An investigation of fission-track etching in apatite and its implications for fission-track dating and modelling

点击翻译按钮获取中文摘要

Methodological experiments indicate that there is a defect in the current model of the fission-track method that has serious consequences for geological applications. New and old evidence points to differences between the etching and annealing of fossil tracks in natural, radiation-damaged apatites and induced tracks in pre-annealed and neutron-irradiated apatites. The focus of this project is thus on etched tracks, investigated by means of step-etch experiments. The approach is to exploit the advantages of modern motorized microscopes for characterizing the track densities and track lengths. This involves determining volumetric as well as surface-track densities, and the lengths of surface tracks, semi-confined and confined tracks. The main aim is to understand the differences between the etching and annealing of fossil and induced tracks and between geological samples and pre-annealed and neutron-irradiated apatites. The final goal is to propose a practical solution for eliminating artefacts from geological fission-track studies. This could take the form of a universal optimal etching time for fossil tracks or a method for determining it for a given sample. The project also aims to develop new methods for counting and measuring fission tracks. Experiments on apatite samples from the Kontinentale Tiefbohrung provide a means of evaluating their geological impact.