either calcite or aragonite. Within our experimental conditions, the fractionation factor, k = DY/DHo, was determined to be ∼0.62-0.77 in calcite and ∼0.50-0.57 in aragonite, respectively. The aqueous complexation of Y and Ho, which is a function of solution chemistry, probably plays an important role in both the partitioning and the fractionation. Further analyses suggest that the difference in covalency between Y and Ho associated with changes in their coordination environments is the determinant factor to the Y-Ho fractionation in the H2CO3-CaCO3 system.

KEYWORDS

partitioning, fractionation, calcium carbonates, seawater, Y/Ho ratios, covalency

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