Study On Ore-Controlling Structure And Prospecting Prediction Of Jinchangyu Gold Deposit In Hebei Province

The Jinchangyu gold deposit is located at the border of North China Valley,it is the important large gold deposit in our country.The previous understanding of ore controlling structure of ore deposit has experienced different views such as ductile shear zone,post-ductile shear zone,ore controlling by fold and fault,ore controlling by fold and extruded foliated zone.On this basis,through the field geological survey,the use of regional geotectonics,tectonic geology,ore deposit science,prospecting methods and other scientific theory methods,the ore control structure geometry,kinematic characteristics and stress field research,plane and section combination;On the basis of the key exploration line tunnel profile measurement,the large scale lithofacies,structure and mineralization alteration three-dimensional mapping was carried out to identify the relationship between structure and mineralization,and the spatial framework of the ore-controlling structure of the Jinchangyu deposit was preliminarily established.Combined with the research results of the geological characteristics of the regional deposit,the prospecting target areas were divided,which provided a theoretical basis for the deep and peripheral prospecting of the mine.（1）Through detailed field geological survey,profile measurement and indoor comprehensive research,the ore-controlling structure of Jinchangyu gold deposit is divided into four stages:D1 is the period of regional schistosity and fold formation;d2 is a ductile shear deformation period,mainly forming a NE-trending ductile shear zone structure.D3 is a brittle deformation period,forming a NNE-and NW-trending fault and joint structural system in the main metallogenic period.D4 is a shallow brittle NE and NW trending fault,joint and brittle schistosity structure.（2）Through the study of the relationship between structure and mineralization,it is considered that there are two types of mineralization in this area.The early stage is the ductile shear zone type gold deposit controlled by the northeast ductile shear zone,which corresponds to the second stage of regional tectonic deformation.The late stage is hydrothermal mineralization controlled by the tectonic system composed of NNE brittle faults and NW and NE joints.The second mineralization is the main mineralization period in this area.（3）Through the investigation of the structural characteristics of the ore bodies in the field,it is found that the ore-controlling structure of the gold deposits in the mining area is mainly composed of a set of structural systems composed of NNE-trending faults,NE and NW conjugate shear joints,detachment parts of fold turning ends,wing faults,ductile shear zones and schistosity zones.Among them,folds and schistosity zones are activated,replaced,filled and mineralized during the second mineralization process.In some positions,the later brittle structures are superimposed on the early fold turning ends and schistosity zones,and superimposed and transformed mineralization occurs.（4）The occurrence of conjugate joints in the main metallogenic period of Jinchangyu mining area is counted and the polar stereographic projection of the joint occurrence is carried out.The results show that the principal stressσ₁ is between 350°～10°,170°～190°,andσ₃ is distributed between 80°～100°,260°～280°.The dip angle is gentle,and the dip angle ofσ₂is steep and nearly upright,which reflects that the main metallogenic period is squeezed by nearly north-south horizontal stress.The results of stress field analysis are consistent with the tectonic background reflected by the previous studies that the North China plate was squeezed by north-south compression in the Indosinian period.（5）Based on the analysis of the types and spatial relationship of the ore-controlling and mineralization-enriched structures in Jinchangyu,the spatial shelving of the ore-controlling structures in the mining area is built.It shows that the six main vein belts in Jinchangyu mining area mainly occur in the schistose zones,fold turning ends and faults on both sides of the folds.Different schistose zones are connected by faults and joints in the metallogenic period to form a set of structural systems.The schistosity zone and fold turning end are the main ore-bearing structures,and the joints are the ore-conducting structures.The fault is the ore-bearing structure and the main ore-conducting structure in this area.In the fold turning end,fault and joint composite parts,the ore body is thickened..（6）Through the analysis of the spatial framework of the regional structure,combined with the research results of the project team,it is considered that the V belt near the 0-55exploration line,-600～-1000m depth,is the key prospecting target area.In addition,the ore-forming space is better in the area where the compressive schistosity zone protrudes westward.Therefore,there may also be ore bodies on the west side of I,III and IV veins.