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JEOL JSM636OLV Scanning Electron Microscope with: Oxford X-max Silicon Drift X-ray Detector Nordlys EBSD detector and Gatan Cathod Luminescence Detctor Purchased with grants from the National Science Foundation What it does: The Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectrometer (EDS) is used for detailed, high magnification, 3-D imaging and qualitative and semi-quantitative chemical analysis of solids. How it works: A beam of high energy electrons is produced in the electron gun at the top of the column by applying high voltage to a tungsten filament and nearby anode. This beam is accelerated down past the anode into the column where it is condensed and aligned by a series of electromagnetic lenses and coils within the column. This focused beam continuously rasters back and forth across the sample. Interactions between the electron beam and the sample result in different types of emissions that are measured by a series of detectors located within the sample chamber. The four types of emissions that are measured are: secondary electrons, backscattered electrons, x-rays, and cathode luminescence. X-ray data is sent to the EDS system where it is translated into elemental plots. The other three detectors are connected to a 'TV' screen where the signal produces a clear, black and white (green actually) image of the sample. Secondary electron imaging provides good 3-dimensional topographic views of the sample. Backscattered electron images show less defined topography but clearly display differences in elemental compositions because higher atomic number elements appear brighter. Cathode luminescence imaging highlights chemical variations within individual grains due to trace element variations and zoning. Instrument Statistics: For more information on our detectors, visit their respective webpages: Oxford X-max Silicon Drift X-ray Detector Nordlys EBSD detector Publications from work done in Colgate SEM lab: Peck, WH, McLelland, JM, Bickford, ME, Nagle, AN*, Swarr, GJ*, 2010, Mechanism of zircon overgrowth formation of a granulite-facies quartzite, Adirondack Highlands, Grenville Province, New York: American Mineralogist, v. 95, p. 1796-1806. Segall, K, Dioguardi, AP, Fernandes, N, Mazo, JJ (2009) Experimental Observation of Fluxon Diffusion in Josephson Rings, Journal of Low Temperature Physics, v. 154, 41-54. Cavosie AJ, Kita NT and Valley JW (2009). Magmatic zircons from the Mid-Atlantic Ridge: Primitive oxygen isotope signature. American Mineralogist 94(7): 926-934. King, EM, Trzaskus, AP, and Valley, JW (2008) Oxygen isotope evidence for magmatic variability and multiple alteration events in the Proterozoic St. Francois Mountains, Missouri, Precambrian Research, Volume 165, Pages 49-60. Bickford, M.E., McLelland, J.M., Selleck, B.W., Hill, Barbara M., and Heumann, M.J.(2008) Timing of anatexis in the eastern Adirondack Highlands: Implications for tectonic evolution during ca. 1050 Ma Ottawan orogenesis; Geol. Soc. America Bulletin, v. 120. Carr, P., Selleck, B., Stott, M., Williamson, P. (2008) Native lead at Broken Hill, New South Wales, Australia; Canadian Mineralogist, v. 46. Kelly JL, Fu B, Kita NT and Valley JW (2007). Optically continuous silcrete quartz cements of the St. Peter Sandstone: High precision oxygen isotope analysis by ion microprobe. Geochimica et Cosmochimica Acta 71(15): 3812-3832. Matthew J. Heumann, Marion Bickford, Barbara M. Hill, James McLelland, Bruce Selleck and M. J. Jercinovic (2006) Timing of anatexis in metapelites from the Adirondack lowlands and southern highlands: A manifestation of the Shawinigan orogeny and subsequent anorthosite-mangerite-charnockite-granite magmatism; Geological Society of America Bulletin, v. 118, no. 8. Selleck, B., McLelland, J.M. and Bickford, M.E. (2005) Granite emplacement during tectonic exhumation: The Adirondack example; Geology, v. 33, p. 781-784. Peck, WH, DeAngelis, MT, Meredith, MT, Morin, E (2005) Polymetamorphism of marbles in the Morin terrane (Grenville Province, Quebec): Canadian Journal of Earth Sciences, v. 42, p. 1949-1965. |
