Allende meteorite measurements

Young ED, Ash RD, Galy A, Belshaw NS (2002) Mg isotope heterogeneity in the Allende meteorite measured by UV laser ablation-MC-ICPMS and comparisons with O isotopes. Geochim Cosmochim Acta 66 683-698... 

Yurimoto H, Nagasawa H, Mori Y, Matsubaya O (1994) Micro-distribution of oxygen isotopes in a refractory inclusion from the Allende meteorite. Earth Planet Sci Lett 128 47-53 Zinner E (1989) Isotopic measurements with the ion microprobe. In WCI Shanks, RE Criss (eds) New Frontiers in Stable Isotope Research Laser Probes, Ion Probes, and Small-Sample Analysis, U S Geol SurvBull 1890 145-162... 

A few reports are available where TIMS has been used for cosmochemical analysis. The recent report of Yamakawa et al. (2009) deals with sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks for precise and accurate determination of elemental concentration. The chemical technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The developed method was tested to a variety of matrixes bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-lb). Concentrations of each element were determined by TIMS. The analytical procedure was further extended to obtain high-precision isotope data for Cr. The method is capable to determine the isotopic ratios of Cr/ Cr and Cr/ Cr with precision of 5 X 10 and 1 x 10, respectively. The method can be equally applicable in cosmochemical studies, like Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites. The elemental concentrations measured by TIMS in Allende are, for example, Cr 3,600 0.007 ppm, Fe 233,400 0.009 ppm, Ni 14,020 0.006 ppm, Cu 107 0.013 ppm, and Zn 117.8 0.01 ppm. The detection of Al (0.7 Ma) in the Allende meteorite proves that nucleosynthesis is still active in the Milky Way as the half-life of A1 is much less than the timescale of galactic evolution (10 years). 

The Allende, Murchison, Murray and Orgueil meteorites are particularly highly prized for research into stellar grains, since several kilograms of this material have been identified in each of them. This is sufficient to be able to take samples of the order of 1 g without damaging the source. Such samples can then be subjected to compositional analysis. But how can we extract these stellar jewels, measuring at most 1 /rm in diameter, from the matrix in which they are embedded The best way of finding a needle in a haystack is to bum the hay. Cosmochemists employ basically the same method when they use chemical processes to isolate star dust trapped in meteoritic stone. They may then analyse... 

Trivalent titanium has been positively identified by optical spectral measurements of a green calcic pyroxene from the meteorite that fell near Pueblo de Allende, Mexico, in 1969. The chemical analysis of this titanian pyroxene (Dowty and Clark, 1973) revealed it to be an iron-free subsilicic diopside (fas-saite) containing coexisting Ti3+ and Ti4+ ions and having the chemical formula Ca1.0lM 0.38,n3+0.34,n4+0.14Alo.87Sil.2606-... 

The Antarctic meteorites are more extensively weathered and fractured than expected because of a misconception about the microclimatic conditions on the ice fields of the polar plateau. Although the air temperature remains below the freezing point of water, the temperature in the interior of a meteorite specimen exposed to solar radiation may rise sufficiently to melt snow on its surface. For example, Schultz (1990) showed in Fig. 18.18 that the internal temperature of a sample of the carbonaceous chondrite Allende placed on the ice of the Far Western ice field adjacent to the Allan Hills in December of 1985, was consistently higher than the air temperature by up to about 15°C and that the temperature dijference increased as the wind speed and cloud cover decreased. The wind apparently cools meteorite specimens exposed on the icefields while the cloud cover modulates the amount of solar energy they receive. On several occasions, when the wind speed decreased to zero, the internal temperature of the test specimen monitored by Schultz (1990) actually rose to +5°C. Similar results were reported by Harvey (2003) who measured the temperature at the... 

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