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Cosmogenic noble gas nuclides in zircons from the Estherville mesosiderite
Author(s) -
Haba Makiko K.,
Nagao Keisuke
Publication year - 2021
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13660
Subject(s) - cosmogenic nuclide , zircon , geology , surface exposure dating , nuclide , meteorite , geochemistry , noble gas , spallation , silicate , cosmic ray , radiochemistry , mineralogy , astrobiology , chemistry , moraine , paleontology , nuclear physics , physics , glacial period , neutron , organic chemistry
Zirconium produces cosmogenic Kr through spallation reactions with cosmic rays. Meteoritic zircons (ZrSiO 4 ) therefore possibly contain a significant amount of cosmogenic Kr in addition to other cosmogenic nuclides. Detection of cosmogenic nuclides from meteoritic zircons would make it possible to determine precise cosmic ray exposure (CRE) ages without knowing the whole rock chemistry because of the robust nature of zircons and limited target elements that produce cosmogenic nuclides in a zircon crystal. Herein, we report the noble gas compositions of zircons separated from the Estherville mesosiderite in addition to those of the silicate and metal parts. The zircons contain cosmogenic noble gas nuclides, and more importantly, cosmogenic 81 Kr ( t 1/2 = 2.29 × 10 5 years) was successfully detected in the zircons. The 81 Kr‐Kr exposure age of the zircons was calculated to be 76 ± 5 million years (Ma). This age corresponds to the CRE ages obtained from cosmogenic 3 He and 21 Ne (82 ± 8 and 88 ± 9 Ma, respectively) of the silicate part and the previously reported 36 Cl‐ 36 Ar age of the metal part (77 ± 9 Ma). The consistent CRE ages using different dating methods demonstrate that the 81 Kr‐Kr dating using meteoritic zircons is a new promising tool for determining the CRE age of meteorites. Moreover, based on the 81 Kr‐Kr age of the zircons, the production rates of cosmogenic 3 He and 21 Ne in a meteoritic zircon were estimated to be (15 ± 2) × 10 −9 and (0.69 ± 0.04) × 10 −9 cm 3 STP g −1 Ma −1 , respectively.