腾冲、长白山年轻火山岩铀系不平衡热电离质谱法年代学研究

在国内首次建立了铀系不平衡热电离质谱法年轻火山岩年龄测定的试验流程，并研究了云南腾冲、吉林长白山天池火山岩的年龄。划分出腾冲晚更新世以来的5个喷发期次：220 ka、80 ka、20 ka、12.8~13 ka、0.75~0.79 ka和长白山天池全新世以来的3次喷发：5.3 ka、1.0 ka、0.75 ka。这些年龄值和其他的方法所得的结果基本一致，表明本方法的可靠性。此外，还介绍了铀系不平衡法火山岩年代学的基本原理，讨论了样品的封闭性、火山岩中钍同位素初始组成均一性等问题。

Chronology of Young Volcanic Rocks of Changbaishan Tianchi and Tengchong, China, by Using the Uranium-series TIMS Method

The experimental procedure of the Uranium Series Disequilibrium TIMS Method for dati ng volcanic rocks was set up for the first time in China, and the ages of samp les from the Ten gchong volcanic field, Yunnan Province, and Changbaishan Tianchi volcano, Jilin P rovince, were obtained. Based on this ages, the cycles of volcanic eruption can b e inferred as follows: 220 ka, 80 ka, 20 ka, 12.8~13 ka, 0.75~0.79 ka for the Ten gchong vo lcanoes since the late Pleistocene and 5.3 ka, 1.0 ka, 0.75 ka for the Tianchi v olcano sinc e the Holocene. All these ages are almost same as those given by variable other met hods indicating that they are reliable. In addition, the principle and some prob lems such as closed system of the samples and homogeneity of Th isotope composit ion in magma are discussed.