| The research area of this thesis is located in the western part of Zhen'an County,Shaanxi Province,the northern part of the South Qinling orogenic belt.The area has experienced long-term multi-stage geological history with different tectonic properties and geological evolution,forming complex and diverse material combinations and complex spatial structural configurations in the area.Tectonic activity in the area is strong,and fold fault structures,thrust nappies,and strike-slip fault structures are developed,providing channels for ore-forming hydrothermal migration.These widely developed main faults have derived a large number of tensile and twisted secondary fault structures,which have become the main deposit spaces.Regional magmatic rocks developed from the Indosinian period to the Yanshan period.The intrusive rocks in the area were mainly the Indosinian period,followed by the Yanshan period,and frequent magmatic intrusion activities provide abundant energy and ore-forming hydrothermal fluid for the ore gathering area.It can be seen that the ore-forming geological potential of the mining area is huge.The writing of this article is based on the support of the project "Magmatism and Tungsten-Molybdenum Metallogenesis in the Western Mine Concentration Area of Zhen'an" undertaken by Changan University entrusted by the Shaanxi Provincial Geological Survey Center.According to the available data,good tungsten-molybdenum mineralization and hydrothermal quartz vein mineralization alteration have occurred in the Wangjiaping concealed rock mass and its surrounding strata,showing a high mineralization correlation.Therefore,in order to further ascertain the geological characteristics of the tungsten-molybdenum ore field in the west of Zhen'an,South Qinling,and to clarify the relationship between the Wangjiaping concealed rock mass and metallogenesis,the Wangjiaping concealed rock mass and Yanggou-Di'ergou in the western Zhen'an mining area were selected.Combined with a series of scientific research methods,such as field geological investigation,ore control structure,metallogenic law and indoor rock and ore geochemical sample test and analysis,the detailed ore field tectonics,petrology,mineralogy,chronology and geochemistry are studied.On this basis,the ore controlling structure,the structural environment of the formation of the concealed rock mass and the nature of the source area are discussed,and the evolution process of tungsten and molybdenum mineralization in the Western ore concentration area of Zhen'an is further studied and analyzed,in order to establish a representative metallogenic model in the western ore concentration area of Zhen'an and predict the favorable areas for ore exploration.Wangjiaping concealed granite body is located in yanggou-dieergou tungsten molybdenum mining area in Western Zhen'an,which is a new concealed granite body discovered by deep drilling in recent years.Regionally,the concealed rock mass is located in the southeast of the harbor like "encirclement circle" composed of granite intrusive rocks such as Dongjiangkou in the north,Lanbandeng in the west,Yanzhiba in the west,Sihaiping in the south,and is about 5km away from Sihaiping in the plane.The samples tested and analyzed in this paper are all collected from the core of wangjiaping concealed rock body.The rock samples are fresh and representative.In this paper,the detailed test and analysis of mineralogy,isotopic geochronology and petrochemistry are carried out for the veinlet and fine-grained granite vein of the concealed rock mass and the intersecting concealed rock mass.The specific results are as follows:Petrological characteristics show that the lithology of the Wangjiaping concealed granite body is medium-fine-grained biotite feldspar.Isotope chronology studies show that the diagenetic age of the hidden rock mass is 201.9 ± 1.8Ma,which indicates that the rock mass was formed at the end of the Late Triassic.Rock geochemical studies show that the concealed rock mass is calc-alkaline quasi-aluminum-weak peraluminous type I granite,which is relatively rich in light rare earth,has a medium negative anthracene anomaly,and is rich in large ions,such as Rb and K Elements and high field strength elements such as Zr and Hf,obviously depleted the characteristics of Nb,Ti,P and HREE.The petrological characteristics of the fine-grained granite vein in the concealed rock mass show that the lithology of the vein is fine-grained adamellite.Isotope chronology studies show that the diagenetic age of the hidden rock mass is 208.7 ± 4.4Ma,which indicates that the rock mass was formed at the end of the Late Triassic.Rock geochemical studies show that the concealed rock mass is calcium-alkaline weak over-aluminum-over-aluminum type I granite,which is relatively rich in light rare earth,has a weak negative anthracene anomaly,and is rich in large ions,such as Rb and K Elements and high field strength elements such as Zr and Hf,obviously depleted the characteristics of Nb,Ti,P and HREE.It is worth noting that,based on the analysis of the interpenetration relationship between actual veins and rock bodies,fine-grained granite veins should be formed later than the Wangjiaping hidden rock body.However,due to the influence of high temperature hydrothermal alteration on the zircon U-Pb dating results,the data has a slightly larger error,which can only be described qualitatively and not quantitatively.Based on the similarity of petrology,chronology and geochemical characteristics,it is judged that the granite veins and the Wangjiaping hidden rock mass are of the same origin and origin,and are the products of two stages of magmatic intrusion.Genesis of concealed rock mass:With the end of the Indosinian plate collision orogeny,the plate compression barrier function disappeared,and the deep melting crust-mantle material and energy were adjusted drastically,melting the unmelted subduction oceanic crust in the earlier period.Together,they overthrew the weak structural tectonic belt along the early area and invaded to the shallow crust,forming the Wangjiaping concealed granite body.Metallogenic model:The Wangjiaping concealed granite body is the leading rock body for mineralization,providing a lot of heat and material sources for mineralization,and preparing for the mineralization;the fine-grained granite veins produced secondary magmatic mineralization,and the ore-forming hydrothermal fluids carried along the northeast-north-northeast faults,joints,and fissures,enriched,and formed northeast-north northeast Hydrothermal quartz vein-type tungsten molybdenum ore;At the same time,the ore-forming hydrothermal fluid also flowed into the Northwest-Near-East-West fault,which formed in the early stage,thereby forming a layered mineralization alteration near-East.It is inferred that the Xiangoutai-Yuehe area and the area around Yanggou-Di'ergou mining area are favorable areas for prospecting in the west of Zhen'an. |
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