Xenon compatibility in magmatic processes: Hadean to current contexts

Q. Chen, C. Sanloup, D. Horlait, G. Shen; Q. Chen; C. Sanloup; D. Horlait; G. Shen

by admin | Apr 22, 2024 | mainpost, vol29

TY  - JOUR
T1  - Xenon compatibility in magmatic processes: Hadean to current contexts
JO  - Geochemical Perspectives Letters
VL  - 29
SP  - 57
EP  - 62
PY  - 2024
AU  - Q. ChenAU  - C. SanloupAU  - D. HorlaitAU  - G. ShenDO  - https://doi.org/10.7185/geochemlet.2413
UR  - https://www.geochemicalperspectivesletters.org/article2413
AB  - Xenon (Xe) behaviour in petrological processes, albeit essential to constrain mantle ingassing and degassing models, is elusive due to its volatile nature, and lack of direct investigation at the pressures (P) and temperatures (T) relevant to magma formation and crystallisation at depth. Xenon stands out amongst noble gases due to its unique reactivity with silicates of the lower crust and upper mantle, which could at least partially explain that published mineral/melt partitioning coefficients span up to six orders of magnitude. We report partition coefficients of Xe using in situ X-ray fluorescence at high P and T, and mass spectrometry analyses. Xenon is found to be moderately incompatible in anorthite-clinopyroxene mix in equilibrium with basalt (partition coefficient value of 0.16 ± 0.06), and compatible in olivine in equilibrium with basalt (partition coefficients in the range 88 ± 22 to 302 ± 46). While Xe is, thus, concentrated in basaltic melts coexisting with crystallising pyroxenes and feldspars, it is strongly retained in olivine at depth. Consequently, Xe originally contained in solid Earth has been preferentially retained at depth throughout Earth’s history, from the magma ocean stages to present day partial mantle melting processes.

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Xenon compatibility in magmatic processes: Hadean to current contexts

Q. Chen¹,

¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, CNRS, Paris, 75005, France

C. Sanloup¹,

¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, CNRS, Paris, 75005, France

D. Horlait²,

²LP2I, UMR5797, Université de Bordeaux, CNRS, Gradignan, 33170, France

G. Shen³

³HPCAT, X-ray Science Division, Argonne National Laboratory, Argonne, 60439, IL, USA

Affiliations | Corresponding Author | Cite as | Funding information

Geochemical Perspectives Letters v29 | https://doi.org/10.7185/geochemlet.2413
Received 12 October 2023 | Accepted 15 March 2024 | Published 22 April 2024

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0

Keywords: xenon, partitioning, high-pressure



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Abstract

Xenon (Xe) behaviour in petrological processes, albeit essential to constrain mantle ingassing and degassing models, is elusive due to its volatile nature, and lack of direct investigation at the pressures (P) and temperatures (T) relevant to magma formation and crystallisation at depth. Xenon stands out amongst noble gases due to its unique reactivity with silicates of the lower crust and upper mantle, which could at least partially explain that published mineral/melt partitioning coefficients span up to six orders of magnitude. We report partition coefficients of Xe using in situ X-ray fluorescence at high P and T, and mass spectrometry analyses. Xenon is found to be moderately incompatible in anorthite-clinopyroxene mix in equilibrium with basalt (partition coefficient value of 0.16 ± 0.06), and compatible in olivine in equilibrium with basalt (partition coefficients in the range 88 ± 22 to 302 ± 46). While Xe is, thus, concentrated in basaltic melts coexisting with crystallising pyroxenes and feldspars, it is strongly retained in olivine at depth. Consequently, Xe originally contained in solid Earth has been preferentially retained at depth throughout Earth’s history, from the magma ocean stages to present day partial mantle melting processes.

Figures and Tables

Figure 1 Energy-dispersive X-ray data sets. (Left) Full data sets collected at 10.031°. For each crystal/melt system, data collected at different T are vertically spaced for clarity: fully molten sample (orange), partially molten sample (red for molten zone, black for crystalline or crystal-rich zone), and quenched crystals (black dashed). Peaks at 33 keV and 47 keV are MgO diffraction peaks from the cell-assembly. (Right) Zoom on the Xe K_α1 and K_α2 fluorescence lines (29.4 keV and 29.7 keV). For olivine-melt experiments, data sets in the zoomed panel were collected at 4.0285° to avoid diffraction peaks from crystals overlapping with Xe fluorescence lines.	Figure 2 Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986); B1992, Broadhurst et al. (1992); H2007, Heber et al. (2007); C2022, Chen et al. (2022); PC265, Cell2, and Cell3 are data from this study (Table 2). Empty symbols indicate room P data; filled symbols indicate data collected between 1.0 and 2.0 GPa (cf. Table 1). Note that Heber et al. (2007) discarded all values above unity due to the observation of gas bubbles in crystals, while at least some might form from exsolution upon quenching. Natural rocks dataset: residual rock/basalt partition coefficients from Batiza et al. (1979).	Table 1 Compilation of literature datasets. Chemical compositions have been rounded at unity, given in wt. % for glass and mol % for gas. Analytical techniques: UV laser ablation (Heber et al., 2007), step heating (Hiyagon and Ozima, 1986; Broadhurst et al., 1992). Data discarded by authors due to contamination of crystals with bubbles are given in italics. For Hiyagon and Ozima (1986), glass composition is bulk sample starting composition. Data where lithium borate was added to lower melting T are not included, as borate modifies melt polymerisation which controls noble gases solubility. Error bars on D are given when available; * error equals D values.	Table 2 Run conditions, coexisting phases, crystalline fraction in crystal-rich areas, Xe content in each phase (wt. %), and partitioning coefficients. Note that crystal and melt fractions do not apply to the whole sample but only to the volume probed by the X-ray beam. *Mass spectrometry measurement. Values in parentheses are errors on the last reported digits.
Figure 1	Figure 2	Table 1	Table 2

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Introduction

Noble gases provide unique clues to unravel the geochemical evolution of volatile elements upon Earth’s formation to present day geodynamics (Ozima et al., 2002

Ozima, M., Miura, Y., Podosek, F. (2002) Revisiting I-Xe systematics, an early solar system chronometer. Geochimica et Cosmochimica Acta 66, A576.

and references therein), assuming their inertness and volatile behaviour. Xenon is also unique for its enigmatic atmospheric depletion relative to lighter noble gases (Anders and Owen, 1977

Anders, E., Owen, T. (1977) Mars and Earth: Origin and Abundance of Volatiles. Science 198, 453–465. https://doi.org/10.1126/science.198.4316.453

), known as the ‘Xe paradox’, and its strong depletion in light isotopes (Krummenacher et al., 1962

Krummenacher, D., Merrihue, C.M., Pepin, R.O., Reynolds, J.H. (1962) Meteoritic krypton and barium versus the general isotopic anomalies in xenon. Geochimica et Cosmochimica Acta 26, 231–249. https://doi.org/10.1016/0016-7037(62)90014-5

). Atmospheric escape and trapping-at-depth scenarios have been proposed to explain both observations (Ardoin et al., 2022

Ardoin, L., Broadley, M.W, Almayrac, M., Avice, G., Byrne, D.J., Tarantola, A., Lepland, A., Saito, T., Komiya, T., Shibuya, T., Marty, B. (2022) The end of the isotopic evolution of atmospheric xenon. Geochemical Perspective Letters 20, 43–47. https://doi.org/10.7185/geochemlet.2207

; Broadley et al., 2022

Broadley, M.W., Byrne, D.J., Ardoin, L., Almayrac, M.G., Bekaert, D.V., Marty, B. (2022) High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters 588, 117577. https://doi.org/10.1016/j.epsl.2022.117577

; Rzeplinski et al., 2022

Rzeplinski, I., Sanloup, C., Gilabert, E., Horlait, D. (2022) Hadean isotopic fractionation of xenon retained in deep silicates. Nature 606, 713–717. https://doi.org/10.1038/s41586-022-04710-4

and references therein), and are not exclusive. Atmospheric escape models stem from the fact that Xe is the easiest to ionise amongst noble gases and to investigate regarding how this could be triggered by extreme UV radiation of the young Sun if sufficient amount of hydrogen or organic matter were present. However, the main challenge is how to lift the heavy Xe through the atmosphere up to levels where it can be lost (Zahnle et al., 2019

Zahnle, K.J., Gacesa, M., Catling, D.C. (2019) Strange messenger: A new history of hydrogen on Earth, as told by Xenon. Geochimica et Cosmochimica Acta 244, 56–85. https://doi.org/10.1016/j.gca.2018.09.017

). Trapping-at-depth scenarios, in turn, suffer from a lack of knowledge on Xe petrological behaviour. Noble gases partitioning between major minerals and melt is indeed a debated issue, with Xe spanning the largest range amongst noble gases crystal/melt partitioning data (noted as D^Xe_crystal/melt), with up to 6 orders of magnitude from 6 × 10⁻⁴ to 351 for D^Xe_{olivine/basalt} (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

; Broadhurst et al., 1992

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

; Heber et al., 2007

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

).

The published experimental D^Xe_crystal/melt values were obtained from samples brought to high T, equilibrated with a noble gas medium either at atmospheric P or ∼110 MPa, and quenched to room conditions for chemical analysis. A few experiments were carried out at higher P up to 1.5 GPa (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

) but with only adsorbed air on starting sample as noble gas source. After correction for eventual melt inclusions in crystals, the very large range of D^Xe_crystal/melt values partly results from the interpretation of bubbles in minerals, i.e. whether they should be excluded from measurements or not. Indeed, while noble gas content in melts is homogeneous, such is not the case in minerals, with almost systematic reports of heterogeneous distribution of heavy noble gases, often at the micron or sub-micron scale (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

; Broadhurst et al., 1992

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

; Heber et al., 2007

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

). Some data were discarded on this ground, despite sometimes clear elemental fractionation from the original gas (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

), which is not expected for passively trapped gas. Indeed, Xe was observed to retro-diffuse out of olivine in high P experiments upon T-quenching (Sanloup et al., 2011

Sanloup, C., Schmidt, B.C., Gudfinnsson, G., Dewaele, A., Mezouar, M. (2011) Xenon and Argon: A contrasting behavior in olivine at depth. Geochimica et Cosmochimica Acta 75, 6271–6284. https://doi.org/10.1016/j.gca.2011.08.023

), an exsolution process that could explain at least part of the bubbles observed on quenched samples. It is therefore very challenging to interpret the heterogeneous distribution of Xe in quenched minerals recovered from experiments.

Another source of controversy arises from the impact of noble gases adsorption on minerals, i.e. whether or not it is significant in experiments, and therefore if it should be corrected for or not. Step heating experiments show that heavy noble gases are tightly bound in minerals, with largest fractions being released above 1000 °C (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

), arguing against physical adsorption.

Last but not least, datasets are difficult to compare due to the different compositions used for both melts and crystals (Table 1). For instance, olivine-melt experiment compositions range from synthetic Fe-free forsterite/61 % SiO₂-rich melt (Heber et al., 2007

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

) to natural olivine/basalt (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

). It is, nonetheless, established that melt composition strongly affects trace element partitioning (Schmidt et al., 2006

Schmidt, M.W., Connolly, J.A.D., Günther, D., Bogaerts, M. (2006) Element Partitioning: The Role of Melt Structure and Composition. Science 312, 1646–1650. https://doi.org/10.1126/science.1126690

), with one order of magnitude difference between gabbroic and granitic melts, an effect also expected to be strong for noble gases based on solubility values in melts (Carroll and Stolper, 1993

Carroll, M.R., Stolper, E.M. (1993) Noble gas solubilities in silicate melts and glasses: New experimental results for argon and the relationship between solubility and ionic porosity. Geochimica et Cosmochimica Acta 57, 5039–5051. https://doi.org/10.1016/0016-7037(93)90606-W

; Schmidt and Keppler, 2002

Schmidt, B.C., Keppler, H. (2002) Experimental evidence for high noble gas solubilities in silicate melts under mantle pressures. Earth and Planetary Science Letters 195, 277–290. https://doi.org/10.1016/S0012-821X(01)00584-2

).

Table 1 Compilation of literature datasets. Chemical compositions have been rounded at unity, given in wt. % for glass and mol % for gas. Analytical techniques: UV laser ablation (Heber et al., 2007

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

), step heating (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

; Broadhurst et al., 1992

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

). Data discarded by authors due to contamination of crystals with bubbles are given in italics. For Hiyagon and Ozima (1986)

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

, glass composition is bulk sample starting composition. Data where lithium borate was added to lower melting T are not included, as borate modifies melt polymerisation which controls noble gases solubility. Error bars on D are given when available; * error equals D values.

Run (ref.)	Thermal treatment (duration @ °C)	P (GPa)	Glass composition (wt. %)	Crystal	Gas composition (mol %)	D^Xe (error)
olivine-melt partitioning
V (B1992)	18 d @ 1300	10⁻⁴	54SiO₂-15Al₂O₃-14MgO-17CaO	natural forsterite	5Ne-93Ar-1Kr-1Xe	90
RB587 (H2007)	1 h @ 1165 + 3 h @ 1045 + 6 h @ 990	0.1	61SiO₂-15Al₂O₃-23Na₂O	Mg₂SiO₄	25He-23Ne-25Ar-22Kr-5Xe	3.9 × 10⁻³–351
RB588 (H2007)	1 h @ 1165 + 3 h @ 1045 + 6 h @ 990	0.1	61SiO₂-16Al₂O₃-24Na₂O	Mg₂SiO₄	25He-23Ne-25Ar-22Kr-5Xe	6 × 10⁻⁴–148
RB589 (H2007)	1 h @ 1165 + 3 h @ 1045 + 6 h @ 990	0.1	58SiO₂-16Al₂O₃-23Na₂O	Mg₂SiO₄	25He-23Ne-25Ar-22Kr-5Xe	0
BH-257 (H1986)	3 h 23 min @ 1370	10⁻⁴	48SiO₂-15Al₂O₃-10FeO-15MgO-7CaO-1Na₂O	(Mg,Fe)₂SiO₄	11He-1Ne-88Ar-0.3Kr-0.1Xe + CO₂-H₂ (0.5 to 1 ratio)	0.197(0.080)
BH-258 (H1986)	7 h 36 min @ 1370	10⁻⁴	48SiO₂-15Al₂O₃-10FeO-15MgO-7CaO-1Na₂O	(Mg,Fe)₂SiO₄	11He-1Ne-88Ar-0.3Kr-0.1Xe + CO₂-H₂ (0.5 to 1 ratio)	0.240(0.069)
BH-276 (H1986)	14 h 20 min @ 1350	10⁻⁴	48SiO₂-15Al₂O₃-10FeO-15MgO-7CaO-1Na₂O	(Mg,Fe)₂SiO₄	115He-1Ne-88Ar-0.3Kr-0.1Xe + CO₂-H₂ (0.5 to 1 ratio)	0.222(0.059)
HPP-1 (H1986)	10 min @ 1350	1.0	48SiO₂-15Al₂O₃-10FeO-15MgO-7CaO-1Na₂O	(Mg,Fe)₂SiO₄	air adsorbed on powder	0.14(0.05)
HPP-3 (H1986)	4 h @ 1360	1.5	48SiO₂-15Al₂O₃-10FeO-15MgO-7CaO-1Na₂O	(Mg,Fe)₂SiO₄	air adsorbed on powder	0.046(0.016)
pyroxene-melt partitioning
IV (B1992)	18 d @ 1300	10⁻⁴	56SiO₂-11Al₂O₃-15MgO-19CaO	natural diopside	5Ne-93Ar-1Kr-1Xe	3.3
V (B1992)	7 d @ 1332	10⁻⁴	56SiO₂-11Al₂O₃-15MgO-19CaO	natural diopside	5Ne-93Ar-1Kr-1Xe	47
VI (B1992)	9 d @ 1332	10⁻⁴	56SiO₂-11Al₂O₃-15MgO-19CaO	natural diopside	5Ne-93Ar-1Kr-1Xe	4.0
RB586 (H2007)	0 h 30 min @ 1290 + 1 h @ 1272 + 6 h @ 1200	0.1	65SiO₂-14Al₂O₃-4MgO-8CaO	(Mg_x,Ca_y)SiO₃	25He-23Ne-25Ar-22Kr-5Xe	0.2–70 × 10⁻³ *
HH355 (C2022)	2 h 30 min @ 950 + 3 h 45 min @ 700	1.6	67SiO₂-15Al₂O₃-1CaO-5Na₂O	jadeite	Xe	3.58
HH357 (C2022)	4 h 20 min @ 850	1.7	60SiO₂-18Al₂O₃-1MgO-2CaO-8Na₂O	omphacite	Xe	2.54
feldspar-melt partitioning
Cell5 (C2022)	6 h 30 min @ 1010	2.0	63SiO₂-24Al₂O₃-5CaO-8Na₂O	plagioclase	Xe	0.76

Facing these experimental controversies, the peridotitic database shows an enrichment in Xe over other noble gases in xenoliths (Hennecke and Manuel, 1975

Hennecke, E.W., Manuel, O.K. (1975) Noble gases in an Hawaiian xenolith. Nature 257, 778–780. https://doi.org/10.1038/257778b0

; Poreda and Farley, 1992

Poreda, R.J., Farley, K.A. (1992) Rare gases in Samoan xenoliths. Earth and Planetary Science Letters 113, 129–144. https://doi.org/10.1016/0012-821X(92)90215-H

; Czuppon et al., 2009

Czuppon, G., Matsumoto, T., Handler, M.R., Matsuda, J.-I. (2009) Noble gases in spinel peridotite xenoliths from Mt Quincan, North Queensland, Australia: Undisturbed MORB-type noble gases in the subcontinental lithospheric mantle. Chemical Geology 266, 19–28. https://doi.org/10.1016/j.chemgeo.2009.03.029

). Consistently, natural measurements of Xe mineral/basalt partitioning obtained by analysing parent and partially crystallised magmas (Batiza et al., 1979

Batiza, R., Bernatowicz, T.J., Hohenberg, C.M., Podosek, F.A. (1979) Relations of noble gas abundances to petrogenesis and magmatic evolution of some oceanic basalts and related differentiated volcanic rocks. Contributions to Mineralogy and Petrology 69, 301–313. https://doi.org/10.1007/BF00372332

), or coexisting magma and olivine crystals (Kaneoka et al., 1983

Kaneoka, I., Takaoka, N., Clague, D.A. (1983) Noble gas systematics for coexisting glass and olivine crystals in basalts and dunite xenoliths from Loihi Seamount. Earth and Planetary Science Letters 66, 427–437. https://doi.org/10.1016/0012-821X(83)90156-5

), show Xe compatibility with D^Xe_{crystal/basalt} a few-fold above unity. Natural measurements must, nonetheless, be considered with caution (Carroll and Draper, 1994

Carroll, M.R., Draper, D.S. (1994) Noble gases as trace elements in magmatic processes. Chemical Geology 117, 37–56. https://doi.org/10.1016/0009-2541(94)90120-1

) due to potential magma degassing processes if minerals and melt did not re-equilibrate, and/or if crystals contain vapour inclusions (Kaneoka et al., 1983

Kaneoka, I., Takaoka, N., Clague, D.A. (1983) Noble gas systematics for coexisting glass and olivine crystals in basalts and dunite xenoliths from Loihi Seamount. Earth and Planetary Science Letters 66, 427–437. https://doi.org/10.1016/0012-821X(83)90156-5

), which as for experiments are difficult to interpret.

To circumvent these problems, we have recently developed a new method combining synchrotron X-ray fluorescence and diffraction techniques with large volume presses (Chen et al., 2022

Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions. High Pressure Research 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290

). The method was first tested on crystal/felsic melt Xe partitioning, and Xe was found to be moderately incompatible to compatible, with a T-dependent behaviour (0.50 ± 0.20 for D^Xe_{plagioclase/melt} at 1010 °C to 3.46 ± 0.25 for D^Xe_jadeite/melt at 700 °C). This method is applied here to a Paris-Edinburgh press energy-dispersive set-up, which has the additional advantage of being optimised for the observation of diffuse X-ray scattering signal from melts.

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Mineral/Melt Xenon Partitioning Measurements

We measured Xe partition coefficient between olivine and basalt, and between feldspar-clinopyroxene mix and basalt, in order to target Xe petrological behaviour in early Hadean contexts (e.g., magma oceans in planetary embryos) and present day subduction zone contexts respectively. Xenon crystal/melt partition coefficients were measured by means of in situ synchrotron X-ray diffraction and X-ray fluorescence simultaneously collected on the same spectrum, using an energy-dispersive set-up and a Paris-Edinburgh press to generate high P-T conditions (Supplementary Information). The starting sample (Supplementary Information) is a synthetic glass relevant for lunar-like magma ocean at the stage of anorthite crystallisation, doped by high P-T synthesis with 0.05 wt. % Xe (Table S-1), i.e. well below Xe solubility in tholeiitic melt (Schmidt and Keppler, 2002

Schmidt, B.C., Keppler, H. (2002) Experimental evidence for high noble gas solubilities in silicate melts under mantle pressures. Earth and Planetary Science Letters 195, 277–290. https://doi.org/10.1016/S0012-821X(01)00584-2

) of 0.41 wt. % at 2 GPa to avoid supersaturation, while being high enough for the Xe fluorescence signal to be significantly above noise level. The starting sample is used either pure to mimic planetesimal magma ocean stages or mixed with 10 wt. % labradorite feldspar to get an analogue of high alumina basalts, relevant for present day subduction zone settings. At each targeted P, T was first raised until recrystallisation, further raised until full remelting, and lowered until crystals grew in equilibrium with melt to ensure chemical equilibrium. The sample was then scanned perpendicularly to the X-ray beam in order to probe either pure melt or crystallised areas. For the olivine/basalt experiments, crystals were efficiently segregated from melt due to their density difference. This was not the case of the pyroxene-feldspar/basalt experiments for which it was not possible to probe only crystals, and the fraction of melt vs. crystals in crystal-rich areas was determined from the X-ray diffraction signal (Supplementary Information). Xenon content in pure melt or crystals was obtained from the Xe K_α fluorescence intensity signal in the fully molten sample pattern and the relevant pattern, either pure melt or crystals, at crystal-melt equilibrium (Supplementary Information). If a pure crystal pattern could not be obtained, Xe content in crystals from mixed crystals + melt pattern was obtained using mass-balance calculation from Xe K_α fluorescence intensity in crystal-rich area and local melt fraction obtained from X-ray diffraction signal (Eq. S-3).

For basaltic melt in equilibrium with feldspar and pyroxene, Xe was enriched in the melt as seen by the stronger Xe fluorescence signal (Fig. 1) and the derived partition coefficient (0.16 ± 0.06; Table 2). Crystal growth partly occurred upon quenching to room T (see microlithic texture of sample in Fig. S-3), hence it is difficult to have a proper estimate of feldspar vs. pyroxene at high P-T conditions, and oriented crystal growth prevents estimate from in situ energy-dispersive X-ray diffraction data. Nonetheless, due to the low global D value, Xe had to be incompatible with both pyroxene and feldspar at our experimental conditions, consistent with the reported T-dependence of D for clinopyroxene/felsic melt (Chen et al., 2022

Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions. High Pressure Research 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290

). In contrast, Xe fluorescence signal was not detected in basalt coexisting with olivine (Fig. 1), which implies a lower limit of 80 for D^Xe_{olivine/basalt}, taking the noise oscillations as a maximum for Xe fluorescence signal in melt. Xenon X-ray fluorescence signal in olivine crystals is strongly affected by quenching T at high P, with a 2.9 factor decrease in intensity (Fig. 1a), indicating important—although incomplete—Xe exsolution back to room T, consistent with previous observation from in situ X-ray diffraction (Sanloup et al., 2011

Sanloup, C., Schmidt, B.C., Gudfinnsson, G., Dewaele, A., Mezouar, M. (2011) Xenon and Argon: A contrasting behavior in olivine at depth. Geochimica et Cosmochimica Acta 75, 6271–6284. https://doi.org/10.1016/j.gca.2011.08.023

).

**Figure 1** Energy-dispersive X-ray data sets. (Left) Full data sets collected at 10.031°. For each crystal/melt system, data collected at different T are vertically spaced for clarity: fully molten sample (orange), partially molten sample (red for molten zone, black for crystalline or crystal-rich zone), and quenched crystals (black dashed). Peaks at 33 keV and 47 keV are MgO diffraction peaks from the cell-assembly. (Right) Zoom on the Xe K_α1 and K_α2 fluorescence lines (29.4 keV and 29.7 keV). For olivine-melt experiments, data sets in the zoomed panel were collected at 4.0285° to avoid diffraction peaks from crystals overlapping with Xe fluorescence lines.

Table 2 Run conditions, coexisting phases, crystalline fraction in crystal-rich areas, Xe content in each phase (wt. %), and partitioning coefficients. Note that crystal and melt fractions do not apply to the whole sample but only to the volume probed by the X-ray beam. *Mass spectrometry measurement. Values in parentheses are errors on the last reported digits.

Run	P (GPa)	T (°C)	Phases	X_crystals	[Xe]^crystals (wt. %)	[Xe]^melt (wt. %)	D^Xe_crystal/melt
Cell2	2.0	1270	Ol + melt	100(5)	0.145(36)	1.65(15) × 10^−3∗	88(22)
PC265	1.3	1100	Ol + glass	83(10)	0.015(6)^∗	1.5(8) × 10^−4∗	104(16)–302(46)
Cell3	1.2	1120	An + Di + melt	34(4)	0.007(2)	0.044(9)	0.16(6)

To further constrain Xe concentration in melt coexisting with olivine, pieces of glass recovered from synchrotron experiments and an additional sample synthesised at similar P-T conditions (Supplementary Information) were analysed by noble gas mass spectrometry. From the additional sample, three fragments of glass and two fragments of mostly crystals could be separated, as olivine crystals had sedimented at the bottom of the capsule. Mass spectrometry analyses were done on bulk sample fragments fully melted by laser heating (Supplementary Information), revealing systematic Xe enrichment in olivine-rich fragments compared to glass. Olivine content in olivine-rich fragments is estimated at 83 ± 10 % from analyses of SEM images (Fig. S-3) using ImageJ software. Our reported values of D^Xe_{olivine/basalt}, 88(22)–302(46) (Table 2), exceed 80 as expected from the lack of Xe X-ray fluorescence signal in the melt. The lower range value was obtained using Xe content in crystals as measured from energy-dispersive X-ray data, and Xe content in glass as measured by mass spectrometry (Table S-2), which is near the 104(16) value obtained on the additional sample using mass spectrometry results only. The upper range corresponds to that value times the intensity ratio between crystals at high P-T and quenched crystals at high P (i.e. 2.9 GPa), to account for Xe exsolution from olivine crystals upon quenching.

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Olivine Retains Xe in Magmatic Processes

Clinopyroxene-feldspar/melt data are broadly consistent with the T-trend reported for pyroxene/felsic melt under similar P (Chen et al., 2022

Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions. High Pressure Research 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290

), and intermediate within the range of literature values at ambient or near ambient P (Broadhurst et al., 1992

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

; Heber et al., 2007

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

). Olivine/melt data (Fig. 2) confirm the compatible nature of Xe in olivine predicted from ab initio calculations (Crépisson et al., 2018

Crépisson, C., Blanchard, M., Lazzeri, M., Balan, E., Sanloup, C. (2018) New constraints on Xe incorporation mechanisms in olivine from first-principles calculations. Geochimica et Cosmochimica Acta 222, 146–155. https://doi.org/10.1016/j.gca.2017.10.028

), are similar to ambient P data from Broadhurst et al. (1992)

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

, and correspond to the higher range from Heber et al. (2007)

Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

. The latter study may underestimate D^Xe_{olivine/basalt} as 1) the melt was enriched in silica (Table 1) while Xe solubility increases by a factor of five, for instance, between a MORB and a haplogranite (Leroy et al., 2019

Leroy, C., Bureau, H., Sanloup, C., Raepsaet, C., Glazyrin, K., Munsch, P., Harmand, M., Prouteau, G., Khodja, H. (2019) Xenon and iodine behaviour in magmas. Earth and Planetary Science Letters 522, 144–154. https://doi.org/10.1016/j.epsl.2019.06.031

), and 2) crystals with bubbles were discarded on the basis of potential contamination while, at least, some of the bubbles are expected to form upon T-quenching, although this effect could be restricted to high P conditions.

**Figure 2** Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986)
Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. *Geochimica et Cosmochimica Acta* 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9
; B1992, Broadhurst *et al.* (1992)
Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. *Geochimica et Cosmochimica Acta* 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W
; H2007, Heber *et al.* (2007)
Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. *Geochimica et Cosmochimica Acta* 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010
; C2022, Chen *et al.* (2022)
Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using *in situ* X-ray synchrotron techniques at high P–T conditions. *High Pressure Research* 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290
; PC265, Cell2, and Cell3 are data from this study (Table 2). Empty symbols indicate room P data; filled symbols indicate data collected between 1.0 and 2.0 GPa (*cf.* Table 1). Note that Heber *et al.* (2007)
Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. *Geochimica et Cosmochimica Acta* 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010
discarded all values above unity due to the observation of gas bubbles in crystals, while at least some might form from exsolution upon quenching. Natural rocks dataset: residual rock/basalt partition coefficients from Batiza *et al.* (1979)
Batiza, R., Bernatowicz, T.J., Hohenberg, C.M., Podosek, F.A. (1979) Relations of noble gas abundances to petrogenesis and magmatic evolution of some oceanic basalts and related differentiated volcanic rocks. *Contributions to Mineralogy and Petrology* 69, 301–313. https://doi.org/10.1007/BF00372332
.

Considered together, the present high P-T clinopyroxene-feldspar/melt and olivine/melt data are consistent with the natural reports of bulk peridotite/melt partitioning coefficient a few-fold above unity from oceanic island basalts (Batiza et al., 1979

Batiza, R., Bernatowicz, T.J., Hohenberg, C.M., Podosek, F.A. (1979) Relations of noble gas abundances to petrogenesis and magmatic evolution of some oceanic basalts and related differentiated volcanic rocks. Contributions to Mineralogy and Petrology 69, 301–313. https://doi.org/10.1007/BF00372332

; Kaneoka et al., 1983

Kaneoka, I., Takaoka, N., Clague, D.A. (1983) Noble gas systematics for coexisting glass and olivine crystals in basalts and dunite xenoliths from Loihi Seamount. Earth and Planetary Science Letters 66, 427–437. https://doi.org/10.1016/0012-821X(83)90156-5

). The P effect on D^Xe_crystal/melt could not be investigated here due to the limited P-T stability field of the mineralogical parageneses investigated. It further cannot be inferred from the comparison of the present and previous datasets (Fig. S-5) as data are either at ambient or near ambient P (10⁻⁴ and 0.1 GPa) or in a restricted P-range between 1.0 and 2.0 GPa. Additionally, the only high P previous dataset for olivine/melt partitioning was obtained with only air adsorbed on samples as a source of noble gases (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

). Pressure is, nonetheless, expected to be important as Xe retention in silicates is P-induced. Importantly, Xe retention does not extend to lower mantle silicates (Shcheka and Keppler, 2012

Shcheka, S.S., Keppler, H. (2012) The origin of the terrestrial noble-gas signature. Nature 490, 531–534. https://doi.org/10.1038/nature11506

), consistent with the plume source being depleted in Xe compared to MORB source (Parai, 2022

Parai, R. (2022) A dry ancient plume mantle from noble gas isotopes. Proceedings of the National Academy of Sciences 119, e2201815119. https://doi.org/10.1073/pnas.2201815119

).

As for any element, Xe crystal chemistry controls its partitioning behaviour, and its knowledge is key to understand its repartition in planetary envelopes. In magmas, noble gases enter the ring structure of silicate melts (Carroll and Stolper, 1993

Carroll, M.R., Stolper, E.M. (1993) Noble gas solubilities in silicate melts and glasses: New experimental results for argon and the relationship between solubility and ionic porosity. Geochimica et Cosmochimica Acta 57, 5039–5051. https://doi.org/10.1016/0016-7037(93)90606-W

), eventually leading to oxidation in the case of Xe in compressed silica-rich melt (Leroy et al., 2019

Leroy, C., Bureau, H., Sanloup, C., Raepsaet, C., Glazyrin, K., Munsch, P., Harmand, M., Prouteau, G., Khodja, H. (2019) Xenon and iodine behaviour in magmas. Earth and Planetary Science Letters 522, 144–154. https://doi.org/10.1016/j.epsl.2019.06.031

). In minerals, the tightly bound nature of Xe leads to the suggestion that either interstitial sites or crystal vacancies are possible sites for the Xe atoms (Hiyagon and Ozima, 1986

Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

). Theoretical calculations have shown that Xe can chemically bond to oxygen in quartz (Probert, 2010

Probert, M.I.J. (2010) An ab initio study of xenon retention in α-quartz. Journal of Physics: Condensed Matter 22, 025501. https://doi.org/10.1088/0953-8984/22/2/025501

; Crépisson et al., 2019

Crépisson, C., Sanloup, C., Blanchard, M., Hudspeth, J., Glazyrin, K., Capitani, F. (2019) The Xe-SiO₂ System at Moderate Pressure and High Temperature. Geochemistry, Geophysics, Geosystems 20, 992–1003. https://doi.org/10.1029/2018GC007779

) and olivine (Crépisson et al., 2018

Crépisson, C., Blanchard, M., Lazzeri, M., Balan, E., Sanloup, C. (2018) New constraints on Xe incorporation mechanisms in olivine from first-principles calculations. Geochimica et Cosmochimica Acta 222, 146–155. https://doi.org/10.1016/j.gca.2017.10.028

) under modest P by substituting a Si atom. This precludes the use of mineral/melt partitioning models considering Xe as a ‘zero’-charge species (Brooker et al., 2003

Brooker, R.A., Du, Z., Blundy, J.D., Kelley, S.P., Allan, N.L., Wood, B.J., Chamorro, E.M., Wartho, J.-A., Purton, J.A. (2003) The ‘zero charge’ partitioning behaviour of noble gases during mantle melting. Nature 423, 738–741. https://doi.org/10.1038/nature01708

). The radius of chemically bonded Xe is, indeed, much smaller than that of inert Xe, with three oxygen atoms located at 2.0 Å in a planar configuration in olivine (Crépisson et al., 2018

Crépisson, C., Blanchard, M., Lazzeri, M., Balan, E., Sanloup, C. (2018) New constraints on Xe incorporation mechanisms in olivine from first-principles calculations. Geochimica et Cosmochimica Acta 222, 146–155. https://doi.org/10.1016/j.gca.2017.10.028

), and two nearest oxygen atoms at 2.0 Å, and two further ones at 2.3 Å in quartz (Crépisson et al., 2019

Crépisson, C., Sanloup, C., Blanchard, M., Hudspeth, J., Glazyrin, K., Capitani, F. (2019) The Xe-SiO₂ System at Moderate Pressure and High Temperature. Geochemistry, Geophysics, Geosystems 20, 992–1003. https://doi.org/10.1029/2018GC007779

). Xenon crystal chemistry has not been reported for pyroxene nor feldspar but for the latter it might be similar to that in quartz, both being tectosilicates. The contrasting D^Xe_crystal/melt values between olivine/basalt and pyroxene-feldspar/basalt may relate to the different local environments of Xe in these minerals.

Over the course of Earth’s history, Xe should have been strongly retained in olivines crystallising from magma oceans, and in olivine-rich residues in present day mantle partial melting processes. Preferential release to the atmosphere is instead expected from high T (>1000 °C) crustal processes, turning to a moderate retention in pyroxenes and feldspars equilibrated with lower T melts such as evolved hydrous magmas in continental crust and arc contexts (Chen et al., 2022

Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions. High Pressure Research 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290

). The petrological behaviour of Xe hence supports the trapping-at-depth scenario (Rzeplinski et al., 2022

Rzeplinski, I., Sanloup, C., Gilabert, E., Horlait, D. (2022) Hadean isotopic fractionation of xenon retained in deep silicates. Nature 606, 713–717. https://doi.org/10.1038/s41586-022-04710-4

), whereby a succession of collisions between pre-planetary embryos led to the depletion in terrestrial and Martian Xe light isotopes due to Xe trapping and oxidation in crystallising magma oceans, while over 99 % (Harper and Jacobsen, 1996

Harper Jr., C.L., Jacobsen, S.B. (1996) Noble Gases and Earth’s Accretion. Science 273, 1814–1818. https://doi.org/10.1126/science.273.5283.1814

) of the initial budget was expelled from growing planetesimals by exsolution from melt at low P in convecting magma oceans followed by atmospheric losses on a few Myr timescale. The late veneer chondritic input to the atmosphere followed by partial-only Xe degassing concomitantly with the emplacement of the continental crust led to the rising Kr/Xe ratio and progressively heavier Xe observed in Archean atmospheric samples (Broadley et al., 2022

Broadley, M.W., Byrne, D.J., Ardoin, L., Almayrac, M.G., Bekaert, D.V., Marty, B. (2022) High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters 588, 117577. https://doi.org/10.1016/j.epsl.2022.117577

) until the late veneer got overprinted, while lighter Xe in the mantle (Peron and Moreira, 2018

Péron, S., Moreira, M. (2018) Onset of volatile recycling into the mantle determined by xenon anomalies. Geochemical Perspectives Letters 9, 21–25. https://doi.org/10.7185/geochemlet.1833

) would result from mixing mass fractionated Xe with subducted Archean atmospheric Xe. This Archean evolution is not observed on Mars where such events did not occur. That the retention of Xe differs in minerals while its impact on isotopic fractionating is similar (Rzeplinski et al., 2022

Rzeplinski, I., Sanloup, C., Gilabert, E., Horlait, D. (2022) Hadean isotopic fractionation of xenon retained in deep silicates. Nature 606, 713–717. https://doi.org/10.1038/s41586-022-04710-4

) implies that Xe elemental and isotopic evolution cannot be modelled by the same Rayleigh distillation law. Indeed, Rayleigh-predicted Kr/Xe ratios for the Archean atmosphere disagree (Broadley et al., 2022

Broadley, M.W., Byrne, D.J., Ardoin, L., Almayrac, M.G., Bekaert, D.V., Marty, B. (2022) High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters 588, 117577. https://doi.org/10.1016/j.epsl.2022.117577

), a mismatch attributed to variable Xe loss over time which is challenging to reconcile with a continuous isotopic evolution.

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Acknowledgements

We acknowledge K. Curtis-Benson for providing parts for cell-assemblies and arranging shipments before and after experiments, O. Boudouma for SEM measurement, N. Rivodini for EPMA analyses. Funding: Q. Chen is funded by CSC scholarship (#201806340094). HPCAT operations are supported by DOE-NNSA’s Office of Experimental Sciences. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Editor: Anat Shahar

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References

Anders, E., Owen, T. (1977) Mars and Earth: Origin and Abundance of Volatiles. Science 198, 453–465. https://doi.org/10.1126/science.198.4316.453

Show in context

Xenon is also unique for its enigmatic atmospheric depletion relative to lighter noble gases (Anders and Owen, 1977), known as the ‘Xe paradox’, and its strong depletion in light isotopes (Krummenacher et al., 1962).
View in article

Ardoin, L., Broadley, M.W, Almayrac, M., Avice, G., Byrne, D.J., Tarantola, A., Lepland, A., Saito, T., Komiya, T., Shibuya, T., Marty, B. (2022) The end of the isotopic evolution of atmospheric xenon. Geochemical Perspective Letters 20, 43–47. https://doi.org/10.7185/geochemlet.2207

Show in context

Atmospheric escape and trapping-at-depth scenarios have been proposed to explain both observations (Ardoin et al., 2022; Broadley et al., 2022; Rzeplinski et al., 2022 and references therein), and are not exclusive.
View in article

Batiza, R., Bernatowicz, T.J., Hohenberg, C.M., Podosek, F.A. (1979) Relations of noble gas abundances to petrogenesis and magmatic evolution of some oceanic basalts and related differentiated volcanic rocks. Contributions to Mineralogy and Petrology 69, 301–313. https://doi.org/10.1007/BF00372332

Show in context

Consistently, natural measurements of Xe mineral/basalt partitioning obtained by analysing parent and partially crystallised magmas (Batiza et al., 1979), or coexisting magma and olivine crystals (Kaneoka et al., 1983), show Xe compatibility with D^Xe_{crystal/basalt} a few-fold above unity. Natural measurements must, nonetheless, be considered with caution (Carroll and Draper, 1994) due to potential magma degassing processes if minerals and melt did not re-equilibrate, and/or if crystals contain vapour inclusions (Kaneoka et al., 1983), which as for experiments are difficult to interpret.
View in article
Natural rocks dataset: residual rock/basalt partition coefficients from Batiza et al. (1979).
View in article
Considered together, the present high P-T clinopyroxene-feldspar/melt and olivine/melt data are consistent with the natural reports of bulk peridotite/melt partitioning coefficient a few-fold above unity from oceanic island basalts (Batiza et al., 1979; Kaneoka et al., 1983).
View in article

Broadhurst, C.L., Drake, M.J., Hagee, B.E., Bernatowicz, T.J. (1992) Solubility and partitioning of Ne, Ar, Kr, and Xe in minerals and synthetic basaltic melts. Geochimica et Cosmochimica Acta 56, 709–723. https://doi.org/10.1016/0016-7037(92)90092-W

Show in context

Noble gases partitioning between major minerals and melt is indeed a debated issue, with Xe spanning the largest range amongst noble gases crystal/melt partitioning data (noted as D^Xe_crystal/melt), with up to 6 orders of magnitude from 6 × 10⁻⁴ to 351 for D^Xe_{olivine/basalt} (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
View in article
Indeed, while noble gas content in melts is homogeneous, such is not the case in minerals, with almost systematic reports of heterogeneous distribution of heavy noble gases, often at the micron or sub-micron scale (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
View in article
Analytical techniques: UV laser ablation (Heber et al., 2007), step heating (Hiyagon and Ozima, 1986; Broadhurst et al., 1992).
View in article
Clinopyroxene-feldspar/melt data are broadly consistent with the T-trend reported for pyroxene/felsic melt under similar P (Chen et al., 2022), and intermediate within the range of literature values at ambient or near ambient P (Broadhurst et al., 1992; Heber et al., 2007).
View in article
Olivine/melt data (Fig. 2) confirm the compatible nature of Xe in olivine predicted from ab initio calculations (Crépisson et al., 2018), are similar to ambient P data from Broadhurst et al. (1992), and correspond to the higher range from Heber et al. (2007).
View in article
Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986); B1992, Broadhurst et al. (1992); H2007, Heber et al. (2007); C2022, Chen et al. (2022); PC265, Cell2, and Cell3 are data from this study (Table 2).
View in article

Broadley, M.W., Byrne, D.J., Ardoin, L., Almayrac, M.G., Bekaert, D.V., Marty, B. (2022) High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters 588, 117577. https://doi.org/10.1016/j.epsl.2022.117577

Show in context

Atmospheric escape and trapping-at-depth scenarios have been proposed to explain both observations (Ardoin et al., 2022; Broadley et al., 2022; Rzeplinski et al., 2022 and references therein), and are not exclusive.
View in article
The late veneer chondritic input to the atmosphere followed by partial-only Xe degassing concomitantly with the emplacement of the continental crust led to the rising Kr/Xe ratio and progressively heavier Xe observed in Archean atmospheric samples (Broadley et al., 2022) until the late veneer got overprinted, while lighter Xe in the mantle (Peron and Moreira, 2018) would result from mixing mass fractionated Xe with subducted Archean atmospheric Xe.
View in article
That the retention of Xe differs in minerals while its impact on isotopic fractionating is similar (Rzeplinski et al., 2022) implies that Xe elemental and isotopic evolution cannot be modelled by the same Rayleigh distillation law. Indeed, Rayleigh-predicted Kr/Xe ratios for the Archean atmosphere disagree (Broadley et al., 2022), a mismatch attributed to variable Xe loss over time which is challenging to reconcile with a continuous isotopic evolution.
View in article

Brooker, R.A., Du, Z., Blundy, J.D., Kelley, S.P., Allan, N.L., Wood, B.J., Chamorro, E.M., Wartho, J.-A., Purton, J.A. (2003) The ‘zero charge’ partitioning behaviour of noble gases during mantle melting. Nature 423, 738–741. https://doi.org/10.1038/nature01708

Show in context

This precludes the use of mineral/melt partitioning models considering Xe as a ‘zero’-charge species (Brooker et al., 2003).
View in article

Carroll, M.R., Stolper, E.M. (1993) Noble gas solubilities in silicate melts and glasses: New experimental results for argon and the relationship between solubility and ionic porosity. Geochimica et Cosmochimica Acta 57, 5039–5051. https://doi.org/10.1016/0016-7037(93)90606-W

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It is, nonetheless, established that melt composition strongly affects trace element partitioning (Schmidt et al., 2006), with one order of magnitude difference between gabbroic and granitic melts, an effect also expected to be strong for noble gases based on solubility values in melts (Carroll and Stolper, 1993; Schmidt and Keppler, 2002).
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In magmas, noble gases enter the ring structure of silicate melts (Carroll and Stolper, 1993), eventually leading to oxidation in the case of Xe in compressed silica-rich melt (Leroy et al., 2019).
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Carroll, M.R., Draper, D.S. (1994) Noble gases as trace elements in magmatic processes. Chemical Geology 117, 37–56. https://doi.org/10.1016/0009-2541(94)90120-1

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Consistently, natural measurements of Xe mineral/basalt partitioning obtained by analysing parent and partially crystallised magmas (Batiza et al., 1979), or coexisting magma and olivine crystals (Kaneoka et al., 1983), show Xe compatibility with D^Xe_{crystal/basalt} a few-fold above unity. Natural measurements must, nonetheless, be considered with caution (Carroll and Draper, 1994) due to potential magma degassing processes if minerals and melt did not re-equilibrate, and/or if crystals contain vapour inclusions (Kaneoka et al., 1983), which as for experiments are difficult to interpret.
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Chen, Q., Sanloup, C., Bureau, H., Rzeplinski, I., Glazyrin, K., Farla, R. (2022) Probing the partitioning behaviour of Xe using in situ X-ray synchrotron techniques at high P–T conditions. High Pressure Research 42, 318–335. https://doi.org/10.1080/08957959.2022.2144290

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To circumvent these problems, we have recently developed a new method combining synchrotron X-ray fluorescence and diffraction techniques with large volume presses (Chen et al., 2022).
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Nonetheless, due to the low global D value, Xe had to be incompatible with both pyroxene and feldspar at our experimental conditions, consistent with the reported T-dependence of D for clinopyroxene/felsic melt (Chen et al., 2022).
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Clinopyroxene-feldspar/melt data are broadly consistent with the T-trend reported for pyroxene/felsic melt under similar P (Chen et al., 2022), and intermediate within the range of literature values at ambient or near ambient P (Broadhurst et al., 1992; Heber et al., 2007).
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Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986); B1992, Broadhurst et al. (1992); H2007, Heber et al. (2007); C2022, Chen et al. (2022); PC265, Cell2, and Cell3 are data from this study (Table 2).
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Preferential release to the atmosphere is instead expected from high T (>1000 °C) crustal processes, turning to a moderate retention in pyroxenes and feldspars equilibrated with lower T melts such as evolved hydrous magmas in continental crust and arc contexts (Chen et al., 2022).
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Crépisson, C., Blanchard, M., Lazzeri, M., Balan, E., Sanloup, C. (2018) New constraints on Xe incorporation mechanisms in olivine from first-principles calculations. Geochimica et Cosmochimica Acta 222, 146–155. https://doi.org/10.1016/j.gca.2017.10.028

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Olivine/melt data (Fig. 2) confirm the compatible nature of Xe in olivine predicted from ab initio calculations (Crépisson et al., 2018), are similar to ambient P data from Broadhurst et al. (1992), and correspond to the higher range from Heber et al. (2007).
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Theoretical calculations have shown that Xe can chemically bond to oxygen in quartz (Probert, 2010; Crépisson et al., 2019) and olivine (Crépisson et al., 2018) under modest P by substituting a Si atom.
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The radius of chemically bonded Xe is, indeed, much smaller than that of inert Xe, with three oxygen atoms located at 2.0 Å in a planar configuration in olivine (Crépisson et al., 2018), and two nearest oxygen atoms at 2.0 Å, and two further ones at 2.3 Å in quartz (Crépisson et al., 2019).
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Crépisson, C., Sanloup, C., Blanchard, M., Hudspeth, J., Glazyrin, K., Capitani, F. (2019) The Xe-SiO₂ System at Moderate Pressure and High Temperature. Geochemistry, Geophysics, Geosystems 20, 992–1003. https://doi.org/10.1029/2018GC007779

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Theoretical calculations have shown that Xe can chemically bond to oxygen in quartz (Probert, 2010; Crépisson et al., 2019) and olivine (Crépisson et al., 2018) under modest P by substituting a Si atom.
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The radius of chemically bonded Xe is, indeed, much smaller than that of inert Xe, with three oxygen atoms located at 2.0 Å in a planar configuration in olivine (Crépisson et al., 2018), and two nearest oxygen atoms at 2.0 Å, and two further ones at 2.3 Å in quartz (Crépisson et al., 2019).
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Czuppon, G., Matsumoto, T., Handler, M.R., Matsuda, J.-I. (2009) Noble gases in spinel peridotite xenoliths from Mt Quincan, North Queensland, Australia: Undisturbed MORB-type noble gases in the subcontinental lithospheric mantle. Chemical Geology 266, 19–28. https://doi.org/10.1016/j.chemgeo.2009.03.029

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Facing these experimental controversies, the peridotitic database shows an enrichment in Xe over other noble gases in xenoliths (Hennecke and Manuel, 1975; Poreda and Farley, 1992; Czuppon et al., 2009).
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Harper Jr., C.L., Jacobsen, S.B. (1996) Noble Gases and Earth’s Accretion. Science 273, 1814–1818. https://doi.org/10.1126/science.273.5283.1814

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The petrological behaviour of Xe hence supports the trapping-at-depth scenario (Rzeplinski et al., 2022), whereby a succession of collisions between pre-planetary embryos led to the depletion in terrestrial and Martian Xe light isotopes due to Xe trapping and oxidation in crystallising magma oceans, while over 99 % (Harper and Jacobsen, 1996) of the initial budget was expelled from growing planetesimals by exsolution from melt at low P in convecting magma oceans followed by atmospheric losses on a few Myr timescale.
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Heber, V.S., Brooker, R.A., Kelley, S.P., Wood, B.J. (2007) Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene. Geochimica et Cosmochimica Acta 71, 1041–1061. https://doi.org/10.1016/j.gca.2006.11.010

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Noble gases partitioning between major minerals and melt is indeed a debated issue, with Xe spanning the largest range amongst noble gases crystal/melt partitioning data (noted as D^Xe_crystal/melt), with up to 6 orders of magnitude from 6 × 10⁻⁴ to 351 for D^Xe_{olivine/basalt} (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
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Indeed, while noble gas content in melts is homogeneous, such is not the case in minerals, with almost systematic reports of heterogeneous distribution of heavy noble gases, often at the micron or sub-micron scale (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
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For instance, olivine-melt experiment compositions range from synthetic Fe-free forsterite/61 % SiO₂-rich melt (Heber et al., 2007) to natural olivine/basalt (Hiyagon and Ozima, 1986).
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Analytical techniques: UV laser ablation (Heber et al., 2007), step heating (Hiyagon and Ozima, 1986; Broadhurst et al., 1992).
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Clinopyroxene-feldspar/melt data are broadly consistent with the T-trend reported for pyroxene/felsic melt under similar P (Chen et al., 2022), and intermediate within the range of literature values at ambient or near ambient P (Broadhurst et al., 1992; Heber et al., 2007).
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Olivine/melt data (Fig. 2) confirm the compatible nature of Xe in olivine predicted from ab initio calculations (Crépisson et al., 2018), are similar to ambient P data from Broadhurst et al. (1992), and correspond to the higher range from Heber et al. (2007).
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Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986); B1992, Broadhurst et al. (1992); H2007, Heber et al. (2007); C2022, Chen et al. (2022); PC265, Cell2, and Cell3 are data from this study (Table 2).
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Note that Heber et al. (2007) discarded all values above unity due to the observation of gas bubbles in crystals, while at least some might form from exsolution upon quenching.
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Hennecke, E.W., Manuel, O.K. (1975) Noble gases in an Hawaiian xenolith. Nature 257, 778–780. https://doi.org/10.1038/257778b0

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Facing these experimental controversies, the peridotitic database shows an enrichment in Xe over other noble gases in xenoliths (Hennecke and Manuel, 1975; Poreda and Farley, 1992; Czuppon et al., 2009).
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Hiyagon, H., Ozima, M. (1986) Partition of noble gases between olivine and basalt melt. Geochimica et Cosmochimica Acta 50, 2045–2057. https://doi.org/10.1016/0016-7037(86)90258-9

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Noble gases partitioning between major minerals and melt is indeed a debated issue, with Xe spanning the largest range amongst noble gases crystal/melt partitioning data (noted as D^Xe_crystal/melt), with up to 6 orders of magnitude from 6 × 10⁻⁴ to 351 for D^Xe_{olivine/basalt} (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
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A few experiments were carried out at higher P up to 1.5 GPa (Hiyagon and Ozima, 1986) but with only adsorbed air on starting sample as noble gas source.
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Indeed, while noble gas content in melts is homogeneous, such is not the case in minerals, with almost systematic reports of heterogeneous distribution of heavy noble gases, often at the micron or sub-micron scale (Hiyagon and Ozima, 1986; Broadhurst et al., 1992; Heber et al., 2007).
View in article
Some data were discarded on this ground, despite sometimes clear elemental fractionation from the original gas (Hiyagon and Ozima, 1986), which is not expected for passively trapped gas. Indeed, Xe was observed to retro-diffuse out of olivine in high P experiments upon T-quenching (Sanloup et al., 2011), an exsolution process that could explain at least part of the bubbles observed on quenched samples.
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Step heating experiments show that heavy noble gases are tightly bound in minerals, with largest fractions being released above 1000 °C (Hiyagon and Ozima, 1986), arguing against physical adsorption.
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For instance, olivine-melt experiment compositions range from synthetic Fe-free forsterite/61 % SiO₂-rich melt (Heber et al., 2007) to natural olivine/basalt (Hiyagon and Ozima, 1986).
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Analytical techniques: UV laser ablation (Heber et al., 2007), step heating (Hiyagon and Ozima, 1986; Broadhurst et al., 1992).
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Data discarded by authors due to contamination of crystals with bubbles are given in italics. For Hiyagon and Ozima (1986), glass composition is bulk sample starting composition.
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Summary of Xe crystal/melt partition coefficients. Data abbreviations: H1986, Hiyagon and Ozima (1986); B1992, Broadhurst et al. (1992); H2007, Heber et al. (2007); C2022, Chen et al. (2022); PC265, Cell2, and Cell3 are data from this study (Table 2).
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Additionally, the only high P previous dataset for olivine/melt partitioning was obtained with only air adsorbed on samples as a source of noble gases (Hiyagon and Ozima, 1986).
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In minerals, the tightly bound nature of Xe leads to the suggestion that either interstitial sites or crystal vacancies are possible sites for the Xe atoms (Hiyagon and Ozima, 1986).
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Kaneoka, I., Takaoka, N., Clague, D.A. (1983) Noble gas systematics for coexisting glass and olivine crystals in basalts and dunite xenoliths from Loihi Seamount. Earth and Planetary Science Letters 66, 427–437. https://doi.org/10.1016/0012-821X(83)90156-5

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Consistently, natural measurements of Xe mineral/basalt partitioning obtained by analysing parent and partially crystallised magmas (Batiza et al., 1979), or coexisting magma and olivine crystals (Kaneoka et al., 1983), show Xe compatibility with D^Xe_{crystal/basalt} a few-fold above unity. Natural measurements must, nonetheless, be considered with caution (Carroll and Draper, 1994) due to potential magma degassing processes if minerals and melt did not re-equilibrate, and/or if crystals contain vapour inclusions (Kaneoka et al., 1983), which as for experiments are difficult to interpret.
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Considered together, the present high P-T clinopyroxene-feldspar/melt and olivine/melt data are consistent with the natural reports of bulk peridotite/melt partitioning coefficient a few-fold above unity from oceanic island basalts (Batiza et al., 1979; Kaneoka et al., 1983).
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Krummenacher, D., Merrihue, C.M., Pepin, R.O., Reynolds, J.H. (1962) Meteoritic krypton and barium versus the general isotopic anomalies in xenon. Geochimica et Cosmochimica Acta 26, 231–249. https://doi.org/10.1016/0016-7037(62)90014-5

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Xenon is also unique for its enigmatic atmospheric depletion relative to lighter noble gases (Anders and Owen, 1977), known as the ‘Xe paradox’, and its strong depletion in light isotopes (Krummenacher et al., 1962).
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Leroy, C., Bureau, H., Sanloup, C., Raepsaet, C., Glazyrin, K., Munsch, P., Harmand, M., Prouteau, G., Khodja, H. (2019) Xenon and iodine behaviour in magmas. Earth and Planetary Science Letters 522, 144–154. https://doi.org/10.1016/j.epsl.2019.06.031

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The latter study may underestimate D^Xe_{olivine/basalt} as 1) the melt was enriched in silica (Table 1) while Xe solubility increases by a factor of five, for instance, between a MORB and a haplogranite (Leroy et al., 2019), and 2) crystals with bubbles were discarded on the basis of potential contamination while, at least, some of the bubbles are expected to form upon T-quenching, although this effect could be restricted to high P conditions.
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In magmas, noble gases enter the ring structure of silicate melts (Carroll and Stolper, 1993), eventually leading to oxidation in the case of Xe in compressed silica-rich melt (Leroy et al., 2019).
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Ozima, M., Miura, Y., Podosek, F. (2002) Revisiting I-Xe systematics, an early solar system chronometer. Geochimica et Cosmochimica Acta 66, A576.

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Noble gases provide unique clues to unravel the geochemical evolution of volatile elements upon Earth’s formation to present day geodynamics (Ozima et al., 2002 and references therein), assuming their inertness and volatile behaviour.
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Parai, R. (2022) A dry ancient plume mantle from noble gas isotopes. Proceedings of the National Academy of Sciences 119, e2201815119. https://doi.org/10.1073/pnas.2201815119

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Importantly, Xe retention does not extend to lower mantle silicates (Shcheka and Keppler, 2012), consistent with the plume source being depleted in Xe compared to MORB source (Parai, 2022).
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Péron, S., Moreira, M. (2018) Onset of volatile recycling into the mantle determined by xenon anomalies. Geochemical Perspectives Letters 9, 21–25. https://doi.org/10.7185/geochemlet.1833

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The late veneer chondritic input to the atmosphere followed by partial-only Xe degassing concomitantly with the emplacement of the continental crust led to the rising Kr/Xe ratio and progressively heavier Xe observed in Archean atmospheric samples (Broadley et al., 2022) until the late veneer got overprinted, while lighter Xe in the mantle (Peron and Moreira, 2018) would result from mixing mass fractionated Xe with subducted Archean atmospheric Xe.
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Poreda, R.J., Farley, K.A. (1992) Rare gases in Samoan xenoliths. Earth and Planetary Science Letters 113, 129–144. https://doi.org/10.1016/0012-821X(92)90215-H

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Facing these experimental controversies, the peridotitic database shows an enrichment in Xe over other noble gases in xenoliths (Hennecke and Manuel, 1975; Poreda and Farley, 1992; Czuppon et al., 2009).
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Probert, M.I.J. (2010) An ab initio study of xenon retention in α-quartz. Journal of Physics: Condensed Matter 22, 025501. https://doi.org/10.1088/0953-8984/22/2/025501

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Theoretical calculations have shown that Xe can chemically bond to oxygen in quartz (Probert, 2010; Crépisson et al., 2019) and olivine (Crépisson et al., 2018) under modest P by substituting a Si atom.
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Rzeplinski, I., Sanloup, C., Gilabert, E., Horlait, D. (2022) Hadean isotopic fractionation of xenon retained in deep silicates. Nature 606, 713–717. https://doi.org/10.1038/s41586-022-04710-4

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Atmospheric escape and trapping-at-depth scenarios have been proposed to explain both observations (Ardoin et al., 2022; Broadley et al., 2022; Rzeplinski et al., 2022 and references therein), and are not exclusive.
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The petrological behaviour of Xe hence supports the trapping-at-depth scenario (Rzeplinski et al., 2022), whereby a succession of collisions between pre-planetary embryos led to the depletion in terrestrial and Martian Xe light isotopes due to Xe trapping and oxidation in crystallising magma oceans, while over 99 % (Harper and Jacobsen, 1996) of the initial budget was expelled from growing planetesimals by exsolution from melt at low P in convecting magma oceans followed by atmospheric losses on a few Myr timescale.
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That the retention of Xe differs in minerals while its impact on isotopic fractionating is similar (Rzeplinski et al., 2022) implies that Xe elemental and isotopic evolution cannot be modelled by the same Rayleigh distillation law. Indeed, Rayleigh-predicted Kr/Xe ratios for the Archean atmosphere disagree (Broadley et al., 2022), a mismatch attributed to variable Xe loss over time which is challenging to reconcile with a continuous isotopic evolution.
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Sanloup, C., Schmidt, B.C., Gudfinnsson, G., Dewaele, A., Mezouar, M. (2011) Xenon and Argon: A contrasting behavior in olivine at depth. Geochimica et Cosmochimica Acta 75, 6271–6284. https://doi.org/10.1016/j.gca.2011.08.023

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Some data were discarded on this ground, despite sometimes clear elemental fractionation from the original gas (Hiyagon and Ozima, 1986), which is not expected for passively trapped gas. Indeed, Xe was observed to retro-diffuse out of olivine in high P experiments upon T-quenching (Sanloup et al., 2011), an exsolution process that could explain at least part of the bubbles observed on quenched samples.
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Xenon X-ray fluorescence signal in olivine crystals is strongly affected by quenching T at high P, with a 2.9 factor decrease in intensity (Fig. 1a), indicating important—although incomplete—Xe exsolution back to room T, consistent with previous observation from in situ X-ray diffraction (Sanloup et al., 2011).
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Schmidt, B.C., Keppler, H. (2002) Experimental evidence for high noble gas solubilities in silicate melts under mantle pressures. Earth and Planetary Science Letters 195, 277–290. https://doi.org/10.1016/S0012-821X(01)00584-2

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It is, nonetheless, established that melt composition strongly affects trace element partitioning (Schmidt et al., 2006), with one order of magnitude difference between gabbroic and granitic melts, an effect also expected to be strong for noble gases based on solubility values in melts (Carroll and Stolper, 1993; Schmidt and Keppler, 2002).
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The starting sample (Supplementary Information) is a synthetic glass relevant for lunar-like magma ocean at the stage of anorthite crystallisation, doped by high P-T synthesis with 0.05 wt. % Xe (Table S-1), i.e. well below Xe solubility in tholeiitic melt (Schmidt and Keppler, 2002) of 0.41 wt. % at 2 GPa to avoid supersaturation, while being high enough for the Xe fluorescence signal to be significantly above noise level.
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Schmidt, M.W., Connolly, J.A.D., Günther, D., Bogaerts, M. (2006) Element Partitioning: The Role of Melt Structure and Composition. Science 312, 1646–1650. https://doi.org/10.1126/science.1126690

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It is, nonetheless, established that melt composition strongly affects trace element partitioning (Schmidt et al., 2006), with one order of magnitude difference between gabbroic and granitic melts, an effect also expected to be strong for noble gases based on solubility values in melts (Carroll and Stolper, 1993; Schmidt and Keppler, 2002).
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Shcheka, S.S., Keppler, H. (2012) The origin of the terrestrial noble-gas signature. Nature 490, 531–534. https://doi.org/10.1038/nature11506

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Importantly, Xe retention does not extend to lower mantle silicates (Shcheka and Keppler, 2012), consistent with the plume source being depleted in Xe compared to MORB source (Parai, 2022).
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Zahnle, K.J., Gacesa, M., Catling, D.C. (2019) Strange messenger: A new history of hydrogen on Earth, as told by Xenon. Geochimica et Cosmochimica Acta 244, 56–85. https://doi.org/10.1016/j.gca.2018.09.017

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However, the main challenge is how to lift the heavy Xe through the atmosphere up to levels where it can be lost (Zahnle et al., 2019).
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