RADIATION EFFECTS IN MINERALS – IMPLICATIONS FOR THERMOCHRONOLOGY

During the past decade, there have been significant advances in the understanding of radiation damage effects and damage accumulation in minerals and crystalline ceramics. Two types of irradiation events: i.) alpha-decay damage and ii.) fission track formation are of particular relevance to geochronology and thermochronology. These types of radiation damage events may be simulated by experiments with materials doped with short-lived actinides or by ion beam irradiation. In some cases, the experimental results can be correlated with observations of damage and recovery in minerals of great age. The physics of both types of experimentally-induced damage are well understood; thus, the integrated results of both actinide-doping and ion beam irradiation, combined with detailed studies of minerals, can provide a clear understanding of radiation damage in-growth and annealing as a function of the type of material, temperature, time and the synergistic effects of ionizing and ballistic interactions with the material. The experimental challenge has been the handling of actinide-doped materials and the access to swift heavy ion irradiations that are used to simulate the damage process. In the latter case, the characterization of very small volumes of material at the nanoscale is required. This has now been accomplished by recent advances in the application of high-resolution transmission electron microscopy, small angle x-ray scattering, total neutron scattering, Raman spectroscopy and studies of changes in physical properties, such as hardness and the elastic modulus. Studies at high pressure have proved useful to understanding the underlying energetics that determine the final damage state of different materials. This presentation will summarize recent results for each of these analytical techniques and identify the issues that are relevant to thermochronology.