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Isotopic constraints on crustal growth and recyclingThe Sm-Nd isotopic data on clastic and chemical sediments are used with the present-day age distribution of continental crustal rocks to estimate the rates of crustal accretion, growth and recycling throughout earth's history. A new method for interpreting Nd model ages on both chemical and clastic sediments is proposed. A general relationship is derived between the mean crustal residence time of material recycled from the crust to the mantle (i.e., sediments), the mean age of the crust, and the crustal growth and recycling rates. This relationship takes into account the fact that the age distribution of material in the continental crust is generally different from the age distribution of material recycled into the mantle. The episodic nature of the present-day age distribution in crustal rocks results in similar episodicity in the accretion and recycling rates. The results suggest that by about 3.8 Ga ago, about 40 percent of the present continental volume was present. Recycling rates were extremely high 3-4 Ga ago and declined rapidly to an insignificant value of about 0.1 cu km/a during most of the Phanerozoic. The Nd model age pattern on sediments suggests a fairly high rate of growth during the Phanerozoic.
Document ID
19890035574
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Jacobsen, Stein B.
(Harvard University Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
November 18, 1988
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 90
Issue: 3
ISSN: 0012-821X
Subject Category
Geophysics
Accession Number
89A22945
Funding Number(s)
CONTRACT_GRANT: NSF EAR-84-51172
CONTRACT_GRANT: NAG9-90
Distribution Limits
Public
Copyright
Other

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