Sedimentary exhalative (SEDEX) Pb-Zn-Ag ore deposits form when metal-bearing hydrothermal fluids are expelled ('exhaled') onto the seafloor within actively subsiding sedimentary basins, typically intra-continental rift basins (extensional basins formed during continental rifting), where the fluids mix with cold seawater in restricted, often anoxic marine or lacustrine sub-basins, precipitating stratiform sulfide mineralization interbedded with fine-grained sedimentary rocks (shale, siltstone).
SEDEX deposits are characteristically associated with intra-continental rift basins, extensional tectonic settings in which continental crust is being pulled apart, generating fault-bounded, rapidly subsiding sub-basins...
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