Cosmogenic radionuclides and noble gases in Antarctic H chondrites with high and normal natural thermoluminescence levels

• Published in: Meteoritics & Planetary Science
• Main Authors: MOKOS, Jennifer L., FRANKE, Luitgard, SCHERER, Peter, SCHULTZ, Ludolf, LIPSCHUTZ, Michael E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2000
• Subjects: Allan Hills; Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/j.1945-5100.2000.tb01455.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.2000.tb01455.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2000.tb01455.x

Abstract— We report noble gas data for 37 H chondrites collected from the Allan Hills by EUROMET in the 1988–1989 field season. Among these are 16 specimens with high levels (>100 krad) of natural thermoluminescence (NTL), originally interpreted as signaling their derivation from a single meteoroid with an orbit that became Earth‐crossin‐100 ka ago. One of these 16 is an H3 chondrite with a cosmic‐ray exposure age of ∼33 Ma and clearly represents a separate fall. The other 15 H4–6 chondrites derive from three separate meteoroids, each of which is represented by a five or six member group. These groups have mean exposure ages of 3.7, 4.1, and 6.6 Ma: the middle‐group members all contain solar Ne. The two younger groups also seem to each include a few H chondrites with normal NTL levels. Measurements of cosmogenic 10 Be (1.5 Ma), 26 AI (710 ka), and 36 CI (301 ka) in 14 of the high‐NTL chondrites indicate that all reflect a simple irradiation history. In contrast, many of a different (38 member) randomly selected suite of Antarctic H chondrites seem to have different cosmic‐ray irradiation histories. The 3.7 and 6.6 Ma groups from the 37 member Allan Hills suite come from about 5–30 and about 5–10 cm depths in 80–125 and 60–125 cm radius meteoroids, respectively.