Geological Characteristics and Ore Genesis of the Laizi Gou Gold Deposit in Muping, Jiaodong

[Objective] To determine the ore-forming age, characteristics of ore-forming fluids, sources of ore-forming materials, and genesis mechanisms of the Lazi Gou gold deposit. [Methods] This study systematically investigated the deposit using a combination of analytical techniques, including LA-ICP-MS Rb-Sr dating of phlogopite, C-O isotopes of calcite, in situ S isotopes of sulfides, laser Raman spectroscopy and microthermometry of fluid inclusions, and LA-ICP-MS trace element analysis of pyrite. [Results] The mineralization age of Lazigou gold deposit is 120.9 ± 6.62 Ma; Au is present in pyrite in the form of solid solution and nano-sized gold; each stage of pyrite shows uniform, sulfur-rich characteristics and is closely related to the surrounding rocks; the mineralization fluid as a whole is characterized by a medium-low temperature, medium-low salinity system. The uniform temperature during the main mineralization period was 123.4 - 238.7℃, the salinity was 2.07% - 12.16% NaCl eqv, the fluid density was 0.88 - 0.94 g/cm³, the minimum trapping pressure was 7.9 - 25.3 MPa, and the mineralization depth was 0.30 - 0.95 km. The mineralizing fluid during the quartz-carbonate stage had characteristics of deep origin. [Conclusion] Under the background of the subduction and retreat of the Early Cretaceous ancient Pacific plate and the enhanced regional crust-mantle interaction, deep fluids rose along fault structures and reacted with the surrounding rocks during their migration process, resulting in the continuous activation, migration and enrichment of ore-forming materials, and ultimately forming gold deposits.