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Samarium dating | USArtQuest
Samarium—neodymium dating is a radiometric dating method useful for determining the ages of rocks and meteorites , based on radioactive decay of a long-lived samarium Sm isotope to a radiogenic neodymium Nd isotope. Neodymium isotope ratios together with samarium-neodymium ratios are used to provide information on the source of igneous melts, as well as to provide age information. It is sometimes assumed that at the moment when crustal material is formed from the mantle the neodymium isotope ratio depends only on the time when this event occurred, but thereafter it evolves in a way that depends on the new ratio of samarium to neodymium in the crustal material, which will be different from the ratio in the mantle material. Samarium—neodymium dating allows us to determine when the crustal material was formed. The usefulness of Sm—Nd dating stems from the fact that these two elements are rare earths and are thus, theoretically, not particularly susceptible to partitioning during sedimentation and diagenesis. In many cases, Sm—Nd and Rb—Sr isotope data are used together. Samarium has five naturally occurring isotopes, and neodymium has seven.
Edwin A. The radioactive decay of samarium of mass Sm to neodymium of mass Nd has been shown to be capable of providing useful isochron ages for certain geologic materials. Both parent and daughter belong to the rare-earth element group, which is itself the subject of numerous geologic investigations.
A technician of the U. Geological Survey uses a mass spectrometer to determine the proportions of neodymium isotopes contained in a sample of igneous rock. Cloth wrappings from a mummified bull Samples taken from a pyramid in Dashur, Egypt. This date agrees with the age of the pyramid as estimated from historical records.