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Tectonic plates, D (double prime) thermal structure, and the nature of mantle plumesIt is proposed that subducting tectonic plates can affect the nature of thermal mantle plumes by determining the temperature drop across a plume source layer. The temperature drop affects source layer stability and the morphology of plumes emitted from it. Numerical models are presented to demonstrate how introduction of platelike behavior in a convecting temperature dependent medium, driven by a combination of internal and basal heating, can increase the temperature drop across the lower boundary layer. The temperature drop increases dramatically following introduction of platelike behavior due to formation of a cold temperature inversion above the lower boundary layer. This thermal inversion, induced by deposition of upper boundary layer material to the system base, decays in time, but the temperature drop across the lower boundary layer always remains considerably higher than in models lacking platelike behavior. On the basis of model-inferred boundary layer temperature drops and previous studies of plume dynamics, we argue that generally accepted notions as to the nature of mantle plumes on Earth may hinge on the presence of plates. The implication for Mars and Venus, planets apparently lacking plate tectonics, is that mantle plumes of these planets may differ morphologically from those of Earth. A corollary model-based argument is that as a result of slab-induced thermal inversions above the core mantle boundary the lower most mantle may be subadiabatic, on average (in space and time), if major plate reorganization timescales are less than those acquired to diffuse newly deposited slab material.
Document ID
19950049897
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lenardic, A.
(University of California, Los Angeles, CA United States)
Kaula, W. M.
(University of California, Los Angeles, CA United States)
Date Acquired
August 16, 2013
Publication Date
August 10, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: B8
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A81496
Funding Number(s)
CONTRACT_GRANT: NAGW-2997
Distribution Limits
Public
Copyright
Other

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