Deep and persistent melt layer in the Archaean mantle
Abstract
Transition from Archaean to Proterozoic eon ended the period of great instabilities at the Earth's surface. The origin of this transition could be a change in the dynamical regime of the Earth's interior, but this remains an open question. In this study, we performed two complementary in situ measurements of the melting curve of the upper mantle and found a solidus that is 200-250 K lower than previously reported at depths higher than 100 km. Such lower solidus temperature makes partial melting today easier than previously thought, particularly in presence of volatiles (H2O, CO2). A lower solidus could also account for the early high production of melts like komatiites. For an Archaean mantle that was 200-300 K hotter than today, significant melting is expected at depths from 100-150 km to more than 400 km. The persistent shell of molten material in the upper mantle progressively disappeared due to secular mantle cooling. The crystallization of the upper mantle increased mantle viscosity, hence the mechanical coupling between the lithosphere and the asthenosphere. Such change could explain the transition from an early Earth's surface dynamics dominated by stagnant lid to modern-like plate tectonics with deep slab subduction.
Andrault et al. (2018) Deep and persistent melt layer in the Archaean mantle. Nature Geoscience 11, 139.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI32A..02A
- Keywords:
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- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8103 Continental cratons;
- TECTONOPHYSICSDE: 8149 Planetary tectonics;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS