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

云母是一种常见的矿物，可以用Rb-Sr、Ar-Ar和FT-方法测定其年龄。云母的反冲径迹测年可以给出高达几Ma的年龄，这意味着低的闭合温度，从而表明形成上地壳的地质过程。这将是地球年代学工具包的一个有价值的扩展，并对多种方法测年有用。虽然裂变径迹和反冲径迹方法相似，年龄大致相同，但一种方法在应用地质研究中具有很大的优势，而另一种方法尚未达到公认的测年方法的地位。主要原因是对其开发投入的研究努力有限，以及在关键问题上采用的实验方法范围狭窄。该项目旨在对反冲径迹测年的原理和实践进行集中和持续的研究。它要求对痕迹蚀刻、观察和(自动)计数进行有限的重新调查，以建立最佳程序。主要的实验目的是采用新的方法来测量云母表面的刻蚀轨迹尺寸和刻蚀速率。新的研究工具(径迹尺寸测量、镜像、蚀刻-退火-刻蚀实验；α径迹探测器)也被应用于反冲径迹密度的刻蚀时间依赖这一中心问题以及其他问题。用径迹法测定云母样品中U、Th-的含量是一个实用的目标。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.