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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Journal ArticleDOI
Uranium Isotope Fractionation
TL;DR: A thorough review on the application of the U-decay series systems within Earth sciences was published in Reviews in Mineralogy and Geochemistry (RiMG) volume 52 in 2003, and will not be discussed further within this review as mentioned in this paper.
Journal ArticleDOI
Constraints on the bulk composition and root foundering rates of continental arcs: A California arc perspective
TL;DR: In this article, an average removal rate of 25-40 km 3 /km Myr is estimated for this Cordilleran-type arc, although root loss could have taken place at least in part after the cessation of arc magmatism.
Journal ArticleDOI
Formation ages and evolution of Shergotty and its parent planet from U-Th-Pb systematics
J. H. Chen,G. J. Wasserburg +1 more
TL;DR: In this paper, the authors determined the age of shergottites using the EETA 79001 data set and showed that the initial leads were highly evolved relative to the primordial lead.
Journal ArticleDOI
Drillhole lavas from the northwestern Deccan Traps, and the evolution of Réunion hotspot mantle
Z.X. Peng,John J. Mahoney +1 more
TL;DR: In this paper, the age-corrected Nd Pb Sr isotopic ratios of these lavas define two distinct trends, Trend 1, reflecting mixing between a mantle end-member very similar to that of modern Reunion Island and high-208Pb/204Pb continental lithospheric material unlike any seen in the well-studied southern Deccan formations.
Journal ArticleDOI
Precise determination of the isotopic composition of potassium: Application to terrestrial rocks and lunar soils
Munir Humayun,Robert N. Clayton +1 more
TL;DR: In this paper, a method for the precise and accurate determination of isotopic variations in the 41K39K ratio with a precision of ± 0.5 µm was presented.
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.