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Zircon geochronology is among the most powerful and widely used methods to reconstruct the growth and evolution of long-lived magma systems. The propensity of zircon crystals to cycle through melt-and cumulate-dominated domains results in a rich repository of magmatic history, but also leads to ambiguity in the interpretation of zircon ages. For example, it can be challenging to distinguish between volcanic zircon autocrysts and antecrysts or among plutonic zircon ages that may reflect magma emplacement, cooling, or solidification. Consequently, conclusive interpretations of magma dynamics from zircon data have proven elusive. We present a model of diffusion-limited zircon growth implemented within a 3-D numerical framework of coupled thermal transfer, major phase equilibrium, and magma dynamics. The time-and space-varying zircon growth rate is expressed as model zircon age populations calculated …