K-Ar age of young volcanic rocks and excess argon - Binary mixing model and quantitative study of excess argon effect

A binary mixing model for excess argon is suggested in the note. According to this model and the data of excess argon component obtained in our experi ment, a quantitative study of the effect of excess argon on real K-Ar age o f young volcanic rocks is done. The result indicates that the effect of 5% excess argon component in samples on K-Ar age of the samples more than 2 Ma is less than 7.36% and can lead K-Ar age of 0.5 Ma samples to increase by 32.4%, while 1% excess argon component leads K-Ar age of 0.5 Ma samples to increase by 6.26%. Therefore, when pre-processed excess argon component is less than or equal to 1%, K-Ar age of the samples more than 0.5 Ma should b e credible. On this basis we suggest a principal opinion for evaluation of previous K-Ar dating results and propose that the matrix is used to determi ne K-Ar age of young volcanic rocks. For the samples less than 0.2 Ma, in t he case of high excess argon content, even if only 1% excess argon componen t exists in their matrix, it can also greatly affect their K-A age. Thus it must be careful to treat the dating result.