Neon isotopes in submarine basalts

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

doi:10.1016/0012-821x(88)90152-5

Cited by 372 publications

(202 citation statements)

References 44 publications

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“…Isotope ratios of the blanks were within error of atmospheric values. An initial heating step at 600°C was used to remove atmospheric gases contained in surface deposits or absorbed into the outer surface of the glass (Sarda et al, 1985(Sarda et al, , 1988Marty and Zimmermann, 1999). Fusion at 1400°C (after extraction) ensured the crucible was purged before receiving a new sample.…”

Section: Methodsmentioning

confidence: 99%

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Macpherson

Hilton

Mertz

et al. 2005

Geochimica et Cosmochimica Acta

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Section: Methodsmentioning

confidence: 99%

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Macpherson

Hilton

Mertz

et al. 2005

Geochimica et Cosmochimica Acta

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“…The initial observation of 20 Ne/ 22 Ne values above atmospheric values in both CO 2 -rich well gas (Phinney et al 1978) and MORB (Sarda et al 1988) was then due to either mass fractionation of an atmospheric component or an original accretionary signature. Honda et al (1991) were able to show that the resolved 3 He/ 22 Ne, assuming an accretionary origin, was similar to solar values.…”

Section: Neon: a Trapped Meteorite Origin For Terrestrial Mantle Volamentioning

confidence: 99%

What CO ₂ well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere

Ballentine

Holland²

2008

Phil. Trans. R. Soc. A.

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Study of commercially produced volcanic CO 2 gas associated with the Colorado Plateau, USA, has revealed substantial new information about the noble gas isotopic composition and elemental abundance pattern of the mantle. Combined with published data from midocean ridge basalts, it is now clear that the convecting mantle has a maximum 20 Ne/ 22 Ne isotopic composition, indistinguishable from that attributed to solar wind-implanted (SWI) neon in meteorites. This is distinct from the higher 20 Ne/ 22 Ne isotopic value expected for solar nebula gases. The non-radiogenic xenon isotopic composition of the well gases shows that 20 per cent of the mantle Xe is 'solar-like' in origin, but cannot resolve the small isotopic difference between the trapped meteorite 'Q'-component and solar Xe. The mantle primordial 20 Ne/ 132 Xe is approximately 1400 and is comparable with the upper end of that observed in meteorites. Previous work using the terrestrial 129 I-129 Xe mass balance demands that almost 99 per cent of the Xe (and therefore other noble gases) has been lost from the accreting solids and that Pu-I closure age models have shown this to have occurred in the first ca 100 Ma of the Earth's history. The highest concentrations of Q-Xe and solar wind-implanted (SWI)-Ne measured in meteorites allow for this loss and these high-abundance samples have a Ne/Xe ratio range compatible with the 'recycled-aircorrected' terrestrial mantle. These observations do not support models in which the terrestrial mantle acquired its volatiles from the primary capture of solar nebula gases and, in turn, strongly suggest that the primary terrestrial atmosphere, before isotopic fractionation, is most probably derived from degassed trapped volatiles in accreting material.By contrast, the non-radiogenic argon, krypton and 80 per cent of the xenon in the convecting mantle have the same isotopic composition and elemental abundance pattern as that found in seawater with a small sedimentary Kr and Xe admix. These mantle heavy noble gases are dominated by recycling of air dissolved in seawater back into the mantle. Numerical simulations suggest that plumes sampling the core-mantle boundary would be enriched in seawater-derived noble gases compared with the convecting mantle, and therefore have substantially lower 40 Ar/ 36 Ar. This is compatible with observation. The subduction process is not a complete barrier to volatile return to the mantle.

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“…Ne measured in hotspots span a similar range in 2 <Ne! 22 Ne ratios as MORB but with corresponding 2 1 Ne/ 22 Ne ratios that are substantially lower 8 • 4…”

mentioning

confidence: 98%

“…The systematics ofNe are analogous to He, and (8) . We define A15' 22 as the isotopic a;hift in the 21 …”

mentioning

confidence: 98%

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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Neon isotopes in submarine basalts

Cited by 372 publications

References 44 publications

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

What CO ₂ well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere

A unified model for terrestrial rare gases

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Neon isotopes in submarine basalts

Cited by 372 publications

References 44 publications

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

What CO 2 well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere

A unified model for terrestrial rare gases

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What CO ₂ well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere