A series of transitional mafic—ultramafic rocks related to both copper—nickel sulfide and vanadium—titanium magnetite occurred in the Eastern Tianshan Mountains, such as the Xiangshanxi, the Niumaoquan, Tudunnan (Er’hongwa) and Hongliangzi mafic—ultramafic rocks. With zircon U-Pb and amphibole 40Ar/39Ar thermochronology method, the ages of the Niumaoquan, the Er’hongwa and the Hongliangzi mafic—ultramafic rocks can be obtained. The results show that the Niumaoquan mafic—ultramafic rock emplaced at the age of (289.7±2.4) Ma, Er’hongwa rock at (274.2±5.7) Ma and Hongliangzi rock at (309.7±1.5) Ma. In addition, the major elements, trace elements, REE and Sr-Nd isotopic compositions of these mafic—ultramafic rocks are analyzed. oft-com:office:office" />