Mantle dynamics beneath the East Pacific Rise at 17°S : insights from the Mantle Electromagnetic and Tomography (MELT) experiment
Chave, Alan D.
Evans, Rob L.
Mackie, Randall L.
MetadataShow full item record
The electromagnetic data from the Mantle Electromagnetic and Tomography (MELT) experiment are inverted for a two-dimensional transversely anisotropic conductivity structure that incorporates a correction for three-dimensional topographic effects on the magnetotelluric responses. The model space allows for different conductivity values in the along-strike, cross-strike, and vertical directions, along with imposed constraints of model smoothness and closeness among the three directions. Anisotropic models provide a slightly better fit to the data for a given level of model smoothness and are more consistent with other geophysical and laboratory data. The preferred anisotropic model displays a resistive uppermost 60-km-thick mantle independent of plate age, except in the vicinity of the ridge crest. In most inversions, a vertically aligned sheet-like conductor at the ridge crest is especially prominent in the vertical conductivity. Its presence suggests that the melt is more highly concentrated and connected in the vertical direction immediately beneath the rise axis. The melt zone is at least 100 km wide and is asymmetric, having a greater extent to the west. Off-axis, and to the east of the ridge, the mantle is more conductive in the direction of plate spreading at depths greater than 60 km. The flat resistive-conductive boundary at 60 km agrees well with the inferred depth of the dry solidus of peridotite, and the deeper conductive region is consistent with the preferred orientation of olivine inferred from seismic observations. This suggests that the uppermost 60 km represents the region of mantle that has undergone melting at the ridge and has been depleted of water (dissolved hydrogen). By contrast, the underlying mantle has retained a significant amount of water.
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): B02101, doi:10.1029/2004JB003598.
Suggested CitationArticle: Baba, Kiyoshi, Chave, Alan D., Evans, Rob L., Hirth, Greg, Mackie, Randall L., "Mantle dynamics beneath the East Pacific Rise at 17°S : insights from the Mantle Electromagnetic and Tomography (MELT) experiment", Journal of Geophysical Research 111 (2006): B02101, DOI:10.1029/2004JB003598, https://hdl.handle.net/1912/3503
Showing items related by title, author, creator and subject.
Urann, Benjamin M.; Le Roux, Veronique; Hammond, Keiji; Marschall, Horst R.; Lee, Cin-Ty A. (2017-05-01)The fluorine (F) and chlorine (Cl) contents of arc magmas have been used to track the composition of subducted components, and the F and Cl contents of MORB have been used to estimate the halogen content of depleted MORB ...
Global mantle flow and the development of seismic anisotropy : differences between the oceanic and continental upper mantle Conrad, Clinton P.; Behn, Mark D.; Silver, Paul G. (American Geophysical Union, 2007-07-26)Viscous shear in the asthenosphere accommodates relative motion between Earth's surface plates and underlying mantle, generating lattice-preferred orientation (LPO) in olivine aggregates and a seismically anisotropic fabric. ...
Sharp thermal transition in the forearc mantle wedge as a consequence of nonlinear mantle wedge flow Wada, Ikuko; Rychert, Catherine A.; Wang, Kelin (American Geophysical Union, 2011-07-08)In the forearc mantle wedge, the thermal field depends strongly on slab-driven mantle wedge flow. The flow is in turn affected by the thermal field via the temperature dependence of mantle rheology. Using thermal modeling, ...