HR: 0800h
AN: V21E-0669    [Abstracts]
TI: Sniffing for Clues to the Dinosaurs Demise: Measurement of Osmium Isotope Compositions and Platinum Group Element Abundances in Volcanic Emissions
AU: * Sims, K W
EM: ksims@whoi.edu
AF: Woods Hole Oceanographic Institution, Woods Hole Rd, Woods Hole, MA 02543 United States
AU: Peucker-Ehrenbrink, B
EM: behrenbrink@whoi.edu
AF: Woods Hole Oceanographic Institution, Woods Hole Rd, Woods Hole, MA 02543 United States
AU: Mather, T
EM: tmat01@esc.cam.ac.uk
AF: Dept of Earth Sciences, University of Cambridge, Downing Street, Cambridge, UK CB2 3EQ United Kingdom
AU: Pyle, D
EM: dmp11@cam.ac.uk
AF: Dept of Earth Sciences, University of Cambridge, Downing Street, Cambridge, UK CB2 3EQ United Kingdom
AU: Martin, R
EM: rsm45@cam.ac.uk
AF: Dept of Earth Sciences, University of Cambridge, Downing Street, Cambridge, UK CB2 3EQ United Kingdom
AU: Gauthier, P
EM: P.J.Gauthier@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, OPGC - Univ. Bl. Pascal - CNRS, 5 rue Kessler, CLERMONT-FERRAND, 68000 France
AU: Aiuppa, A
EM: aiuppa@mail.unipa.it
AF: Dip. CFTA, Via archirafi, Palermo, 3690123 Italy
AB: Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial impact and the related KTB mass extinction by several hundred thousand years [Ravizza and Peucker-Ehrenbrink, 2003]. Distinguishing extraterrestrial from volcanic PGE sources has been difficult due to the similarity in Os isotopic compositions, complex PGE fractionations, and our lack of knowledge of the Os isotopic composition and PGE abundances in volcanic aerosols. These difficulties have fueled vigorous debate about extraterrestrial vs. volcanic triggers of mass extinctions in the geologic record. To assess the volcanic contribution to the global Re-Os-PGE cycle we have initiated a study of Os isotopic compositions and PGE abundances in volcanic emissions from volcanoes around the globe. Here we report preliminary data on PGE abundances and Os isotopes measured in gas and aerosol filter samples from Vulcan Masaya, Nicaragua and Mt Etna, Italy. Samples were analyzed by ID-ICPMS (ThermoFinnigan ELEMENT 2 and NEPTUNE) at the Woods Hole Oceanographic Institution. Osmium isotope compositions of the filters are unradiogenic (0.1272 to 0.187). Osmium concentrations range from 28 to 97 pg/cubic meter and are 3-4 orders of magnitude lower than those measured by Krahenbuhl et al. [1992] during the spring 1984 eruption of Mauna Loa just after the lava fountaining phase. Normalized PGE abundance patterns are fractionated relative to carbonaceous chondrites and two important features distinguish the pattern from other important PGE sources: 1) Os/Ir is much higher than that of the continental crust, the mantle and extraterrestrial matter; and 2) Pt/Pd is much lower than that of the continental crust, mantle, extraterrestrial matter and catalytic converters. If these PGE patterns from Masaya and Etna are typical of volcanic emissions worldwide they indicate that volcanic emission PGE patterns are distinct from the globally integrated KTB patterns [Tredoux et al. 1989; Evans et al., 1993] and that a volcanic source is not the cause of the elevated PGE abundances across the KTB. The PGE pattern of volcanic emissions is also different from catalytic converters enabling us to distinguish between volcanic sources and contamination from catalytic converters in places such as the Greenland Ice sheet [Barbante et al., 2001]. While these data have important implications for understanding the contribution of volcanic emissions to the global Re-Os-PGE cycles they need to be augmented with further analyses from other volcanoes.
DE: 8430 Volcanic gases
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005