原地宇宙成因核素暴露测年方法中石英的提取  

Extraction and Purification of Quartz for in situ Cosmogenic Nuclide Exposure Dating

作　　者：张丽[1,2,3] 武振坤[1,2] 宋少华[1] 常宏[1] 赵国庆[1,2] 

机构地区：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,陕西西安710075 [2]西安加速器质谱中心,陕西西安710061 [3]中国科学院研究生院,北京100049

出　　处：《岩矿测试》2012年第5期780-787,共8页Rock and Mineral Analysis

基　　金：国家重点基础研究发展计划(973计划)项目(2010CB833400);国家自然科学基金项目(41023006)

摘　　要：原地宇宙成因核素10Be和26Al的暴露年龄测定是近年来发展较快的测年技术,已在地学研究中得到广泛应用。该方法需要选用经一系列前处理过程获得的纯净石英作为待测样品,制备成BeO和Al2O3以供加速器质谱仪测量。因此获得高纯度的石英样品,是该测年方法的关键环节之一。本研究在已有报道的石英提纯化学流程的基础上,尝试对流程进行部分优化,通过实验对比不同粒径组分、不同固液比水浴振荡器和滚筒HF-HNO3蚀刻效果,确定使用HF-HNO3(1%或2%,固液比15.0 g/L)滚筒加热法刻蚀样品以去除铝硅酸盐,多钨酸钠重液分离样品中的石英和其他组分。优化的分离纯化流程应用于处理采自祁连山北缘河流阶地含石英的岩石样品,经纯化的石英纯度可达98%以上,Al的含量小于200μg/g,表明采用优化的提取流程获得了高纯度的石英样品,可以满足10Be和26Al暴露测年所需样品要求。^（10）Be and ^（26）Al in situ eosmogenic nuclide exposure dating is a relatively new dating technique, which is widely used in geoscience research. Normally, the BeO and Al2O3 measured by AMS are prepared from purified quartz samples. Therefore, it is key to develop a method to extract pure quartz from rock sampled in fieldwork. Based on the experimental procedure of Kohl and Nishiizumi, a comparison was made for the different etching effects on samples by using heated water bath oscillator and hot-dog machine （roller） with different grain size of 0.25 - 0.50 mm and 0.50 - 1.0 ram. The 1% or 2% HF-HNO3 were applied to dissolve the silicates in the hot- dog roller machine with a solid/liquid ratio of 15. Detailed heavy liquid （sodium polytungstate） separation steps for quartz purification are also described in this paper. The pretreatment method was verified by using quartz from the river area around North Qilian Mountain. The results indicate that SiOz content in the purified quartz is greater than 98% and the A1 content is less than 200 μg/g, by using X-ray Difrraction （XRD） and Inductively Coupled Plasma-Atomic Emission Spectrometry （ICP-AES）. The high purity quartz was obtained by the established pretreatment method which met the requirements for ^（10）Be and ^（26）Al exposure dating.

关 键 词：原地宇宙成因核素 10Be 26Al 石英 提取纯化 

分 类 号：P533[天文地球—古生物学与地层学] O614.21[天文地球—地质学]