Ore deposit type: Magmatic-hydrothermal, porphyry type
Provenance: Assarel Mine, Bulgaria
Description: Porphyric igneous rock with intense hydrothermal alteration (the original texture is largely obliterated) cut by a stockwork of veins made of quartz (white), pyrite (light yellow) and copper sulphides (chalcopyrite, golden yellow and chalcocite, black). Stockwork zones in porphyry-type deposits are produced by hydrofracturing due to overpressurisation of magmatic-hydrothermal fluids. They generally occur above the intrusion and in its country rocks.