ANALYSIS OF RARE-EARTH ELEMENTS IN SILICATES BY ION MICROPROBE USING DOUBLY-CHARGED IONS

A technique for measurement of rare earth element (REE) concentrations in silicates using a Cameca ims-4f ion microprobe and doubly-charged, odd-mass isotopes has been developed. The secondary ion spectra of th e doubly-charged odd-mass REE are virtually free of interferences, all owing measurements to be carried out at low energies and without the n eed for spectral stripping. Calibration lines have been established fo r La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb using a suite of clin opyroxene standards. This technique offers a relatively fast, simple a pproach for the in-situ analysis of REE on spots of <20 mum and detect ion limits of <15 ppb for most elements.