HR: 17:45h
AN: OS24B-04    [Abstracts]
TI: An Updated Method for the Measurement of Silicon Isotopes From Opal, Examples From Cariaco Basin Sediment Traps
AU: * Scher, H D
EM: howie@ucsc.edu
AF: University of California Santa Cruz, Ocean Sciences Department/Institute of Marine Sciences 1156 High St., Santa Cruz, CA 95064, United States
AU: Thunell, R C
EM: thunell@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences 700 Sumter St., Columbia, SC 29208, United States
AU: Delaney, M L
EM: delaney@ucsc.edu
AF: University of California Santa Cruz, Ocean Sciences Department/Institute of Marine Sciences 1156 High St., Santa Cruz, CA 95064, United States
AB: We modified a new method for the complete digestion of silicate minerals (van den Boorn et al., 2006, JAAS, 21, 734-742), replacing a Parr bomb NaOH digestion with a hot plate digestion using Teflon beakers. The method is ideal for amorphous silicate minerals such as opal, and has been tested using diatoms recovered from the >125 μm fraction of sediment trap samples from the Cariaco Basin. A complete digestion of these samples was achieved using this revised method. The method has been used to prepare samples for silicon (Si) isotope analyses on a Neptune MC-ICPMS. The MC-ICPMS method was tested using the Si isotope reference material ‘big batch', correcting for mass bias by standard-sample bracketing. The δ²⁹Si and δ³⁰Si values of big batch, normalized to NIST RM-8546 (formerly NBS-28), are in agreement with published values (van den Boorn et al., 2006). This method will be evaluated with other Si reference materials (e.g., diatomite). Ultimately the new digestion method and MC-ICPMS method will be used to measure Si isotope variability in diatoms from the Cariaco Basin sediment trap samples. Furthermore, replicates will be used in an interlaboratory calibration to test the reproducibility between different techniques (e.g., MC-ICPMS vs. gas source).
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4894 Instruments, sensors, and techniques
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting