Analysis of tectonic fracturing in the Mibladen ore deposit (Upper Moulouya, Morocco) and its impact on the Pb-Ba mineralization emplacement

Abstract The MVT-type Pb-Ba mineralizations of the Mibladen ore deposit are hosted by Jurassic carbonates as well as Infracenomanian conglomerates and sandstones. The mineral paragenesis is mainly composed of galena and barite with lesser chalcopyrite and pyrite, accompanied by supergene oxidation minerals. This ore deposit is the result of a major epigenetic mineral stage with economic orebodies occuring as replacement of pre-existent carbonate rocks, fillings of karst cavities, interstratal joints, collapse-breccias, fractures and faults. Structural and microtectonic analyses we carried out in this ore deposit, allowed us to highlight two main fracture networks controlling ore deposition within karst cavities and interstratal joints: i) NNW-SSE to NNE-SSW trending tension gashes and normal faults; ii) ENE-WSW to E-W trending reverse faults with strike-slip components and transtensive relay zones. All of these structures are developed under a regional compressional tectonic regime divided into extensional and transtensional episodes (σ1-σ2 and σ2-σ3 permutations) with sub-meridian σ1 axis and sub-equatorial σ3 axis. This compressive tectonic event caused the uplift of Mibladen area and favored the circulation of mineralizing fluids along the NW-SE and ENE-WSW major faults such as Amourou and Aouli Faults, during the Infracenomanian period (Upper Jurassic-Early Cretaceous).