Abstract: According to the field survey and K-Ar dating of the rock samples,the existing K-Ar ages and the new data are presented in this paper.It shows a different distribution feature of the trachytes from different stages on the north and northeast flank of the Tianchi volcano,and it is apparent that the ages of the trachytes on the north flank are newer than those on the northeast flank.It is inferred that the K-Ar age of the oldest trachytes composing the composite cone in the northeast flank of the Tianchi volcano is 0.38Ma BP,which is in the middle Pleistocene,and that the trachyte is the product of the third stage of the trachytic composite cone construction.No evidence of the first and second stages of eruption for the composite cone construction has been found on the northeast flank of the Tianchi volcano.At the meantime,new data from the cored samples provide new insight of a much earlier stage for the trachytic eruption beneath the Tianchi volcano.

Key words: Tianchi volcano, trachyte, K-Ar dating

摘要： 根据采集样品的野外产状,结合前人对天池火山造锥阶段粗面岩时代的研究以及本文给出的新的K-Ar年龄,比较了天池火山北坡和东北坡的造锥粗面岩喷发时代,分析了不同期次喷发的粗面岩的覆盖范围,发现天池火山东北坡粗面岩年龄明显新于北坡粗面岩年龄。天池火山东北坡造锥阶段粗面岩的最老年龄距今0.38Ma,属于中更新世晚期,是第3造锥阶段的喷发物。在东北坡未发现第1造锥和第2造锥阶段的喷发物。新给出的天池火山北侧和东侧2个钻孔资料表明,天池火山造锥粗面岩喷发之前存在距今约2Ma和约1Ma左右的更早期的粗面岩喷发过程。造锥阶段碱流质岩浆喷发持续时间可能在距今0.190～0.0192Ma。

关键词: 长白山天池火山, 粗面岩, K-Ar年龄