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

方法学实验表明，目前的裂变径迹方法模型存在缺陷，对地质应用具有严重影响。新的和旧的证据指出，在天然的、受辐射破坏的磷灰石中的化石径迹和在预退火和中子辐照的磷灰石中的诱导径迹之间的蚀刻和退火之间的差异。因此，本项目的重点是通过阶梯刻蚀实验研究的刻蚀轨迹。该方法是利用现代电动显微镜的优势来表征轨道密度和轨道长度。这包括确定体积和表面轨道密度，以及表面轨道、半受限轨道和受限轨道的长度。主要目的是了解化石和诱导径迹的蚀刻和退火之间的差异，以及地质样品和预退火和中子辐照的磷灰石之间的差异。最终目标是为消除地质裂变径迹研究中的人工制品提出一个实用的解决方案。这可以采取化石痕迹的通用最佳蚀刻时间的形式，或者对于给定的样本确定它的方法。该项目还旨在开发计算和测量裂变径迹的新方法。对Kontinentale Tiefbohrung的磷灰石样品进行的实验提供了一种评估其地质影响的方法。

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.