SECONDARY-ION MASS-SPECTROMETRY AND GEOLOGY

Secondary-ion mass spectrometry (SIMS) is the marriage of traditional mass spectrometry with microanalytical in situ surface analysis, Ions produced by selective sputtering of the topmost layers of a sample by a focused primary beam of particles may be areally mapped or quantitatively analyzed. In the absence of a general workable model for sputtering and ionization, quantification is empirical, based upon isotopes implanted for calibration or, more generally, upon homogeneous and well characterized mineral and glass standards. Nevertheless, sensitivity for most elements is in the low ppb range. The early part of this review presents the salient features of the technique, notes the limitations of each mode of use, and provides references to the literature for further reading, In the latter pages, a number of geological applications are briefly described. With their selection, the intent has been to ''whet the appetite'' of potential users and not to attempt an exhaustive account of the many excellent applications to problems in geochemistry and cosmochemistry.