地震地质 ›› 1992, Vol. 14 ›› Issue (4): 361-367.

• 科研简报 • 上一篇    下一篇

几种全岩样品40Ar-39Ar年龄谱的探讨

李大明, 陈文寄, 李齐, 王昕   

  1. 国家地震局地质研究所 北京 100029
  • 收稿日期:1990-05-31 出版日期:1992-12-09 发布日期:2009-11-25

A DISCUSSION ON 40Ar-39Ar AGE SPECTRA OF THREE KINDS OF WHOLE ROCKS

Li Daming, Chen Wenji, Li Qi, Wang Xin   

  1. Institutee of Geology, State Seismological Bureau, Beijing 100029
  • Received:1990-05-31 Online:1992-12-09 Published:2009-11-25

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

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