Fault-controlled barite veins of the eastern Anti-Atlas (Ougnat, Morocco), a far-field effect of the Central Atlantic opening? Structural analysis and metallogenic implications

Abstract

Tectonic and micro-tectonic studies at different scales are of primary importance in a modern metallogenic investigation. In the Ougnat massif of the eastern Anti-Atlas belt (Morocco), the barite ore deposit is hosted within mafic to felsic rocks of the Ediacaran Saghro and Ouarzazate groups together with their folded Paleozoic cover. Here, we provide for the first time new field-based data on the tectonic control of barite mineralization, and their relation with regional tectonic events. The mineralization occurs in brittle-ductile structures as a vein-type system, mainly hosted within NE-SW to E-W and NW-SE strike-slip-normal faults. Economic orebodies spread frequently along the Precambrian-Cambrian contact zone thus acting as open conduits for mineralized fluid flow. The geometry of hosted barite sigmoidal lenses corresponds to “pull-apart” or “tension gashes” openings, commonly arranged en echelon arrays along the bearing transcrustal faults. The occurrence of predominant massive and breccia internal texture implies a tectonic-mineralizing collapse process in an extensional tectonic context. Kinematic pattern, directional distribution and host-rock age relationship point to a syntectonic barite control probably occurred during the NW-SE Atlantic rifting, as already attributed to similar deposits in the neighboring Ougarta and Atlas-Meseta domains.The barite ore is quantitatively and qualitatively more preserved in competent host rocks than those with ductile behavior, thus offering a useful hint for further barite exploration in this part of the Anti-Atlas fold and thrust belt.