HR: 1340h
AN: T13A-1123    [Abstracts]
TI: R/V Sonne Cruise SO193: New Insights Into the Geodynamic History of the Manihiki Plateau, SW-Pacific
AU: * Werner, R
EM: rwerner@ifm-geomar.de
AF: Tethys Geoconsulting GmbH, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Hauff, F
EM: fhauff@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Hoernle, K
EM: khoernle@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Coffin, M F
EM: mcoffin@ori.u-tokyo.ac.jp
AF: University of Tokyo, 1-15-1 Minamidai, Tokyo, 164-8639, Japan
AU: Scientific Party, S
AB: The Manihiki Plateau represents a Cretaceous Large Igneous Province (LIP) in the SW-Pacific. In May/June 2007, R/V Sonne cruise SO193 conducted ~4,700 nm of bathymetric mapping in key areas of the Manihiki Plateau region, and the first hard rock sampling of all major geomorphological units of the plateau as well as of seamounts on adjacent oceanic crust. The research project SO193 MANIHIKI aims to reconstruct the origin as well as spatial and temporal evolution of the Manihiki Plateau and to characterize the relationship between Manihiki and the other LIPs in the western Pacific. SO193 recovered magmatic or sedimentary rocks from 77 locations in the Manihiki Plateau region. Olivine-bearing sheet and pillow lavas dominate, but various types of volcaniclastic rocks are also common, some of them indicating subaerial or shallow water volcanic activity. Minor lithologies are, among others, picritic lavas, serpentinites, evolved lavas, and subvolcanic intrusives. Unexpectedly, the upper, directly accessible portions in some areas of the Manihiki Plateau (e.g., Suvorov Trough, North Plateau, the NE corner of the High Plateau) appear to mainly consist of solidified, indurated or lithified sediments which suggests secondary heating and/or intense tectonic movements. In contrast to the previously surveyed Hikurangi LIP east of New Zealand, guyot-type seamounts only exist in a few restricted areas of the Manihiki Plateau. The recent depth of their erosional platforms vary unsystematically between 1,600 m and 2,500 m below sea level (b.s.l.), implying different ages of these volcanoes or non-uniform subsidence rates. On the other hand, uneroded seamounts rising up to ~600 m b.s.l. occur on and close to the Manihiki Plateau. Pillow lavas dredged at a ~600 m high ridge on the High Plateau, which is believed to have formed under subaerial conditions, also indicate late-stage volcanic activity, after subsidence of the High Plateau. Taken together, the preliminary results of mapping and sampling of SO193 suggest a complex geodynamic history for the Manihiki Plateau, including long-term or repeated volcanism and intense tectonic movements (see also Coffin et al. abstract).
DE: 1033 Intra-plate processes (3615, 8415)
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8415 Intra-plate processes (1033, 3615)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting