Precious Ce Isotope Analysis of Rock Samples by TIMS Method
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摘要: 介绍了对岩石样品的Ce同位素组成进行高精度测量的TIMS方法.采用α-羟基异丁酸(α-HIBA) 离子交换法分离和纯化岩石样品中的La、Ce元素, Ce同位素组成和La、Ce含量测定在Triton热电离质谱仪上完成.质谱标样JMC304的138Ce/142Ce比值统计值为0.0225762±0.0000015, 与大部分文献值一致.应用该方法对USGS玄武岩标样BCR-2和峨眉山玄武岩EQB的138Ce/142Ce比值和La、Ce含量进行了分析, 其结果分别为: 0.0225572±0.0000010、25.2±0.3μg/g、55.8±0.9μg/g和0.0225755±0.0000003、54.2±0.4μg/g、117.4±1.3μg/g.BCR-2的La、Ce含量测定结果与其证书值在误差范围内一致, 其分析精度为0.001%~0.005%.所有样品的140Ce/142Ce比值测定结果统计值为7.9439±0.0002, 介于文献最低值7.941与最高值7.947之间, 可能代表了该比值的最佳估计值.Abstract: A high-precision analysis method of La-Ce isotope ratios for rock samples using TIMS is reported. Separation and purification of La and Ce from matrix elements is carried out using α-HIBA ion exchange procedure. Ce Isotope ratios and La, Ce contents are measured by the mass spectrometry of Triton. A long-term analysis result of standard JMC304 gives a weighted 138Ce/142Ce ratio 0.0225762±0.0000015, which agrees well with the reference values from the literatures. Using the method reported in this study, the Ce isotope ratios and La, Ce contents are analyzed for USGS basalt reference material BCR-2 and an alkali basalt from the Emeishan terrain. The 138Ce/142Ce ratios of BCR-2 and Emeishan basalt (EQB) are 0.0225572±0.0000010 and 0.0225755±0.0000003 with corresponding La contents of 25.2±0.3 and 55.8±0.9μg/g, and Ce contents of 54.2±0.4 and 117.4±1.3μg/g, respectively. It shows that the measured La and Ce contents by isotopic dilution of BCR-2 agree with their certificate values within the analysis error, and this is the first report of Ce isotope for both the standards, which displays a precision range of 0.001% to 0.005%. In addition, a weighted average 140Ce/142Ce ratio of 7.9439±0.0002 is obtained based on 105 analyses, which is likely the representative of a best estimated value for the ratio.
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表 1 La-Ce元素化学分离流程
Table 1. Chemical procedure of separation and purification for La and Ce
表 2 CeO+离子比值测定所用的杯结构
Table 2. Cup configuration for Ce isotopic analysis in CeO+ ion form
表 3 JMC304标样Ce同位素分析结果及其与文献值对比
Table 3. Ce isotope analysis result of JMC304 and its comparison with the data from literatures
表 4 USGS标样BCR-2和峨眉山玄武岩La-Ce同位素组成分析结果
Table 4. La-Ce isotopic compositions of USGS BCR-2 and Emeishan basalt standards
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Amakawa, H., Ingri, J., Masuda, A., et al., 1991. Isotopic compositions of Ce, Nd and Sr in ferromanganese nodules fromthe Pacific and Atlantic oceans, the Baltic and Barents Sea, and the Gulf of Bothnia. Earth and Planetary Science Letters, 105 (4): 554-561. doi: 10.1016/0012-821X(91)90192-K Dickin, A. P., 1987. Ceriumisotope geochemistry of oceanisland basalts. Nature, 326 (6110): 283-284. doi: 10.1038/326283a0 Dickin, A. P., 2004. Radiogenic isotope geology. Cambridge U niversity Press, London. Dickin, A. P., Jones, N. W., Thirwall, M. F., et al., 1987. A Ce/Ndisotope study of crustal contamination processes affecting Palaeocene magmas in Skye, Northeast Scotland. Contributions to Mineralogy and Petrology, 96 (4): 455-464. doi: 10.1007/BF01166690 Hayashi, T., Tanimizu, M., Tanaka, T., 2004. Origin of negative Ce anomalies in Barberton sedimentary rocks, deduced from La-Ce and Sm-Nd isotope systematics. Precambrian Research, 135 (4): 345-357. doi: 10.1016/j.precamres.2004.09.004 Hu, S. H., Chen, A. F., Lin, S. L., et al., 2000. ICP-MS analytical research into 40 trace and ultra-trace elementsin geological samples. Earth Science—Journal of China University of Geosciences, 25 (2): 186-190 (in Chinese with English abstract). Li, Z. C., Fang, X., Liu, W. G., 2002. La-Ce isotope system and Ce isotopic geochemistry. China University of Geosciences Press, Wuhan (in Chinese). Liu, C. Q., Xie, G. H., Masuda, A., 1995. Geochemistry of Cenozoic basalts from eastern China: (Ⅱ) Sr, Nd and Ce isotopic compositions. Geochimica, 24 (3): 203-214 (in Chinese with English abstract). Makishima, A., Nakamura, E., 1991. Precise measurement of cerium isotope composition in rock samples. Chemical Geology (Isotope Geoscience Section), 94 (1): 1-11. doi: 10.1016/0168-9622(91)90035-U Makishima, A., Shimizu, H., Masuda, A., 1987. Precise measurement of cerium and lanthanum isotope ratios. Mass Spectroscopy, 35 (2): 64-72. doi: 10.5702/massspec.35.64 Nier, A. O., 1950. A redetermination of the relative abundances of theisotopes of carbon, nitrogen, oxygen, argon and potassium. Physical Review, 77 (6): 789-793. doi: 10.1103/PhysRev.77.789 Shimizu, H., Amano, M., Masuda, A., 1991. La-Ce and Sm-Nd systematics of siliceous sedimentary rocks: Aclue to marine environment in their deposition. Geology, 19: 369-371. doi: 10.1130/0091-7613(1991)019<0369:LCASNS>2.3.CO;2 Shimizu, H., Lee, S. G., Masuda, A., et al., 1996. Geochemistryof Nd and Ce isotopes and REE abundaces in Precambrain orthogneiss clasts fromthe Kamiaso conglomerate, Central Japan. Geochemical Journal, 30 (1): 57-69. doi: 10.2343/geochemj.30.57 Shimizu, H., Nakai, S., Tasaki, S., et al., 1988. Geochemistry of Ce and Nd isotopes and REE abundances in the Amitsoq gneisses, West Greenland. Earth and Planetary Science Letters, 91 (1-2): 159-169. doi: 10.1016/0012-821X(88)90158-6 Shimizu, H., Sawatari, H., Kawata, Y., et al., 1992. Ce and Nd isotope geochemistry on island arc volcanic rocks with negative Ce anomaly: Existence of sources with concave REE patterns in the mantle beneath the Solomon and Boninisland arcs. Contributions to Mineralogy and Petrology, 110 (2-3): 242-252. doi: 10.1007/BF00310741 Shimizu, H., Tachikawa, K., Masuda, A., et al., 1994. Ceriumand neodymium isotopic ratios and REE patterns in seawater from the North Pacific Ocean. Geochimica et Cosmochimica Acta, 58 (1): 323-333. doi: 10.1016/0016-7037(94)90467-7 Shimizu, H., Umemoto, N., Masuda, A., et al., 1990. Sources of iron-formations in the Archean Isua and Malene supracrustals, West Greenland: Evidence from La-Ce and Sm-Nd isotopic data and REE abundances. Geochimicaet Cosmochimica Acta, 54 (4): 1147-1154. doi: 10.1016/0016-7037(90)90445-Q Tanaka, M., Shimizu, H., Nozaki, Y., et al., 1990. 138Ce/142Ce and 143Nd/144Nd ratios in seawater samples. Geochemical Journal, 24: 309-314. doi: 10.2343/geochemj.24.309 Tanaka, T., Masuda, A., 1982. The La-Ce geochronometer: A new dating method. Nature, 300 (5892): 515-518. doi: 10.1038/300515a0 Tanaka, T., Shimizu, H., Kawata, Y., et al., 1987. Combined La-Ce and Sm-Nd isotope systematics in petrogenetic studies. Nature, 327 (6118): 113-117. doi: 10.1038/327113a0 Tanimizu, M., Hayashi, T., Tanaka, T., 2004. Development of Ce isotope analysis for cosmochemistry using the dynamic multicollector technique. Journal of the Mass Spectrometry Society of Japan, 52 (4): 177-181. doi: 10.5702/massspec.52.177 Tazoe, H., Obata, H., Amakawa, H., et al., 2007. Precise determination of the cerium isotopic compositions of surface seawater in the Northwest Pacific Ocean and Tokyo Bay. Marine Chemistry, 103 (1-2): 1-14. doi: 10.1016/j.marchem.2006.05.008 Yang, H. M., Duan, G. L., Ling, W. L., 2009. A certificating study on La-Ce rock reference material and Ce isotopic standard solution. Geochimica, 38 (2): 179-186 (inChinese with English abstract). Zhang, Z. C., Wang, F. S., 2003. Sr, Ndand Pbisotopic characteristics of Emeishan basalt province and discussion ontheir source region. Earth Science—Journal of China University of Geosciences, 28 (4): 431-439 (in Chinese with English abstract). 胡圣虹, 陈爱芳, 林守麟, 等, 2000. 地质样品中40个微量、痕量、超痕量元素的ICP-MS分析研究. 地球科学———中国地质大学学报, 25 (2): 186-190. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200002014.htm 李志昌, 方向, 刘文贵, 2002. La-Ce法与Ce同位素地球化学. 武汉: 中国地质大学出版社. 刘丛强, 解广轰, 增田彰正, 1995. 中国东部新生代玄武岩的地球化学(Ⅱ): Sr、Nd、Ce同位素组成. 地球化学, 24 (3): 203-214. doi: 10.3321/j.issn:0379-1726.1995.03.001 杨红梅, 段桂玲, 凌文黎, 2009. La-Ce法岩石标准物质和Ce同位素标准溶液研制. 地球化学, 38 (2): 179-186. doi: 10.3321/j.issn:0379-1726.2009.02.011 张招崇, 王福生, 2003. 峨眉山玄武岩Sr、Nd、Pb同位素特征及其物源探讨. 地球科学———中国地质大学学报, 28 (4): 431-439. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200304012.htm