Measuring Noble Gases for Thermochronology

The articles in this issue show how applications of noble gas thermochronology can help answer fundamental questions about Earth and planetary processes. Here, we discuss how noble gas measurements are actually made. We review the different methods used to extract and isolate noble gases from natural materials and to measure those gas concentrations and isotopic compositions using mass spectrometry.

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Noble Gases Deliver Cool Dates from Hot Rocks

Heat transfer in the solid Earth drives processes that modify temperatures, leaving behind a clear signature that we can measure using noble gas thermochronology. This allows us to record the thermal histories of rocks and obtain the timing, rate, and magnitude of phenomena such as erosion, deformation, and fluid flow. This is done by measuring the net balance between the accumulation of noble gas atoms from radioactive decay and their loss by temperature-activated diffusion in mineral grains. Together with knowledge about noble gas diffusion in common minerals, we can then use inverse models of this accumulation–diffusion balance to recover thermal histories. This approach is now a mainstream method by which to study geodynamics and Earth evolution.

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