Geological Characteristics And Their Relationship With Uranium Mineralization Of Vein Rocks In Datian, Panzhihua

The Kang-Dian Axis is one distribution areas of the Proterozoic mixed rock in our country,in which there are a lot of mixed rock type uranium ore?mineralizations?widely distributed.In recent years,a number of ultra-rich uranium deposits containing coarse-grained ulrichile have been discovered in a range extending 300 km from Haita Miyi,Datian Panzhihua to Mouding Yunnan,showing great prospecting potential and metallogenic potential.There are a large number of mafic and intermediate-acid vein which in different scales are founded in migmatites,especially diabase in uranium ore area.Previous studies on uranium deposits in the Kangdian axis have focused on the restriction of migmatization on uranium deposits,while insufficient research has been done on the relationship between vein rocks and uranium deposits.In this paper,diabase and felsic vein bodies in Datian area of Panzhihua are selected for research.Through petrological,geochemical and chronological studies,combined with uranium ore-forming era and deposit characteristics,discussing the relationship between vein rocks and uranium mineralization.In order to find out the nature of magmatism formed by vein and its relationship with uranium mineralization,with the support of the National Key Plan project"Three-dimensional modeling and prediction of deep mineral geochemistry"?ProjectNo.2017YFC0601505?,the national natural science foundation project"Typomorphic Characteristics and Formation Mechanism of Coarse-grained uraninite in Kangdian Axis"?Project No.41872079?and the project"Comparative Study on Neoproterozoic Uranium Mineralization Characteristics of Kangdian Axis"?Project No.201807?,and under the previous investigation in Datianarea,Based on the field geological survey,sample collection and mineralogical identification,rock geochemical classification and U-Pb chronology analysis of the mafic and acidic vein in the area,the following results have been obtained in the discussion of the formation background of vein and the relationship between uranium mineralization:1.Mafic vein major elements are characterized by low Si,high Ti,high Fe and Mg.Trace elements rich in LILE?K,Sr,Rb,Ba,Th?and HFSE?Ta,Nb,Zr?.rich in light rare earth elements and depleted in heavy rare earth elements.The difference between LREE and HREE is obvious.The element composition as a whole have the similar characteristics of OIB basalt.Mg^#=42.10⁶3.07,SI=22.31⁴2.57,combined with Haker diagramand and distribution pattern of Rare Earth,the rock has undergone a degree of fractional crystallization of clinopyroxene and Plagioclase before diagenesis.Acid vein are high-Si,peraluminous and calc-alkaline rocks.Acid vein have obvious depletion of Nb,Ta,P and Ti,and are rich in LIlE such as Ba,Th and U.The content of Sr element is not high when the content of Y and Yb is low and which do not have the characteristics of typical adakite.The differentiation of LREE is obvious but the HREE are not.At the same time,the content of REE in acid vein is low,and has positive anomaly of Eu.Its formation has connection with Ordovician granite.2.The zircon shape of the mafic vein is relatively broken,but its age is relatively concentrated.It is believed that the rocks were influenced by the late Metamorphism,but it has little influence on the element composition of zircon.The diagenetic age of the mafic vein is 770⁷80 Ma,which is consistent with the global Rodinia supercontinent cracking period.Some zircon ages are about 158 Ma,indicating that the rocks in this region were affected by Yanshanian thermal events.The diagenetic age of the acid vein is 760⁷70 Ma.The mafic vein and the acid vein should have formed in the same period of magmatism tectonic activity.3.The inactive element composition characteristics of mafic vein show that the magma comes from EMI-OIB mantle and is the product of partial melting of garnet?more?+spinel?less?lherzolite.As magma rises to the surface,the magma is hybrided by lower crust materials,The rock has the trace element characteristics of WPB.At the same time,although acidic vein have I-type granite geochemical characteristics,combined with tectonic background and chronology,it is believed that both mafic vein and acidic vein were formed in hydrothermal activities related to Rodinia cracking,and the acidic vein should be remelted from rocks with TTG geochemical characteristics under high thermal energy environment during this period.4.During the orogeny in the Jinning period,the ancient strata on the Kangdian axis underwent anatexis to form migmatite and later retrogradation?Chlorite-Epidotite-Zoisite alteration was widely developed in this area?,which resulted in the initial enrichment of uranium in the older migmatite and granitic rocks in this area.During Rodinia cracking period,deep mantle-derived magmatism took place in the region.This magmatism hydrothermal activity played a very important role in the formation of uranium deposits.According to the uranium mineralization characteristics,it is believed that this magmatism did not provide uranium sources for the formation of uranium deposits.However,the tensional environmentmay provide a migration channel and a storage place for for uranium ore formation?uranium mineralization in No.I belt of the deposit controlled by the tensional fissures with steep dip in this area?,and at the same time magmatism activity provide a heat source and mineralizer?CO₂?for the reactivation of hydrothermal activities in the area?the metamorphic hydrothermal solution of migmatite is involved?.Na-rich hydrothermal solution and rocks undergo sodium metasomatism to further extract uranium from migmatite and further enrich it into hydrothermal solution to formed ore under certain suitable conditions.