Geology Scholarship Proposal - Example

Introduction: The Scanning Electron Microscope (SEM) is designed to examine and image objects at magnifications of up to 300,000X.  It uses a filament that sends a beam of electrons towards the sample.  The beam travels through two sets of lenses before reaching the sample, where it is usually rastered in rows.  Electrons bouncing back from the surface of the sample are then used to generate a 3D like image.  The incident electrons can also generate X-rays characteristic of the elements contained in the sample examined. Collection of these X-rays by an energy dispersive spectrometer (EDS) yields information on the elemental composition of the sample (Goldstein et al., 1981; Reed, 1996). However, all of the data collected with the EDS is qualitative. 

The College of Science, Marshall University has had a JEOL JSM-5310LV SEM with an Oxford Instruments EDS detector for at least ten years.  Although this instrument has been successfully used for a variety of projects in Biology, Chemistry, Earth Sciences, Forensics and Anthropology, all of the data collected so far has been qualitative. Advances in software development over the past 15 years have made it possible to obtain quantitative data from spectra collected by EDS detectors. I therefore propose to calibrate the electron beam and EDS detector for the analysis of elements that occur in common rock-forming minerals which would make obtaining quantitative information possible.

Significance: The objectives of this project are: (i) to calibrate the SEM and EDS detector for the elements: Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Cr, Mn, Zn, and Cl using a set of well characterized standards, so that it can be used in the future for analysis of minerals, (ii) to test the precision and accuracy of the calibration using other standards and previously analyzed (and well characterized) minerals; and (iii) to write a protocol for the routine calibration and quantitative analysis of minerals, metals, and alloys.   

Experimental Approach and Work Plan: The department of Chemistry will offer the 4 credit hour class CHM483 “Advanced Microscopic Techniques” next Spring which I plan on taking. This will familiarize me with the procedures of operating the SEM.  In addition, I will be working on the calibration of the electron beam and EDS detector for ~ sixty five hours; averaging four - five hours a week. Calibration will be done using a set of well characterized mineral and oxide standards provided from the Smithsonian Institute that are pure and homogenous. These standards have been mounted on a block that can also hold a standard thin section of a rock or mineral. This design would allow for the analysis of unknowns immediately after standardization. Beam calibration and standardization will be carried out using the LINK ISIS 300 software (v. 3.02) available in the lab and following the procedures outlined in the manuals provided by Oxford Instruments. I will then test the accuracy of my standardization by analyzing multielement Smithsonian standards (not used in the original standardization) and minerals of known composition provided by the Geology faculty. Precision will be gauged by the ability to replicate our results.

Specific Outcomes: Calibration and standardization of the electron beam and EDS will allow for the quantitative analysis of minerals in thin sections. I plan on analyzing coexisting minerals from schists and gneisses from Oman and the Blue Ridge in North Carolina. These analyses will then be used to calculate temperatures and pressures of formation of these minerals based on the use of widely used geothermometers and geobarometers (e.g. Essene, 1982).

References:

Essene, E. J., 1982. Geologic thermometry and barometry. In Ferry, J. M.(ed.) Characterization of metamorphism through mineral equilibria. Reviews in Mineralogy, 1): 153 – 206.

Goldstein, Joseph I.; Newbury, Dale E.; Echlin, Patrick; Joy, David C.; Fiori, Charles; Lifshin, Eric, 1981. Scanning Electron Microscopy and X-Ray Microanalysis: A Test for Biologists, materials Scientists, and Geologists. New York: Plenum Press.

Reed, S.J.B., 1996. Electron Microprobe Analysis and Scanning Electron Microscopy in Geology. Cambridge University Press, Great Britain.

 

Budget:

• Student stipend: $1000

• All the supplies will be provided by the department of Geology at Marshall University.