Abstract In addition to a Zn-rich lens representing the northern prolongation of the Draa Sfar volcanogenic massive sulfide deposit, the Sidi M'Barek deposit includes Cu-rich lenses in which gold is being recovered profitably as a by-product. The Cu-rich mineralization is composed of numerous structurally controlled veins whose morphology suits that of a lode rather than that of a stratiform orebody. Although the Cu-rich and Zn-rich orebodies are dominated by pyrrhotite, pyrrhotite is coarser grained in the Cu-rich lenses and mineralization is polyphase. Pyrrhotite is deformed and recrystallized; it is cross-cut and replaced by pyrite infilling veins. Pyrite also crystallizes along the S 1 cleavage and in pressure shadows around bioclasts in the disseminated ore. Chalcopyrite veins postdate both the pyrrhotite and pyrite phases. The concentration of Co and Au is higher in the Cu-rich lenses relative to the Zn-rich lenses, which have higher concentrations of Pb, Ag and As. Pyrite and pyrrhotite have distinct sulfur and lead isotopic signatures. We propose a polygenetic model in which a pre-existing syngenetic pyrrhotite-rich mineralization is remobilized in shear zones during a major ductile deformation event allowing deposition of pyrite. The shear zones were reopened during a late ductile–brittle deformation event allowing deposition of chalcopyrite.

Abstract Synthesis of structural, petrological and geochronological data for the Maures–Tanneron Massif and its integration in the framework of adjacent massifs (i.e. Sardinia and Corsica) has allowed us to propose a new model of evolution for the southern Variscan belt. After Siluro-Devonian subduction associated with high-pressure–low-temperature (HP/LT) metamorphism M 0 ( c. 10–15 °C km −1 ) and subsequent Carboniferous nappes stacking, the belt underwent strong reworking related to back-thrusting. Nappes stacking and back-thrusting were associated with typical Barrovian metamorphism M 1 ( c. 20–30 °C km −1 ) starting at 360 Ma that progressively evolved to higher temperature metamorphisms M 2 ( c. 40–60 °C km −1 ) and M 3 ( c. 60–80 °C km −1 ) during 330–300 Ma in the internal part of the belt. Progressive increase of the thermal gradient is interpreted as a consequence of gravitational instabilities triggered in the partially molten orogenic root. Continuous compressive forces applied to the belt allowed vertical extrusion of the orogenic root in fold-dome structures. The mass transfer is accommodated by orogen-parallel transpressive shearing synchronous with M 3 during Late Carboniferous time. The orogenic wedge is characterized by two main tectono-metamorphic units decoupled by a major shear belt: an Internal Zone with migmatites and syntectonic granitoids, where HP relicts have been exhumed, and an External Zone that escaped the late HT event and preserved precious structures.