Trace elements and REE geochemistry of Middle Devonian carbonate mounds (Maïder Basin, Eastern Anti-Atlas, Morocco): Implications for early diagenetic processes

• Carbonates from Maïder basin mound were investigated for petrology and REE contents.
• Mounds are made by stromatactis bearing limestone dissected by veins and dykes.
• Dyke fills recorded marine conditions, vein infill precipitated from anoxic fluids.
• Micrite precipitated within high alkaline organic matter-rich oxygenated pore water.
• REEs record microbial activity and early diagenetic organic matter dissolution.

Trace and rare earth elements (REEs) have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds, whose genetic processes are not yet fully understood. Carbonates from the Middle Devonian conical mud mounds of the Maïder Basin (eastern Anti-Atlas, Morocco) have been analysed for their REE and trace element distribution. Collectively, the carbonates from the Maïder Basin mud mounds appear to display coherent REE patterns. Three different geochemical patterns, possibly related with three different diagenetic events, include: i) dyke fills with a normal marine REE pattern probably precipitated in equilibrium with seawater, ii) mound micrite with a particular enrichment of overall REE contents and variable Ce anomaly probably related to variation of pH, increase of alkalinity or dissolution/remineralization of organic matter during early diagenesis, and iii) haematite-rich vein fills precipitated from venting fluids of probable hydrothermal origin.Our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter, whilst venting may have affected the mounds during a later diagenetic phase.