Origin of Light Noble Gases (He, Ne, and Ar) on Earth: A Review

Type Article
Date 2018-04
Language English
Author(s) Peron SandrineORCID1, Moreira Manuel1, Agranier Arnaud2, 3
Affiliation(s) 1 : Univ Paris Diderot, Sorbonne Paris Cite, Inst Phys Globe Paris, CNRS,UMR 7154, Paris, France.
2 : Univ Bretagne Occidentale, Lab Geosci Ocean, CNRS, UMR 6538, Plouzane, France.
3 : Inst Univ Europeen Mer, Plouzane, France.
Source Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2018-04 , Vol. 19 , N. 4 , P. 979-996
DOI 10.1002/2017GC007388
WOS© Times Cited 21
Keyword(s) volatile origin, helium, neon, argon, solar wind implantation

We review the different scenarios for the origin of light noble gases (He, Ne, and Ar) on Earth. Several sources could have contributed to the Earth's noble gas budget: implanted solar wind, solar nebula gas, chondrites, and comets. Although there is evidence for solar-like neon in the Earth's mantle, questions remain as to its origin. A new compilation of noble gas data in lunar soils, interplanetary dust particles, micrometeorites, and solar wind allows examination of the implanted solar wind composition, which is key to understanding the solar-like mantle neon isotope composition. We show that lunar soils that reflect this solar-wind-implanted signature have a Ne-20/Ne-22 ratio very close to that of ocean island basalts. New data and calculations illustrate that the measured plume source Ne-20/Ne-22 ratio is close to the primitive mantle ratio, when taking into account mixing with the upper mantle (that has lower Ne-20/Ne-22 ratio). This favors early solar wind implantation to account for the origin of light volatiles (He, Ne, and possibly H) in the Earth's mantle: they were incorporated by solar wind irradiation into the Earth's precursor grains during the first few Myr of the solar system's formation. These grains must have partially survived accretion processes (only a few percent are needed to satisfy the Earth's budget of light volatiles). As for the atmosphere, the neon isotope composition can be explained by mixing 36% of mantle gases having this solar-wind-implanted signature and 64% of chondritic gases delivered in a late veneer phase.

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