The Geochemical Cycle of Uranium [and Discussion]

If the uranium content of the mantle is based on data from basalts, a homogeneous mantle would contain about 10 parts U/109. This gives a similar mass of uranium in mantle and crust. Sea floor processes may enrich the surface layers of basalt in uranium but do not significantly change the mass of ur...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series A: Mathematical and physical sciences 1979-04, Vol.291 (1381), p.433-445
Main Authors: Fyfe, W. S., Brown, G. C.
Format: Article
Language:English
Subjects:
Andesite
Basalt
Continental crust
Geochemistry
Granite
Mantle
Minerals
Sediments
Subduction
Uranium
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Summary:If the uranium content of the mantle is based on data from basalts, a homogeneous mantle would contain about 10 parts U/109. This gives a similar mass of uranium in mantle and crust. Sea floor processes may enrich the surface layers of basalt in uranium but do not significantly change the mass of uranium subducted in basalts. If pelagic sediments are subducted, they contribute a significant mass of uranium to the mantle. Present rates of andesite production do not seem adequate to return all subducted uranium to the crust but andesites may make a significant contribution to uranium which eventually appears in granitic rocks. Uranium transport and accumulation in sediments may be dominantly biochemical. The problem of uranium distribution in the mantle during evolution of the Earth is unresolved. The main models of crustal evolution suggest continual depletion, early depletion, or early depletion followed by slow replenishment; a constant mantle composition seems unlikely.
ISSN:1364-503X
0080-4614
1471-2962
2054-0272
DOI:10.1098/rsta.1979.0037