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Does subduction zone magmatism produce average continental crustThe question of whether present day subduction zone magmatism produces material of average continental crust composition, which perhaps most would agree is andesitic, is addressed. It was argued that modern andesitic to dacitic rocks in Andean-type settings are produced by plagioclase fractionation of mantle derived basalts, leaving a complementary residue with low Rb/Sr and a positive Eu anomaly. This residue must be removed, for example by delamination, if the average crust produced in these settings is andesitic. The author argued against this, pointing out the absence of evidence for such a signature in the mantle. Either the average crust is not andesitic, a conclusion the author was not entirely comfortable with, or other crust forming processes must be sought. One possibility is that during the Archean, direct slab melting of basaltic or eclogitic oceanic crust produced felsic melts, which together with about 65 percent mafic material, yielded an average crust of andesitic composition.
Document ID
19880020830
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Ellam, R. M.
(Oxford Univ. (England), United States)
Hawkesworth, C. J.
(Open Univ. Milton, United Kingdom)
Date Acquired
September 5, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Lunar and Planetary Inst., Workshop on the Growth of Continental Crust
Subject Category
Geophysics
Accession Number
88N30214
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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