New Data for the Internal Structure of Ultramafic Hosted Seafloor Massive Sulfides (SMS) Deposits: Case Study of the Semenov-5 Hydrothermal Field (13°31′ N, MAR)

The internal structure of Seafloor Massive Sulfides (SMS) deposits is one the most important and complex issues facing study modern hydrothermal ore systems. Semenov-5 field a unique area where mass wasting on slope oceanic core (OCC) exposes subsurface portion deposit offers an exceptional opportunity to observe massive sulfides that have formed not only seafloor but in sub-seafloor zones as well. This paper examines OCC-related along with analysis mineralogy chemistry different parts sulfide deposit. comprised pyrite, marcasite, hematite, goethite, lepidocrocite, rare pyrrhotite, isocubanite Co-rich pyrite. Sulfide indicates prevailing influence ultramafics their composition irrespective spatial relation basalt lavas. Sub-seafloor mineralization associated ultramafic rocks represented by disseminated sulfides. Pyrrhotite, isocubanite, chalcopyrite, quartz rutile, quarts hematite Cr-spinels are fixed subseafloor mineralization. presence well very high Cr content regarded indicators metasomatic nature this part had result replacement. As result, three ore-forming system been described: precipitated from hot vents surface seafloor, due replacement below mineralization-filled cracks hosted which stockwork around Despite differences mineral geochemical mineralization, all minerals subject sample consequence fluid circulation were linked common process.