Radiogenic lead isotopes

Isotopic Ratios of Common, Equal Atom and Radiogenic Lead Isotopic Standards, J. Res. Natl. Bur. Stand. Sec. A (1968) 72A, 261-267. 

Radiogenic isotopes, on the other hand, show differences between crust and mantle reservoirs which are a function of long-lived differences in parent/daughter element ratios and indicate the isolation of the reservoirs from one another for long periods of Earth history. This gives rise to crustal reservoirs which generally are enriched in Sr/ Sr and in radiogenic lead isotopes but depleted in Nd/ Nd relative to the mantle. 

Catanzaro, E.J., Murphy, T.J., Shields, W.R., Gamer, E.L. (1968) Absolute isotopic abundance ratios of common, equal-atom and radiogenic lead isotopic standards./owmaf of Research of the National Bureau of Standards, 72A, 261-267. 

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). 

Natural lead, a metallic element, is a mixture of the following four isotopes lead-204, lead-206, lead-207, and lead-208. Only lead-204 is a primordial isotope of nonradiogenic origin all the others are radiogenic, each isotope being the end product of one of the radioactive decay series of isotopes of thorium or uranium, namely, uranium-238, uranium-235, and thorium-232 the decay series of the uranium isotopes are listed in Figure 12 ... 

According to the model, this isotopic composition was fixed tm years ago (on the separation of the lead minerals from the uranium- and thorium-bearing environment), is unchanged to the present day and is therefore measurable. There are two similar equations for the other two radiogenic stable isotopes of lead. To simplify the manipulation, we can use the following notation ... 

The Pb isotope ratios are consistent with young mineralisation (less than 800 My), Neo-Proterozoic to Palaeozoic and are similar to lead isotope ratios of epigenetic mineralisation. This suggests a radiogenic lead contribution from the upper crust. The isotopic curves generated by the plumbo-tectonic model of Zartman and Doe (1980) show that the isotopic ratios are below 800 Ma and correspond to crustal values. 

The common-lead method looks at the isotopic evolution of lead in systems with U/Pb and Th/Pb ratios similar to or less than the ratios in bulk solar system materials. The original formulation, by Holmes and Houtermans, is a single stage model that accounts for the isotopic composition of any sample of common lead in terms of primordial lead plus radiogenic lead produced in the source up to the time that lead was separated from uranium and thorium. Multistage models that more accurately describe the evolution of natural systems have been developed. The common-lead method is used in cosmochemistry primarily to study the time of differentiation and reservoir evolution in differentiated bodies... 

Nier, A. O. (1939b) The isotopic constitution of radiogenic leads and the measurement of geological time. II. Physical Review, 55, 153-163. 

Collins, C. B., R. M. Farquhar, and R. D. Russel Isotopic Constitution of Radiogenic leads and the Measurement of Geological Time. Bull. Geol. Soc. Amer. 65, 1 (1954). 

The radioactive decay of uranium and thorium results in the formation of a series of isotopes that are radiogenic by themselves and keep disintegrating into stable lead isotopes. These radioactive disintegrations are accompanied by the emissions of 4He atoms. Three such radioactive series exist ... 

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