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To provide insights into the Early Paleozoic tectonic evolution of the southern portion of the long-lived Central Asian Orogenic Belt, we have conducted major and trace element analyses and zircon U–Pb dating of granitoid samples from central Inner Mongolia. Our study area covers three pre-Mesozoic tectonic units from north to south: the Wenduermiao subduction–accretionary complex, the Bainaimiao magmatic belt, and the northern margin of the North China craton. Our new geochronological and geochemical data show the temporal and genetic relationships between the three tectonic units. Accordingly, we suggest that the Wenduermiao subduction–accretionary complex developed in the Middle Cambrian–Late Silurian (509–421 Ma), comprising of coeval oceanic crust, arc magmatism, and forearc deposits. The Bainaimiao continental arc was developed during the Late Cambrian to Early Silurian (501–437 Ma), which superposed on the basement with the affinity of the North China craton. The back-arc basin opened prior to Early Silurian and lasted to the Late Silurian, which is slightly younger than Bainaimiao island arc. The Wenduermiao Ocean, between the Wenduermiao subduction–accretionary complex and the Bainaimiao continental arc, existed in Early Paleozoic. © 2015, Springer-Verlag Berlin Heidelberg.