HR: 0800h
AN: V21D-0627    [Abstracts]
TI: Initiation of Pacific Cenozoic Seamount Chains at Older Fracture Zones
AU: * Winterer, E L
EM: jwinterer@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093 United States
AB: Most of the Cenozoic seamount chains on the Pacific plate are parallel to the Hawaiian chain and most start on the young edge of a fracture zone. Example include the Erben, Moonless and "West Moonless" chains on the Murray FZ, the Crosstrend on the clarion FZ, the Crossgrain Chain on the Clipperton FZ and the Tuamotus and Society chains on the Marquesas FZ. The Hawaiian chain itself is broken and offset at the Murray FZ. Exceptions include the Marquesas and Emperor chains. Many of the chains do not extend past the next FZ to the south. Older FZ-bounded compartments, not older than more than a few million years relative to the adjacent compartment, are relatively free of seamount chains as compared to adjacent younger compartments, even close to the sites of initiation. The site of initiation is commonly at a small change in orientation or style of the FZ at a point or along a segment of the FZ. After initiation, the chain extends itself to the southeast, in a direction roughly opposite to Pacific plate motion. A proposed initiation mechanism for some chains is a new stress on a "flaw" along the FZ, oriented so as to produce a local tensional strain that opens local fissures that allow magmas to separate and rise from the asthenosphere to erupt as a volcano on the thinner lithosphere within or on the young side of the FZ. The mechanism need call only on upper mantle sources for the volcanism and requires no deep plumes.
DE: 1033 Intra-plate processes (3615, 8415)
DE: 3615 Intra-plate processes (1033, 8415)
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8164 Stresses: crust and lithosphere
DE: 8178 Tectonics and magmatism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005