Zircon U-Pb dates, Sr-Nd-Hf isotopic compositions, and major element and trace element geochemistry were determined for the Baiyanghe granite porphyry in the Western Junggar, NW China. The porphyry, has a zircon U-Pb age of 313.4 +/- 23 Ma, is high in SiO2 (7634-78.30 wt.%) and K2O + Na2O (8.04-8.85 wt.%), relatively low in MgO (0.01-0.03 wt.%) and CaO (0.29-0.39 wt.%), and shows characteristics typical of A-type granites. Because its Y/Nb ratio (0.33-0.51) is lower than 1.2, it can be classified into A(1) group. Moreover, due to its positive values of epsilon Nd(t) (4.06-529) and epsilon Hf(t) (8.18-11.07), and high concentrations of incompatible elements, including Rb, Th. U and Nb, the Baiyanghe granite porphyry is suggested to have been derived from an oceanic island basalt-like mantle source. Their extremely high initial Sr-87/Sr-86 ratios (0.7143-0.7469) and high (La/Sm)(N) values (5.13-844) could be caused by the involvement of marine sediments. The low Ba, Sr, and Euconcentrations and high values of DI (973-98.0) of the granite porphyry suggest that its magma had undergone a high degree of fractional crystallization. Characterized by the features of within-plate granites, a back-arc basin tectonic setting is favored for the petrogenesis of the Baiyanghe granite porphyry. Such a setting indicates that the subduction of the lrtysh-Zaysan oceanic lithosphere beneath the Zharma-Saur arc was still active during the Late Carboniferous and the collision between the Siberia and Kazakhstan blocks probably occurred between ca. 316 Ma and 307 Ma. (C) 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.