New constraints on the release of noble gases during in vacuo crushing and application to scapolite Br-Cl-I and Ar-40/Ar-39 age determinations

Abstract

The release of irradiation-produced noble gas isotopes (38ArCl, 80KrBr, 128XeI and 39ArK) during in vacuo crushing scapolite has been investigated and is compared to quartz. Three thousand crushing strokes released ∼98% of fluid inclusion-hosted noble gas from quartz. In comparison, 3000 crushing strokes released only ∼4% of the lattice-hosted 38ArCl from a scapolite gem. In vacuo crushing released lattice Ar preferentially relative to lattice Kr or Xe and prolonged crushing released ∼88% of the lattice-hosted noble gas in 96,000 crushing strokes. We suggest fast diffusion pathways generated by crushing are an important noble gas release mechanism and we demonstrate two applications of prolo..