518 research outputs found
Origin of isotopic fractionation of terrestrial xenon
By taking account of a size distribution of planetesimals, we show that noble gases gravitationally trapped by planetesimals in the solar nebula can explain the isotopic fractionation of terrestrial Xe relative to Xe in primitive meteorites, leaving Kr and other lighter noble gases almost unfractionated. However, this model is not successful in explaining noble gas elemental abundances in the Earth
The 3He/4He ratio in a clay from the K-T boundary,Hokkaido, Japan
We measured the He content and the ^3He/^4He ratio of a K-T boundary clay from Hokkaido. If some meteoritic debris which escaped total melting or evaporation at the K-T event remains in the clay, it may be possible to observe some ^3He in it. However, we could determine only the upper limits of the ^3He/^4He ratois ( for a bulk sample) because of the small amount of ^3He. Three alternatives are considered to explain the result
Radiometric age of lava flows of the Enrei formations in central Japan (1).
Two samples from lava flows of the upper member of the Lower Enrei formations exposed at the top of Utsukushi-ga-hara volcano are dated approximately at 1.3 × 10v K-A years. The dates of these lava flows which are magnetized reversely and eastward are placed in the middle part of the Matuyama reversed epoch. The Ina formations equivalent of the Lower member of the Lower Enrei formations suggest that during this period climatic deterioration had already taken place, so that most parts of the Enrei formations should be younger than the base of the Pleistocene.Article信州大学理学部紀要 1(2): 93-96(1967)departmental bulletin pape
The Dual Origin of the Terrestrial Atmosphere
The origin of the terrestrial atmosphere is one of the most puzzling enigmas
in the planetary sciences. It is suggested here that two sources contributed to
its formation, fractionated nebular gases and accreted cometary volatiles.
During terrestrial growth, a transient gas envelope was fractionated from
nebular composition. This transient atmosphere was mixed with cometary
material. The fractionation stage resulted in a high Xe/Kr ratio, with xenon
being more isotopically fractionated than krypton. Comets delivered volatiles
having low Xe/Kr ratios and solar isotopic compositions. The resulting
atmosphere had a near-solar Xe/Kr ratio, almost unfractionated krypton
delivered by comets, and fractionated xenon inherited from the fractionation
episode. The dual origin therefore provides an elegant solution to the
long-standing "missing xenon" paradox. It is demonstrated that such a model
could explain the isotopic and elemental abundances of Ne, Ar, Kr, and Xe in
the terrestrial atmosphere.Comment: Icarus, in press, 31 pages, 6 tables, and 6 figure
Accurate determination of the absolute 3He/4He ratio of a synthesized helium standard gas (Helium Standard of Japan, HESJ): Towards revision of the atmospheric 3He/4He ratio
The helium standard of Japan, referred to as HESJ, is an inter-laboratory
standard for the 3He/4He ratio. While the ratio of 3He and 4He of the HESJ was
previously determined by a relative comparison to atmospheric helium, the
absolute value of the 3He/4He ratio of the HESJ has not been directly
determined yet. Therefore, it relies on the early measurements of that of
atmospheric helium. The accuracy of the absolute 3He/4He ratios of the
atmosphere and other working standards including HESJ is crucial in some
applications of helium isotopes, such as tritium-3He dating, surface-exposure
age determination based on cosmogenic 3He, and the accurate measurement of the
neutron lifetime. In this work, new control samples of helium gases with
3He/4He ratios of 14, 28, and 42 ppm were fabricated with accuracy of
0.25-0.38% using a gas-handling system for a neutron lifetime experiment at
Japan Proton Accelerator Research Complex (J-PARC). The relative 3He/4He ratios
of these samples and the HESJ were measured using a magnetic-sector-type,
single-focusing, noble gas mass spectrometer with a double collector system. As
a result, the absolute 3He/4He ratio of the HESJ was determined as 27.36 +/-
0.11 ppm. The atmospheric 3He/4He ratio was determined as 1.340 +/- 0.006 ppm,
based on this work.Comment: 18 pages, 8 figures, 4 table
Multiple carriers of Q noble gases in primitive meteorites
The main carrier of primordial heavy noble gases in chondrites is thought to
be an organic phase, known as phase Q, whose precise characterization has
resisted decades of investigation. Indirect techniques have revealed that phase
Q might be composed of two subphases, one of them associated with sulfide. Here
we provide experimental evidence that noble gases trapped within meteoritic
sulfides present chemically- and thermally-driven behavior patterns that are
similar to Q-gases. We therefore suggest that phase Q is likely composed of two
subcomponents: carbonaceous phases and sulfides. In situ decay of iodine at
concentrations levels consistent with those reported for meteoritic sulfides
can reproduce the 129Xe excess observed for Q-gases relative to fractionated
Solar Wind. We suggest that the Q-bearing sulfides formed at high temperature
and could have recorded the conditions that prevailed in the chondrule-forming
region(s)
Inherent tracers for carbon capture and storage in sedimentary formations: composition and applications
Inherent tracers - the “natural” isotopic and trace gas composition of captured CO₂ streams – are potentially powerful tracers for use in CCS technology. This review outlines for the first time the expected carbon isotope and noble gas compositions of captured CO₂ streams from a range of feedstocks, CO₂-generating processes and carbon capture techniques. The C-isotope composition of captured CO₂ will be most strongly controlled by the feedstock, but significant isotope fractionation is possible during capture; noble gas concentrations will be controlled by the capture technique employed. Comparison with likely baseline data suggests that CO₂ generated from fossil fuel feedstocks will often have δ13C distinguishable from storage reservoir CO₂. Noble gases in amine-captured CO₂ streams are likely to be low concentration, with isotopic ratios dependant on the feedstock, but CO₂ captured from oxyfuel plants may be strongly enriched in Kr and Xe which are potentially valuable subsurface tracers. CO₂ streams derived from fossil fuels will have noble gas isotope ratios reflecting a radiogenic component that will be difficult to distinguish in the storage reservoir, but inheritance of radiogenic components will provide an easily recognisable signature in the case of any unplanned migration into shallow aquifers or to the surface
Lunar exploration: opening a window into the history and evolution of the inner Solar System
The lunar geological record contains a rich archive of the history of the inner Solar System, including information relevant to understanding the origin and evolution of the Earth-Moon system, the geological evolution of rocky planets, and our local cosmic environment. This paper provides a brief review of lunar exploration to-date, and describes how future exploration initiatives will further advance our understanding of the origin and evolution of the Moon, the Earth-Moon system, and of the Solar System more generally. It is concluded that further advances will require the placing of new scientific instruments on, and the return of additional samples from, the lunar surface. Some of these scientific objectives can be achieved robotically, for example by in situ geochemical and geophysical measurements and through carefully targeted sample return missions. However, in the longer term, we argue that lunar science would greatly benefit from renewed human operations on the surface of the Moon, such as would be facilitated by implementing the recently proposed Global Exploration Roadmap
Earliest high‐Ti volcanism on the Moon: 40 Ar‐ 39 Ar, Sm‐Nd, and Rb‐Sr isotopic studies of Group D basalts from the Apollo 11 landing site
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93577/1/j.1945-5100.1996.tb02069.x.pd
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