Geochemical Characteristics And Pedogenic Mechanism Of Weathering Crust In The Alkaline Basic Rock Area Of ??Dongchuan, Yunnan

Solid metal mines are damaged and open ecosystems with a natural-artificial landscape-social-economic complex.Mine ecological restoration is one of the hotspots in global mine research.The soil in the metal mining area is the most important part of the ecological environment system.It has important scientific and application value for the study of the soil type,soil formation process and mechanism of the metal mining area.In this paper,the weathered crust section of basalt in Dongchuan rare mine iron-copper mining area in Yunnan was selected as the research object.Through the study of major elements,trace elements,rare earth elements,particle size and magnetic properties,the process and mechanism of soil formation were revealed to gain new understanding.Mainly as follows.?1?During the process of soil formation from parent rock?R??leaching layer?layer A?,K₂O,MnO,P₂O₅ and Al₂O₃ appear to be relatively enriched,and Fe₂O₃,Na₂O,MgO,FeO and TiO₂ have relative losses;Fe₂O₃,MgO,Na₂O and TiO₂ are all higher than the upper crust,Al₂O₃,CaO and K₂O are lower than the upper crust,and the weathering salt base leaching and desilicification are weak.?2?In the section of weathered crust of basalt,the rare earth elements in the soil layer have ?Eu>1 and ?Ce>1,with weak positive anomalies.The LREE/HREE value and?La/Yb?N value reveal that light and heavy rare earths have a certain fractionation effect during the process of soil formation,and the main feature is the enrichment of light rare earths.?3?Compared with diagenetic parent rocks,Ti,V and Ba are depleted,and Cr,Mn,Co,Ni,Cu,Pb,Zn,Sb and Sr are relatively enriched.Cr,Cu,Pb,Zn and As have unity.The weathering index Rb/Sr showed a tendency to increase first,then decrease and then increase,with the parent layer of layer C being the largest and the weathering intensity of layer D being the smallest.?4?The elements in the parent rock are inherited in the soil.The foundation of the elements and magnetic minerals in the parent rock affects the initial content of soil elements and magnetite,but the later period is affected by the process of soil formation,making these elements and Magnetite is newly distributed in the soil.The formed soils are all sandy soils,mainly sandy clays.The magnetic susceptibility revealing that magnetite in the soil has a gradual enrichment trend during the process of slope accumulation.During the process of soil formation of basalt weathering crust,the variation characteristics of silicon-aluminum index and silicon-iron-aluminum ratio are related to the soil formation in the process of soil formation of the parent rock;the change trend of chemical alteration index shows a trend of decreasing first and then increasing,which is The weathered soil?C₁layer? has a low level of chemical weathering;the average value is similar to the moderate chemical weathering level in warmer and humid conditions,revealing that it has experienced the process of mountain uplift and soil formation.