Radiogenic dating of meteorites
Peter Hoppe and I measured the magnesium isotopic ratios and the aluminum/magnesium ratios in many different spots on a single feldspar crystal with such an instrument at the Max-Planck-Institute for Chemistry in Mainz, Germany.Mg excesses as a function of aluminum/magnesium ratios was made with a special type of mass spectrometer, the ion microprobe. Primitive meteorites provide samples that were formed in its earliest days and thus can give us information about this period. (2002) Aluminum-26 in H4 chondrites: implications for its production and its usefulness as a fine-scale chronometer for early-solar-system events. Magnesium shows excesses in the isotope 26 that are correlated with the aluminum/magnesium ratio, indicating that the Al ratio varies in objects that formed at different times.To establish the sequence of events during solar system formation on a time scale of a million years radioactive isotopes that decay with half-lives comparable to this time scale can potentially serve as clocks for dating these events. By measuring the aluminum-magnesium system today, the relative ages of these objects can be established. Although this is so short that all of it has decayed billions of years ago, its presence at the beginning of the solar system has been conclusively established by the discovery of excesses of its daughter isotope Magnesium isotopic ratios measured in different minerals with different ratios of aluminum to magnesium from a refractory inclusion in the meteorite Allende. Mg, a stable isotope, with a half-life of 0.73 million years.Marguerite and Forest Vale and had obtained absolute ages of 4562.7±0..9±0.7 million years.
Because lead isotopes are the daughter products of uranium decay, uranium ages are usually called Pb-Pb ages.
This has generally been interpreted as indicating that chondrules formed approximately 2 million years after CAIs.
However, it could also have meant that chondrules formed at the same time as CAIs but were endowed with less Al was uniformly distributed.
This heating was the cause of metamorphic changes in the rocks making up this asteroid.
Rocks from different depths experienced different peak temperatures and duration of heating.
Search for radiogenic dating of meteorites:
This picture shows the recently installed Nano SIMS at Washington University.