ISSN 1002-1027　　CN 11-2952/G2

### The Principle and Geological Application of Unspiked K-Ar Dating

LEI Yongliang, MU Zhiguo, HUANG Baoling, MIAO Guojun

1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Department of Geology, Peking University, Beijing, 100871
• Received:2002-10-10 Online:2003-11-20 Published:2003-11-20

Abstract: Precise measurement of Argon is considered to be one of the most important geochronological subjects in K-Ar dating of young volcanic materials. Based on the presumption that 40Ar/36Ar ratio is equal to 295.5 during conventional K-Ar dating, it has been studied that dating was constrained in some cases, especially for young samples. A technique of unspiked Argon measurement has been improved and applied in recent years. The merits for this method are that argon will not be contaminated by spike 38Ar systematically, thus, the contents of 40Ar, 38Ar and 36Ar will be measured by calibrating with standard atmosphere. Considering the interference of mass fractionation of argon in volcanic rocks, it is allowed to calibrate 40Ar/36Arratio with 38Ar/36Ar ratio of the sample. Therefore, radiogenic 40Ar* and age of sample will be calculated accurately. At present, unspiked K-Ar dating has been widely used in geological researches. It is able to acquire reliable ages including late Tertiary and Quaternary to interpret the geological events and reconstruct the magmatic history. It implies that, for K-Ar chronology, a powerful means and approach will be used to study volcanic rock younger than late Tertiary by introducing the principle and geological application of unspiked K-Ar dating.