Development of the ^<40>Ar- ^<39>Ar dating method based on the Ar extraction from a sample by using a laser beam.

本研究的主要目的是<40><39>通过激光束辅助从样品中提取Ar气体来发展^ Ar- ^ Ar定年方法。通过这项研究，我们考察了在不同条件下从矿物中提取Ar气的基本问题，并获得了<40><39>用这种方法提取Ar气的量进行~ Ar-~ Ar定年的可能性的前景。如激光束的浓度、激光束到样品表面的入射角、所用透镜的效率、激光发生器的输出功率等。为了观察样品表面的状况，光学显微镜是有效的，但并不总是与激光照射的最佳条件相容。我们正试图使用一个视频系统来观察激光照射过程中的样品。在将来仍然存在一些问题，其中包括在激光照射期间样品表面上的温度的估计、通过激光照射的熔融部分的体积的估计以及高温长石矿物的熔融。此外，对于年龄小于10 Ma的年轻火山岩，用这种方法测定年龄时，必须使用高灵敏度和高精度的质谱仪来测量样品中激光脱气后的微量Ar。

The main aim in this study is to develop the ^<40>Ar- ^<39>Ar dating method by extracting Ar gases from a sample with the aid of a laser beam. Through this study, we have examined fundamental problems in extracting Ar gases from a mineral under different conditions and obtained a prospect that the ^<40>Ar- ^<39>Ar dating would be possible with the amount of extracted Ar gases by this method.Through this study, it has been revealed that the efficiency of heating a sample with a laser beam is controlled by many factors such. as the concentration of a laser beam, an angle of incidence of a laser beam to the surface of the sample, the efficiency of used lenses, the out-put power of the laser generator and so on. To observe the condition of the surface of a sample, an optical microscope is efficient, but is not always compatible with the best condition for the laser irradiation. We are trying to using a video system to observe the sample during a laser irradiation. There remain some problems in future, among which the estimate of the temperature on the surface of a sample during a laser irradiation, the estimate of a volume of a fused part by a laser irradiation and the fusing of a high temperature felscic mineral are included. In addition, to date a young volcanic rock of less than 10Ma with this method, it is essential to use a high sensitive and precise mass spectrometer to measure the very small amount of Ar degassed by a laser beam from a sample.