Geological And Geochemical Characteristics Of Migmatite Type Uranium Deposit In The Haita Area,Miyi Town,Sichuan Province

The paper is extended by the research of the migmatitic uranium mineralization mechanism in Panxi Region?Grant No.41472073?of National Natural Science Foundation,and it is also supported by the key research project,the uranium mineralization mechanism along the Kangdian axis and prospecting direction,of the Department of Geology&Mining CNNC.With the summarization and deep analysis of previous data,main outcomes and knowledge are obtained by systematic study of migmatitic uranium ore in areal geology,mining area geology,petrology and geochemistry in Haita area,Myi town.And the results are listed as follows:?1?The uranium mineralization in Haita area is located in a set of Proterozoic metamorphism-migmatitization rocks.It is classified into migmatitic uranium ore according to its host rock.Wall rock and that near the Uranium mineralization are mainly schist,gneiss,amphibolite,migmatitic schist,migmatite,migmatitic granite,quartz-feldspar vein,quartz vein,etc.Four major types classified by the host rock are migmatitic schist ore,migmatite ore,quartz-feldspar vein ore and quartz Uraninite-rich vein ore.?2?Types are assorted by the features of major and trace elements:one is that mica-quartz schist and gneissic rocks,which originate from shale,claystone,arenaceous rock,greywacke;and the metamorphic rock of this type is the substrate of the migmatite in this area.The other is that amphibolite and hornblende schist,which originate from basic volcanic rocks.?3?Rocks gather simple types of trace elements,generally enriching U,Sc,Bi,Th.Comparing to that in wall rock,elements gathered in rocks are consistent and of more types.U,Sc,Mo,Cd,Pb,Bi,Th significantly or obviously enriched in different types of rocks,which suggests their similar mineralization mechanism.?4?Mica-quartz schist and gneissic rocks of metamorphic rocks are uranium-rich rock formations in Haita area.The migmatitic granite was generated by hypomigmatization in place with the set of metamorphic rocks,which indicates that preliminary enrichment of uranium had been completed in the process of migmatization ultrametamorphism,providing an abundant uranium source for the late hydrothermal activity and superposition mineralization.?5?From the metamorphic rock to the migmatized metamorphic rock,to the migmatite,and to the migmatitic granite,as migmatization deepening,the rules of transportation and transformation are as follows:?1?The content of major elements like SiO₂ obviously increased,while the contents of the Fe₂O₃?MgO?CaO?TiO₂?P₂O₅?MnO obviously decreased.?2?The contents of trace elements U and Pb obviously increased but partly enriched,while that of Sc and Cu obviously decreased.Element Mo has a highest content in migmatite with heterogeneous distribution,while Rb does the same in migmatitic granite.?3?The contents of REE change a few.The distribution model of REE is right-leaning in the orientation,and its inclination drops off from metamorphic rock to quartz-feldspar vein.?6?The main content,trace and rare earth elements characteristics in the ore of Haita region as follows:?1?The metallogenetic process of the uranium goes with metasomatics alterations of rich silicon and poor alkali,comparing with other types of ore,the quartz veins uraninite-bearing has higher SiO₂?TiO₂?P₂O₅,lower Al₂O₃,K₂O,Na₂O,CaO,Fe₂O₃,MgO;?2?Comparing with surrounding rocks,the content of U?Mo?Cd?Pb?Th increased significantly in all kinds of ores;?3?Content of?REE is high and the ore-forming process goes with the process of?REE increase;The degree of fractionation of HREE and LREE is low,and the curves of REE distribution is nearly flat.?7?It is shown that ore and wall rock maintain affinity in some degree,according to the spider diagram of trace elements and the curves of REE distribution,which indicates the close relationship between mineralization and migmatitic granite.And because of the similarity between two curves of REE distributions,the two should have some relations of origin.It is different from the material source of the molybdenite-bearing quartz-feldspar vein mineralization exemplified by A19mineralized spot to that of other uranium mineralization types.?8?The average age of the four uraninite measured by EPMA is 247.93Ma,which indicates that uranium minerals in this area were formed in Hercynian to Indo-Chinese epoch.?9?The uranium mineralization in this area mainly relates to the hydrothermal process:the Ductile-Brittle Shear Zone connects the magma in depth to mineral-bearing hydrothermal solution,shaping a significant fluid-flow channel.The main hydrothermal alterations which has close relationship with the mineralization are silicification,molybdenite,carbonatization and sulfidization.Hydrothermal solution and fault structure control the migmatitic uranium mineralization in this area.