迷坝花岗岩位于甘肃东部的康县和陕西略阳交界处的迷坝一带。用Maniar的主元素判别法判定它为造山后花岗岩类(POG型)。角闪石和黑云母的~(40)Ar/~(39)Ar测年结果表明其侵位时代为239～229 Ma,是印支期岩浆活动的产物。在193.8Ma左右的早燕山期受到一次原因不明的热事件影响,导致了岩体中黑云母的氩同位素系统部分开放。 Mi dam granite is located in the eastern part of Gansu Kangxian and Shaanxi Lanyang junction dam dam area. It is judged as a post-orogenic granite (POG) by Maniar’s principal element discriminant method. The ~ (40) Ar / ~ (39) Ar dating of amphiboles and biotites indicates that the emplacement age is 239 ~ 229 Ma, which is the product of Indosinian magmatism. During the early Yanshanian period of about 193.8Ma, an unidentified thermal event was affected, resulting in the partial opening of biotite’s argon isotope system in the rock mass.