Can slab melting be caused by flat subduction?

Slab melting has been suggested as a likely source of adakitic arc magmas (i.e., andesitic and dacitic magmas strongly depleted in Y and heavy rare earth elements). Existing numerical and petrologic models, however, restrict partial melting to very young (≤5 Ma) oceanic crust (typically at 60-80 km...

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Bibliographic Details
Published in:Geology (Boulder) 2000-06, Vol.28 (6), p.535-538
Main Authors: Gutscher, Marc-André, Maury, René, Eissen, Jean-Philippe, Bourdon, Erwan
Format: Article
Language:English
Subjects:
adakites
flat subduction
geochemistry
Geology
geometry
Geophysics
global
igneous and metamorphic rocks
igneous rocks
magmas
melting
metamorphism
P-T conditions
Petrology
plate convergence
Plate tectonics
slabs
solid Earth (tectonophysics)
subduction
Thermodynamics
Variables
volcanic rocks
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Summary:Slab melting has been suggested as a likely source of adakitic arc magmas (i.e., andesitic and dacitic magmas strongly depleted in Y and heavy rare earth elements). Existing numerical and petrologic models, however, restrict partial melting to very young (≤5 Ma) oceanic crust (typically at 60-80 km depth). Paradoxically, most of the known Pliocene-Quaternary adakite occurrences are related to subduction of 10-45 Ma lithosphere, which should not be able to melt under normal subduction-zone thermal gradients. We propose an unusual mode of subduction known as flat subduction, occurring in ∼10% of the world's convergent margins, that can produce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat subduction regions worldwide, eight are linked to present or recent (
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(2000)28<535:CSMBCB>2.0.CO;2