Abstract: Abstract：In the Darbute-Baogutu area, western Junggar, there outcrop two types of intermediate-acid intrusive rocks：late Hercynian (<270 Ma) granite batholiths and late-mid Hercynian (330–320 Ma) intermediate-acid small porphyry bodies. The Baogutu porphyry copper deposit is hosted in the latter. The Major element and trace element analysis of the rocks indicate that the Baogutu copper-bearing small porphyry in the mine meets the conditions of adakitic rocks, i.e.：SiO2>56%, Al2O3>15%, MgO<3%, Y<18×10-6, Yb<1.9×10-6 and Sr>400×10-6 and pronounced HREE depletion. Its Nd and Sr isotopic compositions are close to that of MORB. However, the composition of some samples, which is characterized by relatively high MgO contents (>3%) and a relatively low LREE abundance), is deviated from the compositional range of adakitic rocks. According to the geochemical composition of porphyries, combined with the regional geological characteristics, the authors think that the Baogutu copper-bearing porphyry originated in an island-arc environment related to intraoceanic subduction but that the initial melt of the oceanic crustal slab was subjected to inhomogeneous contamination with mantle peridotite during its rise.