Genesis of Mud Volcano fluids in the Gulf of Cadiz - A novel model approach. European Geosciences

Mud volcanism and fluid seepage are common phenomena on the continental marginin the Gulf of Cadiz, North East Atlantic Ocean. Over the past 2 decades more than 50 mud volcanoeshave been discovered and investigated interdisciplinarily. Mud volcanofluids emanating at these sites are sourced at great depths and migration is often mediated by strike slip faults in a seismically active region. The geochemical signals of the mud volcanofluids are affected by widespread various processes such as clay mineral dehydration, but also the recrystallization of ancient carbonate rocksand the alteration of oceanic crusthave been suggested (Hensen et al., 2015). We developed a novel fully-coupled, basin-scale, reaction-transport model with an adaptive numerical mesh to simulate the fluid genesis in this region. An advantage of this model is the coupling of a realistic geophysical and geochemical approach, considering a growing sediment column over time together with instant compaction of sediments as well as diffusion and advection of dissolved pore water species and chemical reactions. In this proof of concept study, we looked at various scenarios to identify the processes of fluid genesis for 4 mud volcanoes, representing combinations in different subsurface settings. We can reproduce the fluid signatures (chloride, strontium, 87Sr/86Sr) of all mud volcanoes. Furthermore, we can give additional evidence that alteration of oceanic crustby fluid flow is a likely process affecting the fluid composition.