火山岩样品的预处理及其对K-Ar年龄值的矫正  

Preprocessing of Volcanic Rocks and Its Influence to Age of K-Ar Dating

作　　者：刘玉琳[1] 金小鸿 雷永良[1] 苗国均[1] 黄宝玲[1] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室和地质学系,北京100871 [2]海南省地质综合勘探院,海口570206

出　　处：《北京大学学报（自然科学版）》2004年第2期189-192,共4页Acta Scientiarum Naturalium Universitatis Pekinensis

基　　金：国家重点基础研究发展规划课题 (2 0 0 1CB4 0 980 7)资助项目

摘　　要：K Ar和Ar Ar法是中、新生代火山岩最有效的测年方法之一 ,合适的粒度和有效的预处理程序对于提高年龄资料的质量至关重要。样品粒度选用 6 0～ 80目粒级 (0 2 8～ 0 1 8mm)既能保证样品的均匀性 ,又可以有效去除大气氩的污染。新鲜火山岩需要用稀硝酸浸泡 ,以去除可能的碳酸盐的影响 ;轻微蚀变的火山岩则须用 6 %氢氟酸浸泡 5min ,对年龄值的矫正可达 2 0 %。用电磁选的方法可以在很大程度上剔除捕虏晶的影响 ,对年龄值的矫正可达 5 %～ 1 0 %。K Ar and Ar Ar dating is one of the best dating method to Mesozoic Cenozoic volcanic rocks. Appropriate size and preprocessing procedure are important for the method to get good data. 60～80 mesh (0 28～0 18?mm)sample size is needed for both the need of homogeneity of a sample and to remove atmospheric argon contamination. Thin nitric acid is used to remove out the carbonatization of fresh volcanic rocks. For slightly altered rocks, 6% hydrofluoric acid is needed to etch the rocks and the age would be change up to 20% comparing to original rocks. Magnetic separation can remove the influence of xenocrysts and its age could lower 5%～10%.

关 键 词：火山岩 预处理 K-Ar定年 年龄值矫正 

分 类 号：P588.1[天文地球—岩石学]