Diagenesis of Diapir Flanking Successions: The Moroccan High Atlas and Other Tethyan Salt-Related Basins

During the last decade, several studies have investigated the impact of diapirism in the diagenesis of the flanking sediments, as they are potential targets for the exploration of mining and energetic resources. These diagenetic processes are closely related to the tectonic evolution of the salt structures. The Tazoult and the Toumliline diapirs case studies display excellent exposures in the Central High Atlas (Morocco). Petrographic observations and geochemical analyses of Jurassic carbonate halokinetic sequences bounding both salt diapirs reveal similar diagenetic phases, which are: (1) saddle dolomites replacing both carbonate host-rock and fracture filling cements and (2) calcite cements and calcitized dolomite linked to meteoric water percolation. Coarse crystalline saddle dolomite (δ13C ranging from − 3.56 to − 1.79‰VPDB, and δ18O ranging from − 7.45 to − 5.19‰VPDB) are attributed to the circulation of hot Mg-rich brines in the vicinity of diapir structures during their passive growth. In contrast, meteoric percolation and the associated calcite cements, characterized by Mn content above 2000 ppm, and calcitized dolomite are attributed to later stages in the evolution of diapiric structures, most likely during their Alpine compressional deformation and inversion. Results indicate similar diagenetic evolution and geodynamic context to those described in other salt-related basins in the Tethyan domain such as in the Pyrenean Trough, Betic Margin, Cantabrian Basin, Iberian Basin, Causses Basin, and Tunisian Atlas Margin.