Noble gas constraints on the origin and evolution of Earth’s volatiles

Moreira, Manuel

doi:10.7185/geochempersp.2.2

Cited by 118 publications

(175 citation statements)

References 210 publications

(517 reference statements)

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“…Here, we investigate whether atmospheric Ar and Ne are trapped in minerals during crystallization at mantle depths during subduction zone metamorphism. We present Ar and Ne isotopic data for omphacite and phengite from Late Miocene coesite eclogite that document both the 40 Ar/ 39 Ar age of phengite crystallization and the isotopic composition of Ar and Ne trapped in these minerals during UHP metamorphism.…”

Section: Significancementioning

confidence: 99%

“…Thus, noble gases trapped in material entering (in crust and sediments) and exiting (in high-pressure and UHP metamorphic rocks) forearcs can provide insight into the recycling of atmospheric noble gases within the subduction channel. Previous studies that have investigated noble gases in exhumed high-pressure and UHP rocks focused on (i) 40 Ar/ 39 Ar age determination on irradiated K-bearing minerals (20), (ii) He and Ne isotopic studies aimed at documenting noble gas compositions trapped during diamond formation (21), and (iii) noble gas and halogen studies of serpentinite and peridotite (7,12,15). Here, we investigate whether atmospheric Ar and Ne are trapped in minerals during crystallization at mantle depths during subduction zone metamorphism.…”

Section: Significancementioning

confidence: 99%

“…Subsequently, the coesite eclogite was exhumed from mantle depths to the Earth's surface at average rates of ≥1 cm y −1 (33). 40 Ar/ 39 Ar Age of Phengite from Coesite Eclogite…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

“…We first performed an 40 Ar/ 39 Ar step heat experiment on phengite, a high-silicon variety of muscovite, and the dominant hydrous potassic phase in UHP metamorphic rocks. One objective was to assess whether results could be interpreted within a geologic and tectonic context or yielded anomalously old 40 (22).…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

“…We measured Ar and Ne trapped in phengite and omphacite from the youngest known UHP terrane on Earth to determine the composition of Ar and Ne returned from mantle depths to the surface by forearc recycling. An 40 Ar/ 39 Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40 Ar/ 39 Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38 Ar/ 36 Ar and 20 Ne/ 22 Ne.…”

mentioning

confidence: 99%

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Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Baldwin¹,

Das²

2015

Proc. Natl. Acad. Sci. U.S.A.

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In subduction zones, sediments, hydrothermally altered lithosphere, fluids, and atmospheric gases are transported into the mantle, where ultrahigh-pressure (UHP) metamorphism takes place. However, the extent to which atmospheric noble gases are trapped in minerals crystallized during UHP metamorphism is unknown. We measured Ar and Ne trapped in phengite and omphacite from the youngest known UHP terrane on Earth to determine the composition of Ar and Ne returned from mantle depths to the surface by forearc recycling. An 40 Ar/ 39 Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40 Ar/ 39 Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38 Ar/ 36 Ar and 20 Ne/ 22 Ne. Our study provides the first documentation, to our knowledge, of entrapment of atmospheric Ar and Ne in phengite and omphacite. Results indicate that a subduction barrier for atmosphericderived noble gases does not exist at mantle depths associated with UHP metamorphism. We show that the crystallization age together with the isotopic composition of nonradiogenic noble gases trapped in minerals formed during subsolidus crystallization at mantle depths can be used to unambiguously assess forearc recycling of atmospheric noble gases. The flux of atmospheric noble gas entering the deep Earth through subduction and returning to the surface cannot be fully realized until the abundances of atmospheric noble gases trapped in exhumed UHP rocks are known.subduction | UHP metamorphism | geochronology | noble gas | atmosphere

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Section: Significancementioning

confidence: 99%

Section: Significancementioning

confidence: 99%

“…Subsequently, the coesite eclogite was exhumed from mantle depths to the Earth's surface at average rates of ≥1 cm y −1 (33). 40 Ar/ 39 Ar Age of Phengite from Coesite Eclogite…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

mentioning

confidence: 99%

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Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Baldwin¹,

Das²

2015

Proc. Natl. Acad. Sci. U.S.A.

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Geochemistry

White

2017

Kirk-Othmer Encyclopedia of Chemical Technology

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Geochemistry is a subdiscipline of chemistry whose objective is understanding the processes occurring on and in the earth, its evolution, and its cosmic environment, and to using that understanding to better the human condition. It naturally divides into (a) low‐temperature or environmental geochemistry, focused on processes at or near the earth's solid surface, including the “critical zone,” the oceans, and the atmosphere, and (b) high‐temperature geochemistry focused on processes such as hydrothermal ore deposition, magmatism, and metamorphism. Isotope geochemistry takes advantage of naturally occurring variations in the isotopic composition of elements resulting from natural, nuclear, and chemical processes to further understand earth processes, both in the near‐surface environment and the earth's deep interior. Geochemistry has greatly enhanced our knowledge of nucleosynthesis, solar system formation, plate tectonics, geologic time, biological evolution, and human origins. Of particular interest in geochemistry are geochemical cycles, such as the carbon cycle, in which carbon in various chemical forms is cycled between the atmosphere, the biosphere, the ocean, sediments, and the earth's deep interior and in doing so regulates Earth's climate. Continuous geochemical research is necessary to ensure future supplies of resources critical to modern society and mitigation of the effects of recovery, use, and disposal of those resources that are critical to human health and happiness.

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The evolution of MORB and plume mantle volatile budgets: Constraints from fission Xe isotopes in Southwest Indian Ridge basalts

Parai

Mukhopadhyay

2015

Geochem. Geophys. Geosyst.

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We present high-precision measurements of the fission isotopes of xenon (Xe) Xe is recycled in origin), consistent with results from studies of plume-influenced basalts from Iceland and the Rochambeau Rift. While significant regassing of the mantle is evident, we also find differences in the extent of degassing of the MORB and plume sources. MORB sources are consistently characterized by a lower fraction of fission Xe derived from Pu-fission, indicating a greater extent of degassing relative to the plume source. The prevalence of recycled atmospheric Xe in mantle sources indicates incorporation of depleted recycled material even into mantle sources with primitive He and Ne isotopic compositions. Consequently, depleted lithophile isotopic compositions in mantle sources with primitive He and Ne cannot be interpreted as evidence for a nonchondritic bulk silicate Earth.

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Noble gas constraints on the origin and evolution of Earth’s volatiles

Cited by 118 publications

References 210 publications

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Geochemistry

The evolution of MORB and plume mantle volatile budgets: Constraints from fission Xe isotopes in Southwest Indian Ridge basalts

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