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).
The Zgounder Deposit formed during two (2) distinct stages of hydrothermal fluid alteration and mineralisation (Essaraj et al., 1998, 2016, 2017):
-Deposition of quartz with minor biotite and As-Co minerals from a variety of H2O-CO2-CH4 rich fluids in equilibrium with the metasedimentary host rocks. The fluids were at high temperatures (400ºC to 450°C) over a wide range of pressures, during the early brittle deformation of the Brown Formation, following emplacement of the Askaoun Granite; and
-The main phase of (Cu-Zn)-Ag (Hg) mineral deposition. Silver deposition occurred following crystallization of quartz-sphalerite-chalcopyrite veins, but the Cu-Zn and Ag(Hg) mineralising fluids were NaCl-CaCl2 brines at minimum temperatures of about 160°C to 200°C, during a period of hydrothermal albitization.
Mineralisation
The Zgounder silver mineralisation occurs at the top of the Bro ........
