Magma fluxes regulate the planetary thermal budget, the growth of continents and the frequency and magnitude of volcanic eruptions, and play a part in the genesis and size of magmatic ore deposits. However, because a large fraction of themagmaproduced onthe Earth does not erupt at the surface, determinations of magma fluxes are rareand this compromises our ability to establish a link between global heat transfer and large-scale geological processes. Here we showthat age distributions of zircons, a mineral often present in crustal magmatic rocks6, incombinationwith thermalmodelling, provide an accurate means of retrieving magma fluxes. The characteristics of zircon age populations vary significantly and systematically as a function of the flux and total volume of magma accumulated in the Earth's crust. Our approach produces results that are consistent with independent determinations of magma fluxes and volumes of magmatic systems. Analysis of existing agepopulation data setsusing ourmethod suggests that porphyry-type deposits, plutons and large eruptions each requiremagmainput over different timescales atdifferent characteristic average fluxes.We anticipate thatmore extensive andcompletemagma flux data sets will serve to clarify the control that the global heat flux exerts onthe frequency of geological events such as volcanic eruptions, and to determine the main factors controlling the distribution of resources on our planet.