英语语法分析

These rocks have been dated radiometrically at two billion years old.

经辐射能探测，这些岩石形成于20亿年前。

《牛津词典》

The Lubaka tuff does not contain minerals that can be dated radiometrically.

路贝卡凝灰岩并不包含能通过放射性来确定年代的矿物质。