Fig. 2: Internal structure of TAG and examples of sampled sulfide textures.

a Composite section through the TAG mound and underlying stockwork drawn based on multiple drill cores in each area; TAG-5 is projected onto the section. The samples utilized in this study (yellow diamonds) encompass the main rock types from the vertical and lateral extent of TAG^19,44: massive pyrite and pyrite breccia (types 5 and 6); pyrite-anhydrite breccia (type 7) and pyrite-silica(−anhydrite) breccia (type 8), both with abundant anhydrite veins (type 11); pyrite-silica and silicified wallrock breccia (types 9 and 10a); and chloritized basalt breccia (type 10b). Vent fluid temperatures for the Black Smoker Complex and the (now inactive) Kremlin Area are from ref. ⁴⁹ and isotherms are drawn based on fluid inclusion data^39,71. Figure modified from ref. ⁵² and ref. ⁶⁹. b Massive sulfide mineralization from the upper parts of the mound comprising fine-grained and porous pyrite and marcasite with local chalcopyrite. The top part of the rock piece preserves a colloform texture (TAG-4, 957M, 14.79 m.b.s.f.). c Aggregates of pyrite and chalcopyrite (partly oxidized, greenish in photo) within a fragment of an anhydrite vein from the lower part of the mound (TAG-1, 957C, 46.69 m.b.s.f.). d Pyrite-silica breccia from the upper part of the stockwork comprising clasts of massive granular pyrite in a matrix of quartz and pyrite (TAG-2, 957H, 41.32 m.b.s.f.). e Fragment of chloritized basalt host rock with finely disseminated pyrite from the deeper part of the stockwork. The altered basalt is crosscut by quartz-pyrite stringer veins (TAG-1, 957E, 116.42 m.b.s.f.).