The L3–6 chondritic regolith breccia Northwest Africa (NWA) 869: (II) Noble gases and cosmogenic radionuclides

Abstract

Abstract-We measured cosmogenic radionuclides and noble gases in the L3-6 chondrite breccia Northwest Africa (NWA) 869, one of the largest meteorite finds from the Sahara.

Cosmic-Ray Exposure Ages of Meteorites

“…Several recent studies report 38 Ar ages for eucrites with CRE ages that fall in the range of 81 Kr/Kr ages; some of them add to the cluster near 20 Ma (Llorca et al, 2009;Wakefield et al, 2004;Yamaguchi et al, 2002). Possible biases in 38 Ar production rates on the order of 15% (see Welten et al, 2011a), however, are not yet resolved.…”

“…Interestingly, a few fragments consist not of ureilites but of other meteorite types. Noble gas and cosmogenic radionuclide analyses give a CRE age of 20 AE 3 Ma (Welten et al 2010, Welten et al, 2011a, a value well within the main grouping for ureilites.…”

The L3–6 chondritic regolith breccia Northwest Africa (NWA) 869: (I) Petrology, chemistry, oxygen isotopes, and Ar‐Ar age determinations

“…The results of the corresponding measurements of noble gases and cosmogenic radionuclides on bulk samples and separated lithologies from NWA 869 (see Table 1) are presented in a companion paper (Welten et al 2011).…”

“…An overview of the sample allocation is given in Table 1. The results are summarized in this paper and in a companion paper (Welten et al 2011). Preliminary results have been published by Metzler et al.…”

“…Measurements of 14 C and 10 Be were performed to estimate the terrestrial age of this meteorite. The results of these investigations are presented in Welten et al. (2011).…”