单词 | thorium lead |
释义 | > as lemmasthorium lead thorium lead n. (a) the isotope lead 208, which is the final decay product of the series of radioactive transformations beginning with the common isotope of thorium; (b) used attributively (with hyphen) to designate a method of isotopic dating, and results obtained with it, based upon measurement of the relative amounts in rock of thorium 232 and its ultimate decay product, lead 208. ΘΚΠ the world > matter > chemistry > experiments > [noun] > scientific method > of isotopic dating thorium lead1914 potassium–argon1953 the world > matter > chemistry > elements and compounds > metals > specific elements > thorium > [noun] > final decay product of thorium lead1914 1914 London, Edinb., & Dublin Philos. Mag. 6th Ser. 28 827 It may be concluded with reasonable certainty [though erroneously] that thorium lead is unstable. 1946 F. E. Zeuner Dating Past x. 319 The thorium-family begins with the element thorium (atomic weight 232). In the course of its disintegration, 6 atoms of helium are given off, and thorium-lead remains. 1955 Bull. Amer. Geol. Soc. 66 1141/2 The low thorium-lead age for the zircon could have been the result of addition of thorium to the mineral. 1955 Bull. Amer. Geol. Soc. 66 1141/2 The analysis..demonstrates that small amounts of uranium lead and major amounts of thorium and thorium lead are very loosely bound, chemically. 1971 I. G. Gass et al. Understanding Earth ii. 46/1 (heading) Uranium-lead.., lead-lead..and thorium-lead..methods. < as lemmas |
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