国际标样Durango磷灰石(U-Th)/He年龄测定  

( U-Th) / He dating of international standard Durango apatite

作　　者：吴林[1] 王非[1] 单竞男[1] 张炜斌[1] 师文贝[1] 冯慧乐 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《岩石学报》2016年第6期1891-1900,共10页Acta Petrologica Sinica

基　　金：国家重大专项项目(2011ZX05008-001);国家自然科学基金项目(41503055;41025010;41221022);中国科学院战略性先导科技专项(XDB03020203)联合资助

摘　　要：人们认识到可以用放射性成因4He对矿物进行定年已经有一百年的历史,但是利用富含U、Th的矿物进行（U-Th）/He定年是近三十年来快速发展的一种低温（热）年代学方法。由于U-Th-He同位素体系的封闭温度低（磷灰石4He的封闭温度为-75℃）,该方法极大的拓展了中低温热年代学研究（如40Ar/39Ar,裂变径迹等）的温度范围下限,已经被广泛应用于浅表地质过程的研究中。Durango磷灰石是国际上广泛使用的磷灰石（U-Th）/He定年的标准样品,准确测定其年龄可以对实验方法及流程的可靠性进行验证。中国科学院地质与地球物理研究所（U-Th）/He定年实验室建立于2013年,经过一年多的实验与摸索,我们建立了完整、可行的化学分析流程和仪器测试流程,并采用Durango国际标样进行了流程验证。重复测定了4批共40个Durango磷灰石颗粒,40个年龄结果分布在28.95-34.11Ma之间,全部年龄的概率分布峰值为31.61±2.7Ma,与国际标定值在误差范围内一致;Th/U比范围为16.43-23.72,与国际报道值一致,表明我们所建立的实验流程准确可行,实验室已经可以稳定运行。It has been more than 100 years since radioactive4 He was realized to date mineral age,but using U,Th rich minerals as（ U-Th） /He geochronometer was developed as a new low temperature thermochronological method in recent 30 years. The low closure temperature of U-Th-He isotopic system（ closure temperature for4 He in apatite is - 75℃） makes it expand the lower limit of mediumlower thermochronology（ e. g.40 Ar /39 Ar and fission track）. Therefore,（ U-Th） / He isotopic dating has been widely used in geochronological studies for sub-surface geological processes. Durango apatite is a commonly used international standard for（ U-Th） /He dating. Accurate determination of its age could verify the feasibility of the experimental protocol.（ U-Th） / He dating laboratory of Institute of Geology and Geophysics,Chinese Academy of Sciences（ IGGCAS） was established in 2013. Four batches of a total 40 Durango apatite grains have been tested in this newly-built laboratory. All 40 age results are in the range of 28. 95 Ma to 34. 11 Ma and the peak of the age probability distribution is 31. 61 ± 2. 7Ma,which is consistent with the international calibrated ages. Moreover,Th /U ratios of the all 40 grains are in the range of 16. 43 to 23. 72,which were in agreement with results reported internationally. These results indicate that the experimental procedure we established is accurate and feasible.

关 键 词：Durango磷灰石 国际标样 (U-Th)/He定年 

分 类 号：P597.1[天文地球—地球化学]