Decay equations for common Pb-Pb Dating There are three stable "daughter" Pb isotopes that result from the radioactive decay of uranium and thorium in nature; they are U, and t is the age.
)] It was established by dividing the first equation above by the second, under the assumption that the U/Pb system was undisturbed. As evident by the equation, initial Pb isotope ratios, as well as the age of the system are the two factors which determine the present day Pb isotope compositions. The isotopic constitution of lead and the measurement of geological time 3. The U/Pb ratio was so low that no radiogenic decay was detected in the isotopic composition [(Dickin, A. The isotope composition of this sample was found to lie on the meteorite isochron, therefore giving good evidence that earth had the same origin as the meteorites, as well as the same age, therefore solving the age of the Earth and giving rise to the name geochron. Animation shows progressive growth over 4550 million years (Myr) of the lead isotope ratios for two stony meteorites (Nuevo Laredo and Forest City) from initial lead isotope ratios matching those of the Canyon Diablo iron meteorite. The Pb ratios of three stony and two iron meteorites, where measured. Samples of iron meteroite from )Arizona were found to have the least radiogenic composition of any material in the solar system. Therefore troilite found in Canyon Diablo represents the primeval lead isotope composition of the solar system, dating back to 4.55 +- 0.07 Byr. This was representative of the Bulk Earth composition, and was plotted on the isochron. Patterson to determine the age of the Earth in 1956. )] The Formation of the Geochron The development of the Geochron was mainly attributed to Patterson’s application of Pb-Pb dating on meteorites in 1956. Iron meteorites were identified as pieces of the core, while stony meteorites were segments of the mantle and crustal units of these various planetismals. p 117)] As illustrated in figure 1, this point defines the lower (left) end of the isochron. Patterson also analyzed terrestrial sediment collected from the ocean floor. As planetismals collided, various fragments were scattered and produced meteorites. These samples define an isochron in figure 1, whose slope gives the age of meterites as 4.55 Byr.
The process of isotopic differentiation is identical on Earth as it is on other planets, therefore the core of these planetismals would be depleted of Uranium and Thorium, while the crust and mantle would contain higher U/Pb ratios. pp117)] The stony meteorites however, exhibited very high Pb ratios, indicating that these samples came from the crust or mantle of the planetismal. By dating meteorites Patterson was directly dating the age of various planetismals. Acta 10, 230-7)] The dating of meteorites would then help Patterson in determining not only the age of these meteorites but also the age of Earth’s formation.Biological family: Gabe Sullivan (father)Moira Sullivan (mother)Sam Lane (uncle)Ella Lane (aunt, deceased)Lucy Lane (cousin)Lois Lane (cousin) Marital family: Jimmy Olsen (first - husband, deceased) Oliver Queen (husband)Jonathan Sullivan-Queen (son)Robert Queen (father-in-law, deceased)Laura Queen (mother-in-law, deceased) Freelance journalist, Member of the Justice League, Agent of D. O.; former reporter for the Star City Register, former leader of the Suicide Squad, former manager of the Isis Foundation.former writer/reporter for the Daily Planet is Oliver Queen's wife and Clark Kent's closest friend.She served in the role of Watchtower, where she provided operational support to Clark and Oliver and their team of heroes.