【作者】 李凤春；

【导师】 孙燕； 苏犁；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2010， 硕士

【摘要】 目前常规的激光剥蚀器样品室与等离子体质谱连接的方法是通过一根直径约为3mm的塑料管将激光剥蚀样品与载气混合形成的气溶胶直接送至ICP-MS的炬管,经等离子体质谱仪检测确定样品中各种元素(同位素)的准确含量。由于目前使用的193um激光器剥蚀脉冲频率通常为10Hz,而ICP-MS的信号采集速率快,因此样品分析标准偏差RSD(相对标准偏差)较大,通常接近10%。考虑样品是否能够均匀地由激光样品室运送到等离子体质谱仪炬管是影响样品分析数据精度的关键,本次研究在LA和ICP-MS之间设计添加了一个外置器皿使得LA剥蚀气溶胶可进行适宜体积的积累后再送入ICP-MS,即将LA剥蚀样品向ICP-MS的输送转化为近似连续送样模式。本次研究将不同体积的圆球形和圆柱形玻璃混样器皿在中国地质大学(北京)激光等离子体质谱实验室进行了系统的联机实验,并对不添加混样器皿和将混样器皿加载于New Wave 193um激光器与Agilent 7500a型四级杆等离子体质谱仪之间后的标准样品(NIST 610)测试结果,如轻、中、重质量代表性元素的RSD、CPS值(信号强度计数值),以及等离子体质谱图形态等进行系统分析,综合评价了不同形态和体积混样器皿的优劣。本次研究确定直径30mm、高40mm的圆柱体混样器皿具有较好性能,可使人工合成国际标样NIST610的样品分析标准偏差RSD稳定至5%左右,且样品分析过程中ICP-MS接受信号速度较快,检测灵敏度较高。利用通过加载混样器皿进行仪器性能优化后的中国地质大学(北京)激光等离子体质谱实验室的LA-ICP-MS,对新疆巴楚麻扎塔格碱性基性杂岩体辉长闪长岩中岩浆锆石和新疆榆树沟麻粒岩相变质蛇绿岩地体中石榴二辉麻粒岩中典型变质锆石进行了点状和线状剥蚀取样两组U-Pb年龄测试结果的对比,显示加载30mm、高40mm的圆柱状混样器皿后,点状和线状剥蚀取样的测试结果在误差范围内一致,且榆树沟变质锆石的测试结果与前人进行的该样品中变质锆石SHRIMP U-Pb年龄测定结果也在误差范围内一致。初步研究表明利用加载混样器皿进行优化的LA-ICP-MS,可进行线状浅剥蚀取样方式的锆石U-Pb年龄和微量元素丰度测定,这一测试方法将有效拓展LA-ICP-MS在地学精细研究中的应用,特别是对变质锆石U-Pb年龄和微量元素丰度测定等有重要意义。更多还原

【Abstract】 At present, the conventional device used to link sample chamber of laser ablation and ICP-MS is through a plastic tube whose diameter is about 3mm. The device is used to directly send the aerosol mixed by the laser ablation sample and carrier gas to the torch of ICP-MS. Then ICP-MS detects the exact content of various elements (isotopes) in the sample. Pulse frequency of currently used 193 um laser ablation is usually 10Hz and the ICP-MS signal acquisition rate is fast, so the RSD (relative standard deviation) of the sample analysis is large, usually close to 10%.The key of influencing data accuracy of sample analysis is whether the sample can be uniformly delivered from the laser sample chamber to the torch of ICP-MS. In view of this, I designed to add an external container between LA and ICP-MS in this study. By doing so, the accumulation of appropriate volume of aerosol ablated by LA can be sent to ICP-MS. In this way, the pattern of aerosol delivered to ICP-MS is approximately continuous.The study made spherical and cylindrical glass mixed sample containers of different volume for systematic on-line experiment at the laser plasma mass spectrometer laboratory of China University of Geosciences (Beijing). According to the testing results of standard samples (NIST 610) which were getting from loading non-mixed sample containers and will-mixed sample containers in New Mave193 um laser and Agilent 7500a quadrupole plasma mass spectrometer, such as RSD and cps (signal intensity count) values of light, medium and heavy representative elements and the morphology of plasma mass spectrum, I made a system analysis and evaluated advantages and disadvantages of mixed sample containers of different shape and size. Through making the experiments, I thought the cylinder mixed sample containers with the diameter of 30mm and height of 40mm had good functions which could make RSD of artificial synthesis international standard sample-NIST 610 stably up to 5%. And in the process of sample analysis, ICP-MS had the fast rate of receiving signal and high sensitivity.Using LA-ICP-MS at the laser plasma mass spectrometer laboratory of China University of Geosciences (Beijing) which was optimized by loading mixed sample containers, I did a testing between the Xinjiang Bachumazatage alkaline basic complex body gabbro-diorite igneous zircon and Xinjiang Yushugou granulite facies metamorphism granulite garnet second level typical metamorphism zircon in the ophiolite terrene, and then made a comparison of testing results about punctuate and linear ablation U-Pb age of two samples. It was showed that after loading the cylinder mixed sample containers with the diameter of 30mm and height of 40mm, the testing results of the punctuate and linear ablation sampling were consistent within the error and the testing results of Yushugou metamorphic zircon were consistent with the previous metamorphic zircon SHRIMP U-Pb age testing results carried out in the same samples within the error. Preliminary studies showed that the use of LA-ICP-MS optimized by loading containers, could detect simple linear ablation sampling of zircon U-Pb age and the abundance of trace elements. This kind of testing method will effectively expand the applications of LA-ICP-MS in earth science fine research, especially having significance in detecting metamorphic zircon U-Pb age and the abundance of trace elements.更多还原