238U/230Th disequilibrium measurement for volcanic standard rock samples using a multiple-collector ICPMS.
238U/230Th disequilibrium measurement for volcanic standard rock samples using a multiple-collector ICPMS.
复制标题
使用多接收器 ICPMS 对火山标准岩石样品进行 238U/230Th 不平衡测量。
DOI：
10.2343/geochemj.36.465
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发表时间：
2002
影响因子：
0.8
通讯作者：
S. Nakai
中科院分区：
文献类型：
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作者：
S. Fukuda;S. Nakai
采用多收集器电感耦合等离子体质谱仪（MC-ICPMS）对日本地质调查局和美国地质调查局分布的火成岩进行了238U和230Th放射性不平衡测量。我们改进了样品溶解和Th分离方法，以及Nakai et al.（2001）描述的MC-ICPMS Th同位素分析方法。ICP-MS的高灵敏度使我们能够分析小于10 ng的Th。铀和钍的丰度采用同位素稀释法测定，用235U贫铀试剂和230Th作为峰值，提取天然铀。测定238U/232Th丰度比的精度约为2%。该方法应用于火成岩标准岩样（238U/230Th）放射性不平衡测量。发现年龄超过350 Ka的样品达到长期平衡，表明我们分析的准确性。另一方面，发现年轻火成岩标准岩相对于230Th富集238U， （238U/230Th）活度比bbbb1，这在俯冲带火成岩中是常见的。
The radioactive disequilibrium measurements between 238U and 230Th with a Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) were applied to igneous standard rocks distributed by Geological Survey of Japan and Geological Survey of the United States. We modified sample dissolution and Th separation method, as well as Th isotope analysis by MC-ICPMS described by Nakai et al. (2001). High sensitivity of our ICP-MS enabled to analyze less than 10 ng Th. The abundances of U and Th were determined by an isotope dilution method, using a 235U depleted uranium reagent and 230Th prepared by milking of natural U as spikes. We can determine 238U/232Th abundance ratio with a precision of about 2%. This procedure was applied to (238U/230Th) radioactive disequilibrium measurements of igneous standard rock samples. Samples older than 350 Ka were found to attain secular equilibrium, indicating the accuracy of our analysis. On the other hand, young igneous standard rocks were found enriched in 238U relative to 230Th, (238U/230Th)activity ratio > 1, which is often observed for igneous rocks from subduction zones.
Hirata, T.：“使用多收集器感应耦合等离子体质谱法结合改进的质量辨别效应外部校正方法进行铅同位素分析。”
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