Magnesium isotope

Abstract. AGB stars, in particular those of carbon types, are excellent laboratories to constraint the theory of stellar structure, evolution and nucleosynthesis. Despite the uncertainties still existing in the chemical analysis of these stars, the determination of the abundances of several key species in their atmospheres (lithium, s-elements, carbon and magnesium isotopic ratios etc.) is an useful tool to test these theories and the mixing processes during the AGB phase. This contribution briefly review some recent advances on this subject. 

Ion Probe Magnesium Isotopic Measurements of Allende Inclusions... 

Electron ionization (El) was introduced in 1921 by Dempster, who used it to measure lithium and magnesium isotopes [31]. Modern El sources are, however, based on the design by Bleakney [32] and Nier [33, 34], who both worked in Prof. J. T. Tate s laboratory. In El ions are produced by directing an electron beam into a low pressure vapor of analyte molecules. 

Hidaka H, Ohta Y, Yoneda S, DeLaeter JR (2001) Isotopic search for live Cs in the early solar system and possibility of Cs- Ba chronometer. Earth Planet Sci Lett 193 459-466 Hinton RW, Bischofif A (1984) Ion microprobe magnesium isotope analysis of plagioclase and hibonite from ordinary chondrites. Nature 308 169-172... 

Hutcheon ID (1982) Ion probe magnesium isotopic measurements of Allende inclusions. Amer Chem Soc... 

TERRESTRIAL MAGNESIUM ISOTOPE RESERVOIRS IN THREE-ISOTOPE SPACE IMPLICATIONS FOR MECHANISMS OF FRACTIONATION... 

Clayton RN, Mayeda TK (1977) Correlated oxygen and magnesium isotope anomalies in Allende inclusions, I Oxygen. Geophys Res Lett 4(7) 295-298... 

Kennedy AF, Beckett JR, Edwards DA, Hutcheon ID (1997) Trace element disequilibria and magnesium isotope heterogeneity in 3655A Evidence for a complex multi-stage evolution of a typical Allende type B1 CAL Geochim Cosmochim Acta (7) 1541-1561... 

Norman M, McCulloch M, O Neill H, Brandon A (2004) Magnesium isotopes in the Earth, Moon, Mars, and Pallasite parent body high precision analysis of olivine by laser ablation multi-collector ICPMS. Lunar and Planetary Science Conference XXXV 1447... 

Wasserburg GJ, Lee T, Papanastassiou DA (1977) Correlated oxygen and magnesium isotopic anomalies in Allende inclusions II. magnesium. J Geophys Res 4 299-302... 

Esat TM, Taylor SR (1992) Magnesium isotope fractionation in lunar soils. Geochim Cosmochim Acta 56 1025-1031... 

Nagashima, K., Krot, A.N. and Chaussidon, M. (2007) Aluminum-magnesium isotope systematics of chondrules from CR chondrites (abstr.). Meteoritics and Planetary Science, 42, Supplement, All5. 

Numerous applications of quadrupole ICP-MS (without a collision cell) for isotope ratio measurements can be found in quite different fields. For example, magnesium isotope ratios on... 

Magnesium has three isotopes. Magnesium-24 has a percent abundance of 78.99%. Magnesium-26 has a percent abundance of 11.01%. What is the percent abundance of magnesium-25 Assume that there are no other magnesium isotopes. 

Daughtry, A. C., D. Perry, and M. Williams Magnesium isotopic distribution in dolomite. Geochim. cosmochim. Acta 26, 857 (1962). 

Two methods that have been used in tracer studies with are neutron activation analysis CNAA) and EIMS, mass spectrometry of a volatile chelate with electron impact ionization C15>19,20). Neither technique can match TIMS in accuracy or precision, but both may offer greater sample throughput. Until more precise techniques become more generally available, research utilizing stable metal isotopes will remain limited to the conditions imposed by the analytical facilities at hand. As will be shown below, research with stable magnesium isotopes to date, has had to be tailored to the limitations of available analytical techniques ... 

Since some subjects may require longer fecal collections, polyethyleneglycol (PEG) 4000 was Included with test meals (Table VII). The results showed a constant relationship of %g to PEG in all fecal pools that contained at least 40% of ingested PEG. It should thus be possible to make accurate measurements of fractional magnesium isotope absorption by limiting isotope analyses to the first four or five days of fecal excretion when isotope concentrations are at levels detectable with acceptable precision. 

Mayeda K., Clayton R. N., Krung D. A., and Davis M. (1988) Oxygen, silicon and magnesium isotopes in Ningqiang chondrules. Meteoritics 23, 288. 

Aluminum-magnesium isotope measurements of aluminum-rich chondrules in ordinary and carbonaceous chondrites were summarized by Huss et al. (2001). About 10-15% of all aluminum-rich chondrules smdied show Mg. The inferred ( Al/ Al)o ratio of these chondrules is (0.5-2) X 10 , which is consistent with the values found in ferromagnesian chondrules from type 3.0-3.1 unequilibrated ordinary chondrites (Kita et al, 2000 McKeegan et al, 2000b Mostefaoui et al, 2000 2002). 

Imai H. and Yurimoto H. (2000) Oxygen and magnesium isotopic distributions in a Type C CAI from the Allende meteorite. In Lunar Planet. Sci. XXXI, 1510. The Lunar and Planetary Institute, Houston (CD-ROM). 

Misawa K. and Fujita T. (2000) Magnesium isotopic fractionations in barred olivine chondrules from the Allende meteorite. Meteorit. Planet. Sci. 35, 85-94. 

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