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A Model for the Thermal and Chemical Evolution of the Moon's Interior: Implications for the Onset of Mare VolcanismCrystallization of the lunar magma ocean creates a chemically stratified Moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior. Within the magma ocean cumulates the last liquids to crystallize form dense, ilmenite-rich cumulates that contain high concentrations of incompatible radioactive elements. The underlying olivine-orthopyroxene cumulates are also stratified with later crystallized, denser, more Fe-rich compositions at the top. This paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy. Rayleigh-Taylor instability causes the dense ilmenite-rich cumulate layer and underlying Fe-rich cumulates to sink toward the center of the Moon, forming a dense lunar core. After this overturn, radioactive heating within the ilmenite-rich cumulate core heats the overlying mantle, causing it to melt. In this model, the source region for high-TiO2 mare basalts is a convectively mixed layer above the core-mantle boundary which would contain small and variable amounts of admixed ilmenite and KREEP. This deep high-pressure melting, as required for mare basalts, occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the Moon. Regardless of details implied by particular model parameters, gravitational overturn driven by the high density of magma ocean Fe-rich cumulates should concentrate high-TiO2 mare basalt sources, and probably a significant fraction of radioactive heating, toward the center of the Moon. This will have important implications for both the thermal evolution of the Moon and for mare basalt genesis.
Document ID
19980213246
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1016/0012-821X(95)00138-3
Authors
Hess, Paul C. (Brown Univ. Providence, RI United States)
Parmentier, E. M. (Brown Univ. Providence, RI United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Earth and Planetary Science Letters
Publisher: Elsevier Science Publishers
Volume: 134
ISSN: 0012-821X
Subject Category
Lunar And Planetary Exploration
Report/Patent Number
NAS 1.26:207088
NASA/CR-1995-207088
Report Number: NAS 1.26:207088
Report Number: NASA/CR-1995-207088
ISSN: 0012-821X
Funding Number(s)
CONTRACT_GRANT: NAGw-3613
Distribution Limits
Public
Copyright
Public Use Permitted.

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