K-AR Geochronology Laboratory
The GSU K-Ar Geochronology laboratory published its first data ca 2010. This lab moved from Georgia Tech to GSU Geosciences ca. 2008. This facility is a consolidation of the former K-Ar lab at Georgia Tech run by Prof. Marion Wampler with some new add-ons provided by Crawford Elliott. This facility features a Perkin-Elmer atomic absorption spectrophotometer, formerly part of Seth Rose’s lab, for measurement of potassium. Samples are dissolved for potassium measurement in a fume hood rated for perchloric acid in 615KH. Argon isotopic composition is measured with a mass spectrometer connected to a high vacuum extraction line. To extract argon, samples are heated by an external wire-wound heater (clay minerals only) or melted in an internal resistance-heated furnace, and a known amount of 38Ar is added as a ‘spike’ (an isotopic internal standard). The extracted gases pass through thermal-gradient traps cooled by liquid nitrogen to remove water and CO2 and then are cleaned with heated titanium. The cleaned argon is isotopically analysed by an MS-10 mass spectrometer. This MS-10 mass spectrometer was recently computerized to permit more precise and accurate analyses. LP-6 biotite and other well-known interlaboratory standards are analyzed to monitor the argon spike. Samples are weighed with a Mettler analytical balance accurate to 0.1 mg.
Among the notable accomplishments is the development of a one weigh-out procedure for measurement of the K-Ar age of clay minerals. In this procedure, the clay sample is first heated at a temperatures sufficient to remove all argon (1000 C). That extracted argon is analyzed for its argon isotopic composition. The sample is then retrieved from the extraction line and dissolved in mixed hydrofluoric and nitric acids. Potassium from the dissolved material is then measured. This procedure results in a lower error for the K-Ar age. It is particularly useful for samples with low radiogenic argon and whose amounts are low. This procedure was used by Stroker et al. (2013), Derkowski et al. (2013), and Vandenberghe et al. (2014) and for part of the work by Naumann et al. (2012) . It was first developed for K-Ar measurement of glaucony grains from the Atlantic Coastal Plain with undergraduate student Elizabeth Stephens (Stephens et al., 2007).
Atsushi Nakao and students., Investigation of the mineralogy and geochronology of aeolian fraction in Japanese andisols.
Selahattin Kadir, Geochronology of bentonites in Central Anatolia Basin, Turkey.
Williams, L. Elliott, W.C., Hervig, R., 2015, Tracing hydrocarbons in gas shale using boron and lithium isotopes: Denver Basin USA, Wattenberg Gas Field: Chemical Geology, v. 417, p. 404-413.doi:10.1016/j.chemgeo.2015.10.027
Osborn, S.G., Duffield, L.T., Elliott, W.C., Wampler, J.M., Elmore, R.D., Engel, M.H., 2014, The timing of diagenesis and thermal maturation of the Cretaceous Marias River Shale, Disturbed Belt, Montana: Clays and Clay Minerals, v. 62, p.112-125. http://dx.doi.org/10.1346/CCMN.2014.0620204
Vandenberghe, N., Harris, W.B., Wampler, J.M., Houthuys, R., Louwye, S., Adriaens, R., Vos, K., Lanckacker, T., Matthijs, J., Deckers, J., Verhaegen, J., Laga, P., Westerhoff, W., Munsterman, D., 2014, The implications of K-Ar glauconite dating of the Diest Formation on the paleogeography of the Upper Miocene in Belgium: Geologica Belgica, v. 17, p. 161-174.
Derkowski, A., Bristow, T.F., Wampler, J.M., Środoń, J., Marynowski, L., Elliott, W.C., Chamberlin, C.P., 2013, Hydrothermal alteration of the Ediacaran Doushantuo Formation in the Yangtze Gorges area (South China): Geochimica et Cosmochimica Acta, v. 107, 279-298. http://dx.doi.org/10.1016/j.gca.2013.01.015
Stroker, T.M., Harris, N.B., Elliott, W.C., Wampler, J.M., 2013, Diagenesis of a tight gas sand reservoir: Upper Cretaceous Mesaverde Group, Piceance Basin, Colorado: Marine and Petroleum Geology, v. 40, p. 48-68.http://dx.doi.org/10.1016/j.marpetgeo.2012.08.003
Naumann, T.E., Elliott, W.C., Wampler, J.M., 2012, K-Ar age constraints on the origin of micaceous minerals in Savannah River Site soils, South Carolina, USA: Clays and Clay Minerals. v. 60, 497-507. DOI: 10.1346/CCMN.2012.0600506
Stephens, E., Anderson, J.A., Gullett-Young, C., Wampler, J.M., Elliott, W.C., 2007 Age of the Ocmulgee Limestone (Georgia Coastal Plain) based on revised methodology for the K-Ar age of glaucony: Southeastern Geology, v. 45, no. 1, p. 15-24.
Shaikh, Afshan, “Silt Geochronology and Mineralogy, Mount Daisen, Japan.” Thesis, Georgia State University, 2015.