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全球变化研究已成为第四纪地质学中的热点,其中年代尺度的高灵敏度、高精度测量又成为迫切需要解决的课题之一.Edwards工作表明,用热电离质谱(TIMS)技术研究珊瑚的~(238)U-~(234)U-~(230)Th体系,可以得到高精度的年龄谱.例如, Vanuatu地区 TAN珊瑚的年龄值为(180± 5) a, CWS珊瑚为(845± 8)a, Hispaniola珊瑚为(8294± 44) a, Barbados地区珊瑚为(128.1± 1.7) ka.这些结果引起了年代学工作者的兴趣.与通常的 α谱仪法相比较,质谱铀系法有明显的优点:(ⅰ)样品用量少,千年以下样品约用3～5g,万年以上样品用几百毫克;(ⅱ)测试时间短,铀、钍测量分别为 3～ 4 h;(ⅲ)测年精度高,百年至千年之间精度为 1％～3％,万年至 20万年之间为< 1％;( ⅳ)测年范围宽,可以测试 500 ka年以来的样品. 本实验使用的铀系标样为GBW04412, GBW04413和RKM-4.前两个标样经过《国家铀系标样对比计划》(USIP)的研究.它们取自贵州犀牛洞的石笋.4412为文石,有明显的年轮结构.4413为 50％文石, 50％方解石,两者皆呈白色、纯净. RKM-4采自 Barbados Kendal山阶地,为群体珊瑚Acropora palmata,文石占 99％.此样品经过 USIP研究,有 α谱仪法确定的数据.1 分析方法
Global change research has become a hot spot in Quaternary geology, in which the high sensitivity and high accuracy measurement of the time scale has become one of the urgent problems to be solved.Edwards’s work shows that the thermal ionization mass spectrometry (TIMS) For example, the age value of TAN coral in Vanuatu is (180 ± 5) a, and that of CWS coral is (845 ± 8) U (238) U- ) a, Hispaniola coral (8294 ± 44) a, and Barbados coral (128.1 ± 1.7) ka. These results aroused the interest of geochronology workers. Compared with the conventional α-spectrometer method, (Ii) the test time is short and the measurement of uranium and thorium is 3 ~ 4 h, respectively; (iii) the amount of uranium and thorium is about 3 ~ The accuracy of the dating is high, with the accuracy of 1% -3% between the hundred years and the millennium, <1% between years and 200000 years; (ⅳ) The dating range is wide and can test the sample since 500 ka years. The uranium series standards used were GBW04412, GBW04413 and RKM-4. The first two standards were subjected to the “National Uranium Standard Comparisons Program” (USIP) study Stones from Rhinoceros Cave in Guizhou Province.44412 is aragonite with obvious ring growth structure .4413 is 50% aragonite and 50% calcite, both of which are white and pure. RKM-4 was collected from Barbados Kendal mountainous area, Acropora palmata, aragonite 99%. This sample was USIP study, α spectrometer method to determine the data .1 analysis method