HR: 0800h
AN: V41D-1488    [Abstracts]
TI: Geochemical constraints on the sources of basalt from the Kerguelen Archipelago, Southeast Indian Ocean
AU: * Xu, G
EM: gpxu@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 United States
AU: Frey, F A
EM: fafrey@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 United States
AU: Weis, D
EM: dweis@eos.ubc.ca
AF: Department of Earth Ocean Sciences, University of British Columbia, Vancouver, BC V6T1Z4 Canada
AU: Giret, A
EM: Andre.Giret@univ-st-etienne.fr
AF: Laboratoire de Géologie-Petrologie, Université Jean Monnet, Saint-Etienne, 42023 France
AB: The number and origin of the source components that contributed to the long-term (~120 Ma) volcanism forming the Kerguelen Plateau, the Ninetyeast Ridge and Kerguelen Archipelago are still a matter of debate. Besides the overwhelming contribution of Kerguelen plume there is compelling geochemical evidence for a continental component in basalt recovered by Ocean Drilling Program drilling at diverse locations on the Cretaceous Kerguelen Plateau. Mantle xenoliths found in Cenozoic basalt from the Kerguelen Archipelago also provide evidence for continental material at depth. Previous studies of the 30 - 24 Ma flood basalt forming the Kerguelen Archipelago we have emphasized roles of Kerguelen plume and MORB-related sources. Isotopic and geochemical data for an 860 m section of flood basalt at Mt. Capitole in the central part of the Kerguelen Archipelago show evidence of two stage mixing processes: a first stage, best shown by lavas forming the Northern Kerguelen Plateau, is between sources that are related to Indian Ocean ridge basalt (i.e., ⁸⁷Sr/⁸⁶Sr < 0.7037, ¹⁴³Nd/¹⁴⁴Nd > 0.5129, ¹⁷⁶Hf/¹⁷⁷Hf > 0.2831 and moderate Pb isotope ratios, ~18.1 for ²⁰⁶Pb/²⁰⁴Pb) and the Kerguelen plume (i.e., ⁸⁷Sr/⁸⁶Sr ~0.7053, ¹⁴³Nd/¹⁴⁴Nd ~0.5126 and ¹⁷⁶Hf/¹⁷⁷Hf ~0.28285 and radiogenic Pb isotope ratios). This first stage of mixing is followed by local introduction of a component with relatively high ⁸⁷Sr/⁸⁶Sr (>0.7055) and low ¹⁴³Nd/¹⁴⁴Nd (<0.5125) and ¹⁷⁶Hf/¹⁷⁷Hf (<0.28275) and non-radiogenic Pb isotope ratios (<18.0 for ²⁰⁶Pb/²⁰⁴Pb ratio). This component could either be lower continental crust dispersed into the Indian Ocean lithosphere and asthenosphere during breakup of Gondwana or, since the archipelago is built on the Kerguelen Plateau, it is possible that some of the continental contaminant that is present in the older plateau lavas is also affecting some of the archipelago lavas.
DE: 1000 GEOCHEMISTRY
DE: 1038 Mantle processes (3621)
DE: 1040 Radiogenic isotope geochemistry
DE: 1065 Major and trace element geochemistry
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005