Epigenetic sulfide mineralization associated with Pennsylvanian paleokarst in eastern Iowa, U.S.A.

Paleokarst-associated, sulfide-bearing mineral deposits are wide-spread in the Paleozoic carbonate rocks of eastern Iowa. Minerals occur in nodules enclosed in karst-filling mudstones, as sandstone cements, and as surface coatings on, and fracture fillings in, foundered carbonate rock clasts. Mineralogy and paragenetic sequence vary among the occurrences. Sulfur isotopic compositions exhibit wide variations within and among deposits (??34S = -33.8 to + 35.1???). Oxygen isotopic compositions of fracture-filling calcite spars (??18O = -8.41 to + 3.60???) are similar to the isotopic compositions of their carbonate rock hosts. Calcite spars are somewhat depleted in ??13C relative to host rock [??13C (spars) = - 5.66 to + 0.24??? vs. -1.54 to + 1.21??? (host rock)]. Results of mineralogic, paragenetic and isotopic investigations suggest that: (1) minerals are products of multiple events operating on a local, rather than a regional scale; (2) spatially-disjunct fracture-filling mineral deposits exposed in the same quarries are probably not cogenetic with paleokarst-associated deposits; (3) paleokarst-filling calcite spars formed at near-surface temperatures; and (4) paleokarst-associated deposits are probably not cogenetic with Upper Mississippi Valley ZnPb pitch-flat deposits. ?? 1993.