| The potential of lead-zinc ore resources in northwest Guizhou is huge,it is an important region of the distribution of lead-zinc deposits.With the further study,new deposits have been discovered,and the prospecting prospect is better.As an important part of northwest Guizhou polymetallic ore,the potential of lead-zinc ore resources of Wuzhishan ore-concentral area is better at present,now it has been found Nayong lead-zinc deposits,Dujiaqiao lead-zinc deposits,Narun lead-zinc deposits,Yujiaba lead-zinc deposits,etc.This article selects Dujiaqiao lead-zinc mine as the research focus,based on the field geological investigation,starting from the basic geological characteristics of the deposit,through consolidation,combined with the study of geochemistry and fluid inclusion,then determine the main ore-controlling factors,and summarizes the metallogenic regularity,put forward the deposit genesis,build the metallogenic model.This research has mainly made the following conclusion:(1)The formation of Dujiaqiao lead-zinc deposit is obviously controlled by structure and strata,and there is no obvious connection to the magmatite.The study area is controlled by three major faults,and there has developed two set of fracture and folds,besides,the lead-zinc deposit is usually come from construction side or the intersection area.The ore-formation is the dolomite of the upper Sinian Dengying Formation,easily occur in the stress rupture,then forming joint and fissure,which can provide the favorable places for the migration and enrichment of ore-forming fluid.The overlying strata is the black shale of Niutitang Formation,which forms a favorable “cover”condition,then leads to the migration of the metallogenic fluid in the vicinity of the contact zone.(2)There are two main types of lead-zinc ore-body in this deposit,namely the fault zone type and roughly bedding type lead-zinc ore body.They are mostly vein,strariform and lenticular,and the epigenetic effect is obvious.Mineral composition mainly include sphalerite,galena,pyrite,quartz,dolomite,etc.,with disseminated,massive and brecciated structure,and automorphic,hypidiomrphic,xenomorphic granular textures,metasomatic vein,symbiotic structure.besides,the alteration of surrounding rock is relatively strong,including silicification,pyritization,dolomitization.(3)Based on the field observation and microscopic identification,it is considered that the lead-zinc deposit has multi-period and multi-stage characteristics,and mainly divided into two metallogenic periods,namely the hydrothermal mineralization period and supergene oxidation period.The hydrothermal mineralization period can be divided into two multi-stage,namely quartz-pyrite-sphalerite stage and galena-quartz-pyrite stage,the former for the early mineralization stage,the latter for the late ore-forming stage,which are the main metallogenic stage.(4)Through the study of rock geochemistry and isotope geochemistry,it is considered that the REE in the lead-zinc deposit and the surrounding rock has the similar characteristics,and there is no obvious genetic relationship with the basalt of Emei.The source of sulfur isotope in ore mainly comes from the reduction of sulfates during the same period,Lead isotope has the characteristics of crust source,but it does not rule out the involvement of mantle materials.(5)Based on the study of the fluid inclusion petrography and temperature,it is considered that the content of the fluid inclusion is lower and the particle size is smaller,the gas-liquid ratio is low,and mainly in the form of rules,a few is irregular,besides,the inclusions often distribute in groups or belts,a few inclusions are isolated.The metallogenic temperature of lead-zinc deposit is about 140~220?,salinity is about 6.74%~11.58%,the ore-forming fluid is characterized by low temperature and middle salinity,belonging to the typical low temperature hydrothermal deposit.(6)Through the comprehensive analysis of the geological characteristics of ore deposit,combined with the feature of geochemistry research,summarized the main ore-controlling factors of deposit and the metallogenic geological characteristic.Besides,the Dujiaqiao lead-zinc deposit have some comparison with the typical MVT type lead-zinc deposit,it is found that the two are very similar,so that the lead-zinc deposit is a typical MVT type lead-zinc mine. |
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