This award from the Major Research and Instrumentation Program (MRI) will support the development of a new Thermal Ionization Mass Spectrometry (TIMS) Facility in the Department of Earth Sciences at Boston University. In addition to the TIMS, this facility will include a MicroMill sampling device for collecting spatially-resolved material at the 10-100 micron scale for subsequent chemical preparation and TIMS analysis. The new TIMS/MicroMill Facility gives the Department - and external users - the capability to measure isotope ratios (e.g. Sr, Nd, Ca, Pb) on a wide variety of geological samples at high spatial resolution and high precision. The most recent generation of TIMS is capable of analytical precision not previously obtainable, including when sample size is limited. Modern geoscience research in igneous & metamorphic petrology, weathering & surface processes, and oceanography & paleoclimate - all research strengths of the four PIs - often requires the reconstruction of past geologic events or conditions with fine geochemical and geochronological spatial and temporal resolution only possible by pushing the limits of precision and sample size with the TIMS. The new BU TIMS/MicroMill Facility will be dedicated to pushing those limits. This open regional TIMS Facility will serve the research needs of the four PI's on this proposal, others in the Department and University, and other geoscientists in the region. Our external user management plan providing training for long-term student users, encouraging collaborative research with BU PI's particularly where specialized analysis is needed, and including an appropriate recharge rate, will ensure the integrity of the lab facilities while always providing the best quality isotopic data to BU and external users. The Facility will benefit a wide spectrum of graduate and undergraduate research at BU and in the region.