THE CHARACTER OF THE TRI-STATE (MISSOURI, OKLAHOMA, KANSAS) ZINC-LEAD ORE DEPOSITS AND A COMPARISON WITH THE LEAD-ZINC-COPPER-COBALT DEPOSITS OF THE VIBURNUM TREND, SOUTHEAST MISSOURI

The two world-class Mississippi Valley-type ore districts, located partly or entirely in Missouri, the Tri-State Zn-Pb District and the Southeast Missouri Pb-Zn District (including the Viburnum Trend) are similar in many respects and are significantly different in other respects.

The ores of the Tri-State District (Missouri, Oklahoma, Kansas) are contained within Mississippian rocks. The hostrocks originally were cherty limestones that have been intensively dolomitized, silicified to jasperoid, and thinned in the vicinity of the orebodies. The orebodies were horizontal linear runs and flat sheetlike deposits consisting of chert breccia fragments cemented by jasperoid and ore minerals. The ore runs were about 500 feet wide and tended to form circular map patterns. In both districts, sphalerite and galena were the dominant ore minerals, smaller amounts of chalcopyrite, marcasite, and pyrite were present, and the principal gangue minerals introduced with the ore fluids were dolomite and quartz. Sphalerite dominated over galena in Tri-State, and galena dominates over sphalerite in the Viburnum Trend. Cadmium, germanium, and gallium were recovered from sphalerite.

The ores of the Viburnum Trend are contained within Cambrian rocks. The hostrocks originally were limestones that have been intensively dolomitized and partly thinned in the vicinity of the orebodies. Ore runs trend predominantly north-south, but diverge around buried Precambrian knobs. Mineralized solution collapse dolomite breccias are common at most of the mines, but locally thin flat orebodies occur above reefs extending eastward from the main trend. In addition to the main ore minerals, smaller amounts of other ore minerals, present in the Viburnum Trend but absent from the Tri-State District, include siegenite, millerite, polydymite, tennantite, enargite, gersdorffite, vaesite, nickeliferous pyrite, nickeliferous carrollite, bornite, chalcocite, digenite, djurleite, covellite, blaubleibender covellite, and castaingite. Cadmium is recovered from Viburnum sphalerite, and silver is recovered from both sphalerite and galena.