Hydrothermal Fluids and Diagenesis of Mississippian Carbonates: Implications for Regional Mineralization in Western Kansas, U.S.A

Hydrothermal fluids altered Mississippian (Osagian) carbonates in the Rebecca K. Bounds (RKB) core in western Kansas, U.S.A. Carbonate mineralization is similar to that associated with Mississippian valley type (MVT) mineralization. The RKB core displays fractures, vugs, channels, and breccias filled with saddle dolomite and blocky calcite cements. Homogenization temperature indicates that dolomite (65 to 126 °C, 18.4 to 23 wt. % NaCl) and calcite (67 to 101 °C, 13.2 to 22.4 wt. % NaCl) cements were precipitated by hot, saline fluids. These data are consistent with previous studies on the southern midcontinent. Carbon and oxygen isotope values for dolomite (δ13C 0.15 to 2.08‰, δ18O −6.44 to −4.66‰) and calcite (δ13C −1.01 to 1.79‰, δ18O −9.44 to −8.69‰) indicate multiple pulses of fluids likely sourced from basins to the south and west. Strontium isotopes data (0.7088812 to 0.7094432 in dolomite and 0.7089503 to 0.7111501 in calcite) indicate fluid interaction with granitic basement or basement-derived siliciclastics. These results are consistent with mixing of upwelling Ordovician-sourced fluids and Permian evaporitic brines, transported by advective and/or vertical migration. Although sulfide minerals were not observed in this study, earlier reports in western Kansas document sphalerite linked to hydrothermal brines in underlying strata. This study highlights the potential for MVT mineralization in the Mississippian of western Kansas.