The Haladala pluton in northeast Tekes County is the largest basic-ultrabasic layered pluton in West Tianshan area; nevertheless, little work has been done on its petrogenesis. In this paper, the authors conducted a detailed study of its geochemistry and geochronology. With the data obtained in combination of regional tectonic evolution, this paper discusses its petrogenesis, tectonic setting and geological significance. This pluton consists of a series of gabbroic rocks such as troctolite, olivine gabbro, hornblende gabbro and gabbro. Secondary ion microprobe (SIMS) zircon U-Pb dating indicates that the gabbroic rocks crystallized at the age of 306.2 ± 2.7 Ma, belonging to the Late Carboniferous. These gabbroic rocks have SiO2 values ranging from 44.49% to 48.46% with low content of K2O and Na2O and high average Mg# value of 71.4. Chemical compositions of these rocks are tholeiitic, but show a variation trend with the magmatic evolution from low-K tholeiite series to calc-alkaline series and even high-K calc-alkaline series. Some samples show abnormally high MgO, Al2O3 and CaO content, which may be due to the accumulation of olivine and plagioclase. They are also significantly enriched in LILE such as Rb, Ba, K, Pb and Sr, but depleted in HFSE such as Nb, Ta and Ti, with La/Nb>1.4. All these data indicate characteristics of arcmagmas derived from fluid metasomatized mantle wedge. Their Th negative anomaly suggests that the magmas may have been contaminated by the lower crust. These rocks have low content of total REE with weak differentiation of LREE from HREE. Due to the role of plagioclase accumulation, some samples have significant positive Eu anomalies. Compared with the mafic plutons of different ages exposed in adjacent areas in North Xinjiang, the Haladala pluton has unique petrological and geochemical characteristics, which may imply that they contain both arc-like magma components and components from extensional environment magmatism. The compositional characteristics suggest that the rocks might have been formed during the change of the tectonic framework from compression to extension. Regional tectonic history indicates that there was a shift (from compression to extension) in the tectonic framework of West Tianshan region during Late Carboniferous to Early Permian. The authors made an overall analysis of various rocks concerning their petrologic and geochronologic features at the northern and southern edge of the Yili-Central Tianshan plate, and found out that the Yili plate underwent a transition from the subduction and collision to post-collision circumstances in 293～313 Ma. Based on geochronological and geochemical characteristics of the Haladata pluton, the authors believe that the Tekesi area was at the stage of this transition of tectonic settings. It is suggested that the late Paleozoic gabbroic rocks (the Haladala pluton) in Tekes County might also have been formed in this transition stage. Hence, these rocks may indicate a change of tectonic framework in the West Tianshan area and provide evidence for the presence of magmatism in this region during the tectonic frame change.