Metallogenic Mechanism And Prospecting Direction Of Xiayingfang Gold Deposit In Pingquan Country,Hebei Province

Xiayingfang gold deposit is located in the middle section of the northern margin of North China block,this area has a complex geological evolution history,especially Yanshan period experienced strong tectonic movement,a large gold deposit formed in this period,and with great prospecting potential.Mining area includes Xiajinbaogou porphyry gold deposit,Dadongshan skarn type gold deposit and the Dongliang medium temperature hydrothermal type gold deposit.Xiajinbaogou gold deposit is hosted in altered granite porphyry and contact zone;Dadongshan gold deposit is hosted in the contact zone of quartz monzonite porphyry and the carbonate rocks;Dongliang gold deposit is hosted in the contact zone of Dadongshan complex and Changcheng strata,the orebodies mainly occur in the rhyolitic breccia lava belt,controlled by the annular structure and volcano mechanism.The exposed rock in mining area is Xiayingfang complex,It is composed of the Xiajinbaogou granitic porphyry and the Dadongshan complex,The two are connected as a whole in the deep.The complex is mainly include diorite porphyrite,granite porphyry and quartz monzonite porphyry.The edge of complex have rhyolitic breccia lava and rhyolite.Analysis of geochemical characteristics of granite porphyry and diorite porphyrite show that the Xiayingfang complex can be classified as rich in potassium and weakly peraluminous calc alkaline series of rocks,magmatic source with crust mantle mixed source,it is the homologous sequence evolution and formed in tectonic environment of a major turning point of the North China block,the granite porphyry belong to I type granite of certain differentiation.Research on fluid inclusions of quartz of the main mineralization stage show that fluid inclusions with regular shape,to the main oval,the larger size change,range from 1?m to15?m,but commonly from 3?m⁸?m;the homogenization temperature mainly concentrated in the 200³00?;salinity is mainly distributed in the 7.70wt%¹6.34wt%;density is mainly concentrated in the 0.774⁰.994g/cm³.According to the results of the analysis of fluid inclusions,the ore-forming fluids were mainly derived from the crust mantle mixed source magma residual magmatic hydrothermal,the fluid system should be H₂O-CO₂-NaCl?KCl?system.Hydrogen and oxygen isotope analysis shows that the main mineralization stage is mainly magmatic water,than the meteoritic water participation the mineralization,to completely turned into meteoritic water in the late stage.Carbon isotopic studies indicate that ore-forming advanced atmospheric water brought the carbon of Gaoyuzhuang stratum,hydrogen and oxygen isotope research conclusion been verified too.Sulfur isotope study proved that the derived from deep magma and mantle,Lead isotope research results show that the derived from upper mantle or lower crust,all of that show the characteristics of mantle source and crust source,the same as the characteristics of the complex with crust mantle mixed source.It demonstrate the close relationship between mineralization and intermediate acid magma activity in this region.Combined with the composition of fluid inclusions analysis conclusion of the ore-forming fluids were mainly derived from the crust mantle mixed source magma residual magmatic hydrothermal,You can say that gold mainly derived from magma,but there are also a little from formation of gold.Xiajinbaogou gold deposit,Dadongshan gold deposit and Dongliang gold deposit is the product of the same tectonic-magmatic-metallogenic system.And formed in the same geodynamic background and the same age.So the mineralization also occurred in the turning point of the tectonic environment.By rock age sericitization granitic porphyry and quartz monzonite porphyry,It is inferred that the ore-forming age at about 150Ma,Is a product of the late Jurassic granite—hydrothermal mineralization.The main metallogenic mark is structure,magmatite and wall rock alteration.But the structure,magmatite and wall rock alteration are more importent.The orebodies are mainly controlled by the F4 fault,ring structure,fold structure,contact zone structure and complex.In Xiayingfang complex,the ore-controlling function of granitic porphyry and quartz monzonite porphyry are more importent.In the study area,the influence range of F4fracture and the Xiajinbaogou dome structure under are as favorable area for prospecting.Contact parts of complex and stratum,Layer slip structure belt are important prospecting areas,too.In the region,the late Jurassic magmatite?mainly refers to the intrusive rock and subvolcanic rock?and related similar porphyry—hydrothermal deposit system is a recommendable direction for ore prospecting.