Noble gas measurement in individual micrometeorites using laser gas-extraction system

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All noble gases in 12 individual Antarctic micrometeorites, series F96C and F96D, taken from a water tank at the Dome Fuji Station, were measured by using Nd-YAG CW laser-extraction system. According to the results of light noble gases, the micrometeorites can be separated into two groups, "gas-rich" and "gas-poor". Samples in the gas-rich group have SEP-like ^3He/^4He ratios and Ne isotopic ratios between SEP- and Solar wind-Ne, which are consistent with previous reports on micrometeorites or IDPs. On the other hand, samples in the gas-poor group have very low ^3He/^4He ratios and ^<20>Ne/^<22>Ne ratios lower than the atmospheric values. The ^<40>Ar/^<36>Ar ratios are also separated into two groups, i. e., samples with lower ^<40>Ar/^<36>Ar belong to the gas-rich group. Cosmogenic noble gases were undetected in all the samples and cosmic-ray exposure ages may be shorter than 4.5Ma considering error limits of Ne data. Heavy noble gas elemental compositions are chondritic. There was no correlation between the concentration of volatile elements, sulfur, and that of He and Ne.
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