Genesis of the Panzijian gold deposit in Jiaodong Peninsula, Eastern China: Insights from fluid inclusion and isotopes

Abstract

The Panzijian gold deposit is located in the Jiaobei uplift on the eastern margin of North China Craton. It is a quartz vein-type gold deposit in the southern end of the Qixia-Penglai ore belt. In order to explore the source and properties of ore-forming fluids and materials in the Panzijian gold deposit, explore the ore-forming process and reveal the genesis of the deposit, this work has carried out petrographic observation and temperature measurement of gold-bearing quartz fluid inclusions, laser Raman experiment, gold-bearing quartz H–O isotope study, and gold-bearing pyrite Pb isotope study. The Panjian gold deposit is divided into four metallogenic stages and the metallogenic stage Ⅲ is the main gold mineralization stage. Fluid inclusions show that the ore-forming fluids at the Panzijian gold deposit belong to a CO₂–H₂O–NaCl system with low temperature (172–341 °C), salinity (1.57–10.49 wt% NaCl), and density (0.79–0.96 g/cm³). Gold-bearing Quartz H–O isotopic data (δD = −79.8 to −65.1‰, δ¹⁸O_H2O = 1.33–2.63‰) show that the ore-forming fluid was derived from the mixing of magmatic water and meteoric water. Gold-bearing Pyrite Pb isotopes with crustal signature (²⁰⁶Pb/²⁰⁴Pb = 16.06–16.943, ²⁰⁷Pb/²⁰⁴Pb = 15.337–15.858, ²⁰⁸Pb/²⁰⁴Pb = 37.143–38.081, and ²⁰⁶Pb/²⁰⁷Pb = 1.025–1.105) support that some ore-forming materials were crust-derived. We proposed a metallogenic model for the Panzijian gold deposit: Stress transition of Jiaobei uplift tectonic system inducing asthenospheric upwelling. The lithostatic pressure dropped and fluids were exsolved from the magma. The ore-forming fluid ascended along local faults and the pressure further dropped, resulting in fluid immiscibility and gold deposition along structural traps (e.g., faults).