Autor Thema: Radionuklide, Radiometrie und die Chronologie des Sonnensystems  (Gelesen 695 mal)

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Radionuklide, Radiometrie und die Chronologie des Sonnensystems
« am: September 30, 2014, 16:25:07 nachm. »
Radionuklide, Radiometrie und die Chronologie des Sonnensystems

Als erster Beitrag eine neue Analyse zur Uran-Isotopenkomposition des Sonnensystems:

The Uranium Isotopic Composition of the Earth and the Solar System

Alexander Goldmann, Gregory Brennecka, Janine Noordmann, Stefan Weyer, Meenakshi Wadhwa

Geochimica et Cosmochimica Acta
DOI: 10.1016/j.gca.2014.09.008
In Press, Available online 30 September 2014

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Zitat
The following conclusions can be drawn from this study: (1) The Solar System has a broadly homogeneous U isotope composition, and bulk samples of only a limited number of meteorites display detectable U isotope variations; (2) Bulk planetary differentiation has no significant effect on the 238U/235U ratio since the Earth, achondrites, and chondrites have indistinguishable U isotope compositions in average. (3) The cause of U isotopic variation in Solar System materials remains enigmatic; however, both the decay of 247Cm and isotope fractionation are likely responsible for the U isotopic variations observed in CAIs and ordinary chondrites, respectively. The average 238U/235U of the investigated meteorite groups (including data compiled from the literature) and terrestrial basalts is 137.794 ± 0.027 (at a 95% student’s t confidence level, including all propagated uncertainties) and represents the best estimate for the U isotope composition of the Earth and the Solar System. This value may be used for U-Pb and Pb-Pb dating of Solar System materials, provided the precise U isotope composition of the sample is unknown. Compared to Pb-Pb ages that were determined with the previously assumed value for 238U/235U (137.88), this new value results in an age adjustment of -0.9 Ma.

 

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