53Mn-53Cr dating of fayalite formation in the CV3 chondrite Mokoia: evidence for asteroidal alteration.
Fayalite grains in chondrules in the oxidized, aqueously altered CV3 chondrite Mokoia have large excesses of radiogenic chromium-53. These excesses indicate the in situ decay of short-lived manganese-53 (half-life = 3.7 million years) and define an initial 53Mn/55Mn ratio of 2.32 (+/-0.18) x 10(-6). This ratio is comparable to values for carbonates in CI and CM chondrites and for several classes of differentiated meteorites. Mokoia fayalites formed 7 to 16 million years after Allende calcium-aluminum-rich inclusions, during hydrothermal activity on a geologically active asteroid after chondritic components had ceased forming in the solar nebula.
Hutcheon
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Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94551, USA.
Krot
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Keil
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Phinney
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Scott
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D002859:Chromium Isotopes / Q000032:analysis; D008345:Manganese / Q000032:analysis; D019110:Meteoroids; D018543:Minor Planets; D010087:Oxides / Q000032:analysis; D011868:Radioisotopes
D002859:Chromium Isotopes; D010087:Oxides; D011868:Radioisotopes; D008345:Manganese