Radiogenic Isotope
Definition
An isotope produced by radioactive decay of a parent nuclide over geological time. Its abundance in a rock or mineral increases predictably with age, providing both a geochronometer and a provenance fingerprint.
- Origin
- Radioactive decay of a parent nuclide
- Use 1
- Geochronometer (dating)
- Use 2
- Provenance fingerprint
Common questions
What makes a radiogenic isotope useful as a geochronometer?+
Because it accumulates from parent decay at a known, constant rate, measuring the ratio of daughter to parent isotope in a sample gives a direct estimate of how long that decay process has been running, which corresponds to the material's age.
How does a radiogenic isotope ratio act as a provenance fingerprint independent of dating?+
The ratio in a rock or mineral depends on the local geological history and initial parent-element abundance, so two samples from different regions carry different isotopic signatures even if they are the same age, allowing source-region comparison.
Related terms
- Delta Notation (δ)
- A notation expressing the isotope ratio of a sample relative to an international standard in parts per thousand (per mil, ‰). Positive...
- Epsilon Notation (ε)
- Similar to delta but expressed in parts per ten thousand, used for radiogenic systems where variation is very small. Epsilon Nd and...
- MC-ICP-MS (Multi-Collector Inductively Coupled Plasma Mass Spectrometry)
- An instrument that ionises a liquid or laser-ablated sample in an argon plasma at about 8,000 K and simultaneously collects multiple ion...
- Stable Isotope
- An isotope that does not undergo radioactive decay. Ratios of stable isotopes change only through physical or biological fractionation, such as evaporation...
- TIMS (Thermal Ionisation Mass Spectrometry)
- An instrument that ionises a sample deposited on a metal filament and measures ion beam intensities with Faraday collectors. The gold standard...