Excess K-41 in CV3 chondrites

Details Excess K-41 in CV3 chondrites Excess K-41 in CV3 chondrites

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.536s&link_type=abstract

Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 536

Mathematics

Logic

1

Chondrites, Inclusions, Meteoritic Composition, Potassium Isotopes, Pyroxenes, Solar System Evolution, Calcium Isotopes, Mineralogy, Nuclear Fusion, Petrography, Radioactive Age Determination

Scientific paper

Observation of excess K-41 in Efremovka Ca, Al-rich Inclusions (CAIs) suggests the presence of the short-lived nuclide Ca-41 in the early solar system and an initial Ca-41/Ca-40 ratio of (1.5 +/- 0.3) x 10-8 at the time of formation of Efremovka CAIs. The first hint for the presence of Ca-41 in the early solar system came from the work of Hutcheon (1984) who obtained an upper limit of (8 +/- 3) x 10-9 for initial Ca-41/Ca-40 at the time of formation of the Allende CAIs EGG-3 and 3529-Z. We present results of our K isotopic measurements in CAIs from the CV chondrites Efremovka, Allende, and Leoville. The Efremovka CAI E44 analyzed by us is a type B1 inclusion and is described in detail. We have also analyzed a couple of pyroxene grains from the Allende inclusion EGG-3. The sample of the Leoville CAI L-6 is a compact type A inclusion, whose petrographic and mineralogic characteristics suggest the absence of secondary alterations. The present study consolidates earlier conclusions regarding the presence of Ca-41 in the early solar system. A cosmogenic and/or fossil origin of K-41 excess is not compatible with the magnitude of the observed K-41 excess and its correlation with Ca-40. Whether the variation seen in the initial Ca-41/Ca-40 in Efremovka and Allende pyroxenes is real or resulted from movement of K during small-scale perturbation can only be ascertained by further studies. Irrespective of these variations, the presence of excess K-41 in Efremovka and Allende CAIs constrains the time interval between the cessation of nucleosynthetic input into the solar nebula and the formation of CV3 CAIs to about a million years.

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