Science. 1966 Sep 2;153(3740):1094-101. doi: 10.1126/science.153.3740.1094.
The isotopic compositions of lead and the concentrations lead, uranium, and thorium in samples of oceanic tholeiite and alkali suites are determined, and the genetic relations of the oceanic basalts are discussed. Lead of the oceanic tholeiites has a varying lead-206: lead-204 ratio between 17.8 and 18.8, while leads of the alkali basalt suites from Easter Island and Guadalupe Island are very radiogenic with lead-206: lead-204 ratios between 19.3 and 20.4 It is concluded that (i) the isotopic composition of lead in oceanic tholeiite suggests that the upper mantle source region of the tholeiite was differentiated from and original mantle material more than 1 billion years ago and that the upper mantle is not homogeneous at the present time, (ii) less than 20 million years was required for the crystal differentiation within the alkali suite from Easter Island, (iii) no crustal contamination was involved in the course of differentiation of rocks from Easter Island; however, some crustal contamination may have affected Guadalupe Island rocks, and (iv) alkali basalt may be produced from the tholeiite in the oceanic region by crystal differentiation. Alternatively the difference in the isotopic composition of lead in oceanic basalts may be produced by partial melting at different depths of a differentiated upper mantle.
测定了大洋拉斑玄武岩和堿性套岩样品中的铅同位素组成和铅、铀、钍浓度，并讨论了大洋玄武岩的成因关系。大洋拉斑玄武岩的铅具有在 17.8 到 18.8 之间变化的铅-206:铅-204 比值，而 Easter Island 和 Guadalupe Island 的堿性玄武岩套的铅则非常具有放射性成因，铅-206:铅-204 比值在 19.3 到 20.4 之间。结论是：（i）大洋拉斑玄武岩中的铅同位素组成表明，拉斑玄武岩的上地幔源区是在 10 亿年前从原始地幔物质中分化出来的，目前上地幔不是均匀的；（ii）Easter Island 的堿性套岩的晶体分异过程只需要不到 2000 万年的时间；（iii）Easter Island 岩石的分异过程没有涉及地壳污染；然而，一些地壳污染可能影响了 Guadalupe Island 岩石；（iv）碱性玄武岩可能是由海洋地区的拉斑玄武岩通过晶体分异产生的。或者，大洋玄武岩中铅的同位素组成的差异可能是由分化的上地幔在不同深度的部分熔融产生的。
