GENESIS OF SOUTHEAST MISSOURI LEAD DEPOSITS

The lead deposits of southeast Missouri require a genetic model which is different from those previously presented to account satisfactorily for their distribution relative to patterns of sedimentation and diagenesis, their temperature of formation, and the less-than-conclusive evidence for ″early″ formation. The author proposes that: (1) The source of the lead and zinc was limestone of the back reef facies, enriched in metals extracted from sea water by algae, which is half-surrounded by the 100-mile-long arc of lead mineralization; (2) Fluids which dissolved and transported the metals were dolomitizing brines produced by evaporation; (3) Metals were precipitated when the encountered sulfide ion above the reef facies; and (4) Temperatures of formation, as indicated by studies of fluid inclusions, might have resulted from thermochemical sulfate reduction.