Production rates for cosmogenic krypton and argon isotopes in H-chondrites with known ^<36>Cl-^<36>Ar ages

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We present physical model calculations for the production of cosmogenic Kr isotopes in stony meteorites and compare the model results with measured data for bulk samples of 12 H-chondrites which recently had been investigated for their ^<36>Cl-^<36>Ar cosmic-ray exposure ages and light noble gas production rates. The correlation between P(^<81>Kr)P(^<83>Kr) and P(^<78>Kr)P(^<83>Kr) modelled here is significantly different from the classical relation commonly used to derive ^<81>Kr-Kr exposure ages. For both relations, the ^<81>Kr ages scatter considerably around the respective ^<36>Cl-^<36>Ar ages, but the new relation on average yields a somewhat better agreement between ^<81>Kr-Kr and ^<36>Cl-^<36>Ar ages. The calculations combined with concentration measurements of the main target elements for the production of cosmogenic Kr (Rb, Sr, Y, Zr, and Nb) show that target element chemistry does hardly influence the isotopic composition of cosmogenic Kr in bulk chondrites. These calculations also confirm earlier conclusions that the isotopic systematics of cosmogenic Kr in lunar samples are applicable for chondrites too. We derived an average ^<38>Ar production rate at average shielding (^<22>Ne^<21>Ne=1.11) of (0.0431±0.0035)×10^<-8> cm^3 STP(g×Myr).
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