Massasulfidmalmer

Massasulfidmalmer, also known as Volcanogenic Massive Sulfides (VMS), are a type of metal sulfide deposit formed by hydrothermal activity on the ocean floor. These deposits are characterized by their massive accumulation of sulfide minerals, often containing significant concentrations of copper, zinc, lead, gold, and silver. VMS deposits are typically found in volcanic sequences, particularly those associated with mid-ocean ridges, back-arc basins, and island arcs.

The formation process begins with seawater circulating through the oceanic crust, becoming heated by magma. This hot, acidic fluid leaches metals and sulfur from the surrounding rocks. The superheated, metal-rich fluid then rises through fractures in the seafloor and erupts into the cold, oxygenated seawater. This sudden change in temperature and chemistry causes the dissolved metals and sulfur to precipitate out, forming massive accumulations of sulfide minerals directly on the seafloor or within the underlying volcanic rocks.

The morphology of VMS deposits can vary, but they are often lens-shaped or sheet-like, reflecting the vent system from which they precipitated. The mineralogy is dominated by iron sulfides like pyrite and pyrrhotite, accompanied by zinc sulfides (sphalerite), lead sulfides (galena), and copper sulfides (chalcopyrite, bornite). The economic significance of VMS deposits lies in their high metal grades, making them important sources for base and precious metals. Exploration for these deposits often involves geophysical surveys to detect the conductive sulfide bodies and geological mapping to identify favorable volcanic environments.