The hydrocarbon producing rocks of the Upper Jurassic in the northern Gulf of Mexico are known to contain lithium-rich brines. However, the genesis of the lithium-rich water is not very well understood. Analysis of hydrogeochemical data indicates that the brines are enriched in bromide, Calcium, Lithium, and sodium, and depleted in potassium, magnesium, and sulfate. Considering this, hydrogeochemical, petrographic, and X-ray Powder Diffraction (XRD) data shows that the brines have been significantly altered relative to the original composition of the water, by salt dissolution, freshwater mixing, and dolomitization. Based on the results of this study, the ore-grade lithium brine is being enhanced by the same stratigraphic and geochemical controls that is depositing dolomite in the Upper Jurassic reservoirs of the northern Gulf of Mexico.