The B¶n Phóc intrusion is one of the largest ultramafic bodies in the T¹ Khoa Anticline. The recent researches have been showing that it appears to be the lower part of an open feeder chamber and was intensively eroded. It has a range of ultramafic rocks characterized by high MgO (30.9-46 wt%), low Ti and Cr, and high rare earth elements with moderate light rare earth enrichment. These rocks have primitive textures of adcumulate, mesocumulate, orthocumulate which may correspond to komatiites or picritic tholeite series with very low viscosity and in stable conditions during crystallization. Adcumulate olivinite and mesocumulate olivinite were formed in the first period of crystallization and settled to the base or lower part of magma chamber or basin. The cumulate nickel sulphide mineralizations are directly related to these rocks and mainly located in adcumulate olivinite. The zonation of textures in the ultramafic rocks are guideline for determining the primitive attitude of the intrusion which is the key for exploration and prospecting of magmatic nickel deposits in the T¹ Khoa Anticline area.