Genetic Mineralogy And Deep Prospects Of The Yinggezhuang Gold Deposit In Rushan County, Jiaodong

The Yinggezhuang gold deposit which is a pyrite-quartz vein gold deposit is located in the south of Mouping-Rushan gold-deposit belt of Jiaodong Peninsular,occuring in the contact zone of the Jingshan group and the Kunyushan granitic complex body.The gold deposit is controlled by the Jinniushan fault which strikes in NNE,including 4 gold lodes whose average gold grade is 4.32×10-6.The ore types are mainly quartz-pyrite ores and polymetallic sulfide ores,composed of metal sulfide minerals,quartz and carbonate minerals.The textures of ores are dominated by granular texture and cataclastic texture.The structures of ores are predominant in massive structure , dense disseminated structure and vein structure.The gold minerals including kustelite and electrum occur in the form of enclosed gold,intergranular gold and fissure gold.The mineralization stages contain pyrite-quartz,quartz-pyrite,polymetallic sulfides and quartz-carbonate stages.The types of wall rock alteration include potassic alteration,albitization,sericitization,sericite-quartz alteration , silicification , pyritization , carbonatization and chloritization.The morphological characteristic of pyrite is mainly pentagonal dodecahedron and the combination form of pentagonal dodecahedron,cube and octahedral.The phenomenon that the combination form grows and the crystal shape becomes complicated during the major ore forming stage or in the deeper part shows the fugacity of sulfur and the temperature are increased in these conditions.The fact that the composition of pyrite is depleted in sulfur on the analysis of major element demonstrates that pyrite are magmatic origin.The analysis of trace element indicates that the ore forming fluid are maily magmatic hydrothermal and in the early metallogenic stage the country rocks work in the metallogeny.The analysis of REE reveals that the REE distribution pattern of pyrite is right deviation pattern and is unanimous in the samples of major metallogenic stage.The thermoelectric coefficient of pyrite ranges from -346.1μν/℃to 342.7μν/℃.The conduction type is mainly mixture of type P and type N and the average appearace rate of type P is 64%.The difference of the appearace of type P between the south and north mine shows that the south of gold deposit is higher uplifted.The crystallization temperatures of pyrite of type P and type N are 148.9℃and 349.1℃.On the basis of the accordance of gold grade and the occurrence of type P good ore forming prospects of the concave field of the occurrence of type P mapping and the deep part of II-1 and II-3 ore bodies are presumed.The analysis of stable isotopes of ore mineral(sHe,Pb and S)suggest that the ore forming fluid is the mixture of crust origin and mantle origin fluid,mainly of crust,and the metallogenic materials are originated from the lower crust with a little mantle material and the Jingshan group.The hydrogen-oxygen isotope analysis of quartz demonstrates that the ore forming fluid is a mixture of magma fluid and meteoric water.The measurements and analysis of quartz fluid inclusions show that the gold deposit is a hydrothermal gold deposit formed in mid-shallow,mid-low temperature,low salinity condition.The ore forming fluid is the type of Na+(K+)-(Ca2+)-Cl-(SO42-)on the basis of the liquid phase composition of quartz fluid inclusion and the gas phase composition of quartz fluid inclusion is minaly H2O,as well as CO2,H2,CO,CH4 and N2.On the calculation of the liquid and gas phase composition of quartz fluid inclusion the ore forming fluid of the main ore forming stage is in weak acid and reduction conditions.