Mantle evolution

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Authors:Bickle, M. J.
Author Affiliations:Primary:
Univ. Cambridge, Dep. Earth Sci., Cambridge, United Kingdom
Volume Title:Early Precambrian basic magmatism
Volume Authors:Hall, R. P., editor; Hughes, D. J.
Source:Early Precambrian basic magmatism, edited by R. P. Hall and D. J. Hughes, p.111-135. Publisher: Chapman and Hall, New York, NY, United States
Publication Date:1990
Note:In English; illus. incl. sketch map
Summary:The mantle convects on at least two scales, one related to plate tectonics and one to mantle plumes as mapped by geoid anomalies in the oceans. Evidence supporting this model includes: the termination of subduction-related earthquakes at a depth of approx 650 km, the thermal time constant of the Earth estimated from present-day heat loss, and the existence of at least two geochemical reservoirs within the mantle. The mantle melts where adiabatic upwelling brings mantle material above the solidus. Thermal models for mantle evolution indicate a secular decrease in upper mantle potential T by several hundred degrees since the early Precambrian. Mass-balance calculations indicate that the crust was largely formed by extraction from the upper mantle, although U-Th-Pb and other very incompatible element concentrations in the upper mantle are now buffered by cycling of lower mantle material or bulk-crust through the upper mantle. Heat- loss budgets in the Archaean, together with the evidence for moderate continental thermal gradients and the thick lithosphere, imply a substantial heat loss in ocean-like regions. The precise mechanisms responsible for crustal growth and the fractionation of elements into the crust are still enigmatic. [J.M.H.]
Subjects:Controls; Convection; Geochemistry; Geologic thermometry; IGCP; Lithosphere; Mantle; Precambrian; Thermal history; Evolution; Igneous activity
Abstract Numbers:91M/2095
Record ID:1991002609
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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