Structure Ore-Controlling Mechanism And Ore-Prospecting Direction Of Qingshan Lead-Zinc Deposit In Northwest Guizhou,China

Qingshan Pb-Zn deposit is one of the typical representative deposit of Wei Ning-shuicheng ore-forming subzone in northwest guizhou,ore bodies output strictly controlled by the dual factors of structure and lithology,in order to clarify deposit tectonic ore-controlling mechanism and deep prospecting prediction,In this paper,the integrated use of the ore field geological mechanics,ore mineralogy,structural geochemistry and petrology,such as theory and method of using large scale structural section precision,the tectonite-petrography mapping,tectonic geochemical prospecting techniques,such as tectonic ore-controlling mechanism and prospecting prediction of ore deposits in system study,obtained the following main understanding and results.Based on mechanical properties of structural featuresthe and stage matching are recognized four types of tectonic systems can be identified:Early NW tectonic belt,NE tectonic belt,Late NW tectonic belt,and North-South tectonic belt,which correspond to the Early to Middle Indosinian,Late Indosinian to Early Yanshanian,Middle Yanshanian,Late Yanshanian to Himalayan,respectively.The ore-body production is strictly controlled by NW trending faults,and there are three main ore-control structure forms of xi type,in-type and stepladder.It is further proposed that the NE tectonic belt is the metallogenic tectonic system of the deposit.The tectonic activity in the mine area is strong,which plays a dominant role in controlling the mineralization,and provides the migration channel,ore-bearing space and partial dynamic conditions for mineralization.There are different types,grades and sequences of tectonic features in the mining area,and the structural grades are obvious:Weishui fault and Weishui anticline are the first order structure(ore guide structure)in the mining area,forming the stratum-vein structural mineralization style controlled by fault-fold.The F₁ and F₂ left-hand sloping faults in the mining area constitute the secondary structure(ore blending structure),which forms the structural mineralization style of geese echelon.The secondary fault and interbedded fracture zone between F₁ and F₂ faults constitute the tertiary structure(ore-hosting structure),which forms the strata-like massive mineralization style.The densely developed joints and fractures on the side of the orebody constitute the four-level structure(ore-hosting structure),which forms the parallel vein type mineralization pattern.Further analyzes its forming mechanism,think to NW Weishui fault left twisting derived transtensional the NW fracture F₁,F₂ fault,NW to the F₁,F₂ left derived NW to the subprime interlayer shear fracture,secondary interlaminar fracture analyzed.moreover derived by shear fracture group,formed the order and level relative sequence fracture,at all levels of ore deposits,orebodies vein group,orebody,control of the country has obvious relationship,are controlled by the north east to tectonic belt.At the same time,the structural ore-controlling model of the deposit is established on this basis.Based on the tectonite-lithofacies zoning mapping method,we analyzed joints and frac ture structures in different lithofacies belts,and systematically collected directional tectonite samples in different lithofacies belts for microstructural and geochemical analysis.The tec tonite type,material composition,internal texture and structure,and zoning characteristics were analyzed,and the zoning model of tectonite-lithofacies in this deposit was constructe d.That is,outward from the orebody,the zoning sequence is as follows:the tensile initial cataclasite zone?the sludging zone(middle section of Level13 and above)?the shear initi al cataclasite zone?the compressive initial cataclasite zone.Pyritization,lead-zinc mineraliz ation,calcitization and weak dolomitization occur in the shear initial cataclasite zone,and calcitization occur in the compressive initial cataclasite zone.Mineralization-alteration chan ges from strong to weak as it moves away from the ore body,and the mineralization env ironment gradually decreases with the temperature,showing a tendency foxidation environm ent?weakoxidation?weak reduction?reduction.Based on the geochemical analysis of the tectonic rock profile,it is found that the changes of Pb and Zn elements are positively correlated with Cd,Sb,Ag,Mn and As,showing a similar trend of change,while they are negatively correlated with Sr,Mg,Cr and Ba.At the same time,the clustering analysis and factor analysis of the tectonic geochemical samples in the mining area are carried out by using the mathematical statistics method to delimit the anomaly,summarize the distribution rule and anomaly characteristics of the tectonic geochemical field,point out the direction of ore-forming fluid migration,and provide the basis for ore-forming prediction.The axial zoning sequence of the primary halo is As follows:Ba-V-Cd-Cr-U-Cu?Te-Rb-P-Co-Zr-Ga-Cs-Sb-Li-As-Ni?Mo-Pb-Ag-W-Zn-Sr-Mn.The axial zoning sequence of the tectonic primary halo reflects that the ore-body mineralization has gone through multiple stages,and it is predicted that there may be concealed orebody in the deep of the orebody with good extension.Based on this,an ideal model of the tectonic primary halo of the ore deposit is established.Based on the above research,the comprehensive prospecting model of the mining area is established,the prospecting signs and prospecting directions of the mining area are put forward,a number of key prospecting target areas are selected,and new ore bodies are found in the middle of the sixth and seventh section,which provide important basis for the prospecting of the mining area,and also provide important enlightenment for the deep and peripheral prospecting of the lead-zinc deposit in the ore-concentrated area of northwest Guizhou.