Pyrite Genetic Mineralogy And Deep Prospects Of The Dayin’gezhuang Gold Deposit In Jiaodong Region

The Dayin’gezhuang gold deposit which is a large rotten-rock gold deposit islocated in the central Zhaoping fault belt of northwest Jiaodong Peninsular, occuringin the contact zone of the Jiaodong group and the Guojiaduan granitic body. The golddeposit is mainly controlled by the Zhaoping fault which strikes in NNE, includingabout26orebodies．Basing on field observations and test analysis indoor, combinedwith orebody characteristics, the paper which conducts an intensive study of pyritegenetic mineralogy of No.Ⅱ orebody, discuss the forming material source, energysource, as well as the physical and chemical conditions, and the deep prospective ofNo.Ⅱ orebody.The ore type mainly is beresitization rock, second types are fracturedgranodioritic sericitization rock and beresitization granite, composed of pyrite,sphalerite, chalcopyrite etc metal sulfide minerals, and quartz, sericite, carbonateminerals etc nonmetallic minerals．The textures of ores are predominant in cataclastictexture and granular texture．The structures of ores are dominated by nodular structure,disseminated structure, brecciated structure and vein structure. Gold is mainlyoccurred as inclusion-gold, intercrystal-gold and crack-gold. The mineralizationstages contain beresitization, pyrite-quartz, quartz-pyrite, polymetallic sulfides,quartz-pyrite-siderite and quartz-carbonate stages.The analysis of chemical composition of pyrite shows a magma hydrothermal oredeposit, and it may inherit metamorphic water of Jiaodong Group. The textures ofores (emulsion texture), gold fineness（511.90-830.61）, essential composition andtrace elements of pyrite, ore-forming temperature calculated by pyroelectriccoefficient (76.2-385.8℃) all indicate a medium-low ore-forming temperature and amedium mineralization depth. The essential composition and trace elements of pyriteshow a reduction metallogenic period, temperature relatively lower and fluid activitygradually enhanced from early to main metallogenic stage, vertical temperaturerelative rise. The higher concentrations of Tb in REE of pyrite suggest ore-formingfluid may be rich in F-. The analyses of REE and sulfur lead isotopes of pyrite indicate that theore-forming fluid is the mixture of crust origin and mantle origin which is a majorcrust origin. The metallogenic materials are originated from the lower crust and littlemantle material, with the participation of country rock of Jiaodong group andGuojiadian rock mass. The initial ore-forming materials may contain more mantlematerial, but with the evolution of the metallogenic stage, ore-forming fluid occurstrong crust-mantle interactions with wall rock, which lead to more crustal materialadded into the system. The significant geological events of North China Plate andthe subduction of Paleo-Pacific plate form southwest to northwest, provide thematerial sources, heat and power origin for the formation of Dayin’gezhuang golddeposit.The features of morphological, thermoelectricity and resistivity about pyriteimply that74～79line and blow-400m alone NE trending direction of No.Ⅱorebody may have a strong deep prospecting potential. Thermoelectric coefficient ofpyrite ranges from100μν/℃to300μν/℃may mean a favorable mineralizationsection.