Crustal xenoliths are key subvolcanic material for studying processes that operate in a magma dyke during intrusion into its surrounding country rock. The Biot number is the appropriate parameter to advance knowledge of the rock–magma thermal interaction. We present an interactive approach that combines the petrological study of natural subvolcanic samples, through crustal xenoliths, which represents an essential pilot to explore and constrain the input parameters and boundary conditions in numerical simulations of fluid dynamics under a volcano. Our results – as a function of different dyke depths, aspect ratios and temperature gradients at the host and dyke – allow an accurate interpretation of the thermal history of magma flow in the dyke, revealing significant differences in heat transfer and thermal resistance between the crust and ascending magma. Conclusively, melt flow within rigid-walled channels depends directly on the depth (pressure gradient) and width of the dyke according to a balance between the rate of magma input and heat loss that determines how fast the magma may ascend. In addition, and with implications for crustal assimilation, there is evidence of a strong relationship between the preconditioning temperature and the integrity of the host rock over the time that xenoliths are immersed in the magma dyke.