Noble gas degassing from meteorites as inferred from 40Ar-39Ar analytical data

概要

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'Retention rate of radiogenic ^<40>Ar through a collisional event' (f_r) was estimated on the basis of ^<40>Ar-^<39>Ar analytical data for each meteorite reported. 'The amount of trapped ^<36>Ar' (^<36>Ar_T) seems to be roughly correlated with the determined Ar retention rate, 'f_r', for samples with f_r of less than 0.5. When we extend this correlation to f_x=1,the original amount of trapped ^<36>Ar in ordinary chondrites is estimated to be in the order of 10^<-7>cm^3 STP/g. Even meteorites with no clear sign of impact often show lower amounts of trapped ^<36>Ar, suggesting that the loss of trapped components might have occurred in a stage of meteorite formation for these meteorites. The amounts of trapped ^<36>Ar and ^<84>Kr seem to be correlated with those of trapped ^<132>Xe, reflecting also the degree of equilibrium state of meteorites. Meteorites with signs of impact show lower amounts of trapped heavy noble gases. Such a correlation might be explained by degassing processes through diffusion at relatively high temperatures for prolonged periods of time.
国立極地研究所の論文
1989-10-00