Uranium ocean island basalts

Figure 3 The distribution of neon isotopes in mantle-derived rocks, indicating the presence of an atmospheric component, a radiogenic component adding Ne (produced by neutrons from uranium fission acting on oxygen and magnesium), and a solar component. It is this latter that indicates that gases in the mantle were derived from the capture of solar material in the early history of the Earth. M = MORB (midocean ridge basalts) P = plume or ocean island basalts (OIB) A = atmosphere. Solar neon is represented by the horizontal line at Ne/ Ne = 12.5 MFL is the mass fractionation line. The presence of solar neon in ocean basalts was first identified by Craig and Lupton (Craig H and Lupton JE (1976) Earth and Planetary Science Letters 31 369-385). (Reprinted with permission from Farley and Poreda (1993).

Ocean Basins. The most fundamental rocks upon which to obtain isotopic data are currently the abyssal basalts from oceanic ridges and rises (Tatsumoto, 1966 b) and basalts from islands in open ocean structures such as Hawaii (references in Table 17). The data on abyssal basalts which are given in Table 18 are shown in enclosed areas along with all Hawaiian data in Fig. 18. The isotope ratios are clearly not uniform, although the average of all samples would approach a modern lead within the limits of error that such models may be calculated. The age of origin for the source of abyssal basalts may be quite old, on the order of 1,000 m.y., and there may be little differentiation of uranium relative to lead as Tatsumoto has demonstrated (also see Ulrych, 1967). Tatsumoto has also shown that the Th/Pb is apparently equal to or less than that in the source. 

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