Fluid inclusions at different depths in the Sanshandao gold deposit, Jiaodong Peninsula, China

The Sanshandao gold deposit, located at northwestern edge of the Jiaodong Peninsula, eastern North China Craton, is one of the largest gold deposits in the Jiaodong gold province. In the deposit, disseminated‐ and stockwork‐style ores are hosted in Mesozoic granitoids. Mineralization and alteration are largely controlled by the regional Sanshandao–Cangshang fault. Sericite separated from alteration rocks in the mineralized zone yields an Rb–Sr isochron age of 117.6 ± 3.0 Ma. The ore‐forming fluids in the Sanshandao gold deposit contain CO2‐H2O‐NaCl±CH4 with low to intermediate temperatures and low salinities. Microthermometric analysis shows that homogenization temperatures gradually decrease from the early mineralizing stage (258–416°C) to main mineralizing stage (180–321°C) and to late mineralizing stage (112–231°C). Homogenization temperatures from the same mineralizing stage are nearly same and do not show an increase with depth. The nature of the ore‐forming fluids remains nearly the same over a 2000 m vertical depth interval. The ore‐forming fluids in the Sanshandao gold deposit of eastern North China Craton are of CO2‐H2O‐NaCl±CH4 systematics with low‐intermediate temperatures and low salinities. Nature of the ore‐forming fluids keeps nearly same in the 2000 m vertical depths. These stable circumstances of the fluids are a prerequisite to the formation of this super‐large gold deposit.