title: Asymmetric Electrical Structure in the Mantle Beneath the East Pacific Rise at 17 degrees S.
abstract: The magnetotelluric component of the Mantle Electromagnetic and Tomography (MELT) Experiment measured the electrical resistivity structure of the mantle beneath the fast-spreading southern East Pacific Rise (EPR). The data reveal an asymmetric resistivity structure, with lower resistivity to the west of the ridge. The uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles. Mantle resistivities to the west of the ridge are consistent with a low-melt fraction (about 1 to 2 percent interconnected melt) distributed over a broad region and extending to depths of about 150 kilometers. The asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates.
authors.affiliation: Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. UMR CNRS 6538, Universite Bretagne Occidentale, Brest, France. Flinders University, Adelaide, South Australia 5042, Australia. Scripps Institution of Oceanography, La Jolla, CA 92093, USA. Toyama University, Toyama 930-8555, Japan. Chiba University, Chiba, Japan. Earthquake Research Institute, University of Tokyo, Tokyo 113, Japan. Geophysics Program AK-50, University of Washington, Seattle, WA 98195, USA.
authors.initials: RL
authors.lastname: Evans
authors.initials: P
authors.lastname: Tarits
authors.initials: AD
authors.lastname: Chave
authors.initials: A
authors.lastname: White
authors.initials: G
authors.lastname: Heinson
authors.initials: JH
authors.lastname: Filloux
authors.initials: H
authors.lastname: Toh
authors.initials: N
authors.lastname: Seama
authors.initials: H
authors.lastname: Utada
authors.initials: JR
authors.lastname: Booker
authors.initials: MJ
authors.lastname: Unsworth