This award funds the operation of two ion microprobes at University of California-Los Angeles (UCLA). These machines make many types of geochemical measurements on solid samples, such as pieces of rock, meteorites, and other materials. These ion microprobes can investigate volumes of rock too small for most other methods, making them crucial for studying tiny geological features. These instruments are open to use by outside researchers. The facility will help users to study a wide range of topics and investigate the earliest periods of Earth and Solar System history, date geological events throughout Earth history, and study recent environmental changes recorded in younger rocks. The laboratory will provide data for hundreds of U.S. scientists and contribute to U.S. science education by collecting data for student dissertations and theses. This award provides continuing support for the UCLA ion microprobe laboratory as a national user facility. Use of the facility’s two large radius secondary ion mass spectrometers (SIMS) by members of the U.S. science community are subsidized by this award, providing access to high spatial resolution geochronology, stable isotope, and trace element data for geochemistry and cosmochemistry. During the award period, the laboratory will continue to focus on providing high quality isotopic data to the community while both expanding the range of isotopic analyses offered for users and pursuing fundamental research into the evolution of the early Earth and Solar System, accessory mineral geochemistry, and stable isotopes on a variety of geological and biological materials. The facility plans new technique development activities, enhancing its geochronological capabilities by investigating 40K-40Ca dating in sylvite to characterize the stability of salt deposits and their suitability as nuclear repository sites. Facility scientists will also develop U-Pb dating protocols for accessory minerals they have not previously pursued (e.g.,