A new high vacuum crushing system at the CSIRO noble gas facility

Abstract:

Noble gas measurements in groundwater are an established tool to investigate groundwater processes such as recharge conditions and rates, groundwater velocity, and connectivity and exchange fluxes between aquifers. In geologic formations with very slow to no advective groundwater flow (e.g., aquitards and shales), noble gases, especially helium, are excellent tracers for confirming diffusion-dominated transport. In “dry” formations of extremely low porosity and permeability, such as igneous rocks, noble gases within fluid inclusions are studied to assess the chronology of ancient fluid migration in the rock matrix and of mineralisation processes.

The Environmental Tracer Laboratory (ETL) of CSIRO at Waite Campus, South Australia, is developing a new experimental high vacuum crushing system to extract fluid inclusions from minerals to measure their noble gas concentrations and isotopic composition. It operates with one of only a few High-Resolution Noble Gas Mass Spectrometers in Australia (Helix MC Plus). The preparation system allows purifying the noble gas fractions and measuring in fully automated mode the rare isotope ratios like ¹³⁶Xe/¹³²Xe, ²¹Ne/²⁰Ne and ³He/⁴He in groundwater and pore fluids. In fluid inclusions, these noble gas isotopes are the only means to evaluate how long fluids were isolated from the water cycle and to quantify primordial and radiogenic components. We present the first experimental outcomes of this facility.