Summary:
The new discovery this time includes vein m22 and porphyry-type mineral deposits BK1, BK2, BK3 and BK5, in which porphyry-type mineral deposits BK1 and BK2 are major mineral deposits meeting the exploration standards, while the other mineral deposits meet the general prospecting standards.
The results show that magmatism and metallogeny in the Yixingzhai and Boqiang-Gengzhuang mining regions occurred during 142–130 Ma, starting with felsic granite porphyry with Mo–Cu mineralization, and intermediate magma associated with gold mineralization.
The Yixingzhai gold deposit is located in the southern part of the Hengshan Complex. The Mesoproterozoic-Paleozoic carbonate sedimentary cover has been mostly eroded in the mine area, the relicts of which occur only in the southwest and the top of the collapsed breccia pipe.
The Yixingzhai pluton is the main host rock of the gold veins. The TTG gneisses of the basement were intruded by a series of NW trending meta-dolerite dikes. The NW trending Yixingzhai fault, Longshan fault and the broadly N–S (345–355) trending secondary faults are the main structures controlling magma intrusion and ore mineralization, among which the N–S trending faults are the main host for the auriferous quartz veins.
The granite porphyry, quartz porphyry, diabase and diorite porphyry occurring as stocks and dikes, are widely distributed in the mining area. There are also 4 sub-volcanic pipes, named Hewan, Nanmenshan, Tietangdong and Jinjiling cryptoexplosive breccia pipes, located into the north of the Sunzhuang pluton. Among these, the Hewan cryptoexplosive breccia pipe is composed of breccia-bearing granite porphyry, and cut by quartz porphyry, with molybdenite mineralization occurring at the outside of contact zone. The Nanmenshan cryptoexplosive breccia pipe is composed of quartz porphyry and skarn with breccia, magnetite, and specularite with the gold mineralization in the skarn, suggesting the interaction of magmatic fluid reacting with the collapsed carbonate from cover layer. The Tietangdong cryptoexplosive breccia pipe is mainly composed of breccia rocks, which is cemented by skarn and granite porphyry, and cut by quartz porphyry and diorite porphyry. Magnetite and specularite ore bodies occur at the top and gold mineralization occurs within the space of its ring fracture.
There are more than 15 auriferous quartz veins in the Yixingzhai gold deposits. Among these, No. 5 vein is the largest one, with a length of more than 2000 m and carry 60% of the total gold reserves. According to the mineral assemblage and cross-cutting relations, the main mineralization process can be divided into four stages as follows quartz-sericite stage, mainly composed of quartz, sericite and disseminated pyrite, containing traces of gold; quartz-pyrite stage, which is the main mineralization stage, mainly composed of quartz, and cubic pyrite, with brecciated ore; quartz-polymetallic stage, which marks an important mineralization stage, composed of quartz, pyrite, chalcopyrite, arsenopyrite, chalcocite, sphalerite and galena; and calcite stage, composed of calcite, together with disseminations and veinlets of sphalerite.