2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 40-32
Presentation Time: 9:00 AM-5:30 PM


RAND, Cari, NAWIESNIAK, Julie and ST. JOHN, Kristen, Department of Geology and Environmental Science, James Madison University, Harrisonburg, VA 22807, rand.cari77@gmail.com

The handheld x-ray florescence analyzer (XRF) is a useful analytical tool, allowing for the collection of non-destructive quantitative elemental data for stratigraphic differentiation of rock and sediment units. The purpose of our research was to conduct a methodological study of the Bruker handheld XRF analyzer. We developed protocols for its use and investigated its capacity to produce accurate results by comparing with previously collected data. We focused on the upper 7 m of sediment cored at MD02-2560 from Kane Spur in the Gulf of Mexico. One sample from each core section was scanned 5 times consecutively to determine reproducibility, giving an average standard deviation of the mean of less than one tenth. Once scanned, the data were analyzed using the ARTAX software. This allowed us to graph photon counts by their energies and calculate the areas under the generated curves in order to approximate the abundances of each of 20 identified elements, a process called Region of Interest (ROI) analysis. We compared our results to a data set provided by the IODP Gulf Coast Repository. They had scanned the archive half of the same core using a core track-mounted Avaatech XRF analyzer. We were able to produce data that showed the same glacial to interglacial stratigraphic pattern in elemental abundances by depth, with small variation attributed to different scan parameters (e.g., current, filters, sample spacing). An exception occurred in core section 6, which we believe was due to a puncture in the detector chamber cover of the handheld XRF which lead to contamination of the equipment and artificially deflated elemental counts. A rescan of section 6 is testing this hypothesis. Additionally, we are developing calibrations to move from the semi-quantitative data we currently have to more specific, quantitative elemental percent abundances. The only calibrations currently available are for older lithified mud rocks in the Gulf; we are developing a calibration specific to our sedimentary record. Sample horizons from Sections 3, 4, and 5 of the core have been selected for calibration based on high, low, and intermediate concentrations of elements. ICP-PMS will be used to determine elemental concentrations and be used to generate a calibration curve generated for the each element.