Within a largely steady-state low-flux passive margin, a seafloor seep at the Blake Ridge Diapir transiently releases methane gas and sulfide-laden fluids. Until now, fluid flux estimates on the diapir have been too small to reconcile with seafloor gas emission and the survival of a chemosynthetic community at the seep. Analysis of heat flow and high-resolution seismic data collected across the diapir confirms fluid flux through a sub-vertical chimney with apparent fluid velocities between 20 to 400 m ky⁻¹, ∼100 times larger than previous estimates derived from pore water geochemical data. Away from the chimneys, observations indicate that conductive thermal processes and low fluid fluxes dominate in the hydrate reservoir and that dissolution of the salt diapir does not control the thickness of the hydrate stability zone. The results suggest that, despite limited fluid flux in the larger area, focused flux can be significant enough to sustain a seafloor chemosynthetic community at the diapir.