An ‘extinct’ transform fault hosts fluid flow and methane seepage – implications for understanding the role of transform faults in mid-ocean ridge fluid cycling

The Svyatogor Ridge is the sedimented inside corner high of the Knipovich Ridge – Molloy Transform Fault intersection and despite its mid-ocean ridge system setting, it is host to a well-defined gas hydrate system. There is an extinct transform fault immediately south of the Svyatogor Ridge, which is partially sedimented. Our data suggests that there are distinct locations throughout the area which have elevated heat flow, usually coinciding with evidence of past or present fluid flow.In particular, we show a site along the flank of the extinct transform fault which hosts a seep-like community associated with enhanced anaerobic methane oxidation in the shallow subsurface. While transform faults and fracture zones are important components of mid-ocean ridge systems, their role in fluid exchange between the lithosphere and hydrosphere remains unclear. High resolution seismic data from the inside corner high area at the Knipovich Ridge – Molloy Transform Fault intersection hints towards the important role the Molloy Transform Fault is playing in the fluid flow system in the area. However, integrated seismic, geochemical and heat flow datasets along the extinct transform fault clearly links the fault to elevated heat flow and fluid seepage, and to sites of gas hydrate accumulation. We posit that this site is a type of hybrid seep-vent style of fluid flow system.