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

Abstract

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 Midcontinent are believed to be related to migration of warm basinal fluids from and within the Arkoma and Illinois basins. Because of its hydrologic connection with these two basins, the Reelfoot rift has been postulated as a potential 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 platforms in Missouri (Western platform) and Tennessee (Eastern platform). Temporal geochemical trends within each of the three areas are distinct. Eastern platform carbonate cements and their fluid inclusions exhibit decreasing δ13C, δ18O, homogenization temperatures ( T h), and last ice melting ( T m) values with decreasing age. Reelfoot rift dolomite and calcite cement and their fluid inclusions define a trend of decreasing δ13C and δ18O values and increasing T h and T m values. Western platform dolomite cements, including those in the nearby southeast Missouri Mississippi Valley–type mineral district, display a paragenetic trend of increasing δ13C and δ18O values, followed by a return to lower values during the final stage of cement deposition. Distinct geochemical patterns indicate that stratigraphically controlled fluid flow through carbonate aquifers in the Reelfoot rift was restricted within individual fault blocks that had limited communication with the adjacent carbonate platforms. Lateral fluid migration between fault blocks and vertical migration within fault blocks in the Reelfoot rift likely was restricted by faults, stratigraphic offset, and impermeable units. If significant fluid movement occurred from the Reelfoot rift onto the adjacent Western carbonate platform, it likely occurred along northwest-striking strike-slip faults.