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Growth of early continental crust by partial melting of eclogite

Rapp, Robert; Shimizu, Nobumichi; Norman, Marc

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The tectonic setting in which the first continental crust formed, and the extent to which modern processes of arc magmatism at convergent plate margins were operative on the early Earth, are matters of debate. Geochemical studies have shown that felsic rocks in both Archaean high-grade metamorphic ('grey gneiss') and low-grade granite-greenstone terranes are comprised dominantly of sodium-rich granitoids of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks. Here we present direct...[Show more]

dc.contributor.authorRapp, Robert
dc.contributor.authorShimizu, Nobumichi
dc.contributor.authorNorman, Marc
dc.date.accessioned2015-12-13T22:36:51Z
dc.date.available2015-12-13T22:36:51Z
dc.identifier.issn0028-0836
dc.identifier.urihttp://hdl.handle.net/1885/76973
dc.description.abstractThe tectonic setting in which the first continental crust formed, and the extent to which modern processes of arc magmatism at convergent plate margins were operative on the early Earth, are matters of debate. Geochemical studies have shown that felsic rocks in both Archaean high-grade metamorphic ('grey gneiss') and low-grade granite-greenstone terranes are comprised dominantly of sodium-rich granitoids of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks. Here we present direct experimental evidence showing that partial melting of hydrous basalt in the eclogite facies produces granitoid liquids with major- and trace-element compositions equivalent to Archaean TTG, including the low Nb/Ta and high Zr/Sm ratios of 'average' Archaean TTG, but from a source with initially subchondritic Nb/Ta. In modern environments, basalts with low Nb/Ta form by partial melting of subduction-modified depleted mantle, notably in intraoceanic arc settings in the forearc and back-arc regimes. These observations suggest that TTG magmatism may have taken place beneath granite-greenstone complexes developing along Archaean intraoceanic island arcs by imbricate thrust-stacking and tectonic accretion of a diversity of subduction-related terranes. Partial melting accompanying dehydration of these generally basaltic source materials at the base of thickened, 'arc -like' crust would produce compositionally appropriate TTG granitoids in equilibrium with eclogite residues.
dc.publisherMacmillan Publishers Ltd
dc.sourceNature
dc.subjectKeywords: Earth (planet); Granite; Rocks; Partial melting; Geochemistry; niobium; samarium; sodium; tantalum; zirconium derivative; continental crust; crustal evolution; eclogite; partial melting; article; chemical composition; eclogite; geochemical analysis; geogr
dc.titleGrowth of early continental crust by partial melting of eclogite
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume425
dc.date.issued2003
local.identifier.absfor040299 - Geochemistry not elsewhere classified
local.identifier.ariespublicationMigratedxPub5807
local.type.statusPublished Version
local.contributor.affiliationRapp, Robert, State University of New York
local.contributor.affiliationShimizu, Nobumichi , Woods Hole Oceanographic Institution
local.contributor.affiliationNorman, Marc, College of Physical and Mathematical Sciences, ANU
local.bibliographicCitation.startpage605
local.bibliographicCitation.lastpage609
local.identifier.doi10.1038/nature02031
dc.date.updated2015-12-11T09:33:51Z
local.identifier.scopusID2-s2.0-0142041485
CollectionsANU Research Publications

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