dating relationship books men - Pb pb dating method

The second requirement is that assumptions about the genetic relationship between the Earth and meteorites must be made.

First, measuring the isotope ratio of a single element can be done much more precisely than measuring isotope ratios of two differing elements.

Second, using two isotopes of the same element makes the sample immune to chemical fractionation during a post-crystallization disturbance (Dalrymple 208). This model ultimately led to the development of isochrons, in which two isotopes are plotted against each other to calculate an age for the mineral or rock.

It is possible that a system could undergo a geological process that extracts lead, leaving the new system without any uranium.

If that system were dated at that point in time, it would fall on the isochron and give the correct age of the mineral.

A Pb-Pb isochron plots U, with both normalized to 204Pb.

The resulting line drawn through the plotted points will pass through a point representing the initial lead composition of the system.

In order to be used as a natural clock to calculate the age of the earth, the processes generating lead isotopes must meet the four conditions of a natural clock: an irreversible process, a uniform rate, an initial condition, and a final condition.

Dalrymple (2004) cites examples of lead isotope dating that give an age for the earth of about 4.5 billion years.

This is because Pb, causing the isochron to decrease in slope with increasing age.

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