This award provides funding for the operation, maintenance, and further technical development of the high- transmission, high-resolution ion microprobe system housed in the W. M. Keck Geochemistry Laboratory at the University of California in Los Angeles. The UCLA laboratory will be managed as a multi-user facility providing access by U.S. researchers to the special capabilities (combined mass resolution, spatial resolution, and sensitivity) of the ion microprobe for isotopic and elemental analysis. ***