Link to USGS home page

Resources on Isotopes

Periodic Table--Neodymium

Neodymium is a rare earth element (REE) that occurs in many silicate, phosphate, and carbonate minerals by substitution for major ions. It has seven stable isotopes. Nd and samarium (Sm) are considered "light" REEs and become concentrated in feldspars, biotite, and apatite. The concentrations of Nd and Sm increase in minerals during sequential crystallization, but the Sm/Nd ratio decreases.

147Sm decays by alpha emission to stable 143Nd, with a half-life of 1.53 x 1011 years. Variations in Nd isotopic compositions (143Nd/144Nd) are the result of elemental fractionations occurring between 143Nd and its parent 147Sm during radioactive decay. This has made Nd useful for age dating terrestrial and extraterrestrial materials as well as many other geologic applications (DePaolo, 1988). The growth of 87Sr and 143Nd together provides useful insight into geochemical evolution. Mafic rocks and associated suites of more differentiated rocks can be dated by whole-rock or internal mineral isochrons. These Sm-Nd dates are less susceptible to metamorphic alteration than Rb-Sr dates.

The concentration of Nd in natural waters is extremely low because the natural abundance of Nd is very small, and Nd is non-hydrophilic in low temperature environments. In most geological environments, the isotopic composition of Nd varies systematically, though inversely, with the isotopic composition of Sr. Except in very specific environments, Nd will not be as useful as Sr (due to its higher concentration in natural waters) in the interpretation of the weathering process in rocks and minerals. And because of their similar geochemical behavior, Sm and Nd are not fractionated from one another as severely as Rb and Sr. This fact, combined with the very long half-life of 147Sm make variations in Nd isotopes useful in only very old environments.

Source of text: This review was assembled by Eric Caldwell and Dan Snyder from Nimz (1998), and from the references below.

Bullen, T.D. and Kharaka, Y.K. (1992). "Isotopic composition of Sr, Nd, and Li in thermal waters from the Norris-Mammoth corridor, Yellowstone National Park and surrounding region." In: Water-Rock Interaction. Proceedings of the 7th International Symposium on Water-Rock Interaction, Balkema Publishers, Rotterdam, p. 897.
DePaolo, D.J., 1988. Neodymium Isotope Geochemistry, An Introduction. Springer-Verlag, Berlin, 187 p.
Faure, G. (1986). "The Sm-Nd method of dating." In Principles of Isotope Geology, second edition, John Wiley and Sons, New York, pp. 200-216.
Faure, G. (1986). "Isotope geology of neodymium and strontium in igneous rocks", in Principles of Isotope Geology, second edition, John Wiley and Sons, New York, pp. 217-238.
Faure, G. (1986). "Isotope geology of neodymium in sedimentary rocks", in Principles of Isotope Geology, second edition, John Wiley and Sons, New York, pp. 239-248.
Goldstein, S.J. and Jacobsen, S.B. (1987). "The Nd and Sr isotopic systematics of river-water dissolved material: Implications for the sources of Nd and Sr in seawater." Chem. Geol. (Isot. Geosci. Sect.), 66: 245.
Nimz, G.J. (1998). "Lithogenic and Cosmogenic Tracers in Catchment Hydrology." In: C. Kendall and J.J. McDonnell (Eds.), Isotope Tracers in Catchment Hydrology. Elsevier, Amsterdam, pp. 247-290.
Related Links
Periodic Table
Fundamentals of Stable Isotope Geochemistry
General References
Isotope Publications
Please contact Carol Kendall ( for questions and comments regarding this page.
This page was last changed in January 2004.
To the USGS Home Page
To the Water Resources Information Home Page