The alpha-recoil-track dating method: investigation of its basic principles and further development

云母是常见的矿物，可以用Rb-Sr、Ar-Ar和ft法定年。根据较低的闭合温度，云母的反冲轨迹定年可以给出几个Ma的年龄，从而确定形成上地壳的地质过程。这将是地质年代学工具箱的一个有价值的扩展，对多方法定年很有用。虽然裂变径迹法和反冲径迹法相似且年代相近，但前者在应用地质研究中有很大的优势，而后者尚未达到公认的测年方法的地位。主要原因是投入在其发展上的研究努力有限，以及用于解决关键问题的实验方法范围狭窄。该项目旨在对反冲轨迹测年的原理和实践进行集中和持续的调查。它要求对轨迹蚀刻、观察和（自动）计数进行有限的重新调查，以建立最佳程序。主要的实验目的是为云母表面的可蚀刻轨迹尺寸和蚀刻速率的测量提供新的方法。新的研究工具（轨道尺寸测量，镜像图像，蚀刻-退火-蚀刻实验；α-轨道探测器）也被应用于蚀刻时间依赖于反冲轨道密度的中心问题，以及其他问题。用径迹法测定云母样品中U、th的浓度是一种实用的方法。由此产生的一组相互一致的实验结果应该构成一个强大的理论框架的基础。

Micas are common minerals that can be dated with the Rb-Sr, Ar-Ar and FT-methods. Recoil-track dating of micas can give ages up to several Ma referring to low closure temperatures, and thus to geological processes shaping the upper crust. This would be a valuable extension of the geochrono-logical toolkit and useful for multi-method dating. Although the fission-track and recoil-track methods are similar and about the same age, the one is used to great advantage in applied geological research while the other hasn't attained the status of an accepted dating method. The main reasons are the limited research effort invested in its development and the narrow range of experimental methods that have been brought to bear on the key questions. This project aims to set up a focussed and sustained investigation of the principles and practice of recoil-track dating. It calls for a limited re-investigation of track etching, observation and (automatic) counting to establish optimal procedures. The main experi-ments aim to deploy new methods for measuring the etchable track size and the etch rate of the mica surface. New investigative tools (track size measurements, mirror-images, etch-anneal-etch experi-ments; α-track detectors) are also applied to the central question of the etch-time dependence of the recoil-track densities, and to other problems. It is a practical aim to determine the U,Th-concentrations of the mica samples with track-based methods. The resulting set of inter-consistent experimental results should form the basis of a robust theoretical framework.