Geologic Characteristics And Deposit Genesis Of Changpinggou Gold Deposit In Gansu

Changpinggou gold deposit is another important quartz vein type gold depositfound recently in the Western Qinling area after Shijiba gold deposit andChaijiazhuang gold deposit. Research shows that, Changpinggou gold deposit hasthe classical characteristic of quartz vein type gold deposits. This paper provide moreunderstanding to theories of quartz vein type gold deposits. and also has importantmeanings to the economic development and the exploration development.The research about gold geology of the area is in a lower degree. Based on thepre-study and the outdoors geological survey in specific and detailed ways, Thispaper deeply discussed the geological features, geological features of ore body, oredeposit geochemical features and genesis of mineral deposit of the Changpinggougold deposit, with collecting plenty of rock samples, it combined technology andmethod of petrology,mineralogy,geochemistry and study of ore deposits accordingto the metallogenic background of the area. The following results and understandingsare gained：Changpinggou gold deposit is of quartz vein type,ore body exists in fracturedalteration zone and quartz veins in the forms of vein,lens-shaped and stratiform-liketypes.The main ore minerals are pyrite and chalcopyrity,with limonite,and magnetite.Gold occurs as native gold,mainly in pyrite and quartz. The main gangue mineral isquartz,and secondary gangue mineral is chlorite. The main wall rock alterations ofthe deposit includ pyritization, chloritization, silication, carbonation and fadealteration. Among them,chloritization, silication,carbonation are closely related togold mineralization. Quartz vein is the main prospecting marks.The formation of Changpinggou gold deposit can be divided into hydrothermalstage and supergene stage. The hydrothermal mineralization can be divided into fourstages:（I）quartz-pyrite stage （II）gold-quartz-pyrite stage （III） gold-quartz-polymetallicsulfide stage （IV） quartz-carbonate stage.The change range of sulfur isotopic is between-2.4‰and3.01‰,an average of2.03‰,and a range of5.41‰. Sulfur characteristics in the ore close to magmaticsulfur characteristics. Through the research to hydrogen and oxygen isotope of water in mineral inclusions, D values between-78‰to-62‰, an average of-72.3‰; theδ¹⁸OH₂Ois6.6‰to9.9‰, an average of7.9‰. It shows that ore-forming fluid ismainly magmatic hydrothermal meanwhile, some metamorphic hydrothermalparticipates in it.Mineragenetic epoch of Changpinggou gold deposit is in early Jurassic ofYanshanian. To sum up,the genetic type of the gold deposit of Changpinggou can beclassified as hypabyssal and low-and-medium temperature magmatic hydrothermrelated to continental subvolcanic action.