Vesicle-specific noble gas analyses of ''popping rock'': Implications for primordial noble gases in earth

Gases trapped in individual vesicles in the volatile-rich basaltic glass ''popping rock'' were found to have the same carbon dioxide, helium-4, and argon-40 composition, but a variable Ar-40/Ar-36 ratio (similar to 4000 to greater than or equal to 40,000). The argon-36 is probably surface-adsorbed atmospheric argon; any mantle argon-36 trapped in the vesicles cannot be distinguished from an atmospheric contaminant. Consequently the Ar-40/Ar-36 ratios and He-3/Ar-36 ratios (1.45) determined are minimum estimates of the upper mantle composition. Heavy noble gas relative abundances in the mantle resemble solar noble gas abundance patterns, and a solar origin may be common to all primordial mantle noble gases.