Radiogenic

Radiogenic is an adjective describing a process, material, or signature that originates from radioactive decay or from radiogenic processes. In geology and geochemistry, it specifically refers to isotopes produced by the decay of a parent radioisotope, as opposed to primordial or cosmogenic sources.

Radiogenic isotopes are key to age dating and to understanding thermal and chemical evolution. Common radiogenic dating systems include uranium-lead (U-238 decays to Pb-206; U-235 to Pb-207), rubidium-strontium (Rb-87 to Sr-87), samarium-neodymium (Sm-147 to Nd-143), and potassium-argon (K-40 to Ar-40). The measured ratios of parent to daughter isotopes, together with known decay constants, yield ages for rocks and minerals. Radiogenic heat from the decay of uranium, thorium, and potassium also contributes to a planet’s internal heat and drives geodynamic processes such as mantle convection and volcanism.

Radiogenic signatures must be distinguished from primordially derived isotopes, which have persisted since formation, and from cosmogenic isotopes produced by interactions with cosmic rays. Radiogenic systems assume closed-system behavior after formation, or require corrections for gain or loss of isotopes over time. In planetary science, varying abundances of radiogenic elements influence thermal histories and tectonic evolution of planets and moons, making radiogenic processes central to interpretations of geologic and planetary records.