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This is an archive of data in Yohan et al., 2022, submitted to GRL. The data includes all stress-strain curves shown in the manuscript. Files with a .tifextension are the XRD data (Debye-Scherrer rings) of the deformed MgO analyzed by the software package MAUD. PFs data of exp4 was used for calculation of the seismic wave velocities in Figure 4 using MTEX and Matlab.

Pressure calibrations at room temperature (RT) and high temperatures. Fo, Mg2SiO4, forsterite; Wd, Mg2SiO4 wadsleyite; Rw, Mg2SiO4 ringwoodite; Ak, MgSiO3 akimotoite; Bdg, MgSiO3 bridgmanite; Pc, MgO periclase. Pressures of the phase transitions at high temperatures were taken from Morishima et al. (1994), Suzuki et al. (2000), and Fei et al. (2004). The red point at 790 ton, 23 GPa, and 2273 K is 0.55 GPa away from the green curve of 1873 K, which is comparable to the standard deviation of the fitting curves, 0.4 GPa. Figure S2: Heating power-temperature relationships. Figure S3: Melting temperatures of MgO. The black line represents the melting temperatures calculated in this study, and the dashed gray line represents those by de Koker and Stixrude (2009). The melting temperatures determined by high-pressure experiments and ab initio calculations are also plotted: orange squares, Zerr and Boehler (1994); green triangles, Alfe (2005); blue circles, Zhang and Fei (2008); purple squares, Du and Lee (2014); and red squares, Kimura et al. (2017). Figure S4: Melting phase diagram in the MgO–MgSiO3 system at 24 GPa. The black line represents the phase boundary calculated in this study, and the gray line represents that by Liebske and Frost (2012). The experimental data by Liebske and Frost (2012) are also plotted, where the red circle represents the composition of liquid above liquidus, the green squares represent liquid coexisting with periclase (Pc), the orange squares represent liquid coexisting with bridgmanite (Bdg), and the diamonds represent subsolidus phases. Interaction parameter updated by Ohnishi et al. (2017) was used to calculate the phase relations. Figure S5: X-ray diffraction patterns of the run products. The black short bars beneath the curves denote the peak positions of bridgmanite (Bdg) and rhenium (Re). (PDF 1046 kb)

International audience; Terrestrial planets are thought to experience episode(s) of large-scale melting early in their history. Fractionation during magma-ocean freezing leads to unstable stratification within the related cumulate layers due to progressive iron enrichment upward, but the effects of incremental cumulate overturns during MO crystallization remain to be explored. Here, we use geodynamic models with a moving-boundary approach to study convection and mixing within the growing cumulate layer, and thereafter within the fully crystallized mantle. For fractional crystallization, cumulates are efficiently stirred due to subsequent incremental overturns, except for strongly iron-enriched late-stage cumulates, which persist as a stably stratified layer at the base of the mantle for billions of years. Less extreme crystallization scenarios can lead to somewhat more subtle stratification. In any case, the long-term preservation of at least a thin layer of extremely enriched cumulates with Fe#\textgreater0.4, as predicted by all our models, is inconsistent with seismic constraints. Based on scaling relationships, however, we infer that final-stage Fe-rich magma-ocean cumulates originally formed near the surface should have overturned as small diapirs, and hence undergone melting and reaction with the host rock during sinking. The resulting moderately iron-enriched metasomatized/hybrid rock assemblages should have accumulated at the base of the mantle, potentially fed an intermittent basal magma ocean, and be preserved through the present-day. Such moderately iron-enriched rock assemblages can reconcile the physical properties of the large low shear-wave velocity provinces in the present-day lower mantle. Thus, we reveal Hadean melting and rock-reaction processes by integrating magma-ocean crystallization models with the seismic-tomography snapshot.