Das Strahlungsalter der Eisenmeteorite aus Chlor-36-Messungen

1961 ◽  
Vol 16 (4) ◽  
pp. 379-384 ◽  
Author(s):  
Else Vilcsek ◽  
H. Wanke
Keyword(s):  
Cosmic Ray ◽  
Decay Rates ◽  
Sikhote Alin ◽  
Iron Meteorites ◽  
Exposure Age ◽  
Exposure Ages ◽  
Chlorine 36

Chlorine 36, which is produced by the interaction of cosmic ray particles with nuclei in meteorites, was measured in seven iron meteorites and in one stone meteorite. The decay rates for chlorine-36 in iron meteorites varied between 6.5 and 20.2 dpm/kg. From these and from the concentration of stable spallation products, the exposure ages of these meteorites were calculated. In this way we found for six of the meteorites examined exposure ages close to 500 million years. Only for the Sikhote Alin meteorite the quite different exposure age of 60 million years was measured. As this value is also definitely lower than that found by other authors for this meteorite, it is suggested that the Sikhote Alin had been part of a bigger meteorite which was broken into pieces about 60 million years ago by a collision with another meteorite.

scholarly journals 3. Fragmentation of Asteroids and Delivery of Fragments to Earth

1977 ◽  
Vol 39 ◽  
pp. 283-291 ◽  
Author(s):  
G. W. Wetherill
Keyword(s):  
Cosmic Ray ◽  
Asteroid Belt ◽  
Combined Effects ◽  
Iron Meteorites ◽  
Exposure Age ◽  
Impact Rate ◽  
Dynamical Time ◽  
Spectrophotometric Data ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Ages

Earth-impacting meteoroids are derived from both comets and asteroids, and some uncertainty still exists regarding with which of these bodies some stone meteorites should be identified. In contrast, the long cosmic ray exposure ages of iron meteorites strongly suggest a long-lived asteroidal source capable of providing ~108 g/yr of this material to the earth’s surface over at least much of solar system history. Spectrophotometric data show that differentiated asteroids are concentrated in the inner portion of the asteroid belt. The orbital histories of fragments of inner belt asteroids are investigated, considering the combined effects of close planetary encounters, secular perturbations, and secular resonances. Particular attention is given to the low inclination (<15°) objects with small semimajcr axis (2.1 to 2.6 A.U.), which can make fairly close approaches to Mars (<0.1 A.U.). It is found that the annual yield and dynamical lifetime of collision fragments of these asteroids is in agreement with the observed impact rate and exposure age of iron meteorites. A smaller yield of stone meteorites (-107 g/yr) is expected, because elimination of these objects by collision is probable on the long dynamical time scaTe. Achondrites could be produced in this way; the yield is probably too low to account for chondrites. Chondrites could possibly be derived indirectly from these bodies insofar as these asteroids are also sources of Apollo and Amor objects.

scholarly journals Tritium and Argon-39 in Stone and Iron Meteorites

1969 ◽  
Vol 24 (2) ◽  
pp. 234-244 ◽  
Author(s):  
St. Charalambus ◽  
K. Goebel ◽  
W. Stötzel-Riezler
Keyword(s):  
Cosmic Ray ◽  
Decay Rates ◽  
Earth Atmosphere ◽  
Iron Meteorites ◽  
Production Rates ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Cosmic Ray Flux

Tritium and argon-39 measurements of stone and iron meteorites are reported and discussed. The tritium values of stone meteorites are in general higher than those found in other laboratories. The tritium decay rates in irons were low but a relatively high tritium value was measured in the rim of the meteorites. Factors which may influence the production rates are discussed and it is concluded that the average cosmic-ray flux which irradiated the meteorites must be at least a factor of two higher than the values reported by MacDonald for the cosmic-ray intensity at the top of the earth atmosphere.

scholarly journals Cosmic Ray Exposure Age Determinations of Cosmic Spherules from Marine Sediments

1985 ◽  
Vol 85 ◽  
pp. 179-181
Author(s):  
Kazuo Yamakoshi
Keyword(s):  
Mass Spectrometry ◽  
Cosmic Ray ◽  
High Energy ◽  
High Energy Accelerator ◽  
Exposure Age ◽  
Cosmic Spherules ◽  
Inner Region ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Age ◽  
Cosmic Ray Exposure Ages

AbstractThe cosmic ray exposure ages of deep sea metalic lie spherules were determined by various methods; low level countings (Ni-59), neutron activation analysis (Mn-53), high energy accelerator mass spectrometry (Be-10, Al-26) and mass spectrometry (K isotopes). The exposure ages of 0.3 - 50 Ma were obtained. According to Poynting-Robertson effect, the starting points (supplying sources) are located at inner region of the orbit of Saturn.

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

1962 ◽  
Vol 17 (12) ◽  
pp. 1092-1102 ◽  
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.

γ-spektroskopische Untersuchungen an Steinmeteoriten

1962 ◽  
Vol 17 (10) ◽  
pp. 921-924
Author(s):  
C. Mayer-Böricke ◽  
M.M. Biswas ◽  
W. Gentner
Keyword(s):  
Single Crystal ◽  
Specific Activity ◽  
Cosmic Ray ◽  
Mean Value ◽  
Exposure Age ◽  
Specific Activities ◽  
Exposure Ages ◽  
Cosmic Ray Exposure Age ◽  
Coincidence Spectroscopy

Cosmic ray produced Al26 and Na22 activities in chondrites have been studied by nondestructive γ (511 keV) — γ coincidence spectroscopy. The values of the Αl26 specific activities of the four measured hypersthene chondrite samples are nearly equal, and have a mean value of 0.061 Αl26 e+-decays/min. g.The Na22 specific activity of the Bruderheim chondrite was found to be 0.094 Na22 disint./min. g in agreement with the results obtained by other authors using different methods. From the Na22 activity and the Ne22 content of our sample we have calculated a cosmic ray exposure age of 26 × 106 y for Bruderheim. Exposure ages of other chondrites are discussed.Single crystal γ-spectroscopy of Bruderheim shows in addition to Al26 and Na22 the presence of Mn54 and K40.

Investigations of Cosmic-Ray-Produced Nuclides in Iron Meteorites: 5. More Data on the Nuclides of Potassium and Noble Gases, on Exposure Ages and Meteoroid Sizes

1983 ◽  
Vol 38 (2) ◽  
pp. 273-280 ◽  
Author(s):  
H. Voshage ◽  
H. Feldmann ◽  
O. Braun
Keyword(s):  
Noble Gases ◽  
Cosmic Ray ◽  
Parent Body ◽  
Critical Examination ◽  
Iron Meteorites ◽  
Abundance Patterns ◽  
New Information ◽  
Abundance Anomalies ◽  
Chemical Groups ◽  
Exposure Ages

Abstract The concentrations of the cosmic-ray-produced He-, Ne-, and Ar-nuclides in samples of 31 iron meteorites have been determined by mass spectrometry. Thereby, the number of samples analyzed in this laboratory has grown to 83. A critical examination of all these results was performed. The data of at least 52 samples prove to be useful to describe the "normal" abundance patterns of cosmogenic noble gases in iron meteorites; the description is accomplished by a new system of equations that correlate some properly selected abundance ratios with one another. The correlations serve as an instrument to recognize and diagnose certain abundance anomalies (3He-or 38Ar-deficiencies) which occur in about 25% of all samples analyzed. They allow to select those data which may unhesitatingly be applied in calculations concerning the irradiation histories of the respective meteorites. Another matter of concern for establishing these histories are the cosmic-ray-exposure ages. Mass spectrometric abundance analyses on meteoritic potassium have provided new data on the 41K/40K exposure ages of about 10 iron meteorites as well as on meteoroid sizes and sample depths. For two meteorites of the chemical group IIIAB, Joe Wright Mountains and Picacho, the age values obtained are 685 and 635 Ma, respectively. The results confirm our previous conclusion that the IIIAB-irons resided originally within a more or less contiguous partial volume (metallic core?) of their parent body and were ejected in consequence of a single impact event that happened about 670 Ma ago. Another motive for the present investigation was to measure the exposure ages for meteorites of the chemical groups IIICD and HIE. However, the new information obtained on their age distributions is still inadequate to answer some old questions concerning a possible relationship to the event that produced the IIIAB-meteoroids 670 Ma ago.

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