Co-precipitation reaction for Ba and Ra into calcite

Yoshida, Yasushi*; Yoshikawa, Hideki; Nakazawa, Toshiyuki*; Sato, Tomofumi*

To evaluate incorporation behavior of Me larger than Ca in ion radius, co-precipitation experiment were implemented. Partition coefficient is generally used to estimate co-precipitation reaction and this parameter is reported to be affected by precipitation rate of calcite. Therefore, under the condition of variety of R, D for Me larger than Ca into calcite was measured. For trace elements Ra and Ba were used. As a result of experiment Partition coefficient for Ba (or Ra) are decreasing toward the slow R. This tendency is consistent with the reported data. The values of D of Ba and Ra which are low imply those large radius elements are difficult to incorporated into crystal lattice and inclusion is presumably induced by distortion of lattice structure. In addition there is no notable difference of D for Ra and Ba despite difference of radius length. It indicates an extent of inclusion does not depend on a difference of ion radius between Ra and Ba.