Abstract: The Late Permian granites in northern Sonid Zuoqi occur on the north of the Solonker suture. They are part of the Late Paleozoic suture zone in the southeastern margin of the Siberian plate. Research on the Late Permian granites in this area is helpful to understand the tectonic evolution of the Late Paleozoic in central Inner Mongolia. Major and trace element analyses reveal that the granites are characterized by high silica, high alkali, low magnesium, and low calcium, and the content of Na2O is higher than that of K2O. They belong to the high-K calc-alkaline series. The granites are rich in LREE and LILE, and have a negative europium anomaly. Trace elements Nb, Ta, Sr, P, Ti are poorly concentrated and Pb, Hf, Dy, etc. are well concentrated. Petrologic and geochemical characteristics indicate that these rocks are highly fractionated I-type granites, which were produced in a continental arc setting. This result suggest that the Solonker suture had not yet closed, and the Siberian plate had not completely conjoined to the North China plate during the Late Permian. The northern Sonid Zuoqi region might be formed during a transitional stage from subduction to collisional orogeny.

Key words: I-type granites, geochemical features, Late Permian, Continental arc, Inner Mongolia