HR: 0800h
AN: V31C-1442    [Abstracts]
TI: Geochemistry of the Baie Charrier Basaltic Section, Courbet Peninsula, Kerguelen Archipelago
AU: * Hanano, D W
EM: diane23@telus.net
AF: EOS, University of BC, 6339 Stores Rd, Vancouver, BC V6T1Z4 Canada
AU: Weis, D
EM: dweis@eos.ubc.ca
AF: EOS, University of BC, 6339 Stores Rd, Vancouver, BC V6T1Z4 Canada
AU: Scoates, J S
EM: jscoates@eos.ubc.ca
AF: EOS, University of BC, 6339 Stores Rd, Vancouver, BC V6T1Z4 Canada
AU: Giret, A
EM: Andre.Giret@univ-st-etienne.fr
AF: Laboratoire de G\'{e}ologie, Universit\'{e} Jean Monnet, CNRS-UMR 6524, Saint Etienne, 42023 France
AB: The Kerguelen Archipelago, located in the Southern Indian Ocean, is the third largest oceanic island and represents the emergent part of the Northern Kerguelen Plateau. We present new petrographic and geochemical data from the Baie Charrier basaltic section on the northern Courbet Peninsula. This dataset complements the 1000 m Mont Crozier basaltic section located 16 km to the southwest in the central part of the peninsula. Isotopic compositions of the Crozier basalts are interpreted to be representative of the enriched component of the Kerguelen mantle plume. The Baie Charrier basalts are mildly alkalic and olivine-phyric, with a range of MgO contents (3.1-16.7 wt.%) significantly larger than that observed in the Crozier section. Mafic phenocrysts are normally zoned, with olivine core compositions of Fo$_{86-70}$ and clinopyroxene core Mg\#'s of 0.88 to 0.79. Mineral-melt equilibria constraints indicate a maximum MgO content for the Baie Charrier parental magmas of 8-10 wt.%. Major and trace element concentrations, as well as Sr, Nd, Pb, and Hf isotopic compositions, identify four distinct volcanic units within the Baie Charrier section, reflecting temporal changes in volcanism derived from a heterogeneous source region. A comparison of the Baie Charrier and Crozier sections shows similar Zr/Nb ratios of 6-7.5, enrichments in incompatible and light rare earth elements, and highly radiogenic Pb compositions ($^{206}$Pb/$^{204}$Pb = 18.35-18.64). This suggests that both sections are derived from the same source region and provides further evidence that the Courbet Peninsula is a single volcanic unit. However, the abundance of olivine-phyric basalts at Baie Charrier, and their absence at Crozier, suggests that the eruptive center of this volcano may not coincide with the present geographic center of the peninsula. The Baie Charrier basalts contain a strong signature of the enriched plume component and provide additional constraints on the composition of the Kerguelen mantle plume.
DE: 8439 Physics and chemistry of magma bodies
DE: 1040 Isotopic composition/chemistry
DE: 1065 Trace elements (3670)
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 1010 Chemical evolution
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting