GEOPHYSICAL EVIDENCE FOR THE ORIGIN OF THE LEAD-ZINC DEPOSITS IN THE TRI-STATE MINING DISTRICT, KS, MO AND OK

Northeast Oklahoma, SE Kansas and SW Missouri was one of the major lead-zinc mining districts in the world during the 20th century. The ore generation process was typical of the many Mississippi Valley type (MVT) deposits that occur in the Ozarks region with the ore formation being related to ore fluids being expelled from the Arkoma basin and Reelfoot rift into structurally controlled hydrological regimes. Even though the exact location of deposition of the strata-bound ore minerals are mainly related to carbonate lithologies including dolomitic breccias and bioherms, the fluids were brought into the mining district by regional faults and there is a close association with major ore deposits and intersection of faults. To study the nature and extent of these structures, the existing gravity data which are relatively sparse especially in Missouri and Oklahoma were obtained. To supplement the regional gravity data, 600 additional points were collected in Oklahoma and Missouri at intervals between 1 and 2 km. Aeromagnetic data were also obtained from the USGS. Bouguer gravity and magnetic anomaly maps show that the regional anomalies trend toward the northwest in Missouri and east-west in Oklahoma and Kansas. The NW anomaly trends has been noted elsewhere with the Ozark's region and is inferred to be caused by basement topography however the variation of anomaly amplitude can also be explained by changes in lithologies (e.g., more mafic material causing the large amplitude gravity and magnetic maxima) within the basement. The major mining fields of Pitcher in Oklahoma and Joplin in Missouri occur at the intersection of the east-west and NW trending anomalies. Additionally, these mining fields occur over large amplitude gravity and magnetic maxima which may be caused by Precambrian mafic lithologies. These two features imply that part of the emplacement of the ores may be basement influenced. In order to further investigate these anomalies, a series of residual (wavelength filtered and polynomial trend surfaces) and horizontal derivatives maps, and 2-D dimensional gravity and magnetic models will be constructed.