Radiogene, spallogene und primordiale Edelgase in Steinmeteoriten III

The total content as well as the isotopic composition of helium and neon of 36 stone meteorites have been determined. Except for meteorites with primordial rare gas content, the radiogenic component of 4He has been calculated by subtracting the fourfold amount of 3He from the total 4He in order to allow for the spallation fraction of 4He. From the content of radiogenic 4He the U-Th-He-ages of the investigated meteorites have been calculated.From the content of 3He and 21Ne cosmic ray exposure ages were calculated for all meteorites also.With the new data of the 36 stone meteorites, presented in this paper, the total number of stone meteorites, of which rare gas measurements were carried out so far, amounts to 70 bronzitechondrites and 93 hypersthene-chondrites. The earlier indications for marked differences in the distribution of the U-Th-He-ages as well as for the cosmic ray exposure ages between the bronzitechondrites and the hypersthene-chondrites proved to be undoubtedly correct.During our investigations, we found Elm Creek as one additional bronzite-diondrite with high amounts of primordial rare gases. In two other bronzite-chondrites (Cavour and Dimmit) primordial rare gases were also detected, but in rather small amounts.

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Der Mond als Mutterkörper der Bronzit-Chondrite

Zeitschrift für Naturforschung A ◽

10.1515/zna-1966-1-215 ◽

1966 ◽

Vol 21 (1-2) ◽

pp. 93-110 ◽

Cited By ~ 1

Author(s):

H. Wänke

Keyword(s):

Age Distribution ◽

Cosmic Ray ◽

Parent Body ◽

Gas Content ◽

Rare Gas ◽

Rare Gases ◽

The Mean ◽

Gas Measurements ◽

Exposure Ages ◽

Cosmic Ray Exposure Ages

Knowing the cosmic ray exposure ages of a sufficiently large number of meteorites and using the earth as analyser with special assumptions, criteria can be found to distinguish between a lunar or asteroidal origin of meteorites. Several of the following arguments are based on new and unpublished results of rare gas measurements by HINTENBERGER, SCHULTZ und WÄNKE70.Bronzite-chondrites :1. Arguments for an origin near the surface of the parent body. a) Porosity of the chondrites 0—20%. b) Many bronzite-chondrites contain light primordial rare gases, originating from the exposure of the single meteorite grains to the solar wind. c) Primordial rare gas content always connected with light-dark structure. d) In the distribution of the cosmic ray exposure ages certain groupings can be distinguished. The age distribution of bronzite-chondrites with light primordial rare gases is identical with the distribution of the cosmic ray exposure ages of all bronzite-chondri-tes. The bronzite-chondrites containing primordial gas therefore are probably coming from the very upper layers, and the other bronzite-chondrites from somewhat deeper layers of their parent body.2. Arguments for an origin close to the earth’s orbit. a) Bronzite-chondrites with high cosmic ray exposure ages show a slight tendency to fall in the afternoon (noon until midnight) . b) For the bronzite-chondrites, which are morning falls (midnight until noon), diffusion losses of 3He and 4He are higher and more frequent compared to the afternoon falls. The reason for this can be found in a closer approach to the sun of the first ones. Hypersthene-chondrites do not show this effect. c) Bronzite-chondrites with light primordial rare gas content concentrate among the afternoon falls. d) The mean cosmic ray exposure age of the bronzite-chondrites is considerably lower than that of the hypersthene-chondrites.3. Arguments concerning the size of the parent body. Light primordial rare gas and their connection with light-dark structure indicate a parent body of the size of the moon or a large asteroid.None of these arguments are strictly conclusive. In some cases they are based on observations, which can only be obtained by using statistical methods. Most of these effects are close to the mean error. Adding, however, all observations together, a lunar origin of the bronzite-chondrites becomes nearly undoubtable. A lunar origin of stone meteorites was in recent times first proposed by URET 3.Hypersthene-chondrites :Hypersthene-chondrites with low cosmic ray exposure ages are rare among the morning falls. Their parent body therefore probably has to be found outside the earth’s orbit. Their distribution of the cosmic ray exposure ages may also lead to this conclusion. As proposed by ANDERS 4, the Mars asteroids could possibly be the parent bodies for the hypersthene-chondrites. Mars itself might however be considered also. A lunar origin of the hypersthene-chondrites seems to be completely out of question.

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Radiogene, spallogene und primordiale Edelgase in Steinmeteoriten

Zeitschrift für Naturforschung A ◽

10.1515/zna-1964-0307 ◽

1964 ◽

Vol 19 (3) ◽

pp. 327-341 ◽

Cited By ~ 2

Author(s):

H. Hintenberger ◽

H. König ◽

L. Schultz ◽

H. Wanke

Keyword(s):

Total Content ◽

Cosmic Ray ◽

Uranium Content ◽

Gas Content ◽

Rare Gas ◽

Iron Group ◽

Rare Gases ◽

Average Production ◽

Exposure Ages ◽

Cosmic Ray Exposure Ages

The total content as well as the isotopic composition of helium and neon of 47 stone meteorites have been determined. The concentrations of 3He, 4He, 20Ne, 21Ne and 22Ne are included in the tables. For meteorite samples without primordial rare gas content, the radiogenic component of 4He has been calculated by subtracting the fourfold amount of 3He from the total 4He in order to allow for the spallation fraction of 4He. From radiogenic 4He the U-Th-He ages of the investigated meteorites have been calculated using an average uranium content of 1.1·10-8 g/g (except those cases were uranium determinations existed) and the 3.5 fold amount for thorium.The cosmic ray exposure ages were calculated using the average production rates for 3He and 21Ne derived from the decay rate of tritium and 22Na measured in some meteorites. The calculated values for the exposure ages lie between 0.5·106 years and 40· 106 years.Some of the meteorites show very low 3He/21Ne ratios which indicate diffusion loss of the spallogenic rare gases.Our results indicate differences in the distribution of the U-Th-He ages as well as of the cosmic ray exposure ages between the chondrites of the low iron group (L) and the chondrites of the high iron group (H). On the average the U-Th-He ages of the H group chondrites are considerably higher than those of the L group. In fact, there are only a few H group chondrites with low U-Th-He ages, and for most of these exceptions we show that they lost their radiogenic 4He during the time of cosmic ray exposure. The cosmic ray exposure ages of the H group chondrites are below 10 million years in 74% of the cases, while for those of the L group only 40% are below this value.Investigations on the 47 meteorites also disclosed two additional meteorites (Pultusk and Vigarano) which exhibit a high content of light primordial rare gases, as was earlier found by us for Pantar, Breitscheid and Tabor.

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Über den Helium- und Neongehalt von Steinmeteoriten und deren radiogene und kosmogene Alter

Zeitschrift für Naturforschung A ◽

10.1515/zna-1962-1210 ◽

1962 ◽

Vol 17 (12) ◽

pp. 1092-1102 ◽

Cited By ~ 1

Author(s):

H. Hintenberger ◽

H. König ◽

H. Wanke

Keyword(s):

Neutron Activation ◽

Isotopic Composition ◽

Total Content ◽

Cosmic Ray ◽

Decay Rates ◽

Chemical Compositions ◽

Diffusion Loss ◽

Helium 3 ◽

Exposure Ages ◽

Cosmic Ray Exposure Ages

The total content as well as the isotopic composition of helium and neon of 19 chondrites and 5 achondrites have been determined. A description of the analytical method is given. Large variations of the ratios 3He/21Ne were observed and it is shown that these variations cannot be explained by differences in the chemical compositions of the meteorites only.Radiogenic helium ages and cosmic ray exposure ages have been calculated. The calculation of the helium ages was mainly based on uranium determinations by means of the xenon-method previously developed in this laboratory. The radiogenic helium ages range from 0.42 · 109 to 4.5 · 109 years. The values obtained for the helium ages are compared with the figures for the potassium-argon ages formerly derived by a neutron activation method newly developed and of those stated in the literature. It turns out that in most cases the radiogenic helium ages are lower, sometimes considerably lower than the potassium-argon ages indicating diffusion loss of helium and certainly in smaller quantities also of argon.Using tritium and sodium 22 decay rates from the literature for the calculations of the production rates for helium 3 and neon 22 cosmic ray exposure ages for all the meteorites analysed were obtained. These exposure ages vary between 0.3 ·106 and 29·106 years. No correlation between radiogenic ages and cosmic ray exposure ages and no grouping of the exposure ages have been found.

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Uredelgase in einigen Steinmeteoriten

Zeitschrift für Naturforschung A ◽

10.1515/zna-1960-0706 ◽

1960 ◽

Vol 15 (7) ◽

pp. 600-612 ◽

Cited By ~ 1

Author(s):

J. Zähringer ◽

W. Gentner

Keyword(s):

Large Deviations ◽

Isotopic Composition ◽

Gas Content ◽

Rare Gas ◽

Rare Gases

In the two chondrites Kapoeta and Abee outstanding rare gas content have been found. From the amount and isotopic composition it is concluded that primordial rare gases have been included in these meteorites. Kapoeta contains all rare gases in excess, while Abee has mainly the heavier rare gases as primordial component. The Ne20/Ne22—and A36/A38—ratios show large deviations from atmospheric Neon and Argon. No such large deviations could be found for Krypton and Xenon.

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Eisenmeteorite als Raumsonden für die Untersuchung des Intensitätsverlaufes der kosmischen Strahlung während der letzten Milliarden Jahre

Zeitschrift für Naturforschung A ◽

10.1515/zna-1962-0508 ◽

1962 ◽

Vol 17 (5) ◽

pp. 422-432 ◽

Cited By ~ 2

Author(s):

H. Voshage

Keyword(s):

Interplanetary Space ◽

Cosmic Ray ◽

Gas Production ◽

Rare Gas ◽

Rare Gases ◽

Production Rates ◽

Cosmic Ray Intensity ◽

Long Time ◽

History Of ◽

Exposure Ages

The use of iron meteorites for the establishment of possible long-time variations (108 —109 years) of the cosmic ray intensity in interplanetary space is based upon the study of the production rates of nuclides which are formed by the interaction of cosmic ray particles with nuclei in meteorites. Mass spectrometric measurements of the isotopic composition of meteoritic potassium * are combined with data on cosmogenic rare gases and other elements to give K41-K40-exposure ages and rare gas production rates. The K41-K40-exposure ages are larger than the exposure ages obtained from the study of short-lived activities (e. g. Cl36, A39), by a factor 1.3 to 1.8. This result indicates that the cosmic ray intensity increased during the bombardment history of the meteorites. The data, for example, are consistent with the following assumptions: 1) The cosmic ray intensity was constant during most of the bombarding time and increased by a factor of about 1.5 only a few million years ago. 2) The intensity rose as I(t) =I0 e— γt with —1.1·10-9 ≦ γ ≦ —0.6 · 10-9 a–1. The consequences of this result for the interpretation of meteorite data are discussed.

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The Noble Gas Record in Antarctic and Other Meteorites

Zeitschrift für Naturforschung A ◽

10.1515/zna-1983-0226 ◽

1983 ◽

Vol 38 (2) ◽

pp. 267-272 ◽

Cited By ~ 2

Author(s):

H. W. Weber ◽

O. Braun ◽

L. Schultz ◽

F. Begemann

Keyword(s):

Isotopic Composition ◽

Noble Gas ◽

Cosmic Ray ◽

Retention Model ◽

Meteorite Fall ◽

Exposure Ages ◽

Cosmic Ray Exposure Ages ◽

Independent Individual

Abstract Data are reported for the concentration and isotopic composition of He, Ne, and Ar in 11 Antarctic and 8 other stone meteorites. Cosmic ray exposure ages and whole rock gas retention model ages are given. The noble gas record suggests that all three ALLAN HILLS eucrites analysed so far belong to the same meteorite fall while the three eucrites from the ELEPHANT MORAINE area appear to be three independent individual falls.

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