The determination of 238U, 232Th, 147Sm and 4He contents in apatite is the key to the ( U-Th )/He dating. This paper introduces the measurement of 238U, 232Th and 147Sm contents by Inductively Coupled Plasma-Mass Spectrometry ( ICP-MS ) with non-spike method. This method assumes that the abundances of 238U, 232Th, and 147Sm in samples are identical to the natural isotopic abundances. The 238U, 232Th and 147Sm contents were obtained by the 238U, 232Th, and 147Sm natural abundances and total measured U, Th, and Sm contents. In order to test this method, total U, Th and Sm contents of basalt standard and Durango apatite standard were measured and subsequently used as an analytical standard in ( U-Th )/He laboratory. The results show that the obtained total U, Th and Sm contents for basalt standard are consistent with certified values. From the 238U, 232Th, 147Sm and 4He contents of the Durango apatite, ( U-Th )/He was calculated to have an age of 30. 0 Ma, which agreed with the certified age of (31. 02 ±1.01) Ma( lσ ) within uncertainties obtained by McDowell. The above results indicate that this method of measuring 238U, 232Th and 147 Sm contents is feasible. The method is simple and applicable for the labs having no spike.%准确测定238U、232Th、147Sm同位素含量是磷灰石(U-Th)/He同位素定年方法的关键.本文建立了非稀释剂法电感耦合等离子体质谱测定磷灰石中238U、232Th和147Sm同位素含量的测定流程.该方法假定样品中的238U、232Th和147Sm同位素丰度与其自然丰度是一致的,根据238U、232Th和147Sm同位素的自然丰度和测得的样品中总的U、Th和Sm的含量得到样品中238U、232Th和147Sm同位素的含量.对国内玄武岩标准物质和(U-Th)/He定年法的年龄标准物质Durango磷灰石进行了总U、Th、Sm含量的测试,验证流程的可行性,结果表明玄武岩标准物质的测定值与标准值在误差范围内一致,经计算得到该磷灰石的(U-Th)/He年龄为30.0 Ma,与文献获得的该磷灰石(U-Th)/He年龄(31.02±1.01) Ma(1σ)在误差范围内一致,表明本文建立的238U、232Th和147Sm同位素含量的测定流程是可行的.对于没有稀释剂的实验室,该方法简单适用,值得推广应用.
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