Abstract: The Kalatongke Ni-Cu sulfide deposit is an important Cu-Ni-rich deposit in western China. Geochemical studies of the basic complex closely associated with the deposit show that it is characterized by low Ti, depletion of Nb or Ta and enrichment of LREE and large lithosphile elements. These features, combined with their isotope geochemistry, have led the authors to believe that the magma occurred under an extensional condition following the collision between the Siberian plate and the Junggar plate, and was derived from the depleted asthenospheric mantle, contaminated however by crustal materials within high-level magma chamber. Thus, the addition of crustal silicate material was sufficient to trigger the immiscibility between the sulfides-rich liquid and the silicate-rich liquid.