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

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 mid-ocean 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-air-corrected’ 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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A Comparison of the Noble Gases in Three Meteorite Specimens Labeled Springfield

Zeitschrift für Naturforschung A ◽

10.1515/zna-1976-3-413 ◽

1976 ◽

Vol 31 (3-4) ◽

pp. 293-296

Author(s):

E. W. Hennecke ◽

O. K. Manuel

Keyword(s):

Natural History ◽

Isotopic Composition ◽

Noble Gases ◽

Noble Gas ◽

The Other ◽

Abundance Pattern ◽

Noble Gas Isotopes ◽

Gas Isotopes

The abundance and isotopic composition of the noble gases were measured in three Spring-field specimens identified by the Denver Museum of Natural History with numbers 7029, 379.13 and 6040. The latter specimen contains more cosmogenic noble gas isotopes than the other two specimens and the abundance pattern of trapped noble gases in specimen 6040 is distinct from that in the other two specimens. Specimen 7029 contains about seven times as much radiogenic 40Ar and about four times as much radiogenic 129Xe as does specimen 379.13. These results indicate that the three specimens did not come from a single meteoroid.

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Primordial Noble Gases in Chondrites: The Abundance Pattern Was Established in the Solar Nebula

Science ◽

10.1126/science.198.4320.927 ◽

1977 ◽

Vol 198 (4320) ◽

pp. 927-930 ◽

Cited By ~ 32

Author(s):

L. ALAERTS ◽

R. S. LEWIS ◽

E. ANDERS

Keyword(s):

Solar Nebula ◽

Noble Gases ◽

Abundance Pattern

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On Noble Gas Anomalies in the Great Namaqualand Troilite

Zeitschrift für Naturforschung A ◽

10.1515/zna-1968-0905 ◽

1968 ◽

Vol 23 (9) ◽

pp. 1266-1271 ◽

Cited By ~ 2

Author(s):

E. C. Alexander ◽

J. H. Bennett ◽

O. K. Manuel

Keyword(s):

Neutron Activation ◽

Isotopic Composition ◽

Neutron Capture ◽

Noble Gases ◽

Noble Gas ◽

Helium Neon

The abundances and isotopic composition of the stable noble gases were measured in a troilite nodule from the Great Namaqualand fine octahedrite. Helium, neon and argon show a significant spallation component. The major anomalies in krypton and xenon are from neutron capture on selenium and tellurium and from the decay of extinct I129. The abundances of tellurium, iodine and uranium in the troilite were determined by neutron activation analyses and compared with the xenon anomalies. The results indicate that part of the excess Xe129 is from neutron capture on tellurium and the remainder is due to the retention of radiogenic Xe129 from the decay of extinct I129, about 200 million years after an initial I129/I127 = 3 × 10-3.

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Noble Gases

Oxford Research Encyclopedia of Planetary Science ◽

10.1093/acrefore/9780190647926.013.33 ◽

2018 ◽

Author(s):

Mario Trieloff

Keyword(s):

Solar System ◽

Noble Gases ◽

Noble Gas ◽

Asteroid Belt ◽

Element Abundance ◽

Terrestrial Planets ◽

Abundance Pattern ◽

Terrestrial Atmosphere ◽

The Earth ◽

Protosolar Nebula

Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like the Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, geochemical depletion and enrichment processes mean that noble gases are highly versatile tracers of planetary formation and evolution. When our solar system formed—or even before—small grains and first condensates incorporated small amounts of noble gases from the surrounding gas of solar composition, resulting in depletion of light He and Ne relative to heavy Ar, Kr, and Xe, leading to the “planetary type” abundance pattern. Further noble gas depletion occurred during flash heating of mm- to cm-sized objects (chondrules and calcium, aluminum-rich inclusions), and subsequently during heating—and occasionally differentiation—on small planetesimals, which were precursors of planets. Some of these objects are present today in the asteroid belt and are the source of many meteorites. Many primitive meteorites contain very small (micron to sub-micron size) rare grains that are older than our Solar System and condensed billions of years ago in in the atmospheres of different stars, for example, Red Giant stars. These grains are characterized by nucleosynthetic anomalies, in particular the noble gases, such as so-called s-process xenon. While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the Sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. In contrast, terrestrial planets accreted from planetesimals with only minor contributions from the gaseous component of the protosolar nebula, which accounts for their high degree of depletion and essentially “planetary” elemental abundance pattern. The strong depletion in noble gases facilitates their application as noble gas geo- and cosmochronometers; chronological applications are based on being able to determine noble gas isotopes formed by radioactive decay processes, for example, 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay. Particularly ingrowth of radiogenic xenon is only possible due to the depletion of primordial nuclides, which allows insight into the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters. Applied to large-scale planetary reservoirs, this helps to elucidate the timing of mantle degassing and evolution of planetary atmospheres. Applied to individual rocks and minerals, it allows radioisotope chronology using short-lived (e.g., 129I–129Xe) or long-lived (e.g., 40K–40Ar) systems. The dominance of 40Ar in the terrestrial atmosphere allowed von Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid-ocean ridges, as indicated by outgassing of primordial helium from newly forming ocean crust. Mantle degassing was much more massive in the past, with most of the terrestrial atmosphere probably formed during the first few 100 million years of Earth’s history, in response to major evolutionary processes of accretion, terrestrial core formation, and the terminal accretion stage of a giant impact that formed our Moon. During accretion, solar noble gases were added to the mantle, presumably by solar wind irradiation of the small planetesimals and dust accreting to form the Earth. While the Moon-forming impact likely dissipated a major fraction of the primordial atmosphere, today’s atmosphere originated by addition of a late veneer of asteroidal and possibly cometary material combined with a decreasing rate of mantle degassing over time. As other atmophile elements behave similarly to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, and carbon.

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Noble Gases

10.1093/acrefore/9780190647926.013.30 ◽

2017 ◽

Author(s):

Mario Trieloff

Keyword(s):

Solar System ◽

Noble Gases ◽

Noble Gas ◽

Asteroid Belt ◽

Element Abundance ◽

Terrestrial Planets ◽

The Sun ◽

Abundance Pattern ◽

Terrestrial Atmosphere ◽

Protosolar Nebula

This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1424122112 ◽

2015 ◽

Vol 112 (46) ◽

pp. 14174-14179 ◽

Cited By ~ 8

Author(s):

Suzanne L. Baldwin ◽

J. P. Das

Keyword(s):

Isotopic Composition ◽

Subduction Zones ◽

Noble Gases ◽

Noble Gas ◽

Ultrahigh Pressure ◽

Uhp Metamorphism ◽

Atmospheric Gases ◽

Deep Earth

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 40Ar/39Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40Ar/39Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38Ar/36Ar and 20Ne/22Ne. 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 atmospheric-derived 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.

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Isotopic Fractionation in Slow and Coronal Hole Associated Solar Wind

Symposium - International Astronomical Union ◽

10.1017/s0074180900220007 ◽

2001 ◽

Vol 203 ◽

pp. 562-564 ◽

Cited By ~ 2

Author(s):

H. Kucharek ◽

B. Klecker ◽

F. M. Ipavich ◽

R. Kallenbach ◽

H. Grünwaldt ◽

...

Keyword(s):

Solar Wind ◽

Coronal Hole ◽

Solar Nebula ◽

Isotopic Fractionation ◽

Refractory Element ◽

Plasma Parameters ◽

Magnesium Isotopes ◽

Source Regions ◽

Nuclear Burning ◽

Time Periods

Data from the Mass and Charge Time-of-Flight spectrometers MTOF and CTOF on board SOHO have been accumulated for time periods in which coronal hole and non-coronal hole type plasma has been detected by using different methods in order to determine the abundance ratios of magnesium isotopes in these two different source regions of the solar wind. As indicators for the two different solar wind type plasma we have used several plasma parameters such as, the freeze-in temperatures, the Fe/O and the He/H ratio, which are known as reasonable indicators. For this study we have used the refractory element Mg which is an authentic whitness for matter in the solar nebula because temperatures of the Sun never have been high enough to change their isotopic composition by nuclear burning. In addition Mg has three isotopes with abundance ratios greater than about 10% and therefore they are easy to observe.

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Variation in the terrestrial isotopic composition and atomic weight of argon (IUPAC Technical Report)

Pure and Applied Chemistry ◽

10.1515/pac-2013-0918 ◽

2014 ◽

Vol 86 (9) ◽

pp. 1421-1432 ◽

Cited By ~ 6

Author(s):

J.K. Böhlke

Keyword(s):

Isotopic Composition ◽

Radioactive Decay ◽

Isotopic Fractionation ◽

Atomic Weight ◽

Chemical Processes ◽

Published Data ◽

Nuclear Transformation ◽

Rock Interaction ◽

Physical Chemical ◽

Mass Dependent

AbstractThe isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

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