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.