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Geophysical evidence from the MELT area for compositional controls on oceanic plates
Rob L Evans1, Greg Hirth, Kiyoshi Baba
1Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. revans@whoi.edu
Nature
|September 9, 2005
Summary
The MELT experiment reveals that melt distribution beneath the East Pacific Rise is influenced by decreasing water content, not just cooling. This impacts the early evolution of oceanic lithosphere.
Area of Science:
- Geophysics
- Oceanography
- Solid Earth Science
Background:
- The East Pacific Rise is a key site for studying mid-ocean ridge processes.
- Understanding oceanic lithosphere evolution requires knowledge of melt distribution and physical properties.
Purpose of the Study:
- To constrain melt distribution beneath the southern East Pacific Rise.
- To investigate the early cooling history and evolution of oceanic lithosphere.
Main Methods:
- Utilized magnetotelluric and seismic data from the MELT experiment.
- Analyzed structures approximately 100 to 350 km east of the ridge crest (1.3–4.5 Myr seafloor ages).
Main Results:
- Observed a significant increase in electrical conductivity below 60 km depth.
- Detected a transition from isotropic to transversely anisotropic electrical structure.
- Found that structure is largely age-independent in the studied region.
Conclusions:
- Inferred that decreasing water content above 60 km, due to melting, controls young oceanic plate structure.
- This contrasts with predictions from conductive cooling models.
- The findings provide insights into the magmatic and hydrothermal processes at mid-ocean ridges.
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