Characteristics And Significance For Prospecting Of Accessory Minerals In The Bashisuhong Alkaline Rocks,Atushi,Xinjiang

Bashisuhong basic-alkaline complex is one of the most representative complexes in the southwestern Tianshan alkaline pluton belt.This complex mainly consists of gabbro,quartz syenite with aegirine,and alkaline granite.In the quartz syenite with aegirine and alkaline granite occur a lot of accessory minerals rich in rare or rare earth elements.A detailed field geological investigation on the complex combined with petrographical observation and accessory mineral prospecting mineralogical study on the quartz syenite with aegirine and alkaline granite has been carried out,with a focus on the analyses of complex origin and ore potentiality.Based on their euhedral degree and relation to major minerals,all of minerals except major ones in the quartz syenite with aegirine and alkaline granite are classified into early magmatic,middle magmatic,late magmatic,and magmatic hydrothmal minerals,the first three types of which are accessory minerals,and the last type is hydrothermal mineral.The prospecting mineralogical results show that rare earth elements mainly occur in chevkinite-(Ce),britholite-(Ce),bastnasite,parisite,fergusonite,and monazite in the quartz syenite with aegirine,while rare elements such as niobium-tantalum occur more in pyrochlore,fergusonite,and astrophyllite in the alkaline granite.Isomorphic substitution among rare earth elements is the most common in rare and rare-earth independent minerals.In addition,there is also replacement of Ca,Na,K by rare earth elements.In other accessory minerals,there is also a isomorphic substitute of a small number of rare-earth elements for Ca,Zr and other elements.In order to maintain the equilibrium of electricity price,the replacement of the cations at the cationic position is often accompanied by the replacement of another pair of unequal anions at the anion site.