Radiogenic isotopes

Lead isotopes. Sato and Sasaki (1973) concluded on the basis of a remarkable narrow range in lead isotopic composition of Kuroko ores that lead of Kuroko ore came from deep-seated source which originated from subducting pelagic sediments. 

Lead isotopic data on Kuroko deposits, vein-type deposits in Honshu and volcanic rocks are summarized and plotted in Fig. 1.44 (Fehn et al., 1983). 

Strontium isotopes. Strontium isotopic compositions ( Sr/ Sr) of anhydrite, gypsum and barite from Kuroko deposits are summarized in Fig. 1.45 (Farrell et al., 1978 Honma and Shuto, 1979 Farrell and Holland, 1983 Yoneda et al., 1993 Yoneda and Shirahata, 1995). Sr/ Sr values of anhydrite and gypsum are slightly lower than that of seawater, suggesting that most of the strontium was derived from seawater, but a small amount of 

Isotopic composition of leads from Kuroko deposits (Fehn et al., 1983) 

Sample number Field number 206pb/204pb 207pb/204pb 208pb/204pb 

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Lead occurs naturally as a mixture of four non-radioactive isotopes, and Pb, as well as the radioactive isotopes ° Pb and Pb. All but Pb arise by radioactive decay of uranium and thorium. Such decay products are known as radiogenic isotopes. 

Analytical solutions. Following the approach of Spiegelman and Elliott (1993), the effects of transport of melt through a melting column on the chemistry of radiogenic isotopes can be separated from melting by expressing the concentration of an element as ... 

Despite the uncertainty about the rate of incorporation of °Thxs into Mn deposits, Th chronology can still provide some useful information about their growth rates. For instance, °Thxs has been used to suggest short-term changes in growth rates of Mn crusts (Eisenhauer et al. 1992) and to check the Be chronologies of crusts used to reconstruct the radiogenic isotope history of seawater (Abouchami et al. 1997 Frank 2002). 

Paradis, S., Turner, W.A., Coniglio, M., Wilson, N. Nelson, J.L. 2006. Stable and radiogenic isotopic signatures of mineralized Devonian carbonates of the Northern Rocky Mountains and the Western Canada Sedimentary Basin. In Hannigan, P.K. (ed) Potential for carbonate-hosted lead-zinc Mississippi Valley-type mineralization in northern Alberta and southern Northwest Territories Geoscience Contributions,... 

In K-Ar or zircon U-Pb dating, modeling the loss of radiogenic isotopes by volume diffusion is important. If P0 is the local concentration at t = 0 of a radioactive element decaying with constant X, a source term exists in the transport equation of the radiogenic element which is the local rate of accumulation AP0e Xt. For dual decay,... 

Let us consider in the first place the total concentration N = C + P0e M of radioactive and radiogenic isotopes. Since there is no loss of the radioactive isotope, the variation of N equals the loss of the radiogenic isotope. In other words... 

The same derivation as that used for the accumulation of radiogenic isotope in a slab would lead to the solution but we will take advantage of this case to fully develop an application of Duhamel s principle (Appendix 8C). The assumption of zero initial and surface concentration of the radiogenic isotope is equivalent to... 

An example can be found in the section dealing with the diffusion of radiogenic isotope out of a sphere. 

White, W. M. (1985). Sources of oceanic basalts radiogenic isotopic evidence. Geology,... 

So far, second-order corrections have only found their application for radiogenic isotopes (see a more extensive treatment in Albarede et al. 2004). The linear changes in the apparent mass bias of Nd with mass observed by Vance and Thirlwall (2002) is certainly an indication that high precision may benefit from such an elaborate scheme on at least some instruments. 

Figure 9. Plots of Li and radiogenic isotopes for mantle rocks, (a) 5 Li vs. Sr/ Sr (b) 5 Li vs. Nd/ Nd (c) "Sr/ Sr vs. Pb/ Pb (d) 5"Li vs. Pb/ Pb (Nishio et al. 2003, 2004). Symbols + = south Pacific island basalts (six islands) O = Iherzolite xenolith, Bullenmerri, Australia = Iherzolite xenolith, Sikhote-Alin, Russia (three localities) A = dunite-peridotite-pyroxenite xenolith, Kyushu, Japan (two localities) V = Iherzolite xenolith, Ichinomegata, Japan. The ocean island data are from bulk rocks, the xenolith data are clinopyroxene separates. For explanations of the derivation of radiogenic isotope fields (DM, EMI, EM2, HIMU), see Zindler and Hart (1986). The estimate for Li isotopes in DM is based on MORE. The Li isotopic ranges for the other mantle reservoirs are based on Nishio et al. (2004) and Nishio et al. (2003), but these will require further examination (hence the use of question marks).

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