Summary:
The poly-metallic mineralization at the GC deposit is characteristic of mesothermal vein infill deposits and exhibits the following features:
- Mineralization occurs as structurally controlled veins within broader alteration zones, which can extend several meters along both the hangingwall and footwall of the faults.
- The veins have sharp contacts with the host rocks and steeply dip at angles between 60° and 85°.
Ag-Zn-Pb mineralization generally follows the strike of the faults.
Mineralization at the GC deposit can be categorized into primary and oxidized types. Primary mineralization, which constitutes 95% of the total Mineral Resource, is mainly composed of galena, sphalerite, and silver minerals, appearing sparsely, as disseminations, veinlets, and lumps. Oxide mineralization occurs near the surface, primarily within fault-breccia zones that are oxidized down to about 40 m. These veins display open space and boxwork lattice textures due to sulphide mineral oxidation, with secondary minerals like kaolinite, hematite, and limonite present.
Pyrite is the dominant sulphide mineral, making up a few percent to 13% of the veins. Other minerals include sphalerite, galena, pyrrhotite, arsenopyrite, magnetite, and trace amounts of chalcopyrite and cassiterite. Metallic minerals, found in smaller quantities, include argentite, native silver, bornite, wolframite, scheelite, and antimonite. These occur in narrow bands, veinlets, or as disseminations within the gangue, which consists of chlorite, quartz, fluorite, feldspar, mica, hornblende, and minor or trace amounts of kaolinite, tremolite, actinolite, chalcedony, garnet, zoisite, apatite, and tourmaline.
Alteration minerals associated with the GC veins include quartz, sericite, pyrite, chlorite, clay minerals, and limonite. Silicification is common near the centre of the veins, while chlorite and sericite are found near and slightly beyond the vein margins. Quartz, pyrite, fluorite, and chlorite are closely related to the mineralization.
In addition, the GC deposit exhibits several notable mineralization features:
- High-grade Ag-Zn-Pb mineralization tends to occur at the intersections of NWW and east-west striking faults, leading to east plunging shoots of high-grade mineralization.
- Fault breccia zones host the most intense, continuous, and wide mineralization of Ag-Zn-Pb.
- Grade contours indicate that Zn mineralization is more continuous across the veins, whereas Ag and Pb are more locally concentrated.
The GC deposit consists of 256 mineralized Ag-Zn-Pb veins.