Ore-forming Conditions and Genesis of the Shabaosi Gold Deposit,Heilongjiang Province

The Shabaosi gold deposit in Mohe County,Heilongjiang Province,is a large gold deposit.It occurred in the Middle Jurassic continental clastic rock.There are six ore veins with nearly SN trend in the deposit.The ore bodies are strictly controlled by SN and NNW trend fault and the surrounding rocks and the intrusive rocks are involved in the mineralization.From the study of fluid inclusions,it is concluded that the ore-forming fluid belongs to Ca2+(K+、Na+)-SO2-4(F-、Cl-)type,which is characterized by the low salinity(0.8%~9.2%),low density(0.895g/cm3),alkali(pH:8.05~8.26),high sulfide,low oxidize(Logfo2:-39.4~-39.2) and relative reducing environment(Eh:-0.71~-0.68).The ore-forming temperature ranges from 200~230℃,with pressure of 40MPa and depth of 1.33km.Based on the analysis of Pb,S,C,H and O isotopes and the study of microelements of the gold deposit,it is found that the ore-forming elements are from magma and strata in depth.The ore-forming fluids are mainly derived from magma in depth,with a little atmospheric water.The geological and geochemical characteristics of the Shabaosi gold deposit are similar to those of low sulphidation epithermal gold deposits in the world,and it belongs to low sulphidation epithermal gold deposit.