Vesicle-Specific Noble Gas Analyses of "Popping Rock": Implications for Primordial Noble Gases in Earth

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Science  25 Apr 1997:
Vol. 276, Issue 5312, pp. 568-571
DOI: 10.1126/science.276.5312.568

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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 variable40Ar/36Ar ratio (∼4000 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 the40Ar/36Ar ratios and3He/36Ar 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.

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