This Major Research Instrumentation (MRI) Program grant supports acquisition of an integrated energy dispersive X-ray (EDS), electron backscatter diffraction (EBSD) and panchromatic cathodoluminescence (CL) imaging system for the Department of Geology at Colgate University. The integrated package will be mated to an existing JEOL 6360LV scanning electron microscope (SEM) that was acquired by Colgate with previous NSF/MRI support (EAR-0320639). The enhanced capabilities of the SEM will support PI and student research including rock fabric investigations of footwall mylonites from Cordilleran core complexes using EBSD to infer the kinematics and temperature of their formation, CL-SEM analysis of lower Paleozoic quartz sandstones of the Appalachian basin to infer the diagenetic history of micron-scale cement fabrics, and studies of the biomineralization of barnacle exoskeletons. Colgate University is a non-Ph.D. granting institution. The instrumentation will support undergraduate student training in state-of-the-art electron microscopy research methods with applications to structural geology and sedimentary, igneous and metamorphic petrology.
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This report summarizes the outcomes of an National Science Major Research Instrumentation (NSF-MRI) grant. The grant funding was used to purchase detectors for a Scanning Electron (SEM) system in the Department of Geology at Colgate University. This facility is used by faculty and students in the departments of Geology, Physics and Astronomy, Biology and Chemistry at Colgate, and faculty and student users from nearby colleges and universities. SEM is used to examine very small samples of natural and artificial materials, using magnifications up to 50,000X.The new detectors purchased with these funds include (1) an Energy Dispersive X-Ray Analyzer (EDS) system which determines the chemical composition of materials, and supports mapping of the distribution of elements in samples; (2) an Electron Backscatter Diffraction dectector (EBSD), to determine the crystal structure and orientation of mineral and metal grains; and (3) a Polychromatic Cathodoluminescence dectector (PCL), which supports imaging of component grains based on the visible light produced by the electron beam of the SEM. PCL patterns reveal growth patterns and damage to crystal structures in natural and artificial materials. Examples of research projects making use of this new facility are described below. Rebecca Metzler, of the Colgate Department of Physics and Astronomy has used the new EBSD system to examine barnacle shell microstructure. Barnacles are arthropods dating back ~400 million years. Her undergraduate research students have begun to explore the micro-structure of both fossilized and modern barnacle exoskeletons, allowing for an exploration into the structure changes that have occurred over time. "By combining EBSD with synchrotron techniques (XANES and X-PEEM) andmicro-hardness testing, we have been able to explore the structure, composition, and materials properties of barnacle cement at an unprecedented scale, allowing us to identify two distinct regions within the cement." Co-PI Martin Wong has integrated the EBSD into his undergraduate structural geology course through the use of a lab where students analyze shear zone rocks petrographically and then collect EBSD data on those same samples as a way to learn about slip systems and ductile deformation mechanisms. In addition, many undergraduate research projects that Wong has supervised over the past two years have integrated both the CL and EBSD detectors, including EBSD investigations of mylonites in the Harcuvar, Sierra Mazatan, and Snake Range metamorphic core complexes and CL investigations of zircons dated by LA-ICPMS from the Harcvuar core complex. Co-William Peck notes that the SEM/EDS isthe primary instrument used in Geology 320, taught by William Peck.Students use the system to examine the paragenesis of example ore deposits. and for a final ore deposit project. Senior thesis student Max Ephraim is currently using the SEM-EDS-CL to characterize newly-discovered zircon veins in the Pikes Peak Batholith (CO),and independent study student Avalon Bunge is working on an SEM-EDS project examining the petrology of Fe-Ti oxides in metamorphosed anorthosites. PI Bruce Selleck, Department of Geology, and undergraduate research students have used the SEM system to determine the mineralogy and geochemistry of the Marcellus and Utica gas shales. Currently, Spencer Staley is using the SEM-EDS to quantify mineralogy using phase-component software on the new Oxford EDS system. Recent students have used the EDS to examine the mineralogy and chemistry of sulfide mineral phases in the organic-rich intervals of the Uticaand Marcellus. Selleck and co-workersat the University of Massachusetts have used the SEM-CL system to characterize mineral phases used in radiometric dating. Jonathan Levine, Department of Physics and Astronomy, reports "I've used the SEM in my teaching and research to analyze a pair of long-lived weathered meteorites from Roosevelt County, New Mexico, as part of my experiment to determine how long these meteorites have survived on Earth, and how they been altered by the terrestrial environment. Students MarySegreti '11, Gregory Jack '12, Lucas Gibson '13, and Damian Roesler '13 carried out these measurements using the the BSE detector and the EDS spectrometer. We presented Mary's work at the 42nd Lunar and Planetary Science Conference, March 2011."
