So if you get an ore of the right type of radioactive element, and you wait millions and millions (or even billions) of years, you make a giant underground store of helium !
Lead isotope research shows that lead in ores of Mujiazhuang copper deposit and near ore country rocks is characterized by being rich in radioactive lead.
铅同位素结果研究表明，穆家庄铜矿矿石铅和近矿围岩岩石铅具有富含放射性成因铅的特点。
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By surveying the data, we concluded that the radioactive element contents are higher in the alteration zone, middle in the mixed granite and lower in the ore veins.