暴露测年样品中26Al和10Be分离及其加速器质谱测定

在已有实验流程基础上,建立并优化了石英样品中Be和Al提取、纯化等实验流程,设计的流程条件实验包括实验试剂、器皿和离子交换柱选择、离子交换树脂分离Be和Al时酸浓度选择等。结果表明,选择钢铁研究总院研制的⁹Be标准溶液作为¹⁰Be样品制备的载体;使用一次性实验器皿;选用4 cm规格的离子交换柱;用0.05 mol/L草酸和0.75 mol/L盐酸混合溶液洗脱吸附于阴离子树脂上的Al,可有效提取、纯化样品中的Be和Al。加速器质谱(AMS)测量结果显示,13组化学空白的¹⁰Be/⁹Be和²⁶Al/²⁷Al比值平均值分别为7.48×10^-15和1.96×10^-15,与国内已有宇宙成因核素实验室的结果(5×10^-15~8×10^-15)具有可比性。电感耦合等离子体发射光谱(ICP-AES)的测量结果表明,Be、Al回收率分别达90%和60%。基于新建立的实验流程分析了祁连山北侧金佛寺的一个岩石样品,获得了¹⁰Be和²⁶Al的暴露年代分别为(10.7±1.0) ka和(10.0±1.2) ka,与前人研究结果一致。

The Extraction of in-situ 10Be and 26Al from Rock Sample and Accelerator Mass Spectrometric Measurements

With the development of accelerator mass spectrometry, a variety of long-lived cosmogenic nuclides, especially the in-situ cosmogenic nuclides ¹⁰Be and ²⁶Al, are increasingly applied to earth sciences. Based on published procedures, a modified procedure for ¹⁰Be and ²⁶Al exposure dating has been developed, which includes ¹⁰Be and ²⁶Al extraction, anion exchange column separation, purification and target preparation. In this procedure, NCS ⁹Be was chosen instead of Merck and Fluka as the carrier for the ¹⁰Be sample, with a small amount of ion exchange resin instead of a large one. In particular, the elution curve for an anion exchange column procedure by Purdue University was modified as 0.05 mol/L H₂C₂O₄-0.75 mol/L HCl to elute Al. The results of Accelerator Mass Spectrometry (AMS) show that the average for ¹⁰Be/⁹Be and ²⁶Al/²⁷Al of thirteen chemical blanks were 7.48×10^-15 and 1.96×10^-15, respectively, as low as those of other AMS laboratories. The ICP-AES results indicated the recoveries of Be and Al were 90% and 60%, respectively. One sample from Jinfosi Site, North of Qilian Shan Mountain, was tested based on this new procedure. The dating results of (10.7±1.0) ka for ¹⁰Be and (10.0±1.2) ka for ²⁶Al, were consistent with published geological results.