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Isotopic and chemical constraints on mantle-crust evolution

Authors
Journal
Geochimica et Cosmochimica Acta
0016-7037
Publisher
Elsevier
Publication Date
Volume
52
Issue
6
Identifiers
DOI: 10.1016/0016-7037(88)90205-0

Abstract

Abstract A formalism for the general treatment of three-layer mantle-crust evolution models is presented and various published models are shown to be special cases of this more general model. The Sm-Nd, Lu-Hf, and Rb-Sr isotopic present day mass balance for the continental crust-depleted mantle system is consistent with ~30% of the mantle being depleted. A growth curve for the continental crust is calculated on the basis of total inversion of the Sm-Nd isotopic data for all of Earth history. The curve suggests that by about 3.8 Ga ago, ~40% of the present continental volume was present. Both the estimated continental recycling and addition rates show maxima around 3.0 Ga. The resulting continental addition rates are also very high 4.5−4.0 Ga ago and during the Phanerozoic. The Sm-Nd data are not compatible with a steady state model for the crust over the past 2–3 Ga. The major uncertainty in evaluating crust-mantle evolution models is the extent of exchange between the upper and lower mantle.

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