HR: 0800h
AN: T11C-0397    [Abstracts]
TI: Crustal Xenoliths From Malaita, Solomon Islands: A Window to the Lower Crust of the Ontong Java Plateau
AU: * Shafer, J T
EM: jshafer@nd.edu
AF: Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 United States
AU: Neal, C R
EM: neal.1@nd.edu
AF: Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 United States
AU: Mahoney, J J
EM: jmahoney@soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822 United States
AB: A suite of xenoliths from alnöite pipes on the island of Malaita, Solomon Islands, show evidence of being derived from the lower crust of the Ontong Java Plateau (OJP). Whole-rock major and trace element data have been collected by ICP methods and mineral composition investigated by electron microprobe and laser ablation ICP-MS. The xenoliths range from mafic granulite to garnet-bearing pyroxenite. Major element data indicate the samples are generally basaltic in composition. Most appear to be from deeper sections of the OJP's crust that have been affected by burial metamorphism. Xenoliths containing garnet porphyroblasts and clinopyroxene phenocrysts are used to constrain the depth of origin. However, Nd, Sr, and Pb isotope data on mineral separates indicate significant resetting near the time of alnöite emplacement. These samples are from a deep level of the OJP unlikely to ever be sampled by drilling, and provide a window into the interior of the OJP.
DE: 1040 Radiogenic isotope geochemistry
DE: 1065 Major and trace element geochemistry
DE: 3038 Oceanic plateaus and microcontinents
DE: 3640 Igneous petrology
SC: Tectonophysics [T]
MN: Fall Meeting 2005