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

Abstract

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 20Ne/22Ne ratio very close to that of ocean island basalts. New data and calculations illustrate that the measured plume source 20Ne/22Ne ratio is close to the primitive mantle ratio, when taking into account mixing with the upper mantle (that has lower 20Ne/22Ne 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.

Volcanic record of continental thinning in Baffin Bay margins: Insights from Svartenhuk Halvø Peninsula basalts, West Greenland

“…units. Moreover, a plume imprint on geochemical signatures of Svartenhuk lavas is also consistent with the extremely primitive helium isotopic compositions recently published by Péron et al (2018) for olivines from our V3 samples S33E7 and S35E7 (R/Ra=31.0 and 34.9, respectively), similar to those previously reported for samples from Disko…”

Noble Gases: A Record of Earth's Evolution and Mantle Dynamics

“…Except for the deep mantle plume source, signatures of nebular gases are not found elsewhere on our planet. 20 Ne/ 22 Ne ratios in MORBs do not exceed ∼12.5 within the quoted uncertainties of the measurements , Parai et al 2012, Peron et al 2017, Raquin & Moreira 2009, Sarda et al 2000, Tucker et al 2012, which are similar to values of meteoritic material irradiated by the solar wind (e.g., Peron et al 2017Peron et al , 2018. The maximum measured MORB values are similar to an independent estimate of 12.49 ± 0.04 for the MORB source based on continental well gases (Ballentine et al 2005, Holland & Ballentine 2006.…”

“…Large differences in the primordial Ne isotopic ratio ( 20 Ne/ 22 Ne) among potential sources of Earth's volatiles make Ne a key player in understanding the history of volatile accretion (Ballentine et al 2005;Marty 1989;Moreira 2013;Mukhopadhyay 2012;Peron et al 2017Peron et al , 2018Raquin & Moreira 2009;Yokochi & Marty 2004). The three potential sources of volatiles during the main phase of Earth's accretion are nebular gases, solar wind irradiated meteoritic material, and CI chondrite meteorites.…”

Redox control on nitrogen isotope fractionation during planetary core formation

“…Another possible origin of terrestrial N arises from the combined study of N isotopes and noble gases among solar system bodies. Based on the solar-like Ne isotopic composition of the mantle, Marty (76) discussed the possibility that the mantle has preserved some solar N. This scenario implies that precursor grains accreted during Earth’s formation were first irradiated by the solar wind and preserved their solar volatile isotopic signature during Earth’s accretion and differentiation [δ 15 N IFSW ≤ −240‰; IFSW: implantation-fractionated solar wind (84, 85)]. Alternatively, a primordial solar atmosphere could have been captured by Earth’s gravity and dissolved into the early magma ocean [δ 15 N solar = −383‰ (e.g., ref.…”