Although single-stage leads are difficult to find on Earth due to the constant recycling of Earth's crust, Pb-Pb isochrons remain powerful tools in making age of the Earth calculations.A Pb-Pb isochron plots U, with both normalized to 204Pb.Another situation in which single-stage systems give unreliable information is the extraction of lead from uranium to form lead ore.
Since both decay series contain a unique set of intermediate radioactive isotopes, and because each has its own half-life, independent age calculations can be made from each (Dalrymple 20).
The presence of a stable lead isotope that is not the product of any decay series (204Pb) allows lead isotopes to be normalized, allowing for the use of isochrons and concordia-discordia diagrams as dating tools.
SUMMARY: Primitive meteorites are remnants of the solar nebula, containing intermixed rock and metal flakes.
Processed meteorites are fragments of larger asteroids and therefore can be metallic like a planet's core or rocky like its mantle or crust.
Radioactive dating shows them to be about 4.6 billion years old, meaning that they have remained essentially unchanged since they first accreted in the solar nebula. They are pieces of rock that accreted in the solar nebula and orbited the Sun for billions of years before finally falling to Earth.
The individual flakes may represent the tiny particles that first condensed from the gas of the solar nebula.
Dalrymple (2004) cites examples of lead isotope dating that give an age for the earth of about 4.5 billion years.
Lead isotopes are important because two different lead isotopes (U).
Two other characteristics of lead isotope measurements make it superior to other methods.
First, measuring the isotope ratio of a single element can be done much more precisely than measuring isotope ratios of two differing elements.
This model, which describes the accumulation of lead isotopes in meteorites, the Earth, and the Solar System, was proposed independently by E. The amount of 204Pb will remain constant throughout the history of a rock because it is a stable isotope that is not the product of any decay series, thus allowing for the normalization (Dalrymple 201-163).