line-height-rule: exactly" class=MsoNormal>In this paper, the authors present petrological characteristics, zircon U-Pb ages and Hf isotope compositions as well as the whole rock geochemistry of the quartz dioritic gneisses from west of the Xingxingxia Town. Through integration of the data with the previous results of Precambrian basements, high-grade metamorphic rocks, ophiolitic mélanges and igneous rocks from the Tianshan orogen, the authors suggest that: 1) the Precambrian crustal basements in the Tianshan orogen don’t have much affinity with the Tarim Block, and are inferred to be formed through a magmatic arc accretionary orogen along the margins of Baltica during the Mesoproterozoic; 2) the eastern segment of Central Tianshan was an active continental margin during the Early Paleozoic, due to the subduction of the South Tianshan Ocean; and 3) the closure of the South Tianshan Ocean may be synchronous in its eastern and western segments.