Study on the Method for Quartz Purification and Separation of Cosmogenic ¹⁰Be and ²⁶Al in Samples from Fluvial Terraces

In situ produced ¹⁰Be and ²⁶Al in fluvial terrace samples that have been repeatedly buried and exposed to the evolution process are difficult to separate using conventional methods. Based on prior experiments, ¹⁰Be in carbonate, iron-bearing mineral and ¹⁰Be produced in the atmosphere were separated by manual hand picking, magnetic separator sorting and acid washing methods, improving the procedure of purifying the quartz samples. The results show that anion exchange column, with a length of 9 cm and inner diameter of 1cm, matched 4 mol/L hydrofluoric acid leachate, can effectively separate B, Mg, Ca, Cr, Fe, Mn, Ni, Ti and Mn. The recoveries of Be and Al are 95.7% and 85.7%, resepectively. Be and Al can be separated by ion exchange very well which have recoveries up to 85%. The procedure blanks are 2.19×10^-15 and 1.63×10^-15 for ¹⁰Be/⁹Be and ²⁶Al/²⁷Al, respectively which are comparable with other labs. The exposure ages of Chengdu Plain alluvial elements are 76.36±9.51 ka for ¹⁰Be and 69.44±14.13 ka for ²⁶Al, which provides a chronological basis for evaluating the structural features and activities of buried faults in the front of the Longmenshan.