Both isotopes are the starting points for complex decay series that eventually produce stable isotopes of lead.
Uranium-lead dating was applied initially to uranium minerals, e. The amount of radiogenic lead from all these methods must be distinguished from naturally occurring lead, and this is calculated by using the ratio with Pb, which is a stable isotope of the element then, after correcting for original lead, if the mineral has remained in a closed system, the U: Pb and U: Pb ages should agree.
If this is the case, they are concordant and the age determined is most probably the actual age of the specimen. If the ages determined using these two methods do not agree, then they do not fall on this curve and are therefore discordant. This commonly occurs if the system has been heated or otherwise disturbed, causing a loss of some of the lead daughter atoms.
Because Pb and Pb are chemically identical, they are usually lost in the same proportions. The plot of the ratios will then produce a straight line below the Concordia curve. Wetherill has shown that the two points on the Concordia curve intersected by this straight line will represent the time of initial crystallization and the time of the subsequent lead loss.
June 17, Retrieved June 17, from Encyclopedia. Then, copy and paste the text into your bibliography or works cited list. Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia. Another method of calculating the age of the rocks is to measure the ratio of radiogenic lead Pb, Pb, and Pb present to nonradiogenic lead Pb.
These methods give reliable for ages of the order 10 7 —10 9 years. Cite this article Pick a style below, and copy the text for your bibliography. Learn more about citation styles Citation styles Encyclopedia.
More From encyclopedia. It has four naturally occurring stable isotopes, lead, lead, lead, and lead Although the problem of lead exposure has been reduced in the Unite… Rubidium-strontium Datingrubidium—strontium dating A radiometric dating method based on the radioactive decay of 87Rb to 87Sr. Rubidium has two isotopes 85Rb About this article Uranium-lead dating All Sources .
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