Study On The Geological And Geochemical Characteristics And Genesis Of Hongqigou Gold Deposit, Wulonggou Ore Concentration Area, East Kunlun, Qinghai Province

Wulonggou ore concentration area is located in Dulan County,Qinghai Province.The geotectonic position is in the middle and eastern part of the East Kunming middle belt.The area has experienced multi-stage tectonic movement,and the metallogenic geological background is superior.Our project team has carried out systematic research on the granite body exposed in a large area in Wulonggou ore concentration area.In this paper,chronological and geochemical research has been carried out on a large number of exposed pre mineralization diabase veins.It is believed that they were formed in the middle Triassi and are the products of partial melting of the lithosphere reformed by the subduction plate fluid.The exposed stratum of Hongqigou mining area is mainly the Paleoproterozoic Hutuo Jinshuikou group,which is the main ore hosting stratum of the mining area.The fracture structure in the mining area is distributed in NW direction,and there are four closely related to mineralization,which are nearly parallel banded distribution.The Hongqigou mining area is mainly controlled by the VII,IX and X fracture zones.The Intrusive rock in the mining area are mainly granite,diorite,pyroxenite and gabbro.After study,we think that the mineralization of Hongqigou gold deposit can be divided into two stages:Quartz sulfide stage and calcite sulfide stage.The ore type is mainly quartz vein type;The ore minerals are mainly pyrite,followed by galena,sphalerite and arsenopyrite;gangue minerals are quartz and calcite;ore structure mainly includes granular structure,inclusion structure,metasomatic structure and crushing structure;ore structure is disseminated structure and veinlet structure.The wall rock alteration is mainly silicification,sericitization and Kaolinite.The temperature measurement of the Ore bearing quartz fluid inclusions shows that the completely uniform temperature of inclusions is 192?³40?,the salinity is 0.82%¹5%,and the density is 0.58¹.89g/cm³.The ore-forming fluid as a whole shows the characteristics of medium high temperature,medium low salinity and low density.The hydrogen and oxygen isotopic test results of quartz in mineralized quartz vein show that the estimated?¹⁸O_H2O value is 5.89‰⁷.76‰,and the hydrogen isotope?D‰value is-121.5‰^-80.4‰.Compared with the typical orogenic gold deposits,the?D‰value is lower,which may be that the tested inclusions contain secondary inclusions.It is speculated that the ore-forming fluid is mainly from the metamorphic water in the deep.The?³⁴S_SV-CDT value of sulfide in the mineralized quartz sulfide is 10.53‰¹2.87‰,and the variation range is small;the?³⁴S_SV-CDT value of pyrite in the sericite gneiss is 4.5‰¹1.76‰,and the variation range is large.It is speculated that the formation of the original metamorphic fluid is related to the marine rich sulfate on the subduction plate,which resulted in the fluid rich in heavy sulfur isotopes.The quartz sulfide characterized by heavy sulfur isotopes was directly formed when it was filled in the fault,while the sericite gneiss with relatively light sulfur isotopes and wide range of variation was formed when it was metasomatized with the surrounding rock.The ratio of ²⁰⁶Pb/²⁰⁴Pb of sulfide is 18.26¹8.45,²⁰⁷Pb/²⁰⁴Pb is 15.62¹5.67,²⁰⁸Pb/²⁰⁴Pb is 38.38³8.55,which is similar to the test results of Shenshuitan mine and Huanglonggou mine,but the variation range of lead isotope in Hongqigou mine is smaller,which indicates that it can represent the source of lead in ore-forming fluid more,and the measured data points are in the lead isotope structure diagram,It is located near the evolution line of the orogenic belt,which is consistent with the typical orogenic setting of the ore area.Finally,combined with the regional tectonic background,geological characteristics and geochemical characteristics of the deposit,we believe that the Hongqigou gold deposit is orogenic type,formed after the late Indosinian period,but not earlier than 210 Ma²21Ma.After the late Triassic,the subduction in the East Kunlun area continued under the tectonic background of soft collision.The oceanic crust and marine sediments subducted to the deep were metamorphosed and dehydrated to form metamorphic fluid due to the increase of temperature and pressure.At the same time,a series of deep faults formed by continuous subduction and subsequent soft collision provided a good channel for the migration of ore-forming fluid.When the ore-forming fluid migrates to the shallow part,the pressure decreases,the CO₂ escapes,the fluid carrying capacity decreases,and the ore-forming substance precipitates and forms the integrated ore.