Determination of rare-earth elements in USGS standard rocks by mixed-solvent ion exchange and mass-spectrometric isotope dilution

The development is described of a mixed-solvent ion-exchange technique for separating trace amounts of rare-earth elements from silicate rocks and minerals. A two-column method is used, bulk separation of rare earths from other elements being accomplished on the first, and separation into three groups for mass-spectrometric analysis on the second. This has been applied to the determination of nine REE (La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb) in standard rock samples. Smooth variation of the chondrite-normalized abundance distributions and comparison with other published results indicate that the accuracy of the method, with the exception of La, is generally ± 2%.