SEDEX stands for SEDimentary EXhalative. As the name suggests, these deposits form by minerals being exhaled (through igneous action) from the crust and then concentrated in the same manner as other sedimentary deposits. This process usually occurs in the ocean, and due to the dynamics of geology, SEDEX deposits can be found in the continents, as well. Geologica generates them everywhere, except for volcanic domains. Due to the solubility of sulfur compounds in magma, these deposits are enriched for sulfur-containing minerals, especially sphalerite, galena and barite, but also chalcopyrite. The tungstate mineral scheelite is also found in economic concentrations.
Open-pit mine of sphalerite/galena deposit