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Journal Articles Geophysical Research Letters Year : 2022

Formation of the Lunar Primary Crust From a Long-Lived Slushy Magma Ocean

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Abstract

Classical fractional crystallization scenarios of early lunar evolution suggest crustal formation by the flotation of light anorthite minerals from a liquid magma ocean. However, this model is challenged by the >200$ > 200$ Myr age range of primitive ferroan anorthosites, their concordance with Mg-suite magmatism and by the compositional diversity observed in lunar anorthosites. Here, we propose a new model of slushy magma ocean crystallization in which crystals remain suspended in the lunar interior and crust formation only begins once a critical crystal content is reached. Thereafter crustal formation occurs by buoyant melt extraction and magmatism. The mixture viscosity strongly depends on temperature and solid fraction driving the development of a surface stagnant lid where enhanced solidification and buoyant ascent of melt lead to an anorthite-enriched crust. This model explains lunar anorthosites heterogeneity and suggests a crustal formation timescale of 100s Ma, reconciling anorthosite ages with an early age of the Moon.
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insu-03710174 , version 1 (30-06-2022)

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Attribution - NonCommercial - ShareAlike - CC BY 4.0

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Chloé Michaut, Jerome A. Neufeld. Formation of the Lunar Primary Crust From a Long-Lived Slushy Magma Ocean. Geophysical Research Letters, 2022, 49, ⟨10.1029/2021GL095408⟩. ⟨insu-03710174⟩
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