Rapid progress in investigation of zircon records for U-Th-Pb ages and O and Hf isotopes in igneous rocks require understanding how magma bodies are formed and evolve in the crust. We here present a 2D model of magma bodies formation in granitic crust by injection of rhyolitic or andesitic dikes and sills. We combine this model with our zircon crystallization/dissolution software and compute zircon survival histories in individual batches of magma and country rocks. Simulations reproduces incremental accumulation of intruded magma into magma chambers generating eruptible and interconnected magma batches with melt fraction >50 vol% that form in clusters. The rate of melt production is highly variable in space and time. The volume of eruptible melt strongly depends on the input rates of magma Q and the width W of the dike injection region. For example, dikes injection with Q=0.25 m3/s with W=500 m during 4 ka generate 20 km3 of melt while no significant melt forms if W=4 km. Injection of andesitic dikes produces only slightly more melt than rhyolite to granite injection despite of much larger thermal input. Due to rock melting most of zircons loose significant portion of their old cores and, thus, average age. Magmatic zircons in the periphery of the intrusion form very quickly while in its central part crystals contain old cores and young rims and can grow during several hundreds of ka. We observe diverse proportions of crustal melt/newly intruded magma, which translates into diverse O and Hf isotope distribution in zircons.

We present a 2D model of magma body formation in granitic crust by injection of rhyolitic or basaltic dikes and sills. An elastic analytical solution enables computation of rock displacement in response to magma intrusion. Phase diagrams for magma and host rocks predict melting/crystallization. We combine this model with our zircon crystallization/dissolution software and compute zircon survival histories within individual batches of magma and country rocks. Incremental accumulation of intruded magma generates interconnected magma batches of eruptible melt with melt fractions >50 vol% that form in clusters. The rate of melt production is highly variable in space and time. The volume of eruptible melt strongly depends on the input rates of magma Q and the width W of the injection region of dikes and on eruptions. For example, dikes injection with Q=0.125 m3/s with W=5 km during 100 ka generates ~50 km3 of eruptible melt while no significant melt forms if W=10 km. Injection of basaltic dikes produces more melt for the same flux rate. Frequent and small eruptions led to smaller magma bodies that are located deeper in the system, while systems with rare but voluminous eruption forms large melt. Due to partial melting, most host rock zircons loose significant portion of their old cores and, thus, their average age is reduced. Magmatic zircons in the periphery of the intrusion form very quickly due to rapid dikes cooling while in its central part crystals contain old cores and young rims and can grow during several hundreds of ka.