Uranium–lead dating

Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the <a href="/facts/Radiometric_dating/bDFjdPqV">radiometric dating</a> schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range.
The method is usually applied to <a href="/facts/Zircon/84APfbLt">zircon</a>. This mineral incorporates <a href="/facts/Uranium/n2sGWBzU">uranium</a> and <a href="/facts/Thorium/ysdWH470">thorium</a> <a href="/facts/Atoms/FoQ4kGN5">atoms</a> into its <a href="/facts/Crystal_structure/bJ4bCeHd">crystal structure</a>, but strongly rejects <a href="/facts/Lead/EYljasJN">lead</a> when forming. As a result, newly-formed zircon crystals will contain no lead, meaning that any lead found in the mineral is <a href="/facts/Radiogenic/KXP6MKk6">radiogenic</a>. Since the exact rate at which uranium decays into lead is known, the current ratio of lead to uranium in a sample of the mineral can be used to reliably determine its age.
The method relies on two separate <a href="/facts/Decay_chain/JvTwPNBn">decay chains</a>, the <a href="/facts/Uranium_series/JvTwPNBn">uranium series</a> from <a href="/facts/Uranium-238/QhcHm6q8">238U</a> to 206Pb, with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 4.47 billion years and the <a href="/facts/Actinium_series/JvTwPNBn">actinium series</a> from <a href="/facts/Uranium-235/pe0RznDM">235U</a> to 207Pb, with a half-life of 710 million years.

Uranium–lead dating open-in-new

Uranium–lead dating