The Yamansu Formation, outcropped along the Aqishan-Yamansu belt, is a Late Paleozoic stratigraphic unit that hosts many important iron metallogenetic deposits in eastern Tianshan orogenic belt, Xinjiang. The Yamansu Formation consists of intercalated volcanic and sedimentary rocks. LA-ICP-MS U-Pb analyses of zircons from dacite in the upper part of the Yamansu Formation and syenite cutting across the skarns and iron orebodies in the Yamansu iron deposit area yielded weighted mean ²⁰⁶Pb/²³⁸U ages of 334.4±1.7 Ma (MSWD=0.67) and 325.5±1.7 Ma (MSWD=0.34), respectively. These ages indicate that the Yamansu Formation was formed during the early Carboniferous and the Yamansu iron orebodies and mineralizations preferentially occurred between 334 and 325 Ma. Geochemically, the dacite displays typical arc-like magmatic rocks characteristics, e.g., enrichment of large ion lithophile elements (LILE) and light rare earth element (LREE), strong negative anomalies of Nb, Ta and Ti with positive εHf(t) values (+3.0 to +8.0), and relatively young Hf crustal model ages. They were probably derived from the dehydration melting of juvenile crustal materials with minor mantle melting and underwent fractional crystallization during the upward migration of magma. The basalts resemble dacites in enrichment of LREE, U and Sr and depletion of Nb, Ta, Zr and Hf, and were probably derived from depleted mantle and mantle wedge modified by fluids from subducted materials. The regional geology and geochemical evidence indicate that the Yamansu Formation volcanic rocks were formed during the early Carboniferous in an active continental margin arc tectonic setting, indicating that the Paelo-Asia Ocean had not been closed. The Yamansu Fe deposit hosted in the Yamansu Formation was formed during 334~325 Ma, closely associated with Late Paleozoic volcanism.