Nd142

Nd-142 is a stable isotope of the element neodymium (Nd), which has atomic number 60. It has mass number 142, corresponding to 82 neutrons. It is one of seven naturally occurring neodymium isotopes and exists in trace amounts in Nd-bearing minerals such as monazite and bastnäsite.

As a stable nuclide, Nd-142 does not undergo radioactive decay under ordinary Earth conditions. Its significance arises from cosmochemical and geochronological considerations related to the extinct radionuclide 146Sm, which decayed to 142Nd in the early solar system. 146Sm has a half-life of about 68 million years, and its decay produced radiogenic excesses of 142Nd in planetary materials. The combined Nd isotope system, including 146Sm → 142Nd and 147Sm → 143Nd, is used to study early planetary differentiation and crust–mantle formation.

In practice, Nd isotopes, including 142Nd, are measured with high-precision mass spectrometry. The resulting isotopic data are used to construct Sm-Nd isochrons and to express deviations from a terrestrial Nd reference as epsilon142Nd values, which help constrain the timing of geological processes and the evolution of planetary reservoirs. Nd-142 thus provides a key piece of information in geochronology and cosmochemistry, even though it occurs only in small natural abundances.