Acta Scientiarum Naturalium Universitatis Pekinensis

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

LIU Yulin1, JIN Xiaohong2, LEI Yongliang1, MIAO Guojun1, HUANG Baoling1   

  1. 1The Key Laboratory of Orogenic Belts and Crustal Evolution, Department of Geology, Peking University, Beijing, 100871; 2Hainan Institute of the Geological Integrated Survey, Haikou, 570206
  • Received:2003-01-20 Online:2004-03-20 Published:2004-03-20


刘玉琳1, 金小鸿2, 雷永良1, 苗国均1, 黄宝玲1   

  1. 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

Abstract: 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 (0.28~0.18mm) 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%.

Key words: volcanic rocks, preprocessing, K-Ar dating, age correction

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60~80目粒级(0.28~0.18mm)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5 min,对年龄值的矫正可达20%。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%~10%。

关键词: 火山岩, 预处理, K-Ar定年, 年龄值矫正

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