Physics
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p33a1001s&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #P33A-1001
Physics
8125 Evolution Of The Earth, 5455 Origin And Evolution, 5749 Origin And Evolution, 6040 Origin And Evolution, 1060 Planetary Geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
Scientific paper
The r-process only nuclide 247Cm decays to 235U with a characteristic half-life of ˜16 million years. 247Cm is presently extinct, but offers considerable potential as a short-lived r-process chronometer, providing constraints on the time interval between the last r-process nucleosynthetic event and the formation of the solar system. The existence of "live" 247Cm in the early solar system should be manifested today as variations in 235U/238U, provided Cm was chemically fractionated from U when solids formed in the early solar system. The Cm-U system also has a direct bearing on the fundamental U-Pb cosmochronometer, which currently assumes no Cm effects in early solar system material. Using a Nu Instruments NuPlasma and new techniques in multiple-collector ICPMS, we are able to resolve variations in 235U/238U at the two epsilon level (2σ ; 1 ɛ = 1 part in 10,000) on sample sizes consisting of <20 pg of 235U. The high precision of our measurements offers the potential to resolve 235U anomalies, including samples where Cm-U effects had previously been unobserved. Our first uranium isotopic measurements were acquired on bulk samples of a suite of carbonaceous chondrite, ordinary chondrite and eucrite meteorites, for which conflicting results had previously been obtained. These data show no well-resolved excursions in 235U/238U from the terrestrial value at the ˜2 epsilon level, and constrain the amount of 247Cm-produced excess 235U atoms to less than ˜1 x 108 atoms per gram of chondritic meteorite, with respect to terrestrial 235U/238U (Stirling et al., in press, Geochim. Cosmochim. Acta). We have extended the search for "live" 247Cm in the early solar system to small samples from mineral phases in primitive objects that are likely to display strong Cm-U fractionations. In particular, uranium isotopic measurements have been acquired on acid-etched leachates for a suite of chondritic meteorites, and for a suite of minerals separated from chondrites and angrites. Some of these data show resolvable excursions away from the composition of our terrestrial standard, and as such, have important implications for the 247Cm-235U cosmochronometer and the timing of r-process nucleosynthesis relative to the formation of the first solar system materials.
Andersen Brian Møller
Halliday Alex N.
Potter E.
Stirling Claudine H.
No associations
LandOfFree
In Search of r-Process 247Cm in the Early Solar System does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with In Search of r-Process 247Cm in the Early Solar System, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In Search of r-Process 247Cm in the Early Solar System will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1453389