原地宇宙成因核素测年中石英样品分离提纯的几组实验对比

CONTRAST OF SEVERAL EXPERIMENTS OF QUARTZ ISOLATION AND PURIFICATION FOR COSMOGNEIC DATING

原地宇宙成因核素测年方法在地质及地理研究领域应用广泛,测年对象众多。石英因其致密的晶体结构不易被大气成因10Be污染,以及较低的27Al含量的特点而成为宇宙成因核素测年方法中一种理想的测年物质。在分离石英样品10Be和26Al的实验流程中,石英的提纯是其中的一个关键环节。原始的HCl/H2O2和HF/HNO3蚀刻分离提纯石英方法应用广泛、安全可靠,但处理样品周期长、效率较低。因此,在原始流程的基础上,设计了3组实验流程与原始流程进行对比。结果显示,在样品石英纯度较高的基础上,可以通过减少超声波使用时间、增加蚀刻溶液浓度及每步样品处理量的方法,提高样品的处理效率,同时可以用加热磁力搅拌器替代超声波清洗器进行石英样品的HF/HNO3蚀刻提纯。

Cosmogenic dating（in situ cosmogenic nuclides）has been widely used in geologic and geographic domain along with the application of accelerator mass spectrometry（AMS）and highly sensitive conventional noble-gas mass spectrometry in the early 1980s,since Raymond Davis and Oliver Schaffer proposed that cosmogenic nuclides produced within minerals at the surface of the earth could be applied to geological problems.At present,this dating method is used to study glacier,desert and relief evolution,volcano development and active structure movement etc.There are a lot of materials which can be used in cosmogenic dating method.Because of its tight crystal structure,quartz can minimize possible contamination by meteoric10 Be,and also for its low 27Al content,it becomes an ideal material for cosmogenic dating method.During the process of the isolation of 10Be and 26Al from quartz sample,quartz isolation and purification are one of the key steps.HCl/H2O2 and HF/HNO3 leaching is a safe method used to isolate and purify the quartz samples widely.However,there is defect about the method.It takes more time for sample preparation and curtails the life of instrument.Based on the above method,three experiments were designed to compare with the primary one.The results of experiment reveal that the purification efficiency can be enhanced by increasing the leaching solution concentration and the amount of sample,and ultrasonic cleaner can be replaced by hotplate /magnetic stirrer.