Highlights: Economic Mineralization—It’s The Fault’s Fault

Pressure and temperature are two fundamental controls on diagenesis and formation of economic minerals. To understand the possible influence of fault-related hydrothermal fluids on uranium mineral deposits of Carboniferous to Jurassic siliciclastic deposits in the Tim Mersoï Basin in Niger, Mamane Mamadou  and others examine the P-T conditions of diagenesis using petrography SEM observations and chemical analyses, supplemented thermometric approaches of chlorite compositions and fluid inclusions in quartz overgrowths. Chlorite thermometry indicates that all Carboniferous to Jurassic section was subjected to elevated temperatures of around 125°C (Carboniferous) and 115°C (Jurassic). These temperatures suggest a strong thermal disequilibrium between incoming fluids and reservoirs, reflecting burial temperatures in excess of those expected at maximum burial depth.  The fault-influenced fluid circulation affecting these strata are interpreted to to be linked to major geodynamic events related to the opening of the Atlantic Ocean, and likely have analogs elsewhere.

Hot fluid flows around a major faultidentified by paleothermometric studies (Tim Mersoï Basin, Niger) by Marah Mamane Mamadou, Michel Cathelineau, Franck Bourdelle, Marie-Christine Boiron, Agnes Elmaleh, and Marc Brouand