Abstract: A set of weathering crusts with relatively stable regional thickness developed between the top of the Upper Permian Basalt and the bottom of the Xuanwei Formation in northwestern Guizhou,which is enriched with three rare elements.To reveal the enrichment rules of three rare elements,the Maojiaping section in Shimenkan,Weining County was selected to carry out elemental geochemistry research.The results show that the three rare elements are mainly concentrated in the clay rock of weathering crust,and the content of the three rare elements is high in the upper part and   low  in the lower part.The aluminite clays are obviously richer in niobium and rare earth elements than basalt,especially in kaolinite veins where niobium (w(Nb2O5)=0.059 %) and yttrium (w(Y)=512.0×10-6) are abnormally enriched.The chemical alteration index (CIA) of weathering crust clays is mostly as high as 95-100,reflecting that the rocks have suffered strong chemical weathering.According to the chondrite normalized partitioning model and the primitive mantle normalized cobweb diagram of trace elements,the weathering crust clays rich in niobium and rare earth elements are derived from the Emeishan basalt.The characteristics of the earth elements indicate that the metallogenic environment is mainly a reduction-oxidation transition environment,and the long-term weathering and leach-ing of basalt is the key to the formation of rich in rare earth elements and niobium aluminum clay rocks.