Non-matrix-matched analysis of U-Th-Pb geochronology of bastnasite by laser ablation inductively coupled plasma mass spectrometry
Non-matrix-matched analysis of U-Th-Pb geochronology of bastnasite by laser ablation inductively coupled plasma mass spectrometry
复制标题
激光烧蚀电感耦合等离子体质谱法非基体匹配分析氟碳铈矿U-Th-Pb年代学
DOI：
10.1007/s11430-020-9715-1
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Zhaochu Hu
中科院分区：
文献类型：
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作者：
Tao Luo;He Zhao;Wen Zhang;Jingliang Guo;Keqing Zong;Yongsheng Liu;Junfeng Zhang;Zhaochu Hu
氟碳铈矿广泛存在于碱性花岗岩、碳酸盐岩和稀土矿床中。氟碳铈矿的U-Th-Pb年龄可以制约成矿年龄。目前，缺乏合适的原位分析参考物质是氟碳铈矿U-Th-Pb年代学的主要障碍。本研究以玻璃NIST 610为外标校准参考物，对氟碳铈矿U-Pb和Th-Pb年龄测定的基体效应进行了评价在正常和附加气体激光烧蚀模式下进行 193 nm 准分子 LA-ICP-MS 分析。获得的氟碳铈矿 U-Th-Pb 年龄比正常分析模式（无附加气体）下的参考值低约 7-11%。幸运的是，随着烧蚀室内添加水蒸气，UTh-Pb 测年中确定的系统年龄偏差显着降低（小于 1-2%）。这种降低可能归因于观察到的显着现象。通过在烧蚀室中引入少量水蒸气，抑制~(206)Pb/~(238)U和~(208)Pb/~(232)Th在NIST 610玻璃和氟碳铈矿中的井下分馏。此外，获得氟碳铈矿K-9的~(206)Pb/~(238)U和~(208)Pb/~(232)Th年龄， LZ1384、MAD809与相应的推荐值具有很好的一致性。所得结果表明，在193 nm LA-ICP-MS中以玻璃NIST 610为主要校准标准，采用水蒸气辅助方法，可以同时获得准确、精密的氟碳铈矿U-Th-Pb年龄。这种简单有效的水蒸气辅助非基体匹配激光烧蚀方法有助于促进氟碳铈矿U-Th-Pb年龄的地质应用。地质年代学。
Bastnasite is widespread in alkali granite, carbonatite and REE ore deposits.The U-Th-Pb ages of bastnasite can constrain the mineralization age.Currently, the lack of suitable in situ analysis reference material is the major obstacle of bastnasite U-Th-Pb geochronology.In this study, the matrix effects of U-Pb and Th-Pb age determination in bastnasite using glass NIST 610 as the external calibration reference were evaluated with the 193-nm excimer LA-ICP-MS analysis in normal and additional gases laser ablation modes.The obtained U-Th-Pb ages of bastnasite were approximately 7-11% lower than their reference values in the normal analytical mode(without additional gas).Fortunately, the determined systematic age biases in UTh-Pb dating were significantly reduced(less than 1-2%) with the addition of water vapor within the ablation chamber.This reduction may be attributed to the observed significant suppression of ~(206)Pb/~(238)U and ~(208)Pb/~(232)Th downhole fractionation in both NIST 610 glass and bastnasite by introducing a small quantity of water vapor in the ablation chamber.In addition, the obtained ~(206)Pb/~(238)U and ~(208)Pb/~(232)Th ages of bastnasite K-9, LZ1384, and MAD809 showed great consistency with their corresponding recommended values.The obtained results show that accurate and precise U-Th-Pb ages of bastnasite can be simultaneously obtained by using glass NIST 610 as the primary calibration standard in 193-nm LA-ICP-MS with the water vapor-assisted method.This simple and effective water vapor-assisted non-matrix-matched laser ablation method helps to promote the geological application of bastnasite U-Th-Pb geochronology.