METALS IN PENNSYLVANIAN BLACK SHALES FROM ORE FLUIDS NOT FROM SEAWATER

Molybdenum and zinc tenors of Midwestern Pennsylvanian black shales exceed those of any other black shales except for the Kupferschiefer of northern Europe and other shales known to be products of hydrothermal mineralization. Metal contents of the Pennsylvanian shales far exceed those of any modern black mud except for those directly associated with marine hydrothermal vents. Extreme metal contents, fluid inclusions, alteration patterns and paleochronology (Symons et al., 2005, Economic Geology) imply that the highly metalliferous Pennsylvanian shales of the Midwestern United States were mineralized during the Pennsylvanian by hydrothermal solutions. The conclusion is inescapable that highly metalliferous Pennsylvanian shales of the Midwestern United States derived their contained metals from hydrothermal solutions rather than from sea water. Spatial association implies that the most logical source of the hydrothermal solutions that mineralized the shales is the very same system that mineralized the great lead-zinc deposits of the Midwest, including the Tri-State district.