高精度热电离质谱(TIMS)在南极陨石研究中的应用前景  

THE PROSPECT OF HIGH-PRECISION THERMAL IONIZATION MASS SPECTROMETRY( TIMS) APPLICATIONS IN ANTARCTIC METEORITES

作　　者：彭丽[1,2] 王桂琴[1] 江小英[1,2] 赖永旺 

机构地区：[1]中国科学院广州地球化学研究所同位素地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049

出　　处：《极地研究》2013年第4期425-435,共11页Chinese Journal of Polar Research

基　　金：国家自然科学基金重点项目(40930316);中国科学院广州地球化学研究所公共技术项目资助

摘　　要：热电离质谱(TIMS)是同位素地球化学研究中传统、可靠、分析精度高的主要测试仪器之一,尤其对于微量样品的高精度同位素比值测定,以其高精度和高灵敏度获得广泛的认可,这一特征在天体化学微量样品同位素研究中具有广阔的应用前景。目前,新型TRITON TIMS质谱仪已实现了Re-Os,Cr,Sr,Nd,Pb等同位素的高精度测定。采用TIMS测定Sr同位素比值的Sr含量范围可由10—100 ng以上,87Sr/88Sr比值测定精度可达到5‰—5 ppm;LaJolla Nd同位素标样测试结果为:143Nd/144Nd=0.511 842±0.000 005(2SE,n=28),143Nd/144Nd比值测定精度最佳可达2 ppm;207Pb-204Pb双稀释剂法对Pb含量为5—20 ng样品测定,外部精度206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别达到±0.003 4、±0.004 6和±0.010 0(2SE,n=28);负离子状态(NTIMS)下对Os含量值为几至几十pg的样品进行测定,187Os/188Os比值精度可达0.2‰以内,对Os含量为ng级的样品,187Os/188Os比值精度好于20 ppm;Cr同位素比值50Cr/52Cr,53Cr/52Cr,54Cr/52Cr的分析精度分别可达到1 ppm,2 ppm,2 ppm(2SD)以内。这些方法涵盖了亲石元素、亲铁元素,长寿命放射性同位素和短寿命灭绝核素的同位素研究,为中国南极陨石的深入研究提供了有力技术保障。Thermal ionization mass spectrometry （ TIMS） is one of the most important isotopic measurement techniques . TIMS technology has a broad prospect of application in cosmochemistry because of its high accuracy and sensitivity . TRITON TIMS can measure high-precision isotopic compositions of the Re-Os, Cr, Sr, Nd and Pb systematics of meteorites.Small loads （10 pg to 100 ng Sr） of international standard NBS 987 were analyzed for 87 Sr/86 Sr isotope ratios with a precision of 5‰to 5 ppm by TIMS.The ratio of 143 Nd/144 Nd of LaJolla-Nd is 0.511 842 ±0.000 005 （2 SE, n=28） in our lab, and the best precision is better than 2 ppm.Using the 207Pb-204Pb double spike, the re-producibilities of 206 Pb/204 Pb, 207 Pb/204 Pb and 208 Pb/204 Pb ratios can be better than ±0.003 4, ±0.004 6 and ±0.010 0 （n=28, 2 SD） for samples with a content of 5 to 20 ng Pb, respectively.187Os/188Os isotopic ratios are determined under a negative thermal ion mode with a precision of better than 0.2‰ for approximately tens of pg , and 20 ppm for ~1 ng .In addition , Cr isotopes can also be measured by the TIMS technique in the static multicol-lection mode.The precisions of 50 Cr/52 Cr, 53 Cr/52 Cr, and 54 Cr/52 Cr ratios are 1, 2 and 2 ppm, respectively. These methods include a range of isotope systematics related to lithophile and siderophile elements , long-lived radi-onuclides , and short-lived extinct radionuclides .Additionally , they provide support for the further study of Antarc-tic meteorites.

关 键 词：热电离质谱(TIMS) 陨石 南极 应用前景 

分 类 号：P185.83[天文地球—天文学]