【摘要】 <正> 在用MM—1200质谱计进行K—Ar稀释法地质样品的年龄测定中,采用了³⁸Ar同位素稀释技术。本文对方法实验与样品分析中积累的资料进行统计,分析对比,对³⁸Ar稀释剂的合适用量,标定方法及标定误差的统计,实验中样品量的估计,以及更多还原

【Abstract】 K-Ar age can be determined by means of isotope dilution method with mass-spectrometer MM-1200. Suitable amounts of ³⁸Ar spike range from 10^-11 to 10^-12 mole. A standard biotite ZBH-25 is used for the calibration of ³⁸Ar spike. Initial value of ³⁸Ar spike and its standard deviation are calculated by least-squre method. Approximate weights of samples (⁴⁰Ar/³⁸Ar=1) are listed by computer according to known potassium contents and appoximate age. W（mg） can be obtained from that table, when proper (⁴⁰Ar/³⁸Ar)_m is chosen, the appoximate weight of a sample is (⁴⁰Ar/³⁸Ar)_m·W （mg）.Estimated precision for single age measurements is calculated by using a formula. Estimated standard deviation σ_t of the spike calibration is ±0.6％, obtained from the experiments of ³⁸Ar spike calibration. On the basis of replicate experiments σ_k is estimated. When K₂O>1％, σ_k=±1.3％; when 0.1％<K₂O％<1％. σ_k=±2％; when K₂O％<0.1％, σ_k=±10％. Percentage of radio-genic ⁴⁰Ar Standard deviation of ⁴⁰Ar/³⁸Ar and standard deviation of ³⁶Ar/³⁸Ar are obtained from data of single analysis of argon.更多还原