Data Report: Sulfide textures in the active TAG massive sulfide deposit, 26°N, MidAtlantic Ridge

Ocean Drilling Program Leg 158 recovery from the active Trans-Atlantic Geotraverse (TAG) hydrothermal mound provided an excellent opportunity to study textures developed in an actively forming seafloor-hosted massive sulfide deposit.The TAG mound has a crude lithostratigraphy of approximately vertically stacked breccias that, at the base, consist of silicified and chloritized wall rock of the stockwork zone; at intermediate levels, they consist of sulfide-silica breccia clasts in an anhydrite matrix; and in the upper part they consist of massive sulfide breccias.Colloform pyrite-marcasite-sphalerite structures are the dominant sulfide textures developed in the upper part of the mound.At intermediate depths, sulfide textures are dominated by pyrite and chalcopyrite replacement of wall rock along anhydrite veins and by the recrystallization of sulfide grains.At depth, the deposit contains predominantly disseminated pyrite in a silicified wall-rock matrix, and sulfide veins cut the wall rock and altered basalt clasts.These textures and their distribution within the TAG deposit are remarkably similar to those described for the Cyprus ophiolite-hosted massive sulfide deposits.