LA-ICP-MS标准锆石原位微区U-Pb定年及微量元素的分析测定

    In situ U-Pb dating and trace element determination of standard zircons by LA-ICP-MS

    • 摘要: 利用长安大学成矿作用及其动力学实验室Agilent 7700X四极杆等离子体质谱(ICP-MS)和Photo Machines AnalyteExcite 193nm激光,在激光频率为5Hz,束斑直径为35μm条件下,对91500、GJ-1、Plešovice和Qinghu 4个标准锆石进行了原位微区U-Pb同位素和微量元素测定。结果显示,91500标准锆石20个测试点的206Pb/238U年龄范围为1059~1070Ma,206Pb/238U年龄加权平均值为1063.8±6.6Ma;GJ-1标准锆石28个测试点的206Pb/238U年龄范围为601~610Ma,206Pb/238U年龄加权平均值为605.4±3.0Ma;Plešovice标准锆石28个测试点的206Pb/238U年龄范围为336~341Ma,206Pb/238U年龄加权平均值为338.8±1.4Ma;Qinghu标准锆石40个测试点的206Pb/238U年龄范围为158~165Ma,206Pb/238U年龄加权平均值为159.9±0.7Ma。上述结果表明,91500、GJ-1、Plešovice和Qinghu 4个标准锆石的206Pb/238U年龄都在误差范围内,且年龄加权平均值与前人报道的年龄在误差范围内一致。同时,4个标准锆石的微量元素结果基本落在前人文献报道的范围内。从4个标准锆石的稀土元素球粒陨石标准化曲线可以看出,稀土元素的相对含量较准确。以上结果表明,建立的测试方法实现了对锆石原位微区U-Pb定年及微量元素的同时测定,分析数据结果准确、可靠。

       

      Abstract: The age and trace elements of 91500, GJ-1, Plešovice and Qinghu standard zircons were analyzed simultaneously by using Agilent 7700X inductively coupled plasma-mass spectrometry (ICP-MS) and Photo Machines Analyte Excite 193nm laser ablation at the laboratory of mineralization and dynamics, Chang'an University, with the laser frequency being 5Hz and laser ablation spot size being 35μm. According to the results obtained, the 206Pb/238U age range of 20 test points of 91500 zircon is between 1059Ma and 1070Ma, and its weighted average of 206Pb/238U age is 1063.8±6.6Ma; the 206Pb/238U age range of 28 test points of GJ-1 zircon is between 601Ma and 610Ma, and its weighted average of 206Pb/238U age is 605.4±3.0Ma; the 206Pb/238U age range of 28 test points of Plešovice zircon is between 336Ma and 341Ma, and its weighted average of 206Pb/238U age is 338.8±1.4Ma; the 206Pb/238U age range of 40 test points of Qinghu zircon is between 158Ma and 165Ma, and its weighted average of 206Pb/238U age is 159.9±0.7Ma. The results show that the 206Pb/238U age ranges of four standard zircons 91500, GJ-1, Plešovice and Qinghu are in accordance with the recommended values within reasonable error range, and the weighted average age shows an excellent agreement with the previously reported data. All the trace element compositions of four standard zircons fall into the range of the literature available. Chondritenormalized REE distribution curves of these standard zircons show that the relative content of rare earth elements obtained is accurate. The above results show that in situ U-Pb dating and trace element determination of zircon can be carried out by using the method established in this study, and the results are accurate and reliable.

       

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