Breccia, Hydrothermal Alteration and Structural Geology of the Huangtun Porphyry Au-Cu deposit in the Middle-Lower Yangtze Metallogenic Belt, Eastern China

There were two stages of structure activity in the mining area. The pre-mineralisation structure activity formed F1 and F2 faults, and these faults also controlled location of the emplacement of Au-Cu mineralisation later. Subsequently, the intrusion related to gold and copper mineralisation was emplaced and released fluids, which formed K-Na silicate to illite-smectite altered magmatic-hydrothermal breccia, from the deep to shallow. Hydrothermal breccia with a high matrix/cement ratio then formed when mineralizing fluid permeated the fracture zone. During post-mineralisation activity, the sinistral strike-slip F1 and F2 faults were reactivated, forming tectonic breccia containing some massive carbonate ± quartz ± pyrite clusters clasts.