暴露测年样品中26Al和10Be分离及其加速器质谱测定

摘要

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 l0Be and 26A1 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 HC1 to elute Al. The results of AcceleratorMass Spectrometry (AMS) show that the average for Be/ Be and 26Al/27 Al 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.%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/9 Be和26Al/27Al比值平均值分别为7.48×1O -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.