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A link between large mantle melting events and continent growth seen in osmium isotopes

Pearson, D.G.; Parman, S.W.; Nowell, G.M.


D.G. Pearson

S.W. Parman


Although Earth's continental crust is thought to have been derived from the mantle, the timing and mode of crust formation have proven to be elusive issues. The area of preserved crust diminishes markedly with age, and this can be interpreted as being the result of either the progressive accumulation of new crust or the tectonic recycling of old crust. However, there is a disproportionate amount of crust of certain ages1, 2, with the main peaks being 1.2, 1.9, 2.7 and 3.3 billion years old; this has led to a third model in which the crust has grown through time in pulses, although peaks in continental crust ages could also record preferential preservation. The ¹⁸⁷Re–¹⁸⁷Os decay system is unique in its ability to track melt depletion events within the mantle and could therefore potentially link the crust and mantle differentiation records. Here we employ a laser ablation technique to analyse large numbers of osmium alloy grains to quantify the distribution of depletion ages in the Earth's upper mantle. Statistical analysis of these data, combined with other samples of the upper mantle, show that depletion ages are not evenly distributed but cluster in distinct periods, around 1.2, 1.9 and 2.7 billion years. These mantle depletion events coincide with peaks in the generation of continental crust and so provide evidence of coupled, global and pulsed mantle–crust differentiation, lending strong support to pulsed models of continental growth by means of large-scale mantle melting events.

Journal Article Type Article
Publication Date Sep 13, 2007
Deposit Date Jul 23, 2007
Journal Nature
Print ISSN 0028-0836
Electronic ISSN 1476-4687
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 449
Issue 7159
Pages 202-205
Public URL