Potassium-argon dating: Method for determining the age of igneous rocks based on the amount of argon-40 in the rock.
钾-氩年代测定法： 根据岩石内氩-40的含量来测定火成岩形成年代的方法。
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Because a radioactive form of argon is produced by decay of a naturally occurring radioactive potassium isotope, it can be used to date rocks and samples more than 100,000 years old.