Abstract: Massive Yanshanian magmatic rocks were developed in the Yanshan area of North China. These large-scale magmatic rocks were formed in a short time. However, the heat source of these massive magmatic activities remains unknown. This paper attempts to invert the source of magma with the heat conduct problem by finite element simulation. It is hypothesized that a piece of round-shaped basaltic magma of 905.86 km², underplated into deep crust between 36.6 km and 50 km at the temperature of 1250℃, the geothermal gradient of the crust rose gradually with the evolution of North China craton. The main conclusions of this numerical simulation are as follows: (1) The geothermal temperature curves of J1 reveal that, to make the wall rock melt, the volume of underplating basaltic magma should be considerably huge. Based on the actual output of the acid rock during J1 period in Yanshan area, the amount of underplating basaltic magma required by inversion is 1053 km² to produce 86 km² granites (J1). (2) The temperature field of J1 model shows, the temperature of wall rock at the level of 40~50 km in the horizontal direction was increased significantly and formed a high-temperature zone or melting zone which might be the later tectonic weak surface. And when it transformed into eclogite facies, the density would be greatly increased. The high-density residue fell until caving occurred, as it reached a critical value. This paper supports the occurrence of delamination from the perspective of numerical simulation.

Key words: Magma-heating Supply, Early Jurassic (J1), Delamination, Numerical Simulation, Yanshan Area