激光探针等离子体质谱法(LAM-ICPMS)用于年轻锆石U-Pb定年  

U-Pb isotopic dating of young zircons by laser ablation microprobe-inductively coupled plasma mass spectrometry (LAM-ICPMS)

作　　者：梁细荣[1] 李献华[1] 刘永康[1] 朱炳泉[1] 张海祥[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地球化学》2000年第1期1-5,共5页Geochimica

基　　金：国家杰出青年基金!49725309;中国科学院广州分院1998~1999年测试基金

摘　　要：利用激光探针等离子体质谱（LAM－ICPMS）技术对中生代钻石进行了详细的206Pb／23U定年研究。采用线扫描（Linescan）进样法减小了传统的剥深（Depthprofile）进样法所引起的激光熔蚀分异效应；优化仪器参数可消减ICP－MS对Pb和U的质量歧视效应；测得了精确的206Pb／238U比值及年龄。研究结果表明，均匀颗粒锆石的206Ph／238U比值测量精度为2％～10％，定年精度和准确度优于3％；对大颗粒（100～160μm）及均匀的年轻锆石U－Pb定年可与灵敏的高分辨离子探针（SHRIMP）定年结果相比。A new method of U-Pb isotopic dating for young zircons using Laser Ablation Microprobe-Inductively Coupled Mass Spectrometry (LAM-ICPMS) has been developed. The fractionation of U/Pb during laser ablation sampling was minimized by using a linear scanning method compared to the conventional depth profile method. By optimizing the fore-quadrupole offset voltage, the mass discrimination effect on 206Pb and 238U from ICP-MS was decreased. Precise 206Pb/238U isotopic ratios and ages of four young zircons were successfully measured. For homogeneous single young zircon grains, the 206Pb/238U ratios with precision of 2% ~ 10% (RSD) can be obtained,whilst both precision and accuracy are better than 3%. It can be concluded that, for homogeneous and large (100 ~ 160 μm) young zircons, the U-Pb dating results measured by LAM-ICPMS method can be comparable with that by SHRIMP technique.

关 键 词：激光探针 等离子体质谱 锆石 铀-铅定年 

分 类 号：P597[天文地球—地球化学] P578.941[天文地球—地质学]