Noble gases in mesozoic cherts from the U.S.A. and Japan

Abstract

Noble gases in cherts of various origins were measured by means of the stepwise heating technique. The elemental abundance patterns of noble gases in the samples showed monotonic fractionation from ²⁰Ne to ¹³²Xe relative to the atmosphere; this pattern is designated as type-1 and is similar to that observed in water, natural gases and sedimentary rocks. The noble gas concentrations in cherts were low compared with those in other sedimentary rocks and related samples, and showed scarcely apparent correlations with chemical components. Crystallization from amorphous silica to quartz was responsible for the degassing loss of noble gases in cherts.