Wu Chung-Che, Shen Chuan-Chou, Günther Detlef, Hattendorf Bodo
Jiangsu Key Laboratory of Ocean-Land Environmental Change and Ecological Construction, School of Marine Science and Engineering, Nanjing Normal University, Nanjing 210023, China.
Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich 8093, Switzerland.
Anal Chem. 2024 Aug 6;96(31):12640-12648. doi: 10.1021/acs.analchem.4c01114. Epub 2024 Jul 23.
Here, we present an U-Th dating approach of carbonate speleothems using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) with a detection efficiency of 1-2%. By online addition of a Th-U-U isotope triple spike to the laser-generated aerosol, instrumental mass discrimination and U/Th elemental fractionation could be monitored and corrected. With this approach, the U/U and Th/U activity ratios of a flowstone sample in secular equilibrium could be accurately reproduced as unity with two-sigma uncertainties ±0.053 and ±0.050, respectively. The method was used for the determination of the formation ages of individual layers in natural stalagmites ranging between 210 and 1 thousand years ago (ka). The determined ages corresponded well with those obtained using conventional solution multi collector-ICPMS techniques after isotope separation. Particularly, Holocene stalagmites, as young as 1 ka, could be accurately dated with 2 standard error of ±76 years. This developed microdomain U-Th dating approach thus can be applicable for diverse research areas, such as paleoclimatology, oceanography, geomagnetism, and archeology.
在此，我们展示了一种利用激光烧蚀电感耦合等离子体质谱法（LA - ICPMS）对碳酸盐洞穴沉积物进行铀 - 钍年代测定的方法，其检测效率为1 - 2%。通过在线向激光产生的气溶胶中添加钍 - 铀 - 铀同位素三重标样，可以监测并校正仪器质量歧视和铀/钍元素分馏。采用这种方法，处于长期平衡状态的石笋样品的铀/铀和钍/铀活度比能够被准确重现为1，其2σ不确定度分别为±0.053和±0.050。该方法用于测定自然石笋中单个层的形成年龄，范围在210至1千年前（ka）。测定的年龄与同位素分离后使用传统溶液多接收电感耦合等离子体质谱技术获得的年龄吻合良好。特别是，年龄仅为1 ka的全新世石笋能够以±76年的2倍标准误差被准确测定年代。因此，这种新开发的微区铀 - 钍年代测定方法可应用于多个研究领域，如古气候学、海洋学、地磁学和考古学。
