Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages, meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases

Voshage, H.; Feldmann, Hendrik

doi:10.1016/0012-821x(79)90131-6

Cited by 123 publications

(92 citation statements)

References 29 publications

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“…Another feature of the GCR effect is that cosmogenic " 182 W is approximately linearly correlated with cosmogenic " 184 W, although the sign and value of the slope are both uncertain due to model uncertainties. The negative " 182 W values measured in Tlacotepec, and other meteorites (Table 1) relative to the inferred initial composition of the solar nebula ($À3.5; Yin et al 2002;Kleine et al 2005) is primarily caused by GCR irradiation (Masarik 1997;Leya et al 2003;Markowski et al 2006b), given their relatively long exposure ages (e.g., Voshage & Feldmann 1979). However, this process cannot be responsible for the " 184 W deficiencies measured in IVBs.…”

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confidence: 87%

Tungsten Nuclear Anomalies in Planetesimal Cores

Qin

Dauphas

Wadhwa

et al. 2008

ApJ

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Use of the extinct 182 Hf-182 W chronometer to constrain the timing of planetary accretion and differentiation rests on the assumption that the solar nebula had homogeneous tungsten isotopic composition. Here, we report deficiencies of $0.1 part in 10,000 in the abundance of 184 W in group IVB iron meteorites relative to the silicate Earth. These are most likely due to incomplete mixing at the planetesimal scale (2Y4 km radius bodies) of the products of slow (s-) and rapid (r-) neutron-capture nucleosynthesis in the solar nebula. The correction that must be applied to the 182 Hf-182 W model age of core formation in IVB irons due to the presence of these nuclear anomalies is $0.5 Myr.

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confidence: 87%

Tungsten Nuclear Anomalies in Planetesimal Cores

Qin

Dauphas

Wadhwa

et al. 2008

ApJ

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“…Here we will briefly summarize the 41 K-40 K system developed by Voshage and co-workers (e.g., Voshage and Hintenberger 1961;Voshage 1967;Voshage and Feldmann 1979). According to these authors, the experimental results of the potassium isotopic measurements are summarized as parameter M:…”

Section: The Influence Of the 21 Ne Correction On The 41 K/ 40 K Expomentioning

confidence: 99%

“…Using M values for Grant and Carbo published by Voshage and Feldmann (1979) Note that the N value is a proxy for the K-production rate ratios and is therefore depth dependent as expressed by the dependence on the 4 He/ 21 Ne ratio. Consequently, for determining an exposure age, the M and N values have to be determined on the same sample or at least on samples with the same shielding conditions.…”

Section: The Influence Of the 21 Ne Correction On The 41 K/ 40 K Expomentioning

confidence: 99%

“…This is important because troilite (FeS) and schreibersite ((Fe,Ni) 3 P) are common minerals in iron meteorites. However, the contributions of Ne isotopes from S and P have not been considered for production rate systematics in the past (e.g., Martin 1953;Ebert and Wänke 1957;Nier 1960, 1962;Arnold et al 1961;Voshage and Feldmann 1979). Michlovich et al (1994) noted that S might be an important target element for the production of 26 Al in Canyon Diablo.…”

Section: Introductionmentioning

confidence: 99%

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Noble gases in Grant and Carbo and the influence of S‐ and P‐rich mineral inclusions on the ⁴¹K‐⁴⁰K dating system

Ammon

Masarik

Leya

2008

Meteorit & Planetary Scien

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Abstract-Cosmogenic He, Ne, and Ar were measured in the iron meteorites Grant (IIIAB) and Carbo (IID) to re-determine their preatmospheric geometries and exposure histories. We also investigated the influence of sulphur-and/or phosphorus-rich inclusions on the production rates of cosmogenic Ne. Depth profiles measured in Grant indicate a preatmospheric center location 117 mm left from the reference line and 9 mm below bar B, which is clearly different (~10 cm) from earlier results (~165 mm left from the reference line on bar F). For Carbo the preatmospheric center location was found to be 120 mm right of the reference line and 15 mm above bar J, which is in agreement with literature data. The new measurements indicate a spherical preatmospheric shape for both meteorites and, based on literature 36 Cl data, the radii were estimated to be about 32 cm and 70 cm for Grant and Carbo, respectively. We demonstrate that minor elements like S and P have a significant influence on the production rates of cosmogenic Ne. In our samples, containing on average 0.5% S and/or P, about 20% of 21 Ne was produced from these minor elements. Using measured 21 Ne concentrations and endmember 22 Ne/ 21 Ne ratios for Fe + Ni and S + P, respectively, we show that it is possible to correct for 21 Ne produced from S and/or P. The thus corrected data are then used to calculate new 41 K-40 K exposure ages-using published K data-which results in 564 ± 78 Ma for Grant and 725 ± 100 Ma for Carbo. The correction always lowers the 21 Ne concentrations and consequently decreases the 41 K-40 K exposure ages. The discrepancies between 36 Cl-36 Ar and 41 K-40 K ages are accordingly reduced. The existence of a significant long-term variation of the GCR, which is based on a former 30-50% difference between 41 K-40 K and 36 Cl-36 Ar ages, may warrant re-investigation.

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“…These two factors allow for more parent bodies rich in metallic Fe to be sampled in our meteorite collections. Irons have cosmic-ray exposure ages ranging from hundreds of millions to a few billion years (e.g., Voshage and Feldman, 1979) while stony meteorites tend to have much shorter exposure ages of <100 m.y. (e.g., Marti and Graf, 1992;Scherer and Schultz, 2000).…”

Section: Iron Meteoritesmentioning

confidence: 99%

Smithsonian Institution

2009

Encyclopedia of United States Indian Policy and Law

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Extensive collection efforts in Antarctica and the Sahara in the past 10 years have greatly increased the number of known meteorites. Groupings of meteorites according to petrologic, mineralogical, bulk-chemical, and isotopic properties suggest the existence of 100-150 distinct parent bodies. Dynamical studies imply that most meteorites have their source bodies in the main belt and not among the near-Earth asteroids. Spectral observations of asteroids are currently the primary way of determining asteroid mineralogies. Linkages between ordinary chondrites and S asteroids, CM chondrites and C-type asteroids, the HEDs and 4 Vesta, and iron meteorites, enstatite chondrites, and M asteroids are discussed. However, it is difficult to conclusively link most asteroids with particular meteorite groups due to the number of asteroids with similar spectral properties and the uncertainties in the optical, chemical, and physical properties of the asteroid regolith.

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Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages, meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases

Cited by 123 publications

References 29 publications

Tungsten Nuclear Anomalies in Planetesimal Cores

Tungsten Nuclear Anomalies in Planetesimal Cores

Noble gases in Grant and Carbo and the influence of S‐ and P‐rich mineral inclusions on the ⁴¹K‐⁴⁰K dating system

Smithsonian Institution

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Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages, meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases

Cited by 123 publications

References 29 publications

Tungsten Nuclear Anomalies in Planetesimal Cores

Tungsten Nuclear Anomalies in Planetesimal Cores

Noble gases in Grant and Carbo and the influence of S‐ and P‐rich mineral inclusions on the 41K‐40K dating system

Smithsonian Institution

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Noble gases in Grant and Carbo and the influence of S‐ and P‐rich mineral inclusions on the ⁴¹K‐⁴⁰K dating system