Student Research Projects

EDS Microanalysis of sediment samples derived from the Lower Chlorite-Muscovite Unit of the Evington Group, Fluvanna County, Virginia

Student Ericka Hayes, '17
Faculty Mentor(s)
Department Earth and Environmental Sciences
Course EES 489: Research in Natural Sciences

Abstract

Geological Studies of the Piedmont region of Virginia are hampered by the lack of outcrops, thick soil profiles, and dense vegetation. Despite these difficulties, existing studies of the Piedmont were restricted to traditional methods of outcrop studies and thin sections. These restrictions lead to large gaps in our understanding of the geologic formation of the Piedmont. By studying the sediments derived from Piedmont formations in small watersheds, each of which are restricted to a single formation, it is possible to increase our knowledge of the composition of these formations. To test this method, we chose to study Woodson Creek, Fluvanna County, Virginia, the sediments of which are derived from the Lower Chlorite-Muscovite Unit of the Evington Group. Samples were studied using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The samples were cleaned of clay particles with deflocculating reagent and sorted by sieving. To analyze the finest fraction, tetra-bromoethane was used to separate the information-rich heavy minerals from the abundant and less diagnostic light fraction. Minerals were identified using spectra, produced by EDS which we compared to those of known minerals. Percent oxides were calculated and compared to published data and stoichiometry was calculated to confirm their compositions. We identified thirteen minerals that are not listed in the Virginia Division of Mineral Resources\' bulletin of the Lower Chlorite-Muscovite Unit. The minerals include: Amphiboles, Biotite, Clinozoisite, Garnet, Hematite, Ilmenite, Iron-Magnesium Muscovite, Magnetite, Pyroxenes, Rutilated Quartz, Sphene, Tourmaline and Zircon. This is a far more comprehensive list than those discovered by traditional methods in previous studies of Fluvanna County and the Piedmont.