Characteristics of ore-forming fluids and genesis of Shijia Gold Deposit in Jiaodong
Shijia Gold Deposit is a quartz vein-type gold deposit located in the northern part of the Qixia-Penglai-Fushan Metallogenic Belt.The mineralization process can be broadly divided into 4 stages:quartz-pyrite stage(Ⅰ),gold-quartz-pyrite stage(Ⅱ),gold-quartz-polymetallic sulfide stage(Ⅲ),and quartz-carbonate stage(Ⅳ).The salinity of the ore-forming fluid ranges from 1.83%to 10.74%,with a density of 0.61-0.90 g/cm3,indicating low salinity and low-density fluids.The mineralization temperature is between 275℃ and 325℃,with fluid pressures ranging from 50 MPa to 92 MPa,and a mineralization depth of 1.67-3.07 km.The comprehensive characteristics reveal that this deposit is a medium-temperature hydrothermal vein-type gold deposit controlled by steeply dipping extensional faults in the upper part of a granite dome,with mantle-derived fluids,magmatic fluids,and meteoric water jointly contributing to the mineralization.