Figure 2. Schematic cross section through the Mariana system showing various types of associations of serpentine mud volcanoes with faulting in the forearc wedge. Strike-slip faulting associated with along-strike extension and vertical tectonics related to seamount subduction both play a part in the tectonic deformation of the forearc and provide avenues for egress of slab-derived fluids and fault gouge from both the décollement and the lithosphere of the overriding plate. Decarbonation reactions in the downgoing plate probably take place between ~15 and 20 km (Fryer et al, in press).