HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation
Journal articles

The Extent, Nature, and Origin of K and Rb Depletions and Isotopic Fractionations in Earth, the Moon, and Other Planetary Bodies

Abstract : Moderately volatile elements (MVEs) are depleted and isotopically fractionated in the Moon relative to Earth. To understand how the composition of the Moon was established, we calculate the equilibrium and kinetic isotopic fractionation factors associated with evaporation and condensation processes. We also reassess the levels of depletions of K and Rb in planetary bodies. Highly incompatible element ratios are often assumed to be minimally affected by magmatic processes, but we show that this view is not fully warranted, and we develop approaches to mitigate this issue. The K/U weight ratios of Earth and the Moon are estimated to be 9704 and 2448, respectively. The 87Rb/86Sr atomic ratios of Earth and the Moon are estimated to be 0.072 5 and 0.015 4, respectively. We show that the depletions and heavy isotopic compositions of most MVEs in the Moon are best explained by evaporation in 99%-saturated vapor. At 99% saturation in the protolunar disk, Na and K would have been depleted to levels like those encountered in the Moon on timescales of ~40-400 days at 3500-4500 K, which agrees with model expectations. In contrast, at the same saturation but a temperature of 1600-1800 K relevant to hydrodynamic escape from the lunar magma ocean, Na and K depletions would have taken 0.1-103 Myr, which far exceeds the 1000 yr time span until plagioclase flotation hinders evaporation from the magma ocean. We conclude that the protolunar disk is a much more likely setting for the depletion of MVEs than the lunar magma ocean.
Document type :
Journal articles
Complete list of metadata

https://hal-insu.archives-ouvertes.fr/insu-03661489
Contributor : Nathalie Pothier Connect in order to contact the contributor
Submitted on : Saturday, May 7, 2022 - 7:41:28 AM
Last modification on : Monday, May 16, 2022 - 8:20:27 AM

File

Dauphas_2022_Planet._Sci._J._3...
Publisher files allowed on an open archive

Licence


Distributed under a Creative Commons Attribution 4.0 International License

Identifiers

Collections

Citation

Nicolas Dauphas, Nicole X. Nie, Marc Blanchard, Zhe J. Zhang, Hao Zeng, et al.. The Extent, Nature, and Origin of K and Rb Depletions and Isotopic Fractionations in Earth, the Moon, and Other Planetary Bodies. The Planetary Science Journal, 2022, 3, ⟨10.3847/PSJ/ac2e09⟩. ⟨insu-03661489⟩

Share

Metrics

Record views

4

Files downloads

0