title: 53Mn-53Cr dating of fayalite formation in the CV3 chondrite Mokoia: evidence for asteroidal alteration.
abstract: 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.
authors.affiliation: Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94551, USA.
authors.forename: I D
authors.initials: ID
authors.lastname: Hutcheon
authors.forename: A N
authors.initials: AN
authors.lastname: Krot
authors.forename: K
authors.initials: K
authors.lastname: Keil
authors.forename: D L
authors.initials: DL
authors.lastname: Phinney
authors.forename: E R
authors.initials: ER
authors.lastname: Scott
mesh_terms: D002859:Chromium Isotopes / Q000032:analysis; D008345:Manganese / Q000032:analysis; D019110:Meteoroids; D018543:Minor Planets; D010087:Oxides / Q000032:analysis; D011868:Radioisotopes
chemical_list: D002859:Chromium Isotopes; D010087:Oxides; D011868:Radioisotopes; D008345:Manganese