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

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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.