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Destabilization of a 650 km chemical boundary layer and its bearing on the evolution of the continental crustA mechanism for the production of a chemical change in the mantle, from primordial silicate compositions above the 650 km discontinuity to differentiated compositions below, is reviewed. Some consequences of this are the stabilization of two layer convection with a temperature contrast between the anhydrous mantle solidus and the geotherm which, at 650 km depth, is lower than any other location in the mantle. With thermal contributions from the concentration of the heat producing elements U, Th and K below the 650 km mantle boundary layer and the higher geotherms in the past, widespread or catastrophic melting may have taken place at this location. An episodic breach of this boundary layer by extensive heat and mass transport may have periodically destroyed any simple two-layer convection geometry in the mantle. Such episodic injections of mass and energy into the upper mantle from below may have been the mechanism responsible for episodes of enhanced surface tectonism and thermal activity which appear to be recorded in apparent polar wandering paths and radiometric ages of continental rocks.
Document ID
19830063145
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Herzberg, C. T.
(Rutgers Univ. New Brunswick, NJ, United States)
Forsythe, R. D.
(Rutgers University New Brunswick, NJ, United States)
Date Acquired
August 11, 2013
Publication Date
July 1, 1983
Publication Information
Publication: Physics of the Earth and Planetary Interiors
Volume: 32
ISSN: 0031-9201
Subject Category
Geophysics
Accession Number
83A44363
Funding Number(s)
CONTRACT_GRANT: NAGW-177
Distribution Limits
Public
Copyright
Other

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