Geochemical survey of the Lusk Creek Roadless Area, Pope County, Illinois

The Lusk Creek Roadless Area (Index map) lies along the western edge of the Illinois-Kentucky fluorspar district in which flourite deposits occur as lenticular-type veins emplaced along fult zones or as tratiform-shaped bedding-replacement deposits that occur along fault zones (Grogan and Bradbury, 1967; Trace, 1974). Although mineralogy varies between deposits, Trace (1974) points out that the principal minerals are fluorite (CaF) and calcite (CaCO₃), and associated with these minerals are lesser amounts of sphalerite (ZnS), galena (PbS), and barite (BaSO₄). Minor quantites of iron-rich dolomite (CaMg(CO₃)₂), pyrite (FeS₂),  and alteration products of zinc, lead, and copper minerals also are found.