Discovery of concealed ore-bodies at the Dongping gold deposit, northern China, revealed by the study of ore-controlling structures

The Dongping gold deposit is the largest gold deposit in the Hebei province, China, with proven gold reserves of more than 100 tons. After the main gold ore-bodies were mined out, the Dongping gold deposit faced a shortage in gold reserves with an uncertain future. As a result, we conducted systematic studies on the ore-controlling structures at the Dongping gold deposit, with the aim of finding additional concealed ore-bodies, should these be present. Gold mineralization at Dongping is controlled by two stages of maximum principal compressional stress (sigma 1): NW-trending stress that produced the NE- to NW-trending structures, and sub-vertical stress that produced the circular structure, respectively. The sub-vertical compressional stress may have resulted from the emplacement of a concealed intrusive body, which also led to horizontal extensional stress, generating structures surrounding the intrusion. Development of such structures potentially increased the permeability of the local crust, facilitating the mobilisation of gold-bearing hydrothermal fluids that subsequently precipitated along the structures, forming the gold ore-bodies. We propose that the deep part of the Dongping gold deposit at the lithological contact with the concealed intrusive bodies is prospective for the exploration of additional reserves, which is supported by our subsequent drilling and the discovery of concealed gold ore-bodies beneath the deposit.