Rare gas systematics: formation of the atmosphere, evolution and structure of the Earth's mantle

Allègre, Claude J.; Staudacher, Thomas; Sarda, Philippe

doi:10.1016/0012-821x(87)90151-8

Cited by 463 publications

(183 citation statements)

References 41 publications

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“…This is consistent with the classical view of the generation and evolution of hot spots (Morgan, 1971). In contrast to He, other rare gases in hot spots show isotopic ratios between a MORB end member and the composition of atmospheric rare gases (e.g., Kaneoka and Takaoka, 1980;Allegre et al, 1986). These characteristics reflect either the occurence of a deep, atmosphere-like component and/or atmospheric contamination during the ascent and interaction of the diapir with surface reservoirs.…”

Section: Introductionsupporting

confidence: 88%

“…The 40Ar/36Ar ratios obtained in this study (from 287.6 to 383.6) are low when compared to those of other mantle-derived samples (e.g., Ozima and Podosek, 1983;Allegre et al, 1986) and are close to the 40Ar/36Ar ratio of air (295.5). Lavas from hot spots show Ar ratios lower than those of MORB but generally higher than those obtained here (e.g., Kaneoka et al, 1978;Allegre et al, 1986;Staudacher et al, 1990).…”

Section: Argon Isotopic Ratiossupporting

confidence: 54%

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He, Ar, Sr, Nd and Pb isotopes in volcanic rocks from Afar: Evidence for a primitive mantle component and constraints on magmatic sources.

et al. 1993

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He, Ar, Sr, Nd and Pb isotopic ratios have been determined for a set of submarine basaltic glasses from the Gulf of Tadjoura and subaerial lavas from Afar, Republic of Djibuti. Rare gases were recovered by vacuum crushing and analysed with a new analytical system. Helium isotopic ratios up to 15 Ra show the occurrence of a "high 3He" hot spot beneath Afar and indicate the occurrence of a plume originating from a gas-rich, presumably deep, region of the mantle. He-Ar isotope systematics in dicate a mixing between three geochemical end-members: the plume component, enriched in 3He, a radiogenic, possibly crustal, component, and the atmosphere. Low 40Ar/36Ar ratios are interpreted as the result of selective atmospheric contamination of Afar magmas, but the process of contamination is unclear. In a He-Sr-Nd-Pb space, Afar data are plotted in a field similar to basic lavas emitted in Iceland (Djibuti territory) and in the Reykjanes Ridge (Gulf of Tadjoura) and differ by their He isotopic ratios from lavas emitted in EM (e.g., Gough and Tristan da Cunha) and HIMU (e.g., Saint Helena and Tubuaii) hot spots analysed so far.

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Section: Introductionsupporting

confidence: 88%

Section: Argon Isotopic Ratiossupporting

confidence: 54%

He, Ar, Sr, Nd and Pb isotopes in volcanic rocks from Afar: Evidence for a primitive mantle component and constraints on magmatic sources.

et al. 1993

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“…Measured Ar and Xe from OIB with atmospheric compositions were interpreted as representing the lower mantle reservoir, and confirming atmospheric bulk Earth ratios. Although Staudacher and Allegre 11 originally interpreted the 136 Xe excesses measured in MORB as due to the decay of 244 Pu, this was subsequently reinterpreted as due to the decay of 238 U 18 and the possible role of 244 Pu was not incorporated into their model. This model appeared successful at explaining the data available at that time.…”

Section: Introductionmentioning

confidence: 99%

“…Interaction between the mantle reservoirs has been postulated for 3 He 25 and for Pb 26 • Transfer of these elements is most plausibly by mass transfer 26 • 27 , so that all of the rare gases must also accompany these elements. Although it was postulated 18 that He diffused alone into the upper mantle, a substantial diffusive flux of He does not appear to be a reasonable mechanism for maintaining the global ~e flux at mid-ocean ridges. 5.…”

Section: Introductionmentioning

confidence: 99%

A unified model for terrestrial rare gases

Porcelli¹,

Wasserburg²

1995

AIP Conference Proceedings

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A steady state upper mantle model for the rare gases has been constructed which ex1>lains the available observational data of mantle He, Ne, Ar, and Xe isotope compositions and provides specific predictions regarding the rare gas isotopic compositions of the lower mantle, subduction of rare gases, and mantle rare gas concentrations. The model incorporates two mantle reservoirs; an undegassed lower mantle {P) and a highly degassed upper mantle (D). Chemical species are transferred into D within mass flows from P at plumes and from the atmosphere by subduction. Rare gases in D are derived from mixing of these inflows with radiogenic nuclides produced in situ. The upper mantle is degassed at mid-ocean ridges and hotspots. Flows of each isotope into D are balanced by flows out of D, so that upper mantle concentrations are in steady state. Rare gases with distinct 'He/He, 2utgassed D reservoir, additional isotopic shifts are due to decay of U-and Th-series nuclides and «Kover a residence time of -1.4Ga. Since "He, 21 Ne, 40Ar, and 1~e are produced in proportions fixed by nuclear parameters, the resulting isotopic shifts are correlated. The model predicts that the shift in 21 Ne/ 22 Ne in D relative to that in Pis the same as that for 4 He/ 3 He in the respective mantle reservoirs. This is compatible with the available data for MORB and hotspots. The minimum 40 Ar/ 36 Ar, 1 21Jce/ 1 :WX:e, and 1~e 1 1 :WX:e ratios in Pare found to be substantially greater than the atmospheric ratios. The range in Ne, Ar, and Xe isotopes measured in MORB are interpreted as reflecting contamination of mantle rare gases by variable proportions of atmospheric rare gases. Subduction is not significant for He and Ne, but may account for a substantial fraction of Ar and Xe in D. The rare gas relative abundances in P are different than that of the atmosphere and are consistent with possible early solar system reservoirs as found in meteorites. The 3 He/ 22 Ne and ~e/ 36 Ar ratios of P are within the range for meteorites with 'solar' Ne isotope compositions. The 13 0Xe/ 36 Ar ratio of the lower mantle is greater than that of the atmosphere, and may be as high as tl1e ratio found for meteoritic 'planetary' rare gases.In the model, atmospheric rare gas isotope compositions are distinct from those of the mantle. If the Earth originally had uniform concentrations of rare gases, degassing of the upper mantle would have provided only a small proportion of the nonradiogenic rare gases presently in the atmosphere. The remainder was derived from late-accreted material with higher concentrations of rare gases. However, radiogenic 1 21Jce and 1~e abundances imply a substantial loss of rare gases up to -10 8 years after meteorite formation either from the early Earth or from late-accreting p...

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“…We can therefore use the chemistry of basalts as an accessible record of planetary evolution, which due to subduction recycling not only constrains the history E-mail address: os258@cam.ac.uk. of the solid Earth, but that of the hydrosphere and atmosphere as well (e.g. Allègre et al, 1987).…”

Section: Introductionmentioning

confidence: 99%

Geochemical variability in MORB controlled by concurrent mixing and crystallisation

Shorttle

2015

Earth and Planetary Science Letters

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Rare gas systematics: formation of the atmosphere, evolution and structure of the Earth's mantle

Cited by 463 publications

References 41 publications

He, Ar, Sr, Nd and Pb isotopes in volcanic rocks from Afar: Evidence for a primitive mantle component and constraints on magmatic sources.

He, Ar, Sr, Nd and Pb isotopes in volcanic rocks from Afar: Evidence for a primitive mantle component and constraints on magmatic sources.

A unified model for terrestrial rare gases

Geochemical variability in MORB controlled by concurrent mixing and crystallisation

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