The Hadean–Archaean transition at 4 Ga: From magma trapping in the mantle to volcanic resurfacing of the Earth |
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| Authors: | Anne Nédélec Marc Monnereau Michael J Toplis |
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| Institution: | 1. GET, OMP, Université de Toulouse, Toulouse, France;2. IRAP, OMP, CNRS, Université de Toulouse, Toulouse, France |
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| Abstract: | The Hadean–Archaean transition is poorly known because of the dearth of Hadean rocks. A new conceptual model is presented based on variations in mantle potential temperature (Tp) with time. The critical issue is the depth of melting with respect to a negatively buoyant magma sink between 410 and 330 km (14–11 GPa). Hadean plume magmatism begins below the magma sink, leading to generation of a refractory upper mantle reservoir and the minor production of boninite‐like magmas near the surface. With cooling, the onset of melting migrates above the magma sink, a situation likely occurring since 3.9 Ga and corresponding to Tps of ~1870°C or less. Therefore, a burst of mafic to ultramafic volcanism was produced at 3.9–3.8 Ga. This extensive volcanism may have triggered gravitational instabilities and favoured the recycling of the Hadean crust into the mantle. Results of this model are discussed in the light of existing isotopic data. |
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