| The Kang Dian earth axis is one of the most important metal and rare metal metallogenic belts in China.The study on the metallogenic characteristics and prospecting prospects of the uranium ore has always been paid attention to by the searching for uranium workers.On the basis of the National Natural Science Fund Project"Study on the metallogenic mechanism of migmatite type uranium deposits in Panxi area"(Numbered:41472073)and the key scientific research project of China Nuclear Geology"Study on the study of uranium metallogenic mechanism in the middle and south part of the Kangdian axis in the middle and south section of the mixed rock".Through geological observation,borehole cataloguing,sample collection and analysis,the metallogenic geological characteristics and geochemical characteristics of the migmatite type uranium deposits in the 505 area of Datian,Panzhihua are systematically studied,and the following main achievements and knowledge are obtained:(1)The ore hosting strata in the Datian area of Panzhihua are a set of metamorphic-migmatite assemblages.According to the degree of migmatization,the ore bearing rocks can be divided into substrate(metamorphic rock),migmatization metamorphic rock,migmatite,homogeneous migmatite and neosome-felsic vein in the degree of migmatization.In addition,there are late quartz veins,structural altered rocks,diabase and diabase porphyry veins.(2)According to the lithological characteristics of the ore,the uranium ore in the505 area of Datian can be divided into 5 types:Altered rock type ore,Silicified plagioclase gneiss,Silicified felsic vein ore,Altered hornblende plagioclase pyroxenite and migmatite type ore.Generally,the ore is subhedral or allotriomorphic granular blastic texture,massive,patchy,or shadow form.Uranium minerals are mainly uranium and pitchblende.Metallic minerals in ore generally contain pyrite and chalcopyrite.Some ores also contain perovskite,pyrrhotite,marcasite,limonite and ilmenite.Non metallic minerals are mainly quartz,plagioclase and biotite.Some ores also contain potash feldspar,pyroxene,hornblende and muscovite.(3)The existing form of uranium in the ore is independent uranium minerals,usually in the form of granular,granular aggregate(Uranium)and fine vein(Pitchblende),and the distribution is inhomogeneous.(4)The regional large fault(F1)in the north east of the mining area is the main ore guide structure in the area,and the near EW fault zone is the secondary structure of the NE trending regional large fault(F2,F3),which has the obvious control effect on the uranium mineralization in the area.(5)According to the characteristics of the main and trace elements in the area,the substrate can be divided into two types:one class is schist and gneisses.It has the characteristics of high silicon,low aluminum,iron,magnesium,calcium,manganese,titanium,low Cr,Co,Ni and K2O>Na2O.The other is amphibolite and amphibolite schist.It has the characteristics of low silicon,high aluminum,iron,magnesium,calcium,titanium,high Cr,Co,Ni and so on.The major and trace elements of schist,gneiss and felsic metamorphic rocks are the same,which are metamorphosed from metamorphic sandstone,siliceous tuff or intermediate acid magmatic rock.The major and trace elements of amphibolite and amphibolite are the same as basic metamorphic rocks,which are formed by metamorphism from basic volcanic rocks,siliceous tuff and a significant amount of Ca,Al,Fe and Mg.(6)In the process of migmatization,the characteristic change of the major elements are:As the degree of migmatization increased,the content of oxides changed little,and the formation of homogeneous migmatite changed obviously.The change characteristics of trace elements:As the degree of migmatization increased,the enrichment degree of elements changes very little.The content of U elements in the migmatization action always been low,indicating that the influence of migmatization on the enrichment of elements is less.(7)The ore has the characteristics of high Ca O,P2O5,low K2O,similar to the characteristics of the main elements of the tectonic alteration rock;The ore enriched trace elements U,Pb,Bi,Th and Mo.Some samples also enriched Cu,Be,Sb,Co,Ta and other elements,and their enrichment elements were similar to those of structural altered rocks and metallic sulfide quartz veins,and the distribution curves of the original mantle normalized cobweb map of the original trace elements were similar.The rare-earth distribution pattern of the ore is right deviation type,the light rare-earth and heavy rare earth fractionation are obvious,and the?Eu is generally depleted,which is similar to the curves of structural altered rocks and metallic sulfide quartz veins.In general,the geochemical characteristics of ore are similar to those of tectonic altered rock and quartz vein containing metal sulfide,reflecting certain genetic connections between ore and tectonic altered rocks and metallic sulfide quartz veins.(8)Uranium mineralization in the 505 area of Datian has undergone two major metallogenic stages,namely,the early stage of mineralization is Chengjiang period and the late mineralization stage is late Indosinian-early Yanshan.The study of sulfur isotope composition shows that its composition is relatively stable,which is+3to+10.1,with an average of+7.0,which is obviously characterized by deep source sulfur,which is similar to the sulfur isotopic composition of the post magmatic hydrothermal uranium deposits in China,reflecting the early mineralization fluid as the post magmatic post hydrothermal fluid in the late stage of migmatization.The composition of hydrogen and oxygen isotopes is:the value of?DV-SMOW is-97.4to-87.1,and?18Owater is-4.68to-3.38,reflecting the late metallogenic fluid mainly derived from atmospheric precipitation.The two stage metallogenic material probably came from the Heime granite body in Jinning period. |
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