Premium
Calibration of cosmogenic noble gas production in ordinary chondrites based on 36 Cl‐ 36 Ar ages. Part 1: Refined produced rates for cosmogenic 21 Ne and 38 Ar
Author(s) -
Dalcher N.,
Caffee M. W.,
Nishiizumi K.,
Welten K. C.,
Vogel N.,
Wieler R.,
Leya I.
Publication year - 2013
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.12203
Subject(s) - meteorite , noble gas , chondrite , radiogenic nuclide , isotopes of argon , chemistry , radiochemistry , analytical chemistry (journal) , neon , argon , isotope , nuclear physics , physics , astrobiology , environmental chemistry , organic chemistry
We measured the concentrations and isotopic compositions of He, Ne, and Ar in bulk samples and metal separates of 14 ordinary chondrite falls with long exposure ages and high metamorphic grades. In addition, we measured concentrations of the cosmogenic radionuclides 10 Be, 26 Al, and 36 Cl in metal separates and in the nonmagnetic fractions of the selected meteorites. Using cosmogenic 36 Cl and 36 Ar measured in the metal separates, we determined 36 Cl‐ 36 Ar cosmic‐ray exposure (CRE) ages, which are shielding‐independent and therefore particularly reliable. Using the cosmogenic noble gases and radionuclides, we are able to decipher the CRE history for the studied objects. Based on the correlation 3 He/ 21 Ne versus 22 Ne/ 21 Ne, we demonstrate that, among the meteorites studied, only one suffered significant diffusive losses (about 35%). The data confirm that the linear correlation 3 He/ 21 Ne versus 22 Ne/ 21 Ne breaks down at high shielding. Using 36 Cl‐ 36 Ar exposure ages and measured noble gas concentrations, we determine 21 Ne and 38 Ar production rates as a function of 22 Ne/ 21 Ne. The new data agree with recent model calculations for the relationship between 21 Ne and 38 Ar production rates and the 22 Ne/ 21 Ne ratio, which does not always provide unique shielding information. Based on the model calculations, we determine a new correlation line for 21 Ne and 38 Ar production rates as a function of the shielding indicator 22 Ne/ 21 Ne for H, L, and LL chondrites with preatmospheric radii less than about 65 cm. We also calculated the 10 Be/ 21 Ne and 26 Al/ 21 Ne production rate ratios for the investigated samples, which show good agreement with recent model calculations.