Acquisition of an Electron Microprobe for the MIT User Community

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0841161GroveThis proposal seeks funding of ~$369K to purchase a refurbished JEOL JXA-8200 electron microprobe. The probe will allow significantly enhanced operation over the current probe offering an LaB6 electron gun - offering higher beam currents with smaller spot size and better step resolution, enhanced optical auto-focusing - allowing higher step resolution and reproducibility, automated electron optics, faster motors, better WDS scanning, a cathodoluminescence (CL) system - allowing better phase characterization, enhanced control and imaging software, and remote control capabilities. The co-PI (Chatterjee) will continue to be the prime operator and maintainer for the probe facility. A recent promotion gives him salary support for one year. The co-PI will continue to offer training for students, researchers and faculty. The MIT probe facility operates as a soft-money entity but retains possible departmental support if needed. Rate structure depends on the level of support. Experienced users can opt for less-expensive "off hours" times. The system will be put to immediate use replacing an older probe for studies in petrology - understanding high temperature and pressure igneous and metamorphic rock characteristics. Additionally the water impacts on melts and associated mineral dynamics during geologic time will be studied. The probe will be critical in assessing primitive basalts and contributions from subduction fluids and melts in source magma. These data will feed into the MELTS algorithm. Lunar mare magmas, Martian mantle evolution and asteriodal parent bodies will be assess melting source regions and elucidate melt processes. Preliminary analyses will also be conducted which will help elucidate distinct regions suitable for TIMS U-Pb series analysis. Zircon and monazite localization and U-Th-Pb dating will be used to help trace continental positions and alignments over geologic time. Electron backscattering will be used to analyze minerals whose orientation and stratigraphic (if applicable) position(s) will be determined prior to high-precision dating. Basalts from mid-ocean ridges, convergent plate margins and oceanic "hotspots" will be analyzed to determine age and migration over geologic time. Trace element analysis will also be performed to refine compositional information. Additional projects within the department will study early planetary formation, paleomagnetism, lithospheric evolution, oceanic lithospheric and mantle geochemistry, and hydrothermal systems. The probe will be an essential component of research and teaching activities within the Department of Earth, Atmospheric and Planetary Sciences at MIT. The new probe will be incorporated in an electron microprobe course. Class notes are available over the web. Three undergraduate courses use the microprobe and the probe will be heavily used in graduate research efforts. Research results will be disseminated through the peer-reviewed literature. ***