Hydrothermal systems associated with oceanic core complexes on the Mid-Atlantic Ridge - Big surprises from recent exploration
Oceanic core complexes (OCCs) along slow and ultra-slow spreading ridges expose ultramafic rocks at the seafloor, and almost always host active or extinct hydrothermal systems. As a result, many of the known OCCs on the Mid-Atlantic Ridge (MAR) are exploration targets for seafloor massive sulfide deposits, and several countries have active exploration and resource delineation programs. Here, I will present results from recent exploration cruises to several OCC-hosted hydrothermal sites on the MAR. I will present results that suggest that the massive sulfide deposits forming at these sites may actually not be massive sulfide at all, but clay-dominated, similar to recently-discovered talc-rich hydrothermal deposits on the OCC-hosted Von Damm Vent Field, on the Mid-Cayman Spreading Centre.