Structural Control, Evolution, and Accumulation Rates of Massive Sulfides in the TAG Hydrothermal Field

The Trans‐Atlantic Geotraverse (TAG) hydrothermal field on the Mid‐Atlantic Ridge is one of the best‐studied hydrothermal systems to date. However, high‐resolution bathymetric data obtained in 2016 by an autonomous underwater vehicle (AUV) reveal new information about the distribution of active and inactive hydrothermal deposits, and their relation to structural features. The discovery of previously undocumented inactive vent sites contributes to a better understanding of the accumulation rates and the resource potential of seafloor massive sulfide deposits at slow‐spreading ridges. The interpretation of ship‐based and high‐resolution AUV‐based data sets allowed for the determination of the main tectonic stress regimes that have a first‐order control on the location and distribution of past and present hydrothermal activity. The data reveal the importance of cross‐cutting lineament populations and temporal variations in the prevalent stress regime. A dozen sulfide mounds contribute to a substantial accumulation of hydrothermal material (~29 Mt). The accumulation rate of ~1,500 t/yr is comparable to those of other modern seafloor vent fields. However, our observations suggest that the TAG segment is different from many other slow‐spreading ridge segments in its tectonic complexity, which confines sulfide formation into a relatively small area and is responsible for the longevity of the hydrothermal system and substantial mineral accumulation. The inactive and weakly active mounds contain almost 10 times the amount of material as the active high‐temperature mound, providing an important indication of the global resource potential for inactive seafloor massive sulfide deposits. Plain Language Summary Previously unknown hydrothermal mounds were discovered by an autonomous underwater vehicle in the Trans‐Atlantic Geotraverse (TAG) hydrothermal field in the central Atlantic Ocean. The location of the hydrothermal mounds is controlled by crossing fault and fissure populations that have been active at different times. The material in the newly discovered mounds together with that of the previously known mounds accumulates to ~29 Mt of hydrothermal material. Most of the tonnage is contained in inactive or only weakly active mounds where hydrothermal activity has already ceased or is in a waning stage. The hydrothermal activity likely occurs periodically, and we assume an accumulation rate of ~1,500 t/yr, which is comparable to rates from other hydrothermal fields.