Which minerals are typical of Mississippi Valley base metal deposits?

• A. Sphalerite, Galena
• B. Chalcopyrite, Pyrite
• C. Magnetite, Hematite
• D. Galena, Pyrite

Answer: (A)

Mississippi Valley-type deposits are defined by the precipitation of zinc and lead sulfide minerals from basinal brines in carbonate rocks. The hallmark ore minerals are sphalerite (zinc sulfide) and galena (lead sulfide), which occur together as the main base-metal ore pair in these deposits. Chalcopyrite indicates copper-rich systems and points to other deposit types, while magnetite and hematite are iron oxides typical of iron ore or oxide-dominated systems rather than classic MVT base metals. Pyrite can occur in many sulfide deposits, but it is not the characteristic pairing for MVT; the combination of sphalerite and galena best represents this deposit class, often with associated gangue minerals like barite and fluorite in carbonate hosts.