Acquisition of a Scanning Electron Microscope at Yale Geology and Geophysics

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0216784KaratoThis award will permit the purchase of a scanning electron microscope (SEM) with a range of capabilities for high-resolution analyses of structures and compositions of Earth materials, including biological samples. The SEM we will purchase is a Philips XL30 ESEM-FEG, which operates with both low- and high-vacuum modes with a field emission gun (FEG) and a software/hardware package for an electron backscattered diffraction (EBSD) pattern analysis. This new facility is critical to the diverse research activities at Yale Geology and Geophysics including studies of: (1) deformation microstructures of experimentally and naturally deformed samples (Karato, Brandon), (2) fluid-rock interaction (Ague, Rye), (3) microbial geochemistry and geomicrobiology (Blake). Complete orientation measurements with high-spatial resolution, as provided by the EBSD package attached to this type of state-of-the-art SEM, are critical to microstructural studies on deformed rocks by Karato and Brandon. Geologic application of this technique is widespread in Europe, but has been limited to only a handful of labs in the United States. The spatial resolution of orientation measurements is close to 0.25 mm when the FEG electron source is used with an EBSD package. Such a high spatial resolution is critical, particularly for the experimental studies in Karato's group where microstructural developments under high-pressure conditions are studied using specimens with very fine grain size. Similarly, the ESEM mode of operation of this SEM has major advantages in several research areas at Yale Geology and Geophysics. This includes the study of fluid-rock interaction through the charge-contrast imaging technique (which works selectively at ESEM mode), and the study of microbial geochemistry and geomicrobiology, which requires high-resolution images of the morphology of mineral surfaces and associated microorganisms. Addition of this facility to the existing analytical and other experimental facilities will significantly enhance the research programs of experimental Earth science at the department of Geology and Geophysics at Yale University.***