Metallogenic Geological Characteristics And Metallogenic Prediction Of Uranium And Polymetallic Ore In Rencha Basin Of Northeast Guangdong

Rencha basin is located at the junction between the southwestern end of NE-trending Wuyi polymetallic metallogenic belt and the eastern end of EW-trending Nanling metallo-genic belt.The special geologic structure is a polymetallic metallogenic belt,and have superior regional geological metallogenic conditions.During Indosinian-early Yanshanian,the magma activity was frequent,and in late Yanshanian the volcanic activity was intense.the Rencha basin developed multiple groups of fault structure.At present,a number of U,Mo,Au,Ag and other polymetallic deposits and mineral occurrence have been found with a good metallogenic prospect.Basic geological work in Rencha basin is mainly confined to a few known ore deposits and work blank area is more outside.Many fundamental geological problems have not been studied systematically.In addition,the rich geological,geophysical and geochemical,remote sensing information,has not been analyzed and comprehensively evaluated systematically by modern mineral resources prediction and evaluation theory.This has become one of the main problems restricting the exploration direction and breakthrough in the next step.In this paper,the geological,geophysical,geochemical,Remote Sensing and mineral data related to the basin are systematically collected and collated.On the basis of learning reference and absorbing the previous research results,and combining the results of field geological survey and sample test,the study of typical deposits is carried out on the basis of the analysis and study of the metallogenic geological conditions in the basi.Finally,the main ore-controlling factors of the deposits are identified.In this paper,the spatial distribution of uranium-polymetallic deposits is sorted out,the metallogenic sequence and genesis of the deposits are determined,and the metallogenic model of the basin is established.Using Geological,geophysics,geochemistry and remote sensing information of multi-source Geoscience,the information of ore-forming anomaly is extracted.Under the mixed driving form of"empirical model method+genetic model method"of MORPAS evaluation system data knowledge,"comprehensive information method"was used to carry out metallogenic prediction for all metallogenic units,superposition and analyze the characteristic abnormal information,delineate the target areas for ore exploration,and conduct comprehensive evaluation for each target area.The results obtained in the specific research process are summarized as follows:(1)Based on the research of paleostress element in Rencha basin,this paper recovers tectonic-sedimentary-magma evolution sequence from Indosinian to Eocene.According to the statistical result of stratigraphic unit occurrence and cutting relation in and aroud Rencha basin,four periods conjugate joints are divided.The fourth period joints distribute mainly in Late Cretaceous strata and Paleogene strata,and maximum principal stress axis is EW-trending.The stress state shows extrusion in the EW-trending and extension in the SN-trending.At this stage,extend extensional faulted depression is the mainly characterist-ics of Rencha basin,and this period corresponds to the main metallogenic age stage.By analyzing the coupling relationship between mechanical property of structure with mineralization,this paper discusses that fault structure is the main ore-controlling factors.NNE-trending,NWW-trending,EW-trending structure exist comosite convergence and form stretched region(zone).The stretched region(zone)is the best storage space(ore-hosting structure),and dominates the space of main U-ore deposit or U-ore body.(2)The geochemical characteristics show subrhyolite-porphyry is alkali-rich,potassi-umrich,iron-poor and has the silicon and aluminium supersaturation characteristics of high K calcium-alkali serie or shoshonite series.The magmatic source region may be from the crustal.Subvolcanic rock is not the result of crystal fractionation,and partial remelting of upper-crust rock may be the main formation mechanism.Crystal fractionation characterist-ics of samples is the result of felsic mineral crystallization in the process of ultra-shallow intrusion of magma.Two groups LA-ICP-MS zircon ²⁰⁶Pb/²³⁸U age of graphic granite basement of Rencha Volcanic Basin in northeast Guangdong is respectively 179±1Ma and186±1Ma.The results show the formation age of that graphic granite basement of Rencha Volcanic Basin is late Early Jurassic,Namely the first episode magmatism of yanshan.This age advances geologic knowledge of structure-magma evolution,and provides a new chronology data for lack data report of magmatic activity in northeast Guangdong.(3)This paper dissects the critical ore-controlling factors and deposit genesis,and discusses that buried structure of Chagan polymetallic deposit controls range of distribution of deep mainly ore body.This point changes metallogenic geological knowledge of singel“strata-controlling”.It belongs to reconstituted Sedimentary-volcanic hydrothermal com-plex deposit.Malou deposit is located in 0?30m marginal facies of internal connection internal connection belt(fine subrhyolite-porphyry).Uranium mineralization distributes in Secondary-intensive fracture zone.It belongs to middle-low temperature volcanic hydroth-ermal deposit.Eshi deposit is located in tuffite and breccia-bearing tuff of the third cyclothem(K³_2-?^b)on top of Yetang upper formation in cretaceous.It belongs to sedimentary-volcanic hydrothermal deposit.(4)Based on zircon U-Pb isotope dating,it is concluded that the volcanic rocks in the basin are mainly the products of cretaceous volcanism,which occurred mainly in the early stage of late Cretaceous(K₂).The ²⁰⁶Pb/²³⁸U age results of uranium samples indicate that the metallogenic age extended from the late late cretaceous to the pliocene in the neogene,and has a long history of metallogenic development,so it should be multi-stage metallogenic.According to the ore-forming theory of"geological age(cycle)-deposit metallogenic series(group)-deposit metallogenic subseries-deposit"in the theory of deposit metallogenic series,the metallogenic series of the basin deposits are preliminarily determined,and the basin deposits are classified into three metallogenic subseries under the late Triassic-cretaceous period(yanshan cycle).(5)This paper extracts multiple source geo-information,and identifies 10(U-1?U-10)halo zones and 8(?-1??-8)hydration zones from the study area.Based on the geochemical data of 19 elements measured in river sediment,this paper uses clustering analysis and factor analysis means,and conductes comprehensive anomaly extraction according to the Hg-y-La combination,Bi-Sn-w-Be combination,Zn-Mo-Nb combination,Au-Pb combination and Cu-Zn combination,respectively.Seven hyperspectral bands of ETM remote sensing images were selected for image gain,threshold classification and superposition analysis to identify and extract the abnormal information of iron ion altered minerals,hydroxyl altered minerals,silicification,medium base dyke and other abnormal information,respectively.(6)Based on the metallogenic regularity of the basin and the results of multi-source geo-information extraction,the prospecting criteria of the volcanic type uranium deposits in the study area are established.Based on metallogenic geological setting,relationship between structure and structural plane,metallogenic characteristics,the and metallogenic prediction geological model is established.Using Morpas3.0's function of spatial analysis,this paper uses the hybrid driving form of data-knowledge verification model method and genetic model method to carry on the superposition analysis of characteristic information,and delimits the prospecting target area.Five A-grade target areas(A1?A5)and three b-grade target areas(B1?B3)have been delineated in the area,and prospects of each target area were evaluated respectively.