石英^(40)Ar-^(39)Ar阶段加热法定年的实验技术改进及意义

Some Improvement^(40)Ar-^(39)Ar Setp-Heating Dating Technique of Quartz and Its Significance

40 Ar 3 9Ar阶段加热法测定石英年龄始于 1986年。近年来通过样品清洗、提高真空度、提高质谱计灵敏度、减小样品用量、增加熔样阶段等实验技术改进 ,数据质量比过去有所提高。但关键问题是选择有代表性的石英样品 ,并预先对样品做镜下鉴定和电子探针分析 ,挑选钾含量较高的石英用于定年 ,以便减少失败 ,提高年龄数据测试的成功率。当钾含量高于 0 0 5 %时 ,一般都可在中温 (70 0～ 10 0 0℃左右 )阶段获得 3个以上视年龄构成的坪年龄和等时年龄 ,比过去马鞍型年龄谱中由一个最小视年龄作为成矿年龄要准确。

The determination of mineralization age for quartz started in 1986 byusing 40Ar- 39Ar step heating technique.Recently,we have made some modification to the method.The measurements ed present here show that they are improved significantly compared with the previous data.Argon isotopes of the quartz samples are measured in the modified RGA10 mass spectrometer operated in static mode.Some useful 40Ar/ 39Ar plateau ages, 40Ar/ 36Ar- 39Ar/ 36Ar isochron ages and the initial 40Ar/ 36Ar ratios of these quartz samples are given and their implications are discussed in this paper.