Noble gas abundances in a deep-sea sediment core from eastern equatorial Pacific

Abstract

The dried sediments from a single deep-sea sediment core taken in the eastern equatorial Pacific (1°02.2′N, 121°10.4′W), showed progressive enrichment in heavy noble gases (³⁶Ar, ⁸⁴Kr, ¹³²Xe). Meanwhile, light noble gases (⁴He, ²⁰Ne), especially ²⁰Ne, were severely depleted. The noble gas abundances classified into type 1, observed in terrestrial sedimentary rocks and natural gases, can be formed as a mixture of the observed noble gas abundances with those in water. The concentrations of ⁸⁴Kr and ¹³²Xe show no systematic variation with depth, and correlated directly with the SiO₂ content and inversely with the CaCO₃ content. Leaching experiments to remove CaCO₃ confirmed that siliceous fossils were better adsorbers of heavy noble gases than calcareous fossils. Very high ³He/⁴He ratios of 0.7 × 10^-4 and 1.3 × 10^-4 were observed in these leached samples.