| MVT deposits and mineralization of the western margin of the Yangtze plate lead-zinc ore concentration area has been found up to more than 300, is one of the most important Pb-Zn metallogenic belt in china. Predecessors in the area of this type of Pb-Zn deposit geological exploration and research has done a lot of work, have achieved abundant exploration and research, However, there are different views about the region MVT Pb-Zn deposit metallogenic material source, formation and evolution of the ore-forming fluid migration mechanism and even deposit genetic types of itself, also does not have a recognized regional metallogenic model. Therefore, This paper takes the Yangtze plate margin typical type MVT Pb-Zn deposit with emphasis on the research object(Huize, Daliangzi, Tianbaoshan, Yinchanggou-Qiluogou, Paoma, Wusihe, Baoshuixi, Niuxinshan, Tianqiao, lead-zinc deposits, etc.), In system exploration data and the existing research results, based on the collection from ore rock, sedimentary environment and regional tectonic evolution and magmatic activity its ore-forming geological background, and then to carry out the trace and rare earth, isotope geochemistry, and fluid inclusion characteristics analysis, through the typical MVT Pb-Zn deposit in metallogenic geological conditions, the source of ore-forming materials and ore-forming fluid, ore-controlling factors and metallogenic epoch of research, combining with the regional tectonic evolution in the process of major tectonic events, analysis of the origin of ore-forming fluid and shifting drive and metallogenic mechanism, eventually establish the Yangtze plate MVT Pb-Zn deposit regional metallogenic model, the western margin of the deep looking for the same type Pb-Zn deposit to provide technical support.Knowledge and the results of this paper are as follows:Through to the zone MVT Pb-Zn deposit geological characteristics of typical syste comparison research, the comprehensive summarizes the general characteristics of MVT Pb-Zn deposit in the area: occurence horizon is more, the orebody mainly occurs in the Sinian system integration group and lower carboniferous of the pendulum with group formation, Almost all of ore rock as the dolomite, ore mineral composition is simple, mainly of sphalerite, galena, see a small amount of chalcopyrite and pyrite, silver, pyrargyrite, argentite, paler tetrahedrite; The main ore-controlling factors for lithology and lithofacies change interface, fault and fracture zone between the layers, reefs and barrier deposition, landforms, etc, Within the mining area of wall rock alteration types are mainly silicification, carbonation, pyritization, coking, limonite, part of the Pb-Zn deposit occasional barite.Through the study of the trace of MVT Pb-Zn deposit in the area of the ore, rare earth, isotope geochemistry, and fluid inclusion characteristics research, think the ore-forming metals mainly comes from the basement strata in the area and ore rock, sulfides δ34S values are concentrated in 10.0~20.0‰, showed mainly from sulfur contents marine sulfate mineral formations, ore fluid salinity varied from 0.70~22.17wt%(NaCleq), uniform temperature concentrated in 120~230℃, the performance of low-medium salinity, low temperature characteristics~brine basins, different mineralization solution composed of deposits vary, roughly divided into three categories: Ca-Na-Mg-Cl-HCO3- type, F-CI-Na-Ca type, Ca-Na-Cl-SO42- type mineralization fluids source of water for seawater and meteoric contemporaries.The source of the ore-forming solution water for contemporary water and atmospheric precipitation.By studying the orebody spatial position and attitude, think the MVT Pb-Zn orebody location space closely related to tectonic, the MVT Pb-Zn orebody mainly occurs in fracture, interlayer fracture zone, fold collapse and the composite part between them, part of occurrence in the ancient karst geological formation of the cave, the funnel. Area controlled by interlayer fracture zone of MVT Pb-Zn deposit, ore body dip generally more gently, occurrence and ore formation, main is like a layered ore body form and bedded and lenticular; Mainly controlled by the fracture of MVT Pb-Zn deposit, the inclination of the ore bodies are steep cut and Pb-Zn orebody usually wear formation, orebody shape main vein, tubular or columnar, controlled by karst cave MVT Pb-Zn deposit, ore body morphology mainly showed irregular shape, breccia.Integrated predecessors to MVT Pb-Zn deposit in the area of samples with different isotopic dating method(Rb-Sr, Sm-Nd, K-Ar method, etc.), it is concluded that the chronology of the data found that Zone MVT Pb-Zn deposit metallogenic epoch is mainly concentrated in the 175~230 Ma, reflect the MVT Pb-Zn deposit in the area the main metallogenic epoches in the Indo-Chinese epoch, Yanshan period. In combination with the comprehensive analysis and study of magmatic activity in the studied area, this thesis think the Emeishan basalt eruption has nothing to do with MVT Pb-Zn deposit mineralization in the area, not the product of the same age, both in the Longmenshan, northwestern Guizhou, Panxi region in the late Permian to early late Triassic into basic dike, alkaline dike, the K-Ar isotopic dating for radioactive age more concentrated in the 200 Ma, and MVT Pb-Zn deposit in the metallogenic epoch is very consistent, its for MVT lead-zinc deposit type lead-zinc mineralization in the area to provide the thermodynamic, basic dike, alkaline dike may also for lead-zinc mineralization also provided some ore-forming materials.Previous studies by tectonic events and information and tectonic setting of the region can be the western margin of the Yangtze plate tectonic evolution can be divided into six stages: a base formation stage(Ar-Pt2), passive continental margin sedimentary stage(Z-P2), inland crack Valley evolutionary stage(P3-T1), Paleo-Tethys Ocean closed and collision orogenic stage(T2), and further inland development stage(J-K), modern geology and geomorphology structure shaping Stage(E-Q) Comprehensive study of isotopic dating data of typical MVT Pb-Zn deposit, combined with the division of tectonic units in the study area and its sedimentary sequence of the evolutionary stages and magmatic activity characteristics of tectonic evolution stages, concluded that studies the MVT Pb-Zn deposit in the formation of the dynamic mechanism, is the Indo-Chinese epoch convergence of Eurasia plate and the Yangtze continental orogenic, formation of Longmenshan nappe structure belt of orogeny.Integrated the above characteristics, this paper established the Yangtze plate margin MVT lead-zinc mine regional metallogenic model: crystalline basement and ore rock(carbonate rock) provides a major source of lead and zinc material, Oreforming solution water mainly comes from the sea water and atmospheric precipitation, regional deep fault and high porosity rocks(such as extensive distribution of dolomite) provides a channel for ore fluid migration, fault, karst mining area space, high porosity, high permeability the Sinian system- Permian carbonate rock(especially the dolomite) is the main ore-forming space and mineral ore matching stack space.Indo-Chinese epoch Longmenshan orogeny driving the Yangtze continental block west margin of basin fluid mass, long-distance migration, dissolve the crystalline basement of lead and zinc material and evolution of oreforming fluid, the huge orogenic tectonic stress and gravity gradient under the dual role, along with the Indo-Chinese period basic, the invasion of the alkaline dike,to the ore-forming fluid along the regional deep fault structure and high porosity, high permeability of rock migrated to the mining area.ore-forming materials formed in the favourable metallogenic spatial precipitation precipitation and enrichment of MVT Pb-Zn deposit in medium-low temperature. |
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