【摘要】 <正> 长白山地区自晚第三纪以来有过多次火山活动,形成了大量的玄武岩和粗面岩,笔者运用钾-氩稀释法测定了这些火山岩的年龄,得到30多个表面年龄和4个等时年龄,年龄区间为19.91±0.20—0.0876±0.015百万年。更多还原

【Abstract】 A vast amount of basalts and trachytes are distributed over Changbai Mountainous areas in Northeast China. More than 30 chosen samples of whole rocks of basalts and separated anorthoclass from trachytes were measured with K-Ar isotope dilution method. It has been suggested that these volcanic rocks were erupted from 19.9 to 0.088 Ma ago. The data are of high accuracy. Potassium was analysed by flame photometry and isotope dilution method; extracted in ultra-high vacuum line, mixing with an38Ar spike, argon was isoto-pically analysed in MM1200 and ZhH1301 mass spectrometer. Basalt isochrons of40Ar/36Ar vs. 40K/36Ar made after D. York’s equation (1969) have given the initial 40Ar/36Ar ratio of 280.3-299.8. It shows that the samples do not have distinct excess argon. The measured results agree well with the geological occurrence and paleomagnetic data.更多还原