Ratios In Meteorites Research Articles

いん石中のリチウム同位体比

Many experimental results and theoretical considerations have been reported in relation to the isotope abundances of meteoritic lithium. The methods of the experimental investigations are grouped in two categories. One is surface ionization mass spectrometry and the other is secondary ion mass spectrometry. In almost all isotope analyses, and in using both experimental methods, 7Li/6Li ratios in meteorites are reported not to have any anomaly compared with the ratios for terrestrial samples. However, lithium is one of the less abundant elements together with berillium and boron, and the synthetic mechanism of these elements and isotopes are not clarified both experimentally and theoretically. We have possibility that there may be an anomaly of lithium isotope abundances in meteorites according to several theoretical considerations. In this report, mass spectrometric results of lithium isotope analyses for many kinds of meteorites are reviewed and the theoretical and experimental consideration about the nucleosynthesis of lithium are searched.

Effects of bulk composition on nuclide production processes in meteorites

The bulk chemical composition of meteorites is a major factor influencing the production of cosmogenic nuclides. Numerical simulations using Monte Carlo particle production and transport codes were used to investigate particle fluxes, 38Ar elemental production ratios and 21Ne 22Ne ratios in meteorites with a wide range of compositions. The calculations show that enhanced fluxes of low-energy secondary particles in metal-rich phases explain certain experimentally observed differences in nuclide production in various meteorite classes.

Variable [formula omitted] ratio in stone meteorites and in some of their carbon-rich residues

The 196 Hg 202 Hg ratio has been measured in Hg fractions released by stepwise heating (and in four cases in solvent extracts) from bulk samples of 17 different stone meteorites using the radiochemical neutron activation (RNA) method. Carbon-rich (CR) residues obtained from four stones (Allende, Ambapur Nagla, Plainview and Rangala) by the HF/1bHCI demineralisation process have been studied. About 50% of the Hg fractions of bulk samples (from 14 meteorites) have given both positive and negative types of anomalies (10–40%). The distillates of solvent extracts (Hg contents = 0.008–0.120 ppm) showed no clear anomaly. The residual meteoritic materials (SR-residues) after these extractions did show Hg isotopic anomalies in some distillates. In 17 out of 22 distillates from the CR-residues, large negative anomalies are noted. In some of these distillates the depletion of 196Hg was > 90. Replicate measurements did not always give consistent results, presumably due to the heterogeneous dispersion of the anomalous components. The depletion of 196Hg is more frequent in stone meteorites compared to irons, particularly in high-temperature distillates. Isotopic anomalies in Hg suggest either the presence of primitive grains with isotopic anomalies in stones or introduction of the anomalous components from other objects into the parent bodies of meteorites after their solidification.

Platinoid element Eh-pH diagrams (25 °C, 1 bar) in the systems MOHS with geochemical applications

Theoretical Eh-pH diagrams for the platinoids (Ru, Rh, Pd, Os, Ir, Pt) have been constructed for 25 °C, 1 bar conditions. Thermodynamic data from recent sources are adequate for these diagrams. With caution these diagrams may be applied to higher P, T conditions. These diagrams help explain the following geochemical observations: 1. (1) Ru and Os form M (IV) -sulfides but not M (II,III) -sulfides, hence Ru and Os are segregated somewhat from Ir (III,IV), Pd (II,IV) and Pt (II,IV) during magmatic sulfide formation. 2. (2) Rh occurs as native Rh and as Rh (III) -oxide, but forms no sulfides, thus it is segregated from the other platinoids during sulfide mineral formation. 3. (3) Deep-sea nodules are enriched in Pt over Pd because Pt (IV) forms a stable oxide whereas Pd does not. 4. (4) Pt is enriched over Os in magmatic sulfides [see (1) above], but much less so in sedimentary rocks due in part of existence of aqueous Os (VI, VIII) oxyions. 5. (5) Os is enriched in sedimentary rocks for the same reason over Ir. 6. (6) PtIr segregation is complex; under magmatic sulfide conditions PtS forms earlier than Ir 2S 3 with Pt enriched over Ir, but under alkaline oxidizing conditions Ir as IrO − 4 may be mobile thus accounting for the extreme Pt/Ir variation in sedimentary rocks. 7. (7) In the iridium-anomaly clay zones from the KT boundary, the Os/Ir, Pt/Ir and Os/Pt ratios are near one as are these ratios in meteorites. These same ratios in sedimentary rocks vary widely, and only rarely approach 1. The Eh-pH diagrams suggest that no simple terrestrial mechanism(s) can result in these ratios being near one. 8. (8) The Eh-pH diagrams calculated are useful in addressing platinoid element behavior in rocks.

Vacuum Energy in Cosmic Dynamicsa

Annals of the New York Academy of SciencesVolume 470, Issue 1 p. 363-363 Vacuum Energy in Cosmic Dynamicsa H. J. BLOME, H. J. BLOME Sonderforschungsbereich Radioastronomie und Institut für Astrophysik und Extraterrestrische Forschung Auf dem Hügel 71 D-53 Bonn, Federal Republic of GermanySearch for more papers by this authorW. PRIESTER, W. PRIESTER Sonderforschungsbereich Radioastronomie und Institut für Astrophysik und Extraterrestrische Forschung Auf dem Hügel 71 D-53 Bonn, Federal Republic of GermanySearch for more papers by this author H. J. BLOME, H. J. BLOME Sonderforschungsbereich Radioastronomie und Institut für Astrophysik und Extraterrestrische Forschung Auf dem Hügel 71 D-53 Bonn, Federal Republic of GermanySearch for more papers by this authorW. PRIESTER, W. PRIESTER Sonderforschungsbereich Radioastronomie und Institut für Astrophysik und Extraterrestrische Forschung Auf dem Hügel 71 D-53 Bonn, Federal Republic of GermanySearch for more papers by this author First published: May 1986 https://doi.org/10.1111/j.1749-6632.1986.tb47989.x a This paper appeared in full length in: Blome, H. J. & W. Priester. 1985. Vacuum energy in cosmic dynamics. Astrophys. Space Sci.117: 327–335. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume470, Issue1Twelfth Texas Symposium On Relaivistic AstrophysicsMay 1986Pages 363-363 RelatedInformation

Determinations of osmium isotope ratios in iron meteorites and iridosmines by ICP-MS.

Determinations of osmium isotope ratios in iron meteorites and iridosmines by ICP-MS.

Vacuum energy in cosmic dynamics

The analysis of the Th/U ratio in meteorites and the evolutionary ages of globular clusters favour values of the cosmic age of (19±5)×109 yr. This evidence together with a Hubble parameterH 0>70 km s−1 Mpc−1=(14×109 yr)−1 cannot be reconciled in a Friedmann model with Λ=0. It requires a cosmological constant in the order of 10−56 cm−2, equivalent to a vacuum densityρ v =10−29 g cm−3 The Friedmann-Lemaitre models (Λ>0) with a hot big-bang have been calculated. They are based on a present value of the baryonic matter density ofρ 0=0.5×10−30 g cm−3 as derived from the primordial4He and2H abundances. For a Hubble parameter ofH 0=75 km s−1 Mpc−1, our analysis favours a set of models which can be represented by a model with Euclidean metric (density parameter Ω0=1.0, deceleration parameterq 0=−0.93, aget 0=19.7×109 yr) and by a closed model with perpetual expansion (Ω0=1.072,q 0=−1.0, aget 0=21.4×109 yr). A present density parameter close to one can indeed be expected if the conjecture of an exponential inflation of the very early universe is correct. The possible behaviour of the vacuum density is demonstrated with the help of Streeruwitz' formula in the context of the closed model with an inflationary phase at very early times.

Planetary science: Evolution by bombardment?

Planetary science: Evolution by bombardment?

ALHA 81005 Meteorite: Chemical evidence for Lunar Highland Origin

Based on the well‐established characteristic lunar and meteoritic ratios of FeO/MnO, Cr2O3/V and K/La, and REE patterns, ALHA 81005 meteorite is undoubtedly of lunar highland origin. The ALHA 81005 meteorite is an anorthositic gabbro (72% Pl) and matches closely in chemical composition to Apollo 15 15418 and Luna 16 21013 highland rocks. The rock is a non‐KREEPY and VLT type. The siderophiles Au, Ni and Ir content is high (1.5% Cl equivalent) and similar to other lunar highland breccias. The clast has a different ancient meteorite component than the bulk and matrix. The meteorite has a young terrestrial age implying a recent lunar cratering event. Therefore, during major lunar basins formation in early eons, the earth must have received a significant amount of lunar material which is now mixed in the crust. The finding of a lunar meteorite lends credibility to the suggestion that SNC achondrites may come from Mars.

Primitive Helium in Diamonds

Thirteen diamond stones from various unspecified mines in South Africa were analyzed for the isotopic ratio of helium-3 to helium-4. Values of the ratio ranged from less than 10(-7) to (3.2 +/- 0.25) x 10(-4). The latter value is higher than the primordial helium-3/helium-4 ratio in meteorites and close to the ratio for solar-type helium. Such extremely high values may represent primitive helium that evolved very little (that is, showed very little increase in radiogenic helium-4) since the formation of the earth.

Isotopes in Galactic Cosmic Rays

The data on isotopic ratios of elements in Galactic Cosmic Rays (GCR) is steadily improving and has recently reached the point where some information can be extracted, which has bearing on the problem of the origin of the cosmic rays. By and large, these data have generally confirmed the similarity between solar-type matter and GCR source, when spallation effects and selective acceleration are taken into account. The silicon and iron isotopic ratios, for instance, are consistent with meteoritic ratios. For iron, this is particularly important since two or perhaps even three different nucleosynthesis mechanisms are required to account for the species 54Fe, 56Fe, 58Fe. For carbon, nitrogen and oxygen the problem is that the spallation corrections are large compared to the solar system ratios but nevertheless the present upper limits are not in contradiction with the solar system ratios.

Procrustean science: Indigenous siderophiles in the lunar highlands, according to Delano and Ringwood

The best estimate of indigenous lunar siderophiles comes from 29 pristine lunar rocks, characterized by low siderophile abundances, plutonic textures, and high age. Delano and Ringwood's blanket rejection of these rocks, on the contention that they are impact melts, is not justified by the petrologic evidence. Contrary to their claims, gold in highland breccias is largely meteoritic and is unaffected by fumarolic volcanism, as shown by its correlation with Ir and noncorrelation with fumarolic T1 (r=0.896 and 0.272). Delano and Ringwood's approach, involving subtraction of an H-chondrite meteoritic component from highland breccias, ignores the variation of Ir/Au ratios in modern and ancient meteorites, and hence leads to spurious excesses of Au, Ni, and volatiles, and in some cases to physically meaningless, negative residuals. Their ‘excess volatiles’ in highland crust relative to mare basalts disappear when the highland composition is based on pristine lunar rocks rather than under-corrected breccias. Contrary to claims by Delano and Ringwood, the Ni/Co trend in Apollo 16 samples cannot be explained by an indigenous component rich in Ni (150–200 ppm) and Co (30–45ppm); mixing lines show that much lower Ni and Co contents are required (e.g.,∼ 7 ppm each).

The beryllium and boron abundance in the meteorites - A synthesis in interstellar grains

view Abstract Citations (3) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The beryllium and boron abundance in the meteorites: a synthesis in interstellar grains. Dwek, E. Abstract It is suggested that the high abundance of beryllium and boron found in the carbonaceous chondrites is due to the presence of irradiated interstellar graphite grains in those meteorites. The beryllium and boron are produced in the grains by an energetic proton irradiation that occurred at some stage in their lifetime. The identical B-11/B-10 ratio in the earth and in the meteorites and the limited variations in the Li-7/Li-6 ratio between terrestrial and meteoritic samples indicate that these graphite grains were uniformly distributed over large portions of the preplanetary disk. The lower solar photospheric boron and beryllium abundance shows that no BeB-bearing graphite grains were mixed into the sun, pointing to a distinct nuclear origin, quite possibly a synthesis in the interstellar medium by high-energy cosmic rays. The model therefore predicts a solar boron isotopic ratio of 2.3, compatible with that produced in the galactic cosmic-ray propagation model, but distinct from the terrestrial and meteoritic ratio of 4 that is produced in the grains. A measurement of this ratio in the solar photosphere will thus support or disprove the proposed model. Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/182814 Bibcode: 1978ApJ...225L.149D Keywords: Abundance; Beryllium; Boron; Carbonaceous Chondrites; Interstellar Matter; Meteoritic Composition; Astronomical Models; Cosmic Dust; Cosmic Rays; Granular Materials; High Energy Interactions; Nuclear Reactions; Photosphere; Solar Atmosphere; ABUNDANCE; BORON; BERYLLIUM; CARBONACEOUS CHONDRITES; METEORITES; GRAINS; ISOTOPIC RATIOS; IRRADIATION; PROTON IRRADIATION; CARBON; SOLAR SYSTEM; EARTH; INTERSTELLAR; ELEMENT RATIOS; LITHIUM; GRAPHITE; COSMIC DUST; SAMPLES; TERRESTRIAL; METEORITE; SUN; Lunar and Planetary Exploration; Meteorites; Element Abundances:Meteorites; Interstellar Matter:Meteorites full text sources ADS |

The origin and relative abundances of C, N and the noble gases on the terrestrial planets and in meteorites

RASOOL and Le Sergeant1 adopted the inhomogeneous accretion model for planets discussed by Turekian and Clark2 and considered the question of whether carbonaceous chondrites or LL chondrites could better explain the relative abundances of volatile elements found on Earth and Mars. In the inhomogeneous accretion model the volatile elements of the terrestrial planets are attributed to a component which is added late in the accretional history of the planet. Turekian and Clark2 presumed this late-stage component to be like carbonaceous chondrites. But, Rasool and Le Sergeant1 compared the relative concentrations of H, C, N, Ne, Ar, Kr, and Xe (normalised to C) for the Earth, C1 (carbonaceous) chondrites, and LL (ordinary) chondrites and concluded that relative volatile abundances for the Earth have greater similarity to LL chondrites than to C1 chondrites. Specifically, these authors noted that relative to carbon, abundances of the noble gases (Ne, Ar, Kr, and Xe) are within a factor of 3.8 for the Earth and LL chondrites, but differ by factors of 15–37 between the Earth and C1 chondrites. Abundances of H and N relative to C were indicated to be the same within a factor of 2.5 for both meteorite types and the Earth. Turekian and Clark2 had previously made similar comparisons between the Earth and C1 chondrites and concluded that terrestrial volatiles were acquired from material having H/N/C ratios similar to C1 chondrites, but with order-of-magnitude higher abundances of the noble gases. Rasool and Le Sergeant, on the other hand, concluded that volatiles on Earth and, by extention of their arguments, also volatiles on Mars can better be explained by late accretion of material similar to LL chondrites rather than material similar to C1 chondrites. We disagree with the conclusion reached by Rasool and Le Sergeant and with the LL-chondrite data which they used to reach their conclusion. Our purpose here is to demonstrate (1) that the noble gas/C and noble gas/N ratios presently determined for the Earth differ by an order of magnitude from these ratios in most meteorites; (2) that as a group LL chondrites show no better agreement with the Earth in these ratios than do C1 chondrites; (3) data are too incomplete to lead to any conclusions about the type of meteoritic material which may have supplied volatiles to Mars. In addition we suggest that the noble gas/C and noble gas/N ratios for Venus are likely to be more like the Earth's than like meteorites.

Comments on 'Extinct radioactivities: Trapped residuals of presolar grains'

It has recently been suggested that extinct I-129 and Pu-244 were trapped in primitive-solar-nebula ('presolar') grains and decayed into radiogenic Xe-129 and fission Xe before the grains were incorporated into meteorite bodies. This idea is reconsidered in light of the thermal and metamorphic history of meteorites. The criteria that parent and daughter species should never separate and that minerals or grains containing the anomalous xenon should not be subjected to temperatures exceeding 500 C are applied to iron meteorites, achondrites, and chondrites to determine whether presolar grains could be the carriers of rare-gas anomalies to meteorites. The results strongly indicate that the xenon anomaly could not have originated in presolar grains. Other difficulties with the presolar-grain model are discussed, including insufficiently small grain sizes, large variations in Xe-129/I-127 ratios in various meteorites, and apparently unrealistic meteorite formation times and locations.

Argon 37/argon 39 activity ratios in meteorites and the spatial constancy of the cosmic radiation

Argon 37 and argon 39 have been measured in a bulk sample and a metal-rich fraction of the Lost City stone meteorite. In the bulk sample the activity of both isotopes is in fair agreement with the activities reported previously for this meteorite. The activities calculated for the pure metal phase (37Ar = 15.1 ± 2.5 dpm/kg, 39Ar = 20.0 ± 1.5 dpm/kg), however, are different. In particular, the activity ratio of 0.75 ± 0.10 is considerably higher than the previously published values. Consequently the radial heliocentric gradient of the galactic cosmic radiation is found to be much smaller. The data available for the activity ratios in the metal of different meteorites are discussed. Because the wide scatter in the ratios observed in meteorites that fell at comparable times during the solar cycle is due to different decay rates of 37Ar, it is argued that at least during solar maximum the ratios depend essentially on the perihelions of the meteoroid orbits and on whether the meteorites fall on earth when they are on their inward-bound trip or when they are going out. Except in special cases like Lost City, different aphelions will have a noticeable influence only for meteorites falling near solar minimum, provided that the spatial gradient of the cosmic-ray intensity is small or zero at solar minimum.

The solar abundance of calcium and collision broadening of Ca i- and Ca ii-Fraunhofer lines by hydrogen

An abundance analysis of the solar calcium spectrum is carried out using 46 lines with known f-values in the visible and near infrared spectral region. Resonance, forbidden and autoionizing lines are included. The solar abundance of calcium resulting from the 25 weaker, nearly damping-independent lines only is log eCa=6.36±0.07, on the scale log ɛH = 12. The great variety of transitions involved in the solar calcium spectrum, ranging from 0 eV lines of CaI to 7.5 eV lines of CaII and including autoionizing lines, are in reasonable agreement (Figure 1b). Therefore notable non-LTE effects on their equivalent widths can be excluded. Together with the sodium abundance log ɛ Na = 6.30 determined earlier, the solar abundance ratio Ca/Na = 1.15 is obtained with an accuracy of ≈ 10%. Comparison with meteorites (carbonaceous chondrites I) shows that solar and meteoritic ratio agree within these limits. The line broadening by collisions with hydrogen atoms is determined empirically from a comparison of weak and strong Fraunhofer lines of CaI and CaII, thereby using the solar atmosphere as an absorption tube of comparatively well-known physical state. The damping half-widths γH turn out to be larger than predicted from pure van der Waals interaction, the average enhancement factor being 3.0 for CaI and 1.7 for CaII, independent of term properties to a first approximation. Regardless of the reason for this enhancement — inaccurate van der Waals theory or predominance of repulsive interaction these results can be used in the spectroscopy of other stars.

Morphology of Apollo 11 and 12 Soil Samples and the Quest for Biogenic Forms

The Apollo 11 and 12 missions to the moon returned valuable samples for scientific study. The morphology of the loose sediment and breccia from Apollo 11 have been studied extensively in our laboratory using light microscopy, electron microscopy, scanning electron microscopy and the electron probe. The Apollo 12 sample is now undergoing similar treatment.Even though conditions on the moon, especially on the surface, are known to be extremely hostile to life as we know it, an extensive search was carried out for evidence of past life. Since numerous reports exist purporting evidence of life forms in carbonaceous chondrites coming to the Earth from outer space, such material would also be expected to be embedded in the lunar surface. Enders calculates about 2% carbonaceous chondrites on the lunar surface and Keil had measured nickel iron meteoritic ratios in his sample as about 1%. Thus influx to the surface and undetermined past history add interest to the search. However, an estimated turnover rate of 120 million years for a few inches of lunar soil does mean long exposure of this material to radiation, severe temperature changes, high vacuum, etc.

Mass discrimination introduced by the optical properties of a sputtering ion source during the isotopic analysis of lithium in stony meteorites

In the search for the origin of the 7Li/ 6Li anomalies found previously in stony meteorites, it has been observed that the use of a sputtering ion source in mass spectrometric measurements can introduce a variable mass discrimination. Depending on the operating conditions of the ion source, the deviation from the actual value of the isotopic ratio may be ± 10%. It is shown that the nature of the sputtering process, the geometry of the ion source and the size of the sample analyzed is responsible for this isotopic discrimination. This finding leads to the conclusion that the observed variations of the 7Li/ 6Li ratio in stony meteorites described in our previous work were due to an instrumental bias.

Formula omitted] fractionation by plagioclase feldspars

Calcic plagioclases from basaltic-gabbroic rocks and anorthosites exhibit a strong fractionation of K and Rb. The trend of K Rb ratio with K content is similar to that shown by oceanic tholeiites. Such a K-Rb relationship is not shown by metamorphic plagioclase. High K Rb ratios in gabbroic or anorthositic rocks may not indicate a “mantle” origin but may only reflect partitioning of K and Rb between liquid and plagioclase. The K Rb ratios in stone meteorites appear to be largely controlled by their constituent plagioclase.