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Crystallization of a hydrous magma ocean in the shallow lower mantle

Titelangaben

Xie, Longjian ; Walter, Michael ; Katsura, Tomoo ; Xu, Fang ; Wang, Jianhua ; Fei, Yingwei:
Crystallization of a hydrous magma ocean in the shallow lower mantle.
In: Earth and Planetary Science Letters. Bd. 633 (2024) . - 118651.
ISSN 0012-821X
DOI: https://doi.org/10.1016/j.epsl.2024.118651

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Abstract

The solidification of a deep magma ocean occurred early in Earth's history. Although the initial amount of H2O in Earth's magma ocean is predicted to be low (e.g., <3000 ppm), as an incompatible element it becomes highly enriched (e.g. >10 wt) in the final few percent of crystallization. In order to understand how a hydrous magma ocean would crystallize at the top of the lower mantle, we determined liquidus phase relations in the MgO-FeO-CaO-Al2O3-SiO2-H2O system at 24 GPa. We find that the bridgmanite (brg) + stishovite (st) + melt and bridgmanite (brg) + ferropericlase (fp) + melt cotectic boundary curves trend to Mg-rich melt compositions with decreasing temperature and extend to very high H2O contents (∼80 mol H2O). The brg+st+melt curve is a subtraction curve at < ∼18 mol H2O and a reaction curve at higher H2O contents, whereas the brg+fp+melt is a subtraction curve throughout its length. The density of melts along the two cotectics leads to neutral buoyancy with respect to shallow lower mantle and transition zone minerals at H2O contents up to ∼25 mol. A transient melt-rich layer can form at the top of the lower mantle during late-stage crystallization in a mushy magma ocean when melt percolation dominates. When crystallization exceeds ∼98, hydrous melts (>25 mol H2O) become buoyant and can percolate into and hydrate the mantle transition zone.

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Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Keywords: Magma ocean; Water; Silicate melt; Phase diagram; Lower mantle; High pressure
Institutionen der Universität: Forschungseinrichtungen > Zentrale wissenschaftliche Einrichtungen > Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik - BGI
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
Eingestellt am: 02 Jun 2025 11:50
Letzte Änderung: 02 Jun 2025 11:50
URI: https://eref.uni-bayreuth.de/id/eprint/93843