THE SMACKOVER FORMATION IN ALABAMA: AN UNCONVENTIONAL POTENTIAL SOURCE FOR CRITICAL MINERALS

The identification of potential rare earth and other critical mineral resources is a major priority for multiple agencies in the United States. The upper Jurassic Smackover Formation occurs throughout the northern Gulf of Mexico basin, with an up-dip limit that overlaps a regional peripheral fault system and extends from Texas to Alabama. Smackover carbonates were deposited in near-shore moderate energy marine environments in up-dip regions of the depositional basin and inner ramp marine environments in downdip portions. The Smackover overlies fluvial, alluvial, and eolian deposits of the upper Jurassic Norphlet Formation and the Louann Salt, and both the Smackover and the Norphlet are productive host rocks for oil and gas accumulations throughout the northern Gulf of Mexico basin. Brine water produced during extraction of oil and natural gas from the Smackover Formation in Arkansas contains proven unconventional sources of lithium and bromine with reported concentrations as high as 190 mg/L and 6,500 mg/L, respectively. Reconnaissance sampling of Smackover well water in Alabama was conducted to evaluate the potential for lithium-bromine extraction from existing water disposal wells. Analytical results indicate lithium and strontium concentrations as high as 128 mg/L and 1,770 mg/L respectively, comparable with levels in Arkansas. However, bromine concentrations are much lower, reported at less than 0.1 mg/L. All of the sampled wells are located in highly permeable Smackover carbonates along the peripheral fault system at the up-dip limit of the Louann Salt. Elevated concentrations of these critical elements in waters from the sampled wells are interpreted to have resulted from water-rock interactions in the Louann Salt with subsequent up-gradient fluid movement along the peripheral fault system into the Smackover reservoir. Future sampling of additional wells in similar geologic settings may result in establishing the Smackover Formation in Alabama as an unconventional source for these high priority critical elements.