Cooling magma plutons and intrusions are the heat sources for
hydrothermal systems in volcanic settings. To explain system longevity
and observed heat transfer at rates higher than those explained by pure
conduction, the concept of fluid convection in fractures that deepen
because of thermal rock contraction has been proposed as a heat-source
mechanism. While recent numerical studies have supported this half a
century old hypothesis, understanding of the various regimes where
convective downward migration of fractures can be an effective mechanism
for heat transfer is lacking. Using a numerical model for fluid flow and
fracture propagation in thermo-poroelastic media, we investigate
scenarios for which convective downward migration of fractures may
occur. Our results support convective downward migration of fractures as
a possible mechanism for development of hydrothermal systems, both for
settings within active zones of volcanism and spreading and, under
favorable conditions, in older crust away from such zones.