Annealing of ion tracks in apatite under pressure characterized in situ by small angle x-ray scattering

Abstract

Fission track thermochronology is routinely used to investigate the thermal history of sedimentary basins, as well as tectonic uplift and denudation rates. While the efect of temperature on fssion track annealing has been studied extensively to calibrate the application of the technique, the efect of pressure during annealing is generally considered to be negligible. However, a previous study suggested elevated pressure results in a signifcantly diferent annealing behaviour that was previously unknown. Here, we present a method to study track annealing in situ under high pressure by using synchrotronbased small angle x-ray scattering (SAXS). To simulate fssion tracks in a controlled environment, ion tracks were created in apatite from Durango, Mexico using 2GeV Au or Bi ions provided by an ion accelerator facility. Samples were annealed at 250°C at approximately 1GPa pressure using diamond anvil cells (DACs) with heating capabilities. Additional in situ annealing experiments at ambient pressure and temperatures between 320 and 390°C were performed for comparison. At elevated pressure a signifcantly accelerated annealing rate of the tracks was observed compared with annealing at ambient pressure. However, when extrapolated to geologically relevant temperatures and pressures, the efects become very small. The measurement methodology presented provides a new avenue to study materials behaviour in extreme environments. Show more