玄武岩全岩元素含量快速、准确分析新技术:双铱带高温炉与LA-ICP-MS联用法

Quick and accurate LA-ICP-MS analyses of major and trace elements in basalt,coupled with glass fusion method by double iridium strip heater

全岩样品主元素和微量元素的准确测试是地球科学研究的重要手段和依据。传统溶液进样ICP-MS元素测试方法制样和测试所需周期较长(两周以上)。相对溶液进样法而言,激光剥蚀系统与ICP-MS联用测试全岩粉末熔融玻璃的方法可以大大地提高测试效率。在前人研究基础上,针对前人熔融制样中Pb、Zn元素的严重丢失问题,研究了Pb、Zn等挥发性元素在熔融过程中的行为,成功改进并研制了一种双铱带高温炉。采用该装置直接熔融全岩粉末样品时,Pb、Zn等挥发性元素的丢失得到了有效抑制。进而结合BIR-1G、BCR-2G和BHVO-2G多玻璃外标、无内标元素校正的方法,建立了双铱带高温炉与LA-ICP-MS联用快速并且同时测试岩石样品中的主元素和微量元素的分析技术。采用该法对国际玄武岩标准物质BHVO-2、BCR-2(USGS)和国内玄武岩标准物质GSR-3(IGEMG)岩石粉末直接熔融(1400℃,80 s)制样,而后利用LA-ICP-MS进行测试。测试结果表明,绝大多数元素测试的准确度优于±10%,精密度优于10%。采用该法熔融制备一个玄武岩样品并完成LA-ICP-MS分析测试仅需15 min,较传统方法极大地提高了测试效率。

Quick and accurate analyses of major and trace elements in rock samples are important for geochemical research. Major disadvantage of the traditional solution-ICP-MS analysis is time consuming, which takes about two weeks to prepare and determine a sample. In order to increase analytical efficiency, some researchers tried to directly analyze fused glass of rock powder by LA-ICP-MS. Based on the previous researches, we propose a modified method to fuse the geological sample without flux by double iridium strip heater, which effectively suppresses the volatilization of Pb and Zn, a major disadvantage of traditional fusing method. Applying multiple reference material （BIR-1G, BCR-2G and BHVO-2G） calibration combined with ablation yield correction, the results of LA-ICP-MS analyses on the fused glasses prepared at 1400 ℃for 80 s, show that measured values of most major and trace elements agree with the preferred values within 5%–10%. Comparing to the traditional method of solution-ICP-MS analysis, this work provides a much more rapid （less than 15 min） way to accurately determine major and trace elements for basalts.