Abstract: Some problems emerging during analysis of basalt, diabase and clay minerals from fault gouge using ⁴⁰Ar-³⁹Ar method are discussed. Difference between ⁴⁰Ar-³⁹Ar total gas age and K-Ar age can be explained by inhomogeneous loss of Ar from different minerals during fast neutron irradiation. ⁴⁰Ar-³⁹Ar age spectra of three diabase samples from diabase viens indicate intrusive ages of the veins and show that despersion of K-Ar age values in the same area could be caused by effect of later geologic events. For clay mineral samples from fault gouge, ³⁹Ar recoil loss during fast neutron irradiation could increase ⁴⁰Ar-³⁹Ar total gas ages of <1μm grain-size fraction. Lower step ages at lower temperature in ⁴⁰Ar-³⁹Ar age spectra of <1μm and 2-10μm grain-size fractions may be a result of stronger late movement alone the fault.

Key words: ⁴⁰Ar-³⁹Ar age spectrum, Total gas age, Inhomogeneous Ar loss, Fault movement

摘要： 探讨了玄武岩、辉绿岩和断层泥中粘土矿物3种全岩样品在⁴⁰Ar-³⁹Ar分析中的某些问题。利用快中子照射过程中不同矿物发生不均匀Ar丟失的模式解释了玄武岩⁴⁰Ar-³⁹Ar全熔年龄与K-Ar年龄间的差异。对辉绿岩样品的⁴⁰Ar-³⁹Ar分析确定了辉绿岩脉的侵入时代,并说明该地区其它辉绿岩样品K-Ar年龄的离散是受后期变质作用的影响。对于断层泥中粘土矿物,快中子照射中³⁹Ar的反冲丢失导致<1μm粒级部分的⁴⁰Ar-³⁹Ar全熔年龄偏高。<1μm和2～10μm粒级样品的⁴⁰Ar-³⁹Ar年龄谱中,低温区较低的阶段年龄可能是断层后期较强烈活动的结果。

关键词: ⁴⁰Ar-³⁹Ar年龄谱, 全熔年龄, 不均匀Ar丢失, 断层活动