sedimentaryexhalative

Sedimentaryexhalative deposits, often abbreviated as SEDEX, are a significant class of mineral deposits formed by the interaction of hydrothermal fluids with sedimentary basins. These deposits are typically found in marine or lacustrine environments and are characterized by their stratiform or lens-like geometries, conformable with the host sedimentary layers. The formation process involves the circulation of hot, metal-rich brines derived from deep within the Earth's crust, often driven by basement faulting. These fluids migrate upwards through permeable sedimentary rocks and eventually vent into cooler, less saline waters at the seafloor or lakebed.

Upon encountering the ambient water, the dissolved metals in the hydrothermal fluids precipitate out of solution, forming solid mineral deposits. Common metals found in SEDEX deposits include lead, zinc, silver, and copper, often occurring as sulfides such as galena (PbS) and sphalerite (ZnS). The host rocks are usually shale, siltstone, or limestone. Features associated with SEDEX deposits include hydrothermal breccias, massive sulfide bodies, and disseminated mineralization. These deposits are economically important, representing a major source of lead and zinc globally. Examples include the Mount Isa deposit in Australia and the Red Dog deposit in Alaska. Their exploration often involves understanding regional geological structures, basin evolution, and geochemical anomalies.