Structural controls and palaeostress analysis of hydrothermal circulation and fluorite–baryte ore genesis at Jbel Merguechoum, Moroccan Eastern Meseta

Abstract

The Jbel Merguechoum fluorite–baryte ore is hosted in Late Hercynian granite, situated beneath the Paleozoic–Triassic unconformity in the Moroccan Eastern Meseta. This deposit represents a key example of rift-related hydrothermal mineralisation. This study integrates detailed structural mapping and palaeostress analysis to evaluate the role of fracture systems in ore genesis and to constrain the relative timing of mineralisation. The fluorite–baryte ore is spatially associated with NNE–SSW to NE–SW normal faults, NE–SW tension gashes, and minor NNW–SSE normal faults that were reactivated during Triassic–Jurassic extension. Palaeostress reconstructions indicate an extensional regime with a subvertical σ1 and a subhorizontal NNW–SSE σ3. This configuration generated crustal-scale normal faults that enhanced permeability. During the Triassic–Jurassic rifting related to the breakup of Pangea, marine basins developed, providing a source of seawater that infiltrated deeply along these active structures. This tectonic-structural model underscores fault reactivation and rift-induced convection as critical ore-forming processes, providing insights for the exploration of unconformity-related deposits in extensional settings.