用钾-氩法求地质事件真实年龄的方法探讨

钾-氩法所测出的地质事件的表面年龄一般小于地质事件发生的真实年龄,其中很多没有地质意义。本文利用随机过程理论,在对地质体内⁴⁰Ar的逸散作用进行分析的基础上,推导出如下年龄计算公式: 在一定条件下,利用这些公式,可以据钾-氩法测试资料求出地质体形成时代t+t⁰、热扰动结束时代t⁰及热事件所持续的时期t’。据所导出的公式,对冀东迁西群地层的年龄进行讨论,求得2500Ma左右结束的那期热事件所持续的时期t’为4.76亿年,迁西群形成时代为3000—3300Ma。检验表明,公式有效。

NEW FORMULAE TO CALCULATE THE REAL AGE OF GEOLOGICAL EVENT BY POTASSIUM-ARGON DATING

Potassium- argon dating gives an age that is often less than the real age of a geological event according to the following formula:There is no other reported potassium-argon dating method that can be used to calculate the real ages of most geological events.New formulae are developed in this paper by using stochastic processes theory to analyse the argon spreading process during a geothermal event, they are:These formulae give the real age of the studied geologic body, t t(0), the age of gecthermal event, t(0), and the time t' which shows how long the geothermal event proceeded by measuring the potassium-argon isotopes.New formulae are proved to be efficient when used in east Hebei Province to calculate the age of rocks in Qianxi group which is the oldest strata in China. The new calculating ages are ranged between 3000Ma - 3300Ma,and t' is equal to 476 Ma.