Geological, geochemical characteristics and metallogenic model of Shanping-Donghuanggou lead-zinc deposit in Mian-Lue-Ning Area, northern margin of the Yangtze Block

During the Neoproterozoic Era, the large-scale marine volcanic activity, which occurred in the Mian （xian）-Lue （yang）-Ning （qiang） Area, eastern section of Bikou on the northern edge of the Yangtze Block, had formed a NE directional distributed volcanic apparatus group and the widely distributed Bikou rock-group （Pt₃BK） bimodal volcanic rocks. Along with large-scale volcanic sedimentation and gas-liquid mineralization, a series of marine volcanic rock-type iron, copper, lead-zinc polymetallic deposits are formed, which includes the Shanping-Donghuanggou lead-zinc deposit, located in Daijiaba Town, Ningqiang County. In order to reveal the genesis of the deposit and establish the metallogenic model, a systematic geological and geochemical study of this deposit has been carried out in this paper. It indicates that the Shanping-Donghuanggou lead-zinc deposit is located in an approximately dome-shaped ancient volcanic apparatus, sandwiched by NW, NNW, and NE trending faults. The main ore bearing rock is the eruptive phase spilite keartophyry of the Da’an Formation （Pt₃d）, which belongs to the Na-rich and low Ti-calcium alkaline spilite keartophyry series. In terms of mineralization characteristics, the mining area has a zoning feature of upper “black ore （galena+sphalerite）” and lower “yellow ore （pyrite+chalcopyrite）”, upper blocky （banded, disseminated ores） and lower vein-like ores, and develops exhalation sedimentary rocks such as hematite and barite. The S-Pb isotope characteristics indicate that the ore-forming materials mainly originated from the underlying sodium-rich spilite keartophyry. The H-O isotope characteristics indicate that the ore-forming fluid mainly came from deep-seated fluids. The inclusion composition shows that the ore-forming fluid belongs to the K⁺- Ca²⁺- Cl - SO₄ ²⁻ type. The zircon U-Pb age obtained from the ore-bearing spilite keartophyry is 857.2 Ma, indicating a similar mineralization age in the middle to late Neoproterozoic. In summary, it is believed that the Shanping Donghuanggou lead-zinc deposit belongs to the “black ore” VMS-type Zn Pb - （Cu） deposit, which was formed in the northern margin of Yangtze Block cracking background in the late stage of the Neoproterozoic Era. The deposit was formed by marine volcanic hydrothermal mineralization during the late period of the first cycle of bimodal volcanic activity, containing a large amount of H₂S, CO₂, CH₄, Cl⁻, SO₄ ²⁻ and Pb, Zn, Cu and other substances. The ore-forming fluid surged up the volcanic pipeline, mixed with volcanic rocks and seawater, forming a mineral-bearing fluid. In the low-lying areas near the volcano, it enriched and precipitated mineralization near the interface between explosive spilite keartophyry and eruptive spilite tuff facies, forming layered polymetallic Zn Pb-（Cu） sulfide deposit.