Al dating system

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.

al dating system-48

This picture shows the recently installed Nano SIMS at Washington University.

The Nano SIMS is a new type of ion microprobe that allows elemental and isotopic analysis with very high spatial resolution and with high sensitivity.

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.

These nagging doubts were amplified by the recent discovery by Kevin Mc Keegan (University of California, Los Angeles) and colleagues that another short-lived isotope, beryllium-10 (half-life 1.5 million years) was also originally present in CAIs.

This radioisotope is not produced by stellar nucleosynthesis but most likely formed as energetic particles from the early sun bombarded material in the accretion disk.The temperature at which the uranium-lead system stops being equilibrated during decreasing temperature is believed to be approximately 730 degrees Kelvin.This temperature is reached at different times for different H chondrites.The ions are accelerated and analyzed for their mass in a mass spectrometer.This analysis technique is therefore called secondary ion mass spectrometry (SIMS).With my collaborators Christa Göpel (Laboratoire Géochimie et Cosmochimie, Paris, France) and Peter Hoppe (Max-Planck-Institut für Chemie, Mainz, Germany) I selected feldspar grains from two ordinary chondrites of type H4, Ste.

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