Abstract: The Jiaojia fault zone, along which many large and medium-sized gold deposits are distributed, is one of the most important fault zones in the northwest of Jiaodong Peninsula.In this work, we have collected core samples from the "China's deepest drill-hole controlling gold orebody" to carry out a fluid inclusion study.This drill-hole conducted by Shandong Institute of Geological Sciences lies at Wuyicun village of Laizhou city and penetrates the deep part of the Jiaojia fault zone.The samples include fresh and altered granites, phyllic rocks with pyrite-sericite-silicic alteration and ores at different alteration stages and different depths on the hanging wall and footwall of the main fault zone.Through detailed field investigation and petrographic study of the samples we have identified three metallogenic stages, five generations of quartz and two types of fluid inclusions in the ores.Microthermometry and Laser Raman analysis were performed on the representative fluid inclusions.The results have suggested that the fluids responsible for gold mineralization in the deep part of the Jiaojia fault zone belong to the H₂O-NaCl-CO₂±CH₄ fluids with medium to low salinity, which were generated by mixing of the mantle-origin metal-rich fluid and the shallow meteoric fluid with possible participation of the crustal metamorphic fluid.The gold in the ore-forming fluids occurs mainly as hydrosulphide complexes(AuHSo).Both fluid inclusion petrography and microthermometry have shown the phase separation(immiscibility)of H₂O-NaCl-CO₂±CH₄ fluids took place during the main ore mineralization stage and caused gold deposition.The immiscibility occurred at the P-T conditions of 210 ~ 260 ℃ and 150~210 MPa, respectively.In the Mesozoic, the ancient Pacific plate initially subducted northwesterly towards the Eurasian continent that caused intense compresional deformation and magmatism(e.g.formation of the Linglong granite)in Jiaodong region.Later in Early Cretaceous, tectonic transition from transpression to trnastension in the region resulted in the Guojialing granite emplacement and strike-slip movement of the Tanlu fault as well as development of a series of subsidiary NE—NNE trending faults, which provided channels for the ascending of magmas and fluids from the deep.In this process the magmatic-hydrothermal fluids were mixed with metamorphic and meteoric fluids circulating in the middle and upper crust, and finally led to the formation of gold deposits in the Jiaodong region.