Journal ArticleDOI
Isotopic Determination of Uranium in Picomole andSubpicomole Quantities
J. H. Chen,G. J. Wasserburg +1 more
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In this paper, a procedure for the separation of U and measurement of UIsotopes in meteoritic, lunar, and terrestrial samples is described, and the results show the same Isotopic values within limits of errors as that measured on normal terrestrial U to within 4Abstract:
A procedure for the separation of U and measurement of U
Isotopes in meteoritic, lunar, and terrestrial samples Is described. Accurate ^(238)U/^(235)U ratios and U concentration measurements can be done on a routine basis at the level of ~ 10^(-13) mol of U by Isotope dilution using a double tracer composed of ^(233)U and ^(238)U. Precise determination of the number of U atoms In a sample can be done at the level of 10^8-10^9 atoms. The technique Involves careful control of the chemical procedures to eliminate laboratory contamination and precise calibration of the mass spectrometer In order to obtain high reproducibility. The ^(238)U/^(235)U ratios were measured
on a wide variety of samples which Include bulk
meterorltes, lunar samples, coarse-grained Ca-AITI-
rlch Inclusions and fine-grained AI-Mg-Na-rich Inclusions from the Allende meteorite, and phosphates from three meteorites. The results show the same Isotopic values within limits of errors as that measured on normal terrestrial U to within 4‰. All of the analyzed meteorite samples are very ancient and several of them show large fractionations of U relative to Th and Nd. These data Imply that ^(247)Cm was not abundant In the early solar system (^(247)Cm/^(235)U « 4 X 10^(-3)) and that the last major "r" process terminated at ~ 10^8 years prior to the formation of the solar system.read more
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An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry
TL;DR: In this article, a more accurate extraction chromatographic/a-spectroscopy method has been developed, which is concluded that due to involving preconcentration and chemical separation, the extraction Chromatographic and a-Spectroscopy (ECS) method is a more selective, very sensitive and accurate, and low cost method.
Journal ArticleDOI
Further investigations on optimized tail correction and high-precision measurement of uranium isotopic ratios using multi-collector ICP-MS
TL;DR: In this paper, the authors examined the optimum conditions for rapid, precise and accurate determination of 234U/238U ratios in geological materials by multiple collector (magnetic-sector) inductively coupled plasma mass spectrometry (MC-ICP-MS).
Journal ArticleDOI
The behavior of actinides, phosphorus, and rare earth elements during chondrite metamorphism
M. T. Murrell,D. S. Burnett +1 more
TL;DR: In this article, a provisional picture was assembled of the chemistry of these elements and for the rare earth elements in ordinary chondrites and the changes brought about by chondritic metamorphism.
Journal ArticleDOI
Isotopic Evidence for Reductive Immobilization of Uranium Across a Roll-Front Mineral Deposit
Shaun T. Brown,Shaun T. Brown,Anirban Basu,Anirban Basu,John N. Christensen,Paul W. Reimus,Jeffrey M. Heikoop,Ardyth M. Simmons,Giday WoldeGabriel,Kate Maher,K. L. Weaver,James T. Clay,Donald J. DePaolo,Donald J. DePaolo +13 more
TL;DR: Characterization of U isotopic ratios at the mine planning stage, in conjunction with routine geochemical analyses, can be used to identify where more or less postmining remediation will be necessary.
Journal ArticleDOI
Deformation resulting from regional extension during pluton ascent and emplacement, central Sierra Nevada, California
TL;DR: In this article, the authors used microgranitic enclaves as markers to measure the deformation in the shear zone of the Mt Givens pluton during the ascent and emplacement of the MGP.
References
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Journal ArticleDOI
A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations
TL;DR: In this paper, Krogh et al. developed a simple procedure for the decomposition of zircon and the extraction of U and Pb for isotopic age determinations.
Journal ArticleDOI
Sm-Nd-Pu timepieces in the Angra dos Reis meteorite
G.W. Lugmair,Kurt Marti +1 more
TL;DR: In this paper, the ultramafic pyroxenite Angra dos Reis meteorite was estimated to have an internal isochron age of 4.55 plus or minus 0.04 eons.
Journal ArticleDOI
The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates
J. H. Chen,G. J. Wasserburg +1 more
Journal ArticleDOI
Isotopic and chemical investigations on Angra dos Reis
TL;DR: In this article, extensive isotopic studies of Pb, Sr and Xe and on chemical abundance measurements of K, Rb, Sr, Ba, Nd, Sm, U and Th for total meteorite and mineral separates of the Angra dos Reis achondrite.