Magmatic processes in the continental crust such as crustal convection, melt ascent, magma emplacement, and batholith formation are not well understood. We solve the conservation equations for mass, momentum, and energy for two‐phase flow of melt and solid in 2D, for a thick continental crust heated from below by one or several heat pulses. A simplified binary melting model is incorporated. We systematically vary (a) the retention number, characterizing melt mobility, (b) the intensity of heat pulses applied at the bottom, and (c) the density of the solidified evolved rock. Two characteristic modes are identified: (a) in the “batholith emplacement mode,” segregation is sufficiently strong allowing melts to separate from the convective flow. This melt freezes to form buoyant SiO2‐rich layers. (b) In the “convective recycling mode,” melts are formed in the lower crust, rise together with the hot rock with little segregation, freeze at shallow depth but are partly recycled back to the lower crust where they remelt. Phase‐change‐driven convection dominates. Mode (a) is favored by high heat input, multiple heat pulses, high melt mobility, and low density of the evolved rock. Mode (b) is favored by less intense heating, less melt mobility, and denser evolved rocks. A scaling law is derived based on the thermal, melt, and compositional Rayleigh numbers and the retention number. The Altiplano‐Puna low‐velocity zone (LVZ) could represent the batholith emplacement mode with buoyant and voluminous magmas causing intense volcanism. The Tibetan LVZ is not associated with intense volcanism and might represent the convective recycling mode.
N2 - Key Points: Two‐phase flow models of crustal magmatic systems identify two modes: batholith emplacement versus convective recycling of evolved rock.High melt mobility, multiple heating pulses, and low density of solidified evolved rock favor batholith emplacement.
The Altiplano‐Puna low‐velocity zone (LVZ) is in the batholith emplacement mode and the Tibetan LVZ is in the convective recycling mode.