exhalative

Exhalative is a term used in economic geology to describe ore-forming processes in which hydrothermal fluids vent or exhale metals onto the seafloor or into sedimentary basins, precipitating sulfide minerals. The concept encompasses deposits formed by submarine hydrothermal activity as well as those developed in sedimentary environments where exhaled fluids interact with basinal sediments.

The two principal varieties are volcanic-hosted massive sulfide (VHMS) deposits and sedimentary exhalative (SEDEX) deposits. VHMS deposits form from high-temperature hydrothermal fluids at submarine volcanic centers, often near mid-ocean ridges or in back-arc basins, producing stratiform to mound-like sulfide bodies. SEDEX deposits form when exhaled fluids vent into sedimentary basins, typically producing large, tabular zinc, lead, and silver ore bodies with characteristic stratiform sulfide horizons. Although their settings differ, both types owe their metal richness to exhaled fluids that cool and react with surrounding rocks or seawater, causing rapid mineral precipitation.

Minerals commonly associated with exhalative deposits include sulfides such as pyrite, chalcopyrite, sphalerite, and galena, along with gangue minerals like quartz, calcite, and barite. Textures range from massive sulfide lenses to disseminated and vein-hosted sulfides, often accompanied by distinctive alteration halos.

Exhalative deposits are major sources of copper, zinc, lead, silver, and sometimes gold. They are explored through integrated geophysical surveys, geochemical pathfinder studies, and drilling, with exploration strategies tailored to the seafloor or sedimentary settings where exhalative mineralization occurs.