HR: 0800h
AN: V41A-1419    [Abstracts]
TI: A new calibration of H measurements by SIMS in glasses and nominally anhydrous minerals: application to experimental determinations of H partitioning
AU: * Aubaud, C
EM: aubau001@umn.edu
AF: Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455
AU: Withers, A C
EM: withe012@umn.edu
AF: Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455
AU: Hirschmann, M M
EM: hirsch022@umn.edu
AF: Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455
AU: Guan, Y
EM: yunbin.guan@asu.edu
AF: Department of Geology, Arizona State University, Tempe, AZ 85287
AU: Leshin, L A
EM: laurie.leshin@asu.edu
AF: Department of Geology, Arizona State University, Tempe, AZ 85287
AU: Mackwell, S J
EM: mackwell@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Blvd, Houston, TX 77058
AU: Bell, D R
EM: david.r.bell@asu.edu
AF: Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85282
AB: We present new SIMS calibrations of H concentrations in basalt (0.17 to 7.37 wt% H₂O, n = 13), rhyolite (0.3 to 6.2 wt% H₂O, n = 10), and quartz (4 wt% H₂O, n =1) glasses, and olivine (~0 to 243 ppm H₂O, n = 5), opx (~0 to 263 ppm H₂O, n = 5), cpx (~0 to 490 ppm H₂O, n = 6), pyrope garnet (~0 to 194 ppm H₂O, n = 8) minerals using the CAMECA 6f ion microprobe at ASU. Standards include experimental and natural samples characterized for H content by unpolarized (glasses and garnet) and polarized (on oriented olivines and pyroxenes) FTIR and nuclear reaction analysis (for olivine, Bell et al. JGR 2003). Careful attention to vacuum quality, including epoxy-free sample mounting using aluminium disks filled with indium, yielded routine detection limits of 5-10 ppm H₂O, measured on H₂O-free synthetic olivine. Calibration curves for basaltic, rhyolitic and quartz glasses show negligible compositional effects when ¹H/³⁰Si measured by SIMS is compared to sample H₂O/SiO₂, indicating that matrix effects for SIMS analsyses of H with Cs⁺ beams may be minimal. Experimental measurements of mineral/melt partition coefficients, including new experiments analyzed at ASU and our previous results (Aubaud et al., GRL 2004) are consistent with mineral/melt partition coefficients applicable to the mantle as follows: D^(ol/melt) = 0.0017, D^(opx/melt) = 0.019, and D^(cpx/melt) = 0.023 and D^(perid/liq) = 0.009. Mineral/melt Ds do not show obvious dependences on pressure between 1-3 GPa or H₂O concentrations in glasses between 3.1 and 8.8 wt% H₂O, though such effects may occur at higher pressure or lower H₂O.
DE: 1000 GEOCHEMISTRY
DE: 1094 Instruments and techniques
DE: 3600 MINERALOGY AND PETROLOGY
DE: 3900 MINERAL PHYSICS
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005