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Interrelationships between continental freeboard, tectonics and mantle temperatureOceanic hypsometry and isentropic melting models are combined to address the question of freeboard from the middle Archean to the present. In addition to the fraction of continental crust, the factors governing the long-term balance of the continental freeboard include the mantle potential temperature (TP), the oceanic lithosphere thickness, and the plate creation rate (C0). It is shown that variation in TP far outweighs the other factors in importance, with freeboard decreasing by 1 km for every TP increase of about 80 C. The huge ten- to thirtyfold increases in C0 backward in geological time that have been invoked to explain near-constant freeboard are shown to be unnecessary. The low value found for TP is consistent with the preservation of ancient diamonds in the deep South African lithosphere. It is concluded from this that the present cooling rate of the earth of about 46 C/Ga has general applicability over much of geological time.
Document ID
19910066701
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Galer, S. J. G.
(California, University La Jolla, United States)
Date Acquired
August 14, 2013
Publication Date
July 1, 1991
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 105
Issue: 3-Jan
ISSN: 0012-821X
Subject Category
Geophysics
Accession Number
91A51324
Funding Number(s)
CONTRACT_GRANT: NAG9-49
Distribution Limits
Public
Copyright
Other

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