A synthetic element produced in trace quantities by helium isotope bombardment of curium.

锎一种合成元素，由氦同位素轰击锔可得到微量的这种元素。

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These minerals can be dated by radioactive decay techniques because of the very small quantities of radioactive trace elements they, in turn, contain.

这些矿物可以用放射性衰变技术测定年代，因为它们所含的放射性微量元素非常少。

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The rest of the chemical elements occur in only minor or trace quantities.

其余的化学元素仅以少量或微量出现。

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Trace quantities of vitamins occupy the same essential phenomenological niche in our food that trace amounts of rare earths occupy in our technologies.

FORBES: Tech's Mineral Infrastructure - Time to Emulate China's Rare Earth Policies