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Cosmic ray exposure ages of Rumuruti chondrites from North Africa

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2011
Author Vogel N, Baur H, Bischoff A, Wieler R,
Project High energy particle irradiation in the early solar system and stellar nucleosynthesis studied with noble gases in primitive meteorites
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Original article (peer-reviewed)

Journal CHEMIE DER ERDE-GEOCHEMISTRY
Volume (Issue) 71(2)
Page(s) 135 - 142
Title of proceedings CHEMIE DER ERDE-GEOCHEMISTRY

Abstract

We analyzed noble gases and determined He-3, Ne-21, and Ar-38 cosmic ray exposure ages (CREAs) of Rumuruti chondrites from North West Africa (NWA) to rule on potential pairings and/or source pairings of North Africa R chondrite samples. The 21Ne exposure ages range between 10 and 74 Ma, with NWA 2897 and 1668 having the highest known exposure ages among R chondrites. We also include other R chondrites from North Africa (Schultz et al., 2005) and, based on their noble gas characteristics and their Ne-21 CREAs, propose pairings of the following samples: NWA 2198, 5069, 755, 4615, 845, 851, 978, 1471, and possibly DaG 013 belonging to one fall with a CREA of similar to 10 Ma, and NWA 753, 4360, 4419, 5606, 1472, 1476, 1477, 1478, and 1566 representing one fall with a CREA of similar to 14 Ma. NWA 2821, 2503, 2289, 3364, 3146, 4619, 4392, 3098, and 2446 seem to belong to one single fall with a CREA of 20 Ma, and NWA 2897 and 1668 seem to be paired and show a common CREA of similar to 66 Ma. Overall, all R chondrite samples from North Africa analyzed for noble gases so far represent similar to 16 individual falls. Comparing falls from North Africa to literature CREAs of R chondrites worldwide, it seems possible that a significant number of all R chondrite falls studied for noble gases were ejected from the R chondrite parent body during one large collisional event between 15 and 25 Ma ago. However, the database is still too small to draw definitive conclusions. The large portion of brecciated R chondrites in collections suggests severe impact brecciation of the R chondrite parent body. (C) 2011 Elsevier GmbH. All rights reserved.
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