Massive Sulfide Deposition at the 13°30’N Oceanic Core Complex: Lessons Learned From Coupled Hydro-Thermo-Mechanical Modeling

Young oceanic lithosphere created at mid-ocean spreading centers is subject to complex magmatic, tectonic and hydrothermal processes, especially in regions of widespread detachment faulting. This study focuses on the oceanic core complex (OCC) at the Mid Atlantic Ridge at 13°30’N. The OCC hosts the active Semenov-2 vent field and four inactive fields, including the exceptionally large Semenov-4 sulfide deposit ($\sim$10 Mt), which is located near the emergence of a detachment fault. To study the relationship between tectonic detachment faulting and fluid circulation we couple models for mechanical deformation and hydrothermal fluid flow. Our aim is to identify the role of the detachment in controlling location and size of sulfide deposition. First, we develop a baseline model for the tectono-magmatic evolution of the OCC using a data-based sequence for magnitude and position of axial magmatic diking. The resulting history of tectonic deformation provides a dynamic framework for modeling hydrothermal flow through porous rock, incorporating regions of active faulting and seafloor topography evolution. We then examine the impact of various fault zone permeability structures and heat sources on hydrothermal sulfide deposition. Our results show that a combination of a topographic influence, anisotropic permeability along the fault zone, transient shallow heat sources and plume interactions can efficiently reorganize the hydrothermal system. Increasing horizontal distance between heat source and vent field, however, significantly reduces hydrothermal plume stability. Modeled mass flow rates suggest that vent fields like Semenov-4 and TAG result from the focusing of fluid flow across the entire along-axis extent of the detachment structure.