This award provides support for two-years for the operation of the ion microprobe laboratory in the Department of Earth, Atmospheric and Planetary Sciences at the Massachusetts Institute of Technology. The laboratory will be run as a regional/national facility and will be available for trace element and isotope microanalysis of geological materials. The facility provides U.S.earth scientists access to analyses with high mass resolution as well as excellent spatial resolution (10 to 20 micrometers) for a number of nuclides that are very significant in interpreting large- and small-scale mass transfer processes within the Earth.