![]() Magnesium isotopic ratios measured in different minerals with different ratios of aluminum to magnesium from a refractory inclusion in the meteorite Allende. The ratio of 26Mg excess measured now relative to the amount of the stable isotope 27Al yields the original 26Al/ 27Al ratio. If these objects containing 26Al at the time of their formation remained relatively undisturbed (i.e., did not experience high temperatures), the decay product 26Mg was frozen in and today provides a record of the original 26Al. 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 26Mg in the most primitive solar system objects. XXXIII, Abstract #1204.ΔΆ6Al is a radioactive isotope that decays into 26Mg, a stable isotope, with a half-life of 0.73 million years. Marguerite and Forest Vale plagioclase: can 26Al be used as chronometer? Lunar Planet. (2002) Aluminum-26 in H4 chondrites: implications for its production and its usefulness as a fine-scale chronometer for early-solar-system events. It appears that 26Al can indeed be used as a fine-scale chronometer for early solar system events. Comparison measurements with two different clocks, 26Al and the decay of uranium isotopes, in refractory Ca-Al-rich inclusions (CAIs) and in feldspar crystals from ordinary chondrites indicate that both techniques give the same ages. However, for this to be the case, 26Al had to be uniformly distributed in the early solar system and this fact had not been clearly established. 26Al, which has a half-life of 0.73 million years appeared to be an ideal chronometer. 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. Primitive meteorites provide samples that were formed in its earliest days and thus can give us information about this period. Our solar system formed 4.6 billion years ago. Correspondence between 26Al and Pb-Pb ages shows that 26Al records a detailed record of events in the early solar system. Using Aluminum-26 as a Clock for Early Solar System Events
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