How does uranium-lead dating work?

Uranium-lead dating is one of the oldest and most refined radiometric dating techniques, used to determine the age of rocks and minerals formed from one million to over 4.5 billion years ago. The method relies on mineral crystals like zircon that initially incorporate uranium while rejecting lead, meaning any lead found later is radiogenic decay. By measuring the current ratio of lead isotopes to uranium isotopes, scientists can reliably calculate the age of the sample using known radioactive decay rates.

What we know

• U-Pb dating can be applied to date rocks formed from about 1 million years to over 4.5 billion years ago with precisions in the 0.1 to 1 percent range. [2]
• Zircon crystals incorporate uranium and thorium into their structure while strongly rejecting lead, meaning newly formed crystals contain no initial lead. [2]
• The uranium-lead method relies on two separate decay chains: uranium-238 decaying to lead-206 with a half-life of 4.47 billion years, and uranium-235 decaying to lead-207 with a half-life of 710 million years. [2]
• Radiometric dating compares the abundance of a naturally occurring radioactive isotope to its decay products, which form at a known constant rate of decay. [4]

Where to go next

• the bigger pictureWhat is radiometric dating?
• how it workedHow does zircon mineral structure trap uranium?
• compared withHow does uranium-thorium dating differ?
• whoWho pioneered radiometric dating methods?
• a case in pointHow is uranium-uranium dating performed?
• an unexpected connectionHow do decay series connect uranium-lead dating to uranium-thorium techniques?Both methods exploit the same underlying multi-step radioactive decay series originating from uranium isotopes, even though they measure completely different stages and end products.

Sources

• [1]uranium-lead dating (Wikidata Q1930710) · CC0 1.0
• [2]Uranium–lead dating · CC BY-SA 4.0
• [3]Uranium–uranium dating · CC BY-SA 4.0
• [4]Radiometric dating · CC BY-SA 4.0
• [5]Uranium–thorium dating · CC BY-SA 4.0