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We recognize that there is some debate over the age of the Solar System, but conclude that an age of 4567.30 ± 0.16 Ma based on four CAIs dated individually by the same method in two different laboratories is presently the best constrained published value.
We further conclude that nebular chondrules dated by the Pb–Pb method require that they formed contemporaneously with CAIs and continued to form for at least ∼4 Myr, a conclusion that implies heterogeneous distribution of the short-lived Al nuclide in the protoplanetary disk.
To see how we actually use this information to date rocks, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.
By definition, D* = N-1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.
Planetesimals were already forming by ∼1 Myr after CAI formation, consistent with their growth predominantly through the accretion of chondrules.
The primary goal of this project is to improve the precision and accuracy of routine uranium-lead dating of zircon, expanding our LA-SC-ICPMS dating technique to other uranium-rich minerals (e.g., monazite, apatite, xenotime), and developing novel LA-ICPMS in situ lead and strontium isotopic tracer methods applicable to studies of ore mineralization and the framework geology of Mineral Resources Program research study areas.
The open system behaviour of the U-Th-Pb system is clearly the norm, as is the resultant mixing of radiogenic Pb with ‘common’ or background Pb, even in soils in the surrounding region, apparently even up to 17 km away!
Because no geologically meaningful results can be interpreted from the U-Th-Pb data at Koongarra (three uraninite grains even yield a Pb ‘age’ of 0 Ma), serious questions must be asked about the validity of the fundamental/foundational basis of the U-Th-Pb ‘dating’ method.
We anticipate that the ability to obtain precise and accurate in situ age and isotopic tracer information for USGS minerals-related projects will continue to be vitally important in the future.
Our LA-SC-ICPMS has the capability of providing cost-effective in situ geochronological and mineral isotope tracer data, but the analytical techniques need to be developed further to reach their full potential.
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Pb, respectively, have appropriate half-lives to resolve the ages of meteorites and their components formed in the first 5 Myr of the Solar System.