lowsulfidation

Low-sulfidation refers to a class of epithermal hydrothermal ore deposits formed by fluids that ascend toward the surface in volcanic or tectonically active regions. They are distinguished from high-sulfidation systems by lower sulfur fugacity, cooler temperatures, and less acidic fluids. Mineralization occurs principally in quartz veins and breccias within altered rock, and is typically enriched in gold and silver with relatively modest sulfide content. Fluid temperatures are generally lower than in high-sulfidation settings, often near shallow crustal levels.

Alteration associated with low-sulfidation systems is dominated by illite and sericite with silica; adularia-bearing quartz veins and calcite are common. Advanced argillic alteration is limited in comparison to high-sulfidation styles. The ore minerals commonly include native gold or electrum, paired with sulfides such as pyrite, sphalerite, and galena, typically hosted in vein networks, stockworks, or breccias. Textures often show colloform or banded quartz and clear silica halos around veins.

Geographic and tectonic settings include volcanic arcs, volcanic calderas, and extensional regions where fluids ascend along faults close to the surface. Low-sulfidation deposits can form in a range of ages and can be the source of major gold-silver districts. Exploration indicators include quartz-adularia vein systems, shallow illite-dominant alteration halos, pervasive silica cement, and a lack of intensely acidic alteration.

Low-sulfidation deposits are an important class within epithermal mineralization, contrasted with high-sulfidation systems that form under higher temperatures and more acidic fluids. They contribute to global gold-silver production and are the subject of ongoing geological and mineral exploration studies.