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Lead source materials, isotope ratios

During the geological formation of major lead deposits the lead is separated from the parent uranium and thorium, and the isotopic composition of the lead so separated depends on the geochemical history of the source materials, specifically on the U/Pb and Th/Pb ratios and the timing of any variations in these ratios including the time of the final separation of lead. In theory, it is possible for each lead deposit in the world to have its own unique isotopic composition. [Pg.274]

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... [Pg.268]

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Isotope ratios

Isotope ratios, lead

Isotopic sources

Lead isotopes

Ratio source

Source lead

Source material

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