EGU2020-8428
https://doi.org/10.5194/egusphere-egu2020-8428
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
Numerical Insights into the Formation and Stability of Cratons
Charitra Jain1, Antoine Rozel2, Emily Chin3, and Jeroen van Hunen1
Department of Earth Sciences, Durham University, Durham, United Kingdom of Great Britain and Northern Ireland
1
Institute of Geophysics, Department of Earth Sciences, ETH Zurich, Zurich, Switzerland
2
Scripps Institution of Oceanography, UC San Diego, La Jolla, United States
3
Geophysical, geochemical, and geological investigations have attributed the stable behaviour of
Earth's continents to the presence of strong and viscous cratons underlying the continental crust.
The cratons are underlain by thick and cold mantle keels, which are composed of melt-depleted
and low density peridotite residues [1]. Progressive melt extraction increases the magnesium
number Mg# in the residual peridotite, thereby making the roots of cratons chemically buoyant [2,
3] and counteracting their negative thermal buoyancy. Recent global models have shown the selfconsistent production of Archean continental crust by two-step mantle differentiation [4]. These
models exhibit intense recycling of crust with delamination and eclogitic dripping in the first 500
million years and this behaviour is similar to the "plutonic-squishy lid'' that has been suggested for
the early Earth. However, no stable continents form and no major regime transition from "vertical
tectonics'' towards "horizontal tectonics'' is observed. This points to the missing ingredient of
cratonic lithosphere in these models, which could act as a stable basement for the crustal material
to accumulate on and may help initiate plate tectonics. Based on the bulk FeO and MgO content of
the residual peridotites, it has been proposed that cratonic mantle formed by hot shallow melting
with mantle potential temperature, which was higher by 200-300 °C than present-day [5]. We will
introduce Fe-Mg partitioning between mantle peridotite and melt to track the Mg# variation
through melting, and parametrise craton formation using the corresponding P-T formation
conditions. Grain-size evolution, which has been shown to influence mantle rheology [6] is another
mechanism that may contribute towards cratonic strength and will be explored using selfconsistent global geodynamic models.
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