Abstract: Lying in the Beishan rift zone in the northeastern part of the Tarim plate,the Pubei basic-ul-trabasic belt,striking ENE,is controlled by the Baidiwa deep fault inside the rift zone. This deepfault is flanked by a mantle dome on the northwest and by a south- dipping mantle slope in thesoutheast,and the rock belt is just located between the mantle dome and the mantle slope. On thebasis of isotope age data and the age of the emplaced strata,this rock belt should be the Middle-Late Carboniferous product. It is composed of gabbro ,olivine gabbro ,olivine clinopyroxenite andwehrlite resulting from at least 4-5 intrusions. Basic rocks are characterized by high Al and Ca,low alkalis and relatively high Mg/Fe ratio;while ultrabasic rocks are characterized by low-Al andCa,alkali-poor ultramafic rocks,derived from a slightly or relatively high degree of partial melt-ing of mantle materials. Study of metallogenic specialization indicates that this rock belt has agood prospect for the formation of Cu-Ni sulfide deposits.