从1789年铀被发现以来,天然铀的三个同位素(1907年发现 ~(238)U 和 ~(234)U,以及1935年发现 ~(235)U)组成比例在长期内一直被认为是“永恒不变”的(这里不讨论在地质历史时期内仅由于放射性衰变而引起的变化),因而是很好的地质时间标志。1953年契尔登采夫和恰洛夫等人经过了对大量的铀次生矿物和天然水中铀同位素的 Since the discovery of uranium in 1789, the compositional proportions of the three isotopes of natural uranium (~ 238 U and ~ 234 U found in 1907 and ~ 235 U in 1935) have long been considered “Immutable” (not talking about changes that are only caused by radioactive decay during geological history) and are thus good geologic time markers. In 1953, Kirtundsev and Chalok et al. Passed a large amount of uranium secondary minerals and uranium isotopes of natural water