HR: 0800h
AN: V21D-0760    [Abstracts]
TI: Volcanic, tectonic, and hydrothermal features identified in the Lau Basin with near-bottom multibeam sonar data
AU: * Ferrini, V L
EM: ferrini@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory, Marine Geology and Geophysics, Palisades, NY 10964, United States
AU: Tivey, M K
EM: mktivey@whoi.edu
AF: Woods Hole Oceanographic Institution, Dept. of Marine Chemistry and Geochemistry, Woods Hole, MA 02543, United States
AU: Carbotte, S M
EM: carbotte@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory, Marine Geology and Geophysics, Palisades, NY 10964, United States
AU: Martinez, F
EM: fernando@hawaii.edu
AF: University of Hawaii at Manoa, School of Ocean and Earth Science Technology, Honolulu, HI 96822, United States
AB: We present high-resolution bathymetric maps of six hydrothermal vent fields located along the Eastern Lau Spreading Center and Valu Fa Ridge in the Lau backarc basin. Generated with near-bottom SM2000 multibeam sonar data collected with ROV Jason 2, these maps provide sufficient detail to quantify tectonic, volcanic, and hydrothermal features that reveal important differences in these hydrothermal systems, their geologic settings, and the nature of their volcanic substrate. The Kilo Moana and Tow Cam vent fields, hosted in basaltic substrate, have bathymetric characteristics that distinguish them from the Mariner and Vai Lili fields that are hosted in andesitic substrate. The basalt-hosted vent fields are located on relatively flat seafloor crosscut by extensive faults and fissures. At these sites, the high-resolution bathymetry indicates that volcanic activity pre-dates tectonic activity. Pillow and lobate flows at these sites can be discerned as sub-meter roughness, with amplitudes of 0.1- 0.4 m over length scales of 0.5-1 m. Vent structures (5-15 m tall) are clearly identifiable. In contrast, the andesite- hosted vent fields have more relief, and roughness is evident as finger-like flow fronts related to more viscous andesitic flows. Volcanic domes (15-30 m diameter), some with collapse craters (10-20 m diameter), are also evident at these vent fields. Hydrothermal structures at Mariner are as tall as 25m, while at Vai Lili vents are smaller and difficult to distinguish from the rough seafloor that surrounds them. The detailed bathymetry at these vent fields is consistent with the tectonic activity pre-dating volcanic activity. The bathymetric features documented at the ABE and Tui Malila vent fields are transitional to the contrasting features observed to the north (at Kilo Moana and Tow Cam) and south (Mariner and Vai Lili). Bathymetric maps from ABE and Tui Malila reveal pillow and lobate flows, faults that post-date volcanic activity, finger-like flow fronts, and volcanic domes (Tui Malila). Hydrothermal structures at these sites are <5m tall.
DE: 3001 Back-arc basin processes
DE: 3045 Seafloor morphology, geology, and geophysics
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting