Located in Nanjiang County and Wangcang County of northern Sichuan, alkaline rooks in 1Vlicangshan area might be divided into ijolite-essexite series (I)and syenite series(11).Nephelines are present in large quantities, whe- reas there are no or very few alkaline dark minerals. Clinopyroxenes, amphi.- boles and nephelines in alkaline rocks are richer in aluminium than those minerals from the same sort of rocks in other areas, with: alumoferro-diopside (fassaite) exhibiting this feature most obviously. Pyroxenes from Series I are different from those from Series II in composition and evolution trend. Rooks of Series I were crystallized in the temperature range of 775-1023℃，whereas those of Series II ，700-950℃，indicating that the depth for their crystalliza- tion was larger than 10 km. The richness of aluminium in pyroxenes should be attributed to the abundant aluminium in rocks and the crystallization of minerals at fairly great depth .In other areas, alkaline rocks often have alka- line dark minerals, which contain very high Fe3+.In this area, however, the low oxygen fugacity hindered Fe2+ from converting into sufficient Fe3+, and hence it was quite impossible for alkaline dark minerals to crystallize from magma. The low-fO2 alkaline rocks without alkaline dark minerals in this area were crystallized from alkaline magma in a closed environment, whereas high- fO2 alkaline rocks that contain alkaline dark minerals in other areas were formed by crystallization of a1kulIne magma in an open system.