Geophysical evidence from the MELT area for compositional controls on oceanic plates
Geophysical evidence from the MELT area for compositional controls on oceanic plates
Date
2005-06-29
Authors
Evans, Rob L.
Hirth, Greg
Baba, Kiyoshi
Forsyth, Donald W.
Chave, Alan D.
Mackie, Randall L.
Hirth, Greg
Baba, Kiyoshi
Forsyth, Donald W.
Chave, Alan D.
Mackie, Randall L.
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Compositional controls on oceanic plates :
geophysical evidence from the MELT area
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Abstract
Magnetotelluric (MT) and seismic data, collected during the MELT
experiment at the Southern East Pacific Rise (SEPR) constrain the distribution
of melt beneath this mid-ocean-ridge spreading center and also the evolution of the
oceanic lithosphere during its early cooling history. In this paper, we focus on
structure imaged at distances ~100 to 350 km east of the ridge crest, corresponding
to seafloor ages of ~1.3 to 4.5 Ma, where the seismic and electrical conductivity
structure is nearly constant, independent of age. Beginning at a depth of about 60
km, there is a large increase in electrical conductivity and a change from isotropic
to transversely anisotropic electrical structure with higher conductivity in the
direction of fast propagation for seismic waves. Because conductive cooling
models predict structure that increases in depth with age, extending to about 30
km at 4.5 Ma, we infer that the structure of young oceanic plates is instead
controlled by a decrease in water content above 60 km induced by the melting
process beneath the spreading center.
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Author Posting. © The Authors, 2005. This is the author's version of the work. It is
posted here by permission of Nature Publishing Group for personal use, not for redistribution. The
definitive version was published in Nature 437 (2005): 249-252, doi:10.1038/nature04014.