CHEMISTRY OF SOME ANADARKO BASIN BRINES CONTAIINING HIGH CONCENTRATIONS OF IODIDE

This study was made to determine the geochemical relationships between the subsurface fluids and some of the geologic strata in the Anadarko Basin. Samples of brines, cores, and petroleums from Pennsylvanian and Mississippian age sediments were obtained and analyzed. The brine samples obtained from Mississippian and Pennsylvanian age sediments in the northern Oklahoma Platform area of the Anadarko Basin contain the highest concentration of iodide ever recorded. The highest concentrations were found in the Pennsylvanian samples. The brines are a Na/1bCa/1bCl type. The brines probably have undergone diagenesis such as dolomitization, as indicated by the Mg/Br and Mg′/Br ratios and by plots of their concentrations of chloride cs. magnesium and calcium. The bromide concentrations of these brines indicate that they probably are relict. The Mg′/Mg ratios indicate that some of the brines were in equilibria with sandstones, some with dolomites, and some with limestones. Compared to sea water that was subjected to solar evaporation, most of these brines were enriched in concentrations of bromide, calcium, lithium, strontium; and iodide, and depleted in concentrations of magnesium and potassium. Most of the brines from Mississippian age sediments were enriched in boron concentrations, and most from Pennsylvanian age sediments were depleted in boron. The high concentrations of iodide in these brines was attributed to concentration by an abundant shallow water ancient fauna and flora and preservation by rapid sedimentation. Additional concentration of iodide in these brines occurred during sediment compaction and associated phenomena. © 1969.