Crustal growth and differentiation processes (‘cratonization’) highlighted by in situ zircon Hf and O isotopes. Zircon Hf and O isotopes reflect multi-component sources and shallow crustal processes associated with magma emplacement. Identified previously unknown crustal reservoir in the Capricorn Orogen. Crustal differentiation associated with an increase in the Th/U ratio of magmatic zircon. Cratonization process may lead to shallow parts of the crust more susceptible to reworking.