What is a model age, and why do we need to know it? How can we test whether ore-forming fluids carry a mantle signature? What is the difference between a SHRIMP and a LA-ICPMS U–Pb age and is it significant? Isotopes provide important information on many geological processes, with key relevance to the mining and petroleum industries, yet the techniques to obtain, process and interpret the data can be complex to master. This accessible book provides broad coverage of radiogenic isotopes in geochronology and geochemistry, explaining the basic principles and state-of-the-art techniques used to study them, with an emphasis on industry applications. The major isotopic systems are fully summarised with relation to real-world applications, enabling readers to decide which technique is most relevant for the problem they want to solve, and then to rigorously evaluate existing data, or recalculate and reassess data sets to avoid duplication of effort. Written at a level appropriate for advanced undergraduate students, the book also includes detail which allows more experienced practitioners to maximise the potential value of isotopic data sets.