Fluid migration and associated diagenesis in the Greater Reelfoot rift region, Midcontinent, United States

The sources and pathways of basinal fluid flow on the North American craton have been the subjects of intense debate, Regional dolomitization and the distribution of petroleum and sulfide mineralization on the southern Midcon tinent are believed to be related to migration of warm basinal fluids from and within the Arkoma and Illinois basins, Because of its hydrologic connec tion with these two basins, the Reelfoot rift has been postulated as a pote ntial source and/or conduit for one or more of these fluids. Cathodoluminescence petrography has revealed nine distinct carbonate cement microstratigraphies in the Reelfoot rift and on its adjacent carbonate pla tforms in Missouri (Western platform) and Tennessee (Eastern platform), Tem poral geochemical trends within each of the three areas are distinct, Easte rn platform carbonate cements and their fluid inclusions exhibit decreasing delta C-13, delta O-18, homogenization temperatures (T-h), and last ice me lting (T-m) values with decreasing age, Reelfoot rift dolomite and calcite cement and their fluid inclusions define a trend of decreasing delta C-13 a nd delta O-18 values and increasing T-h and T-m values. Western platform do lomite cements, including those in the nearby southeast Missouri Mississipp i Valley-type mineral district, display a paragenetic trend of increasing d elta C-13 and delta O-18 values, followed by a return to lower values durin g the final stage of cement deposition, Distinct geochemical patterns indicate that stratigraphically controlled fl uid flow through carbonate aquifers in the Reelfoot rift was restricted wit hin individual fault blocks that had limited communication with the adjacen t carbonate platforms, Lateral fluid migration between fault blocks and ver tical migration within fault blocks in the Reelfoot rift likely was restric ted by faults, stratigraphic offset, and impermeable units, If significant fluid movement occurred from the Reelfoot rift onto the adjacent Western ca rbonate platform, it likely occurred along northwest-striking strike-slip f aults.