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Published on: August 5, 2016
Asymmetric Electrical Structure in the Mantle Beneath the East Pacific Rise at 17 degrees S
1Woods 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.
The Mantle Electromagnetic and Tomography (MELT) Experiment revealed asymmetric mantle electrical resistivity beneath the East Pacific Rise. Lower resistivity west of the ridge suggests interconnected melt, unlike the dry mantle east of the ridge.
Area of Science:
- Geophysics
- Mantle Geodynamics
- Electromagnetic Methods
Background:
- The East Pacific Rise (EPR) is a fast-spreading mid-ocean ridge.
- Understanding mantle electrical resistivity is key to constraining melt distribution and mantle composition.
Purpose of the Study:
- To investigate the electrical resistivity structure of the mantle beneath the southern East Pacific Rise (EPR).
- To understand melt distribution and mantle processes associated with asymmetric seafloor spreading.
Main Methods:
- Magnetotelluric (MT) measurements were employed as part of the Mantle Electromagnetic and Tomography (MELT) Experiment.
- Analysis of electrical resistivity variations in the upper mantle.
Main Results:
- An asymmetric mantle resistivity structure was observed beneath the EPR.
- Lower resistivities were found west of the ridge, indicative of a 1-2% interconnected melt fraction down to 150 km.
- Higher resistivities east of the ridge suggest a depleted, dry olivine mantle (upper 100 km).
Conclusions:
- Asymmetric mantle resistivity is linked to asymmetric spreading rates and ridge migration.
- Distinct styles of melt generation and transport exist beneath the two plates of the EPR.
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