Application of integrated geological and structural investigations to the discovery of new mineral zones related to the Daping gold deposit, Southwest China

Abstract

The Daping gold deposit is one of the largest gold deposits in the Ailaoshan gold belt of SW China. It has proven gold reserves of more than 70 tonnes and has been mined for 36 years. Finding new orebodies to extend the mine life has become urgent since the main gold orebodies are almost depleted. Ore deposit types in the Daping area include quartz-vein and porphyry gold types of mineralization. The quartz-vein ores are hosted in late Proterozoic diorite and Silurian limestones and controlled by NW trending faults. We have studied the ore-controlling structures to determine palaeo-stress directions of V1-2-3 and V37 orebodies, and the distribution of gold mineralization in the V1-2-3 orebodies. Based on the field observation, we identified six stages of structure in the Daping gold deposit, i.e., pre-mineralization (stage 1), syn-mineralization (stages 2 to 4), and post-mineralization (stages 5 and 6). The spatial distribution of gold orebodies at Daping is mainly controlled by the compressional faults of stage 1 that is associated with the Ailaoshan orogenic belt, and overprinted by structures of later stages. Orebodies from gold deposits in orogenic belts commonly have greater vertical dimensions than horizontal dimensions, suggesting that V1-2-3 orebodies may extend to deeper area.Our data indicate that higher gold grades and the thickest parts of the orebodies are associated with deeper parts of the V1-2-3 orebodies (up to 800 m in depth), and are likely related to a concealed mineralized porphyry which was intersected in drill core and identified as xenolith in lamprophyre dikes in the underground mine workings. The quartz-vein type gold mineralization at the Daping gold deposit was possibly overprinted by the porphyry gold mineralization, as indicated by the discovery of the new quartz-vein-associated orebodies beneath the current levels of Daping gold deposit and associated porphyry gold orebodies at Daping gold area.