Thus the current ratio of lead to uranium in the mineral can be used to determine its age.
The method relies on two separate decay chains, the uranium series from Pb) leads to multiple dating techniques within the overall U–Pb system.
The dating method is usually performed on the mineral zircon.
The mineral incorporates uranium and thorium atoms into its crystalline structure, but strongly rejects lead.
If a series of zircon samples has lost different amounts of lead, the samples generate a discordant line.
Most scientists today believe that life has existed on the earth for billions of years.Zircon is very chemically inert and resistant to mechanical weathering—a mixed blessing for geochronologists, as zones or even whole crystals can survive melting of their parent rock with their original uranium-lead age intact.Zircon crystals with prolonged and complex histories can thus contain zones of dramatically different ages (usually, with the oldest and youngest zones forming the core and rim, respectively, of the crystal), and thus are said to demonstrate inherited characteristics.Most people are not aware of the many processes that take place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios.Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.