Analysis Of Ore-controlling Structure And Prospecting Model Of The Hongqiling Hydrothermal Vein Sn-W-Pb-Zn Deposit In Southern Hunan

The Hongqiling Sn-W-Pb-Zn polymetallic deposit in southern Hunan is located in the outer contact zone of the northeast side of the Dongpo ore field.It is the largest vein tin deposit in Hunan Province.The ore-bodies are strictly controlled by structure and has obvious horizontal/vertical mineralization zoning phenomenon.In this paper,using the theory and method of geological mechanics of ore field,through the fine analysis of large-scale structural section,the mechanical properties of typical rock-controlling and ore-controlling structures are identified,the ore-controlling structural characteristics of different types of ore bodies in the mining area are identified,the ore-controlling structural types are analyzed,and the structural ore-controlling laws are summarized.On this basis,with the U-Pb dating of cassiterite,the metallogenic-tectonic system is clarified,and the tectonic evolution history of the ore field is established.Combined with the geophysical inversion information,the structural ore-controlling model is established,and the deep favorable ore-bearing structure is proposed.The main achievements and understandings of this paper are as follows:（1）The ore deposit is affected by the Qianlishan granite,and the tectonic-magmatic-mineralization is closely related.The formation of the deposit is closely related to the multi-stage magmatic intrusion and regional stress field of the Qianlishan rock mass.In different tectonic events from Caledonian to Indosinian,the nearly EW-near SN-trending structures were repeatedly activated.Under the background of NWW-SEE regional stress in the early and middle Yanshan period,the NNE-trending F₄ compressive-torsional fault,the NNE-trending tensional space at the anticline turning point(F₁₀₁,F₁₀₂,F₁₀₃)and the reactivated NEE-trending tensional-torsional structure(_F27)in the basement structure jointly controlled the distribution of Sn-W-Pb-Zn（Ag）deposits in Hongqiling mining area（2）Ore bodies are divided into four categories:1)No.4 cassiterite sulfide ore bodies controlled by F₄ fault;2)A group of parallel occurrences of Nos.101,102 and103 Sn-W quartz vein ore bodies controlled by F₁₀₁,F₁₀₂ and F₁₀₃ faults;3)No.27sulfide Pb-Zn-（Ag）ore body controlled by F₂₇ fault;4)Controlled by No.3Sn-W-Pb-Zn mixed ore-body of F₃ fault.Among them,the No.4 ore-controlling fault F₄ mainly experienced the mechanical property transformation process from pre-mineralization pressure to metallogenic pressure and torsion.The No.101,102and 103 ore-controlling faults(F₁₀₁,F₁₀₂ and F₁₀₃)were characterized by tension during the metallogenic period.The spatial distribution of the two faults was characterized by the intersection of tin and deep under tungsten.The spatial distribution of Pb-Zn ore bodies（veins）was generally controlled by NE-NEE faults,and experienced the transformation process from tension and torsion during the metallogenic period to left-lateral torsion after mineralization.The mineralization of No.3 NEE to lead-zinc ore body has a certain zoning on the plane.From SW to NE:W and Sn mineralization gradually weakened,and Pb and Zn mineralization gradually increased.（3）By LA-MC-ICP-MS U-Pb dating of cassiterite,the metallogenic age of Hongqiling deposit is 158.4±0.8 Ma and 158.9±0.7 Ma,which is consistent with the metallogenic age of lead-zinc deposit in Congshuban ore section in the same belt,and is consistent with the error range of metallogenic age of many deposits in Dongpo ore field and Qianlishan rock mass.Comprehensive shows that the proximal W-Sn mineralization and the distal Pb-Zn-Ag mineralization have a certain inheritance relationship,which is the evolution of a set of magmatic-hydrothermal system of Qianlishan rock mass and is closely related to the early and mid-Yanshanian tectonism.The NE-trending tectonic belt is the main metallogenic structural system and an important part of the Qinhang metallogenic belt.The metallogenic structural system in the region is consistent.（4）Based on the change of ore-controlling characteristics and mechanical properties of faults,combined with the horizontal and vertical zoning laws of ore bodies,combined with geophysical exploration methods such as wide-area electromagnetic and ground high-precision magnetic survey,it is comprehensively considered that the deep part of Hongqiling ore section on the SW side of the mining area has good tungsten-tin prospecting potential,and it is speculated that there is a large vein-mega vein type tungsten-tin ore body.A group of NE-NEE trending faults and secondary tensile joints in the Congshuban ore section in the E side of the area have good prospecting potential for tungsten and tin.