Main -> Dating -> About Uranium-Lead Dating

About Uranium-Lead Dating

Decay scheme of K-Ar, U-Pb and Sm-Nd, petrogenetic implications-part B

Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable. Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence. Uranium comes in two common isotopes with atomic weights of and we'll call them U and U. Both are unstable and radioactive, shedding nuclear particles in a cascade that doesn't stop until they become lead Pb. The two cascades are different—U becomes Pb and U becomes Pb. What makes this fact useful is that they occur at different rates, as expressed in their half-lives the time it takes for half the atoms to decay. The U—Pb cascade has a half-life of million years and the U—Pb cascade is considerably slower, with a half-life of 4.

The straight line takes the zircons off the concordia. This is where data from many zircons is important. The disturbing event affects the zircons unequally, stripping all the lead from some, only part of it from others and leaving some untouched. The results from these zircons therefore plot along that straight line, establishing what is called a discordia.

Do you tell your age? – High-precision U–Pb dating

Now consider the discordia. If a million-year-old rock is disturbed to create a discordia, then is undisturbed for another billion years, the whole discordia line will migrate along the curve of the concordia, always pointing to the age of the disturbance.

This means that zircon data can tell us not only when a rock formed, but also when significant events occurred during its life. The oldest zircon yet found dates from 4.

With this background in the uranium-lead method, you may have a deeper appreciation of the research presented on the University of Wisconsin's " Earliest Piece of the Earth " page, including the paper in Nature that announced the record-setting date.

Share Flipboard Email. Andrew Alden is a geologist who writes extensively about all aspects of geology, and leads research expeditions for professional organizations. Updated February 10, Continue Reading.

As rocks contain of various minerals, geochronologists need to select the minerals that contain the most uranium. One of the mostly dated minerals is zircon ZrSiO 4.

In order to get the age of the rock with precisions better than 0. This is done by crushing the rock and separating the zircon crystals.

Those get dissolved by chemical dissolution, followed by chemical separation procedure to separate the uranium from the lead. The final product is a solution containing the uranium and lead from the initial zircon crystals.

This solution gets loaded onto a metal filament, heated and ionized in the mass spectrometer and separated on mass.

With this, one can determine age variations within the zircon crystal. Next to the uranium-lead technique, geochronologists also use Ar-Ar radiometric dating to get age information, for example, sanidine crystals from volcanic tuff.

Radiogenic Isotope Geology 2nd ed. Cambridge: Cambridge University Press.

Periods Eras Epochs. Canon of Kings Lists of kings Limmu.

date? 3. Analytical techniques. 4. Focus on high-precision U-Pb . Minerals used in U-Th-Pb dating. Mineral Detection of age domains in complex zircon. Mixing of Different Age Domains. Pb Loss. the most commonly utilized mineral for U–Pb dating. (Hanchar and. 2) Concordant U-Pb dates. 3) Discordant U-Pb dates and open. system behavior. 4) Common Pb-Pb dating. 5) The Geochron. Cross-section of a zircon grain.

Chinese Japanese Korean Vietnamese. Lunisolar Solar Lunar Astronomical year numbering. Deep time Geological history of Earth Geological time units.

Chronostratigraphy Geochronology Isotope geochemistry Law of superposition Luminescence dating Samarium—neodymium dating. Amino acid racemisation Archaeomagnetic dating Dendrochronology Ice core Incremental dating Lichenometry Paleomagnetism Radiometric dating Radiocarbon Uranium—lead Potassium—argon Tephrochronology Luminescence dating Thermoluminescence dating.

Fluorine absorption Nitrogen dating Obsidian hydration Seriation Stratigraphy.

U-Pb Zircon Geochronology - for determining the age of a rock

Molecular clock. Categories : Radiometric dating.

U-pb age dating

Hidden categories: Articles with short description Wikipedia articles needing clarification from October Namespaces Article Talk. Views Read Edit View history. By using this site, you agree to the Terms of Use and Privacy Policy.

So the Pb isotope ratios measured in these rocks today must be interpreted before their U-Pb ages can be calculated. Various methods have. Introduction. The U-Th-Pb age dating technique is a powerful and precise method to date crystallisation ages and metamorphic events. The mineral zircon . A person's age can be risky to determine without asking directly. But what about rocks and other materials on Earth? How do scientists actually.

The Wikibook Historical Geology has a page on the topic of: Other isochron methods. Concepts Deep time Geological history of Earth Geological time units. Absolute dating Amino acid racemisation Archaeomagnetic dating Dendrochronology Ice core Incremental dating Lichenometry Paleomagnetism Radiometric dating Radiocarbon Uranium—lead Potassium—argon Tephrochronology Luminescence dating Thermoluminescence dating.

Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the Finally, ages can also be determined from the U–Pb system by analysis of Pb isotope ratios alone. This is termed the lead–lead dating method. This assumption cannot be made for other minerals, young ages, and high U- Pb dating grants access to two separate geochronometers (Pb/U and. Of all the isotopic dating methods in use today, the uranium-lead If you took rocks of all ages and plotted their two Pb/U ratios from their two.

2 comments Add your comment below

Leave a Reply

Your email address will not be published. Required fields are marked *