Manganese–chromium dating
Manganese–chromium dating uses the extinct isotope manganese-53, decaying to chromium-53, to date early processes.
Manganese–chromium dating uses manganese-53, which decays to chromium-53 with a half-life of about 3.7 million years. Like aluminium-26, it is extinct now, but its decay left excess chromium-53 in minerals that were rich in manganese when they formed.
The method is particularly suited to minerals that form at low temperatures and take up manganese, such as carbonates and fayalite. It has given some of the best ages for aqueous alteration in carbonaceous chondrites: carbonates in CM and CI chondrites formed roughly 4 to 5 million years after CAIs. It has also been used for eucrites, angrites and other achondrites.
Because the half-life suits the first ten million years or so, manganese–chromium dating fills a useful gap between aluminium–magnesium and hafnium–tungsten. To convert relative ages to absolute ones, researchers anchor them to angrites, which have been dated by both manganese–chromium and lead–lead methods.
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