| Detailed research has been carried out to study essentials of the HuayangchuanU-Nb-Pb (uranium-niobium-lead) deposit with respect to mineralogy, petrology,geochemistry, geochronology and tectonics. Mineral composition, chemicalcomposition and physical property of ore were partly solved by detailed research ofore. The study on petrology, geochemistry and geochronology of different types ofmineralization country rocks points out: types, U-Pb ages of zircon (207Ma and225Ma-229Ma), evolution processes and origins of granite; protoliths and ages ofmetamorphic rocks; genesis and fluid characteristics of carbonatite veins; Veins arecommon features in rocks and here we provide a general profile of morphology,transect relationships, spatial distribution characteristics of leads by detailed workingsdocumentation. Combined with the study on ore composition, the correlationsbetween minerals, hydrothermal alteration, this paper presents an overview aboutore-forming geochemistry processes, genetic type (magmatic hydrothermalmulti-origin type) and metallogenic model. There are the specific results:(1) Distinctive formation conditions of U、Nb and Pb mineralization indicate thatmineralization can be divided into U-Nb-mineralization and Pb-mineralization, whichdo not occur in same place. In terms of comprehensive utilization, we emphasizeanother mineralization of U-Nb-Pb-mineralization, which means U-Nb-mineralizationand Pb-mineralization have a close occurrence location. At the same time, the types ofore can be divided into U-Nb ore, Pb ore and U-Nb-Pb ore. U ore are mostlyimpregnation structure, veinlet structure, network structure and irregular crumbstructure. Rarefaction spotted structure and network structure are common structuresin Pb ore. Rarefaction crumb structure and veinlet structure can be observedsometimes. Betafite precipitate around the margin of biotite、monazite, and in thefractures of microcline、biotite. Galena that precipitates in the intergranular space ismostly xenomorphic granular texture.(2) U、Pb、Nb、rare earth elements (REE) are the major useful elements. Ag(silver), Bi (bismuth), Sr (strontium), Rb (rubidium) and other elements are regarded as useful associated elements. Betafite, uraninite and galena are major ore minerals,and other minerals include monazite, allanite, apatite, magnetite, strontianite, baritefamily. Microcline, quartz, plagioclase, amphibole, biotite and calcite are majorgangue minerals.(3) Betafite hosts93.245%total UO2, uraninite contains5.98%total UO2, andthe rest disseminates in monazite, allanite, apatite and titanite as isomorphic andabsorbed components. Galena is the major plumbeous mineral that contains87.32%Pb, and12.68%Pb disseminates in other minerals. Betafite contains95.982%Nb2O5,and the rest disseminates in monazite, allanite, apatite and titanite as isomorphic andabsorbed components. The contents of REE in monazite, allanite, betafite, titanite,apatite account for63.20%, and the rest disseminates in calcite, barite etc.(4) Country rocks in this region are metamorphic rock and igneous rock. Bearingbiotite plagioclase gneiss is the product of medium and high grade metamorphism.Igneous rocks include granite porphyry, granitic pegmatite, carbonatite. These countryrocks have an abnormal light REE (LREE) enrichment relative to heavy REE (HREE),to some extent, show a negative Eu (europium) anomaly and faint negative Ce(cerium) anomaly. And chondrite normalized REE abundance patterns of countryrocks apparently present a trend of right incline. The REE abundance patternscharacteristics of ores are similar to country rocks’.(5) Detailed research shows that granite in this region that can be distinguishedas I-type granite may derive from medium-lower crust (Taihua group and Xiongergroup in this region). The diagenesis ages are207Ma and225Ma-229Ma. Inheritancezircon gives two ages of1907Ma and2420Ma. Taihua group protolith diagenesis ageand metamorphic events occurrence age are2.7Ga and2.2-2.3Ga, respectively.Metamorphic events and granite diagenesis may occur at an approximate time.(6) Carbonatite veins group is controlled by the tectonic fractures of Taihuagroup gneiss. Macroscopic and microscopic evidences show that the rock-formingsubstances of carbonatite veins and associated alkaline veins come from immiscibilitycrystallization differentiation products of alkaline silicate-carbonate melt-solution thatcome from enriched mantle type1(EMI). Carbonatite veins have higher abundances of REE compared with alkaline rock veins probably because melt have an enrichmentof REE, especially LREE, during the liquid immiscibility process. There are thedivisions of carbonatite fluid inclusions: CO2-H2S gaseous inclusions; CO2-H2Oliquid inclusions. Homogenization temperature and freezing temperature are195.0-197.0℃a nd-13.7--12.4℃, respectively. The preliminary conclusionis that thecarbonatite veins of Huayangchuan deposit may derive from EMI.(7) Leads of different types and sizes inject into fractures with differentdirections and characteristics. Distinctive stages leads that superimpose and transecteach other show a complex network morphology in space. The overall trend directionsof leads, especially the master leads, are predominant directions of NW and NNW.The NW leads have a large size and extend relatively widely. Leads density zones thatveins commonly account for50%to60%, even up to at least90%, down to20%,generally distribute along NWW. Leads pitch NW, and occur in en-échelon arrays onthe section.(8) Field geological works and microgeology facts provide an overview aboutgeneration of minerals: in pegmatitic stage, U mainly occour in forms of thorite,uranothorite, monazite, allanite, zircon, together with a small amount of betafite. TheU-mineralization is faint; in hypothermal-mesothermal stage, betafite form. Betafite,apatite, and monazite are paragenetic mineral association. This stage is the mainbetafite-mineralization stage; in mesothermal-epithermal stage, galena, pyrite,Ba-Sr-sulphate, carbonate occur. In this main sulfide-mineralizaiton stage, Ag, Bi, Se,Te, In that geochemistry characteristics are similar to Pb, disseminate in galena; in thelate stage, the carbonate veins that consist of a large amount of zeolite, calcite, barite,quartz and other epithermal minerals occur; in supergene stage, wad, limonite, clay, asmall amount of calcite and the main oxide of Pb including cerussite, anglesite,minium are the main minerals.(9) Hydrothermal alteration process related to betafite mineralization is mainlyhydrothermal alteration in mixing pegmatite veins and quartz carbonatite veins.Alterations occur in country rocks including silication, biotitization, carbonation.Albitization related to late magmatic crystallization autometamorphism and microclinizaiton, albitization, epidotization, chloritization, sericitization related tomigmatization disseminate in research area. |
PDF Full Text Request