Ore-Forming Fluid Features and Metallogenesis of Dongwujiazi Gold Deposit, Chaoyang City, Liaoning Province

The tectonic position of Dongwujiazi gold deposit is in the middle section of the north margin of North China Craton,Chifeng-Chaoyang gold mineralization concentration area.In the north,it separates the Inner Mongolia-Xing an Fold-orogenic Belt from the Chifeng-Kaiyuan deep fault,and its south border with Yanshan subsidence zone is the Lingyuan-Beipiao deep fault.The NW trending faults are the main ore-hosting structure in the mining area,the spessartite in the vein rock is greatly related with the mineralization.The natural type of the ore is quartz-vein type,the sulfide in the ore is mostly pyrite,while chalcopyrite and galena are in the second place,noble metal minerals include native gold and hessite.The wall-rock alterations include silicification,sericitization,and carbonatization,the zoning of the alterations is obvious.The telluride can be easily found in the ore.The developing of spessar tite closely related with mineralization and the δ³⁴S‰ value of the ore is nearly zero which implies that the ore-forming fluid has the features of mantle-derived fluid.The fluid inclusions in quartz are poorly developed.The inclusions are all aqueous two-phase inclusions,which belong to the H₂O-NaCl system.The fluid salinity is between 9.86_WB% NaCl.eqv and 16.92_WB% NaCl.eqv,and it increases with t he decrease of temperature.The fluid density is between 0.94g/cm³ and 1.08g/cm³ and the ore-forming temperature is between 172.3℃ and 212.6℃.The ore-forming pressure is between 19Ma and 24M Pa,and the forming depth is between 1.9km and 2.4km.Compared to the typical or ogenic gold deposit from home and abroad,it belongs to the hy pabyssal orogenic gold deposit.The metallo genic dynamics background is North China craton and Siberian craton intra-ontinental orogeny after ollision in early Yanshanian.