Pb pb isochron dating
These plots are also self-checking and are useful for dating old rocks with complex histories.
The plots can still produce valuable and accurate data using rocks that have been subjected to heating and metamorphic events (Dalrymple 20).
An example isochron from Dalrymple (2004) is shown in Figure 4.8 below. Unlike other isochrons, the slope of the Pb-Pb isochron decreases with increasing age.
First, measuring the isotope ratio of a single element can be done much more precisely than measuring isotope ratios of two differing elements.
The first is that it requires single-stage leads, which are systems that begin at some initial lead composition and remain on the same growth curve throughout their histories (Dalrymple 209).
The second requirement is that assumptions about the genetic relationship between the Earth and meteorites must be made.
Another situation in which single-stage systems give unreliable information is the extraction of lead from uranium to form lead ore.
It is possible that a system could undergo a geological process that extracts lead, leaving the new system without any uranium.