Tera, Fouad Department of Terrestrial Magnetism, Carnegie Institution, Washington, DC.
- Single-stage model
- Two-stage model
- Congruency of conformable galenas
- Links to Primary Literature
- Additional Readings
An estimate of the age of the planet Earth based on the lead isotope systematics. The first meaningful estimate was calculated from the average isotopic composition of terrestrial lead (Pb) available at the surface of the planet. The feasibility of the calculation stems principally from the unique circumstance that two isotopes of the element uranium (235U and 238U) decay to two daughters that are also isotopes of another element, lead (207Pb and 206Pb, respectively). This eliminates the requirement of determining the planetary budget of either of the two elements. The total number of 206Pb and 207Pb atoms are related to their respective parents by the equation of radioactive decay, expressed as Eq. (1) for lead-206 and Eq. (2)
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