Geological Characteristics And Genisis Of Jinlonggou Gold Deposit Qinghai

Jinlonggou gold deposit is located at about 90 km north-west of Dachaidan Town,Haixi Prefecture,Qinghai Province.Its tectonic location is located in the northern margin of Qaidam Basin.It is adjacent to the Oulongbrook Block in the north and Qaidam Block in the south.The East and West ends are cut off by the Wahongshan Fault and the Aljin Fault respectively.The metallogenic geological conditions are very favorable.The outcropped strata in the mining area are mainly the Mesoproterozoic Wandonggou Group?Pt₂W?,a set of greenschist facies shallow metamorphic rock series subjected to regional and dynamic metamorphism,and the main host rock of the orebody.The faults in the area are well developed and can be divided into two groups:NW-trending and NE-trending.The NW-trending is the ore-guiding structure in the area and NE-trending is the ore-controlling structure in the area.The ore bodies in the area mainly occur in the NE-trending interlayer slip faults.The magmatic rocks in the mining area are mainly Hercynian intermediate-acid intrusive rocks,formed in the extensional geodynamic background.Some veins have undergone alteration and mineralization,which are closely related to gold veins in space and provide thermal power and some minerals for mineralization.The ore types of Jinlonggou gold deposit are altered schist type and altered vein type.The main metal minerals are pyrite,followed by toxic sand,galena,sphalerite and gold minerals.The wall rocks are altered into silicification,sericitization,carbonation and a small amount of chloritization,reflecting the combination and alteration characteristics of mesothermal minerals.The ore structure mainly includes filling structure,inclusion structure and metasomatic residual structure.The ore structure mainly includes sparse disseminated structure and vein-reticular structure.The Jinlonggou gold deposit mainly develops gas-liquid two-phase inclusions with homogeneous temperatures ranging from 138.9?to 295.9?,fluid salinity ranging from5.85 to 17.74 wt%NaCl and fluid density ranging from 0.88 to 1.05 g/cm³.It belongs to low salinity and low density fluids,and its main ore-forming depth is 1.54³.55 km.It belongs to epithermal vein type gold deposit.H-O isotopes:?D_?values ranging from-89‰to-80.7‰and?¹⁸O_?values ranging from 6.7‰to 7‰;C-O isotopes:?¹³C_V-PDB values ranging from-2.23‰to-0.51‰and?¹⁸O_V-SMOW-SMOW values ranging from 13.43‰to 14.45‰.Fluids come from deep-source magmatic water.Later,fluids formed by atmospheric precipitation and dissolution of carbonate rocks are added.S isotope:?³⁴S_CDT values is 6.38‰⁸.66‰.The ore-forming material is derived from magmatic hydrothermal fluid,with the addition of metamorphic sulfur in certain strata.Composition shows that ore-forming fluids and ore-forming materials mainly come from deep-source magma,and only a small part of ore-forming fluids and ore-forming materials come from strata.Based on the above understanding,the Jinlonggou gold deposit is identified as a meso-epithermal and mesothermal vein type gold deposit.The ore-forming material mainly comes from deep-source magma and partly from strata.The ore bodies are strictly controlled by interlayer slip structures.The metallogenesis is closely related to the Hercynian intermediate-acid magmatic rocks and formed in the geodynamic background of continental extension.