Shipboard Geophysical Indications of Asymmetry and Melt Production Beneath the East Pacific Rise Near the MELT Experiment
Daniel S. Scheirer,
*
Donald W. Forsyth,
Marie-Hélène Cormier,
Ken C. Macdonald
Near the Mantle Electromagnetic and Tomography (MELT)
Experiment, seamounts form and off-axis lava flows occur in a zone that extends farther to the west of the East Pacific Rise than to the east,
indicating a broad, asymmetric region of melt production. More
seamounts, slower subsidence, and less dense mantle on the western
flank suggest transport of hotter mantle toward the axis from the west.
Variations in axial ridge shape, axial magma chamber continuity,
off-axis volcanism, and apparent mantle density indicate that upwelling
is probably faster and more melt is produced beneath 17°15'S than
beneath 15°55'S. Recent volcanism occurs above mantle with the lowest
seismic velocities.
D. S. Scheirer and D. W. Forsyth, Department of
Geological Sciences, Box 1846, Brown University, Providence, RI 02912, USA.
M.-H. Cormier, Lamont-Doherty Earth Observatory of Columbia University,
Palisades, NY 10964, USA.
K. C. Macdonald, Department of Geological Sciences, University of
California, Santa Barbara, CA 93106, USA.
*
To whom correspondence should be addressed. E-mail:
scheirer{at}emma.geo.brown.edu
