HR: 1340h
AN: V33A-1174    [Abstracts]
TI: Penguin Bank: A Loa-Trend Hawaiian Volcano
AU: * Xu, G
EM: gpxu@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avuene, 54-1210, Cambridge, MA 02139, United States
AU: Blichert-Toft, J
EM: jblicher@ens-lyon.fr
AF: Ecole Normale Superieure de Lyon, Laboratoire de Sciences de la Terre, Lyon, CNRS 5570, France
AU: Clague, D A
EM: clague@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, United States
AU: Cousens, B
EM: bcousens@earthsci.carleton.ca
AF: Carleton University, Department of Earth Sciences, Ottawa, ON K1S 5B6, Canada
AU: Frey, F A
EM: fafrey@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Avuene, 54-1210, Cambridge, MA 02139, United States
AU: Moore, J G
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AB: Hawaiian volcanoes along the Hawaiian Ridge from Molokai Island in the northwest to the Big Island in the southeast, define two parallel trends of volcanoes known as the Loa and Kea spatial trends. In general, lavas erupted along these two trends have distinctive geochemical characteristics that have been used to define the spatial distribution of geochemical heterogeneities in the Hawaiian plume (e.g., Abouchami et al., 2005). These geochemical differences are well established for the volcanoes forming the Big Island. The longevity of the Loa- Kea geochemical differences can be assessed by studying East and West Molokai volcanoes and Penguin Bank which form a volcanic ridge perpendicular to the Loa and Kea spatial trends. Previously we showed that East Molokai volcano (~1.5 Ma) is exclusively Kea-like and that West Molokai volcano (~1.8 Ma) includes lavas that are both Loa- and Kea-like (Xu et al., 2005 and 2007).The submarine Penguin Bank (~2.2 Ma), probably an independent volcano constructed west of West Molokai volcano, should be dominantly Loa-like if the systematic Loa and Kea geochemical differences were present at ~2.2 Ma. We have studied 20 samples from Penguin Bank including both submarine and subaerially-erupted lavas recovered by dive and dredging. All lavas are tholeiitic basalt representing shield-stage lavas. Trace element ratios, such as Sr/Nb and Zr/Nb, and isotopic ratios of Sr and Nd clearly are Loa-like. On an εNd-εHf plot, Penguin Bank lavas fall within the field defined by Mauna Loa lavas. Pb isotopic data lie near the Loa-Kea boundary line defined by Abouchami et al. (2005). In conclusion, we find that from NE to SW, i.e., perpendicular to the Loa and Kea spatial trend, there is a shift from Kea-like East Molokai lavas to Loa-like Penguin Bank lavas with the intermediate West Molokai volcano having lavas with both Loa- and Kea-like geochemical features. Therefore, the Loa and Kea geochemical dichotomy exhibited by Big Island volcanoes existed at ~2.2 Ma when the Molokai Island volcanoes formed and has persisted until the present. References: Abouchami et al., 2005 Nature, 434:851-856 Xu et al., 2005 G³, doi: 10.1029/2004GC000830 Xu et al., 2007 G³, doi: 10.1029/2006GC001554
DE: 1025 Composition of the mantle
DE: 1037 Magma genesis and partial melting (3619)
DE: 1038 Mantle processes (3621)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting