Hydrothermal circulation and the melt plumbing system at slow spreading ridges
Mathilde Cannat
CNRS-Institut de Physique du Globe de Paris
The chemistry of black smoker fluids provides clear evidence that high temperature hydrothermal circulations at (fast and slow) mid-ocean ridges root into hot rocks that have crystallized, or are crystallizing, from basaltic magmas. Fast spreading ridges have a steady melt lense at depths of a few kilometers. This is not the case at slow spreading ridges, where petrological and geophysical data concur to indicate that melt is emplaced discontinuously, both spatially and in time, in the shallow axial lithosphere, commonly interacting with large offset axial normal faults. In this presentation I discuss the probable consequences of this complex melt plumbing system on the distribution and fluxes of black smoker vents, using monitoring data from hydrothermal fields at slow-spreading ridges, and geological observations from slow and ultraslow spreading ridges.
