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The upper mantle transition region - EclogiteThe upper mantle transition region is usually considered to be peridotite which undergoes a series of phase changes involving spinel and post-spinel assemblages. There are difficulties associated with attempts to explain the 220, 400 and 670 km discontinuities in terms of phase changes in a peridotitic mantle. Moreover, in a differentiated earth there should be large quantities of eclogite in the upper mantle. Eclogite is denser than Al2O3-poor mantle to depths of 670 km, but it stays in the garnet stability field to pressures in excess of those required to transform depleted mantle to denser phases such as ilmenite and perovskite. Eclogite, therefore, remains above 670 km. The seismic properties of the transition region are more consistent with eclogite than peridotite. Most of the mantle's inventory of incompatible trace elements may be in this layer, which is a potential source region for some basalt magmas. The radioactivity in this layer is the main source of mantle heat flow, 0.7 microcalorie/sq cm-sec, and drives upper mantle convection.
Document ID
19790068162
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Anderson, D. L.
(California Institute of Technology Pasadena, Calif., United States)
Date Acquired
August 9, 2013
Publication Date
June 1, 1979
Publication Information
Publication: Geophysical Research Letters
Volume: 6
Subject Category
Geophysics
Accession Number
79A52175
Funding Number(s)
CONTRACT_GRANT: NGL-05-002-069
Distribution Limits
Public
Copyright
Other

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