Primordial noble gas isotopes from immoderate crushing of an Icelandic basalt glass

Noble gas isotopes carry important information about volatile accretion, mantle differentiation and the preservation of early formed radiogenic isotope hetero-geneities. However, extremely low abundances and pervasive atmospheric contamination make precise determinations of mantle source heavy noble gas isotopic compositions challenging. Furthermore, the precision achieved in ratios of the rarest noble gas isotopes (the primordial isotopes) is typically poor. Here an approach that combines heavy crushing of a large quantity of sample along with more traditional temperate crushing is adopted to analyse noble gases in a basalt glass from Iceland. The method yields high precision Xe primordial isotope data resolved from the atmospheric composition. ¹²⁸Xe/¹³⁰Xe–¹²⁹Xe/¹³⁰Xe systematics indicate a distinct, low ¹²⁹Xe/¹³⁰Xe in the plume mantle source compared with that in the upper mantle, demonstrating the survival of an early formed (>4.45 Ga) radiogenic isotope heterogeneity in the modern mantle. Future sampling efforts may plan to dedicate large quantities (>20 g) of material for high precision noble gas analysis to leverage the advantages of a mixed analytical approach.