Authors: Scaillet, Bruno; Prouteau, Gaëlle

Source: Science Progress, Volume 84, Number 4, November 2001 , pp. 335-354(20)

Publisher: Science Reviews 2000 Ltd

Abstract:

Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (<50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (<1000°C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.

Document Type: Research article

DOI: http://dx.doi.org/10.3184/003685001783238943

Affiliations: 1: Institut des Sciences de la Terre d'Orléans (ISTO), 1a Rue de la Férollerie, 45071, Orléans, France

Publication date: 2001-11-15

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