Basalts lead isotopes

It is shown in Fig. 2.57 that the lead isotopic variation of the Besshi-subtype is similar to that of midoceanic ridge basalt, suggesting the lead in the Besshi-subtype was derived from mantle. The data from the Shimokawa, and Yanahara deposits (Group B) are slightly more radiogenic than Group A, suggesting that crustal lead was involved in the formation of the Shimokawa deposit, and lead isotopic values for the Shimokawa and Yanahara plot between MORB and Cretaceous-Tertiary deposits in Japan (Kuroko, skarn, vein-type deposits). 

O Hara MJ (1968) The bearing of phase equilibria studies in synthetic and natural systems on the origin and evolution of basic and ultrabasic rocks. Earth Sci Rev 4 69-133 O Nions RK, McKenzie D (1993) Estimates of mantle thorium/uranium ratios from Th, U and Pb isotope abundances in basaltic melts. Phil Trans Royal Soc 342 65-77 Oversby V, Gast PW (1968) Lead isotope compositions and uranium decay series disequilibrium in reeent volcanic rocks. Earth Planet Sci Lett 5 199-206... 

Figure 8. ° Pb7 Pb vs. Th/Us (derived using Eqn. 5 in the text) diagram for mid-ocean ridge and ocean island basalt based on a recent data set with mostly mass spectrometry measurements (Turner et al. 1997 Bourdon et al. 1996 Dosso et al. 1999 Claude-lvanaj et al. 1998, 2001 Sims et al. 2002). The data show a relatively well defined array that intersect a closed-system hne for the bulk Earth starting with an initial lead isotope composition equal to Canyon Diablo (T = 4.55 Ga). This intersect was used by Allegre et al. (1986) to define the Th/U ratio of the Earth.

Sarda, P., Moreira, M., Staudacher, Th. (1999) Argon-lead isotope correlation in mid-Atlantic Ridge basalts. Science, 283, 666-9. 

Schiano P., Birck J.-L., and Allegre C. J. (1997) Osmium-strontium-neodymium-lead isotopic covariations in midocean ridge basalt glasses and the heterogeneity of the upper mantle. Earth Planet. Sci. Lett. 150, 363-379. 

Burnard P. (1999) Origin of argon-lead isotopic correlations in basalts. Science 286, 871. 

Sarda P., Moreira M., and Staudacher T. (1999) Argon—lead isotopic correlation in Mid-Atlantic ridge basalts. Science 283, 666-668. 

Brimhall et al. (1991) used lead isotopes in zircons within a bauxite profile from Western Australia to differentiate between zircons derived from the underlying bedrock and zircons of eolian origin. Borg and Banner (1996) applied both neodymium and strontium isotopes to constrain the sources of soil developed on carbonate bedrock. Using these isotopes and Sm/Nd ratios, they were able to delineate the importance of atmospheric versus bedrock contributions in controlling the composition of the soil. Kurtz et al. (2001) used neodymium and strontium isotopes to determine the amount of Asian dust in a Hawaiian soil chronosequence. They found that the basaltic bedrock isotope signatures in soils had, in many cases, been completely overprinted by dust additions, demonstrating the profound effect of Asian dust on soil nutrient supplies. 

Muller and colleagues identified four major rock units in the potential homelands of the Iceman on the basis of strontium and lead isotope ratios (Fig. 9.9). These include Eocene basalts (ca. 0.705-0.708), Mesozoic limestones (ca. 0.710-0.714), and Permian volcanics (ca. 0.717-0.719), and a mixed unit of phyllites and gneisses (ca. 0.720-0.724). These last two geological units overlap slightly in their isotope ratios. Strontium isotope ratios in the enamel of the Iceman averaged 0.721 and values in bone were approximately 0.718. These values are most congruent with the... 

Sarda P, Moreira M (2002) Vesiculation and vesicle loss in mid-ocean ridge basalt glasses He, Ne, Ar elemental fractionation and pressure influence. Geochim Cosmochim Acta 66 1449-1458 Sarda P, Moreira M, Standacher T (1999a) Argon-lead isotopic correlation in Mid-Atlantic Ridge basalts. 

Sarda P, Moreira M, Standacher T (1999b) Response Origin of argon-lead isotopic correlation in basalts. 

Vidal Ph. and Clauer N., 1981, Pb and Sr isotopic systemadcs of some basalts and sulfides from the East Pacific Rise at 2rN (project RITA). Earth Planet. Sci Lett., SS, 237-246. Vitrac A.M., Albarede F. and Allegre C.J., 1981, Lead isotopic composition of Hercynian. granidc K-feldspars constrains condnental genesis. Nature, 291, 460-464. 

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