Allan Hills 88019: An Antarctic H‐chondrite with a very long terrestrial age

• Published in: Meteoritics & Planetary Science
• Main Authors: SCHERER, P., SCHULTZ, L., NEUPERT, U., KNAUER, M., NEUMANN, S., LEYA, I., MICHEL, R., MOKOS, J., LIPSCHUTZ, M. E., METZLER, K., SUTER, M., KUBIK, P. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1997
• Subjects: Antarc*; Antarctic; Antarctica
• Online Access: http://dx.doi.org/10.1111/j.1945-5100.1997.tb01567.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.1997.tb01567.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.1997.tb01567.x

Abstract— We have measured the concentrations of the cosmogenic radionuclides 10 Be, 26 Al and 36 Cl (half‐lives 1.51 Ma, 716 ka, and 300 ka, respectively) in two different laboratories by accelerator mass spectrometry (AMS) techniques, as well as concentrations and isotopic compositions of stable He, Ne and Ar in the Antarctic H‐chondrite Allan Hills (ALH) 88019. In addition, nuclear track densities were measured. From these results, it is concluded that the meteoroid ALH 88019 had a preatmospheric radius of (20 ± 5) cm and a shielding depth for the analyzed samples of between 4 and 8 cm. Using calculated and experimentally determined production rates of cosmogenic nuclides, an exposure age of ∼40 Ma is obtained from cosmogenic 21 Ne and 38 Ar. The extremely low concentrations of radionuclides are explained by a very long terrestrial age for this meteorite of 2 ± 0.4 Ma. A similarly long terrestrial age was found so far only for the Antarctic L‐chondrite Lewis Cliff (LEW) 86360. Such long ages establish one boundary condition for the history of meteorites in Antarctica.