Gran Colombia Gold Corp. Marmato gold deposit. Colombia.
The deposit mainly comprises sulfide-rich veinlets and veins composed of minor quartz, carbonate, pyrite, arsenopyrite, Fe-rich sphalerite (i.e. marmatite), pyrrhotite, chalcopyrite and electrum in the epithermal upper zone, and quartz, pyrrhotite, chalcopyrite, bismuth sulfide and telluride minerals and free gold in the mesothermal lower zone. Pervasive early propylitic alteration is over-printed principally by phyllic and intermediate argillic alteration related to the gold mineralized veins of low to intermediate sulfidation epithermal type, with weak and patchy potassic (biotite) alteration at depth.
Low to intermediate sulfidation epithermal style mineralization. 0.25 m @ 17.5 g/t Au, 19 g/t Ag.
Mesothermal style mineralization
Dacite porphyry with stockwork of veinlets of quartz-pyrrhotite-minor chalcopyrite with narrow illite halp, overprinting biotite alteration. MT-1498 at 854.0 m. Sample 2.0 m at 17.3 g/t Au, 3.5 g/t Ag and 330 ppm Cu.
Veinlet of quartz-pyrrhotite-chalcopyrite with halo of green sericite-smectite in dacite porphyry with weak biotite alteration. MT-1498 at 847.3 m. Sample 2.0 m at 2.88 g/t Au, 0.7 g/t Ag, and 225 Cu