激光显微探针^(40)Ar/^(39)Ar同位素定年

THE LASER MICROPROBE^(40)Ar/^(39 ) Ar DATING METHOD

已有 5 0年历史的K Ar定年法 ,由于过剩Ar和Ar丢失的普遍发现 ,使其最广泛的应用面临着严重挑战。40 Ar/ 3 9Ar分步加热释氩法是常规K Ar定年法的发展 ,它克服了常规K Ar定年法的一些局限 ,又可以测定岩浆构造热事件。激光显微探针40 Ar/ 3 9Ar定年法是在 2 0世纪末把聚焦激光束应用在40 Ar/ 3 9Ar分步加热释氩法中而发展起来的一种定年方法。它既具有常规K Ar定年法和40Ar/ 3 9Ar分步加热释氩法的所有优越性 ,又把定年引入微观领域。特别是在 2 0世纪的最后几年 ,以激光显微探针40 Ar/ 3 9Ar定年方法的完善和精度的提高为标志 ,把K Ar年代学研究推向了一个新的里程碑。微区微量高精度高分辨定年 ,把定年时限扩展到人类历史范畴 ,精细的分析技术拓宽了年代学的应用范围 ,使之解决的地质问题更广泛和深入 ,并且开始冲击着地球科学中的某些热点和难点课题。

K Ar age dating method is facing a serious challenge to its application due to that both Ar loss and Ar excess are widespread found even though it has been used for 50 years. 40 Ar/ 39 Ar step heating dating method was developed from the conventional K Ar method. There are some advantages of 40 Ar/ 39 Ar dating over conventional K Ar dating and a geothermal event may be analyzed by 40 Ar/ 39 Ar dating. The laser microprobe 40 Ar/ 39 Ar dating ,a new dating method, was founded on the basis of the conventional 40 Ar/ 39 Ar dating method since a focused laser beam was applied in geochronology. The advantages of both conventional K Ar and 40 Ar/ 39 Ar dating methods were inherited while it made dating into the microcosmic field. Within the latest few years of the twentieth century, studies on K Ar geochronology have been pushing on a new step as a sign of method perfected and precision enhanced. High precision and high resolution 40 Ar/ 39 Ar dating, can be used in both micro area and a single grain, extends dating limit into the historical realm. Application range of K Ar geochronology is getting bigger and bigger due to fine analytical techniques for solving geological problems are getting wider and wider. It is a milestone in the geochronological history. A lot of 'hotpot' and puzzle are being struck by the new dating method in Earth science.