Geological Characteristics And Genesis Of ZhongJing Gold Deposit In Daiwangshan Gold Ore Field In Aohan Banner,Inner Mongolia

The Daiwangshan gold Ore Zhongjing gold deposit is located in the northern Xinhui Town,the government of Aohan banner,the Inner Mongolia Autonomous Region.Geotectonic location is located at the junction of the North China Craton and the Xingmengorogenic?The daiwangshan gold Ore Zhongjing gold deposit is a small gold deposit currently being explored and exploited.The large gold deposits on the region are located in the platform area,while the gold deposits found in the geosyncline area are relatively small.Predecessors have not studied the gold deposits in the geosyncline area in depth.The Zhongjing gold deposits in the platform area are also different in the ore bearing strata,the metallogenic characteristics and genesis of the deposit are analyzed and discussed in this paper,so as to provide theoretical basis for prospecting,exploration,evaluation and mining of similar deposits.There are 5 valuableore bodies in Zhongjing gold deposit,which are numbered I,II,IV,VI and VII.The larger two are I and II orebodies.Ore body is controlled by NE fault.Ore minerals are mainly pyrite,chalcopyrite,arsenopyrite,galena,sphalerite,etc;ore structure are mainly granular structure,crushed structure and inclusion structure;Ore structures include massive,fine veins,infecting structures,etc.The Zhongjing gold deposit are stronglyalterated?silicification,chlorinification and carbonation,etc.?,indicating low temperature hydrothermal alteration.Comprehensive research shows,there is a close genetic relationship between the quartz monzonite and the formation of the Zhongjinggold deposit.Age of diagenesis approximately represents the age of gold deposit formation.Zircon U-Pb dating indicates that the quartz monzoniteage is 258±2Ma,which belongs to the early Permian.The geochemical characteristicsindicate that the rock is a quasi aluminum high potassium calc alkaline rock series,Characteristics of A type granite,formed in post collisional tectonic setting related to the closure of paleo Asian oceans,the"late orogenic"stage equivalent to the evolution of the orogenic belt.Fluid inclusions shows that Zhongjing gold deposit were dominated by gas and fluid phases,the ore forming fluids are characterized by low temperature,low salinity and low density.The homogeneous temperature of the main mineralization stage is between189.7²85.7?,peak value is 240²80?.Salinity is between 1.90⁸.54 wt%NaCl.In the late stage of mineralization,the homogenization temperature ranges of 120.6²11.2?,peak value is 160?²00?,Salinity is between 1.39⁷.01wt%NaCl.In the process of fluid evolution from the main metallogenic stage to the late stage of the mineralization,the salinity increases slightly with the decrease of the homogeneous temperature,and the subsequent salinity shows a sharp decline,reflecting the variation of the metallogenic environment and the possibility of the fluid boiling in the main metallogenic stage,which leads to the increase of the salinity of the flow body and the precipitate of mineral deposits.The capture pressure range of fluid inclusions can be estimated at 20³5 MPa based on correlation diagrams,the depth of mineralization is 2 to3.5 km,belonging to the category of shallow depth.Results show that stable isotope,value of calcite Delta?¹³C_V-PDB-PDB varies from-8.35^-1.47‰,average value is-4.7‰;value of?¹⁸O_V-SMOW is 6.27‰¹9.70‰,average value is 10.28‰,within the range of granite?¹⁸O_V-SMOW?7‰¹3‰?,indicating that quartz monzonite may be one of the sources of ore-forming fluid in the Zhongjing gold deposit.³⁴S_V-CDT composition of the gold deposit in the contracted area?0.06‰⁰.96‰?,it can be considered that the S of the Zhongjing gold deposit should also come from deep source magma.The mineralization fluid of the ZhongJing gold deposit is characterized by low salinity?1.90⁸.54wt%NaCl?,for a simple H₂O-NaCl system.At the same time,it is formed under the tectonic background related to orogeny,which is consistent with the characteristics of orogenic gold deposits.In summary,the genetic type of the Zhongjing gold deposit is orogenic type gold deposit,belongs to Grovesdefinition of shallowsub class.