Reactive infiltration instability of a granitization front during the generation and development of granite-gneiss domes

The origin of granite-gneiss domes is traditionally attributed to gravity tectonics, the ascent of granite-gneiss diapirs in a gravitational field owing to a relative decrease in the density of granitized rocks compared with their protolith. This is usually considered by the example of a two-layer medium with a lower layer of granitized rocks overlain by a denser protolith layer; the development of gravitational instability in the system results in the ascent of a granite-gneiss diapir. However, the diapiric process can be initiated only if Archimedes?? buoyancy forces at the roof of the granite-gneiss layer will overcome the resistance of the protolith rocks related to their long-term strength. Under the conditions of plastic deformations, this requires the existence of a large-scale irregularity in the relief of the layer boundary, namely, an antiform cusp in the roof of the granite-gneiss layer. The model is based on the assumption that such antiforms appear owing to the reactive infiltration instability of the morphology of the granitization front caused by an increase in the fluid permeability of granitized rocks compared with that of the protolith. The results of computer modeling support the geological feasibility of the reactive infiltration mechanism of the generation and development of the protodiapiric forms of the granitization front triggering the development of the diapiric process of the gravitational upwelling of granite-gneiss domes. The model of a protodiapir stage allows us to consider dome formation as a result of the development of two sequential instabilities: the reactive infiltration instability of the granitization front related to an increase in the permeability of the transformed rock followed by the gravitational instability related to a relative decrease in rock density.