Ulrych T J
Science. 1967 Oct 13;158(3798):252-6. doi: 10.1126/science.158.3798.252.
A modified form of a model proposed by Gerling and Shukolyukow is used to study the development of lead isotopic ratios in oceanic basalts. This modified model yields an age for the earth which is calculated to be 4530 +/- 40 million years. The significance of this calculation is that it is independent of the knowledge of the ages of the samples studied. It is also found that although the source of the basalts is not generally homogeneous, the differentiation of this source from a closed system has occurred fairly recently geologically. The oldest time for the differentiation, 1230 +/- 350 million years ago, has been found for Mid-Atlantic tholeiites.
采用Gerling和Shukolyukow提出的模型的一种改进形式来研究大洋玄武岩中铅同位素比率的演变。这个改进后的模型得出地球年龄为45.3亿±4000万年。该计算结果的重要意义在于它不依赖于所研究样本的年龄知识。还发现，尽管玄武岩的源区一般并非均一，但从地质角度来看，该源区从封闭系统中的分异作用是在较近时期发生的。已发现大西洋中部拉斑玄武岩的最古老分异时间为12.3亿±3.5亿年前。
