Zgounder is a Neoproterozoic age, sedimentary rock-hosted, low-sulphidation epithermal silver deposit.
The Zgounder Silver Deposit is cross-cut by fractures of variable orientations. There are at least four (4) fracture systems:
1. Late sub-vertical E-W fractures and shear zones;
2. N-S fractures/faults dipping steeply to the east;
3. NNE-NNW-oriented system dipping 60° at a strike of 75°E; and
4. A sub-horizontal system of fractures oriented NNE and NNW, which displaced the Brown Formation to the north with depth (Bounajma, 2002).
Mineralisation
The Zgounder silver mineralisation occurs at the top of the Brown Formation (sandstone), predominantly along the contact and within the dolerite sill. The economic silver concentrations at Zgounder are present mainly as vertical bodies, complex clusters, shear zones, and veinlets, and at the intersection of the E-W and N-S fractures, though preferentially at the contact zones between schist and dolerite (Petruk, 1975; Popov et al., 1989). Native silver occurs in complex sets of microfractures, mainly at intersections with sulphide veinlets, and locally accompanied by chloriterich alteration. Small Ag grains (average size = 50 µm) occur in corrosion zones of early sulphides or disseminated within the schist and dolerite.
According to Marcoux et al. (2015), the paragenetic sequence shows two successive stages of mineralisation: 1) an early Fe–As stage and 2) an Ag-bearing polyme ........
