Noble gas and carbon isotopic compositions of petit-spot lavas from southeast of Marcus Island

摘要

We measured noble gas isotopic compositions of quenched lavas sampled from seamounts, so-called petit-spot volcanoes, on the 160-million-year-old northwestern Pacific Plate. The samples He-3/He-4 and Ar-40/Ar-36 ratios were, respectively, 2.5-8.3 Ra and up to 1735, where Ra stands for atmospheric He-3/He-4, which are analogous to or lower than those of MORB. Considering narrow sampling regions, a secondary effect might be responsible for variation of the data.