Study On The Occurrence Form And Enrichment Mechanism Of Scandium In The Weathering Crust Of Emeishan Basal

As an important strategic key metal resource,scandium is widely used in various cutting-edge fields due to its special physical and chemical properties.Due to its extreme dispersion,the global scandium is in short supply for a long time.As a key mineral,the stability of supply and demand of scandium resources is of great strategic significance to the development,stability and international competitiveness of the country.In recent years,the search for rare earth resources in the weathering crust system has become a new prospecting direction.Some scholars have found and reported that there are polymetallic enrichment layers such as Nb,Sc,and REE in the weathering crust of the Emeishan basalt in the Yangtze region of South China,and have a wide distribution range.The characteristics of stable extension horizon and large thickness as a whole.The current research stays in the exploration of resources,and the mineralization type,element super-abnormal enrichment mechanism and mineralization process still need to be further determined.In this paper,the typical section of Emeishan basalt weathering crust in Yulong area of Northwest Guizhou is selected to carry out systematic research.The formation and evolution process of basalt weathering crust is compared,the geochemical behavior of scandium and other elements is analyzed,and the occurrence state and enrichment mechanism of scandium are discussed.The specific conclusions are as follows :(1)Through element geochemistry,rock and mineral identification(optical-electron microscope)and in-situ micro-area test analysis,the mineral assemblage changes from the bottom to the top of the weathering crust are clarified.It is determined that Sc is mainly enriched in the iron rock series,and its occurrence state is mainly in the form of isomorphism and adsorption inclusion in hematite,and a small amount is enriched in clay minerals.(2)The geochemical element ratio method is used to discriminate the sedimentary environment of the iron-aluminum rock series in the study area.It is considered that the layer is deposited in the warm and humid climate of oxidation-weak oxidation,alkaline,continental-sea-land transition facies,and that the three types of weathering crust are caused by the differential deposition caused by paleogeomorphology(3)Based on the analysis of rare earth element distribution inheritance and zircon U-Pb dating,it is concluded that the iron rock series and aluminum rock series in the weathering crust of Emeishan basalt have different material sources.The iron rock series is derived from the weathering of early basic high titanium basalt(262-258Ma),and the aluminum rock series is derived from intermediate-acid magmatic material(about 255Ma).