Abstract: The volcanic rocks of the Chaotugou Formation in Chifeng area of Inner Mongolia consist of meta-basalts and metarhyolites and exhibit typical "double peaks", with the SiO₂ content being 46.24%-56.6% and 77.59%-85.75% respectively. Zircon LA-ICP-MS U-Pb dating of rhyolite yielded U-Pb ages of(359±1) Ma-(360±1) Ma, which represent the time of crystallization of the volcanic rocks. The volcanic rocks were formed in late Devonian Famennian age. Geochemically, meta-basalts (or basaltic andesites) are characterized by enriched LREE, depleted HREE, slightly negative Eu, Nb, Ta, Sr and Ti anomalies and high abundances of LILE and HFSE, with the (La/Yb)_N ratios from 2.4 to 8.76, and the ⁸⁷Sr/⁸⁶Sr initial values from 0.705076 to 0.707770; in addition, they have relatively high positive ε_Nd(t)values (+0.51 to +4.90) and relatively young T_DM (964-1090 Ma) ages. The mafic rocks might have resulted from the mixture of depleted mantle with crustal source. Meta-rhyolites are generally characterized by rich silicon, alkali and poor magnesium. They are characterized by enriched LREE, depleted HREE, noticeable negative Eu (δEu 0.12-0.43), Nb, Ta, Sr, P and Ti anomalies, relatively high U, Th and rather low Ba, Sr, Ti and P; the (La/Yb)_N ratios are from 7.07 to 11.07, ⁸⁷Sr/⁸⁶Sr initial values are high (0.713757-0.739647), negative ε_Nd(t) values are low (-1.75 to +2.54), and T_DM ages are relatively young (846-1156 Ma); besides, most zircons have the positive ε_Hf(t) values (-2.3 to +6.9) and relatively young T_DM ages (707-1074 Ma). The felsic rocks show an A-type affinity and might have come from a juvenile crustal source. According to their geochemistry and previous regional geological studies, the late Devonian volcanic rocks are basalts and rhyolites, suggesting a typical bimodal volcanic rock association and implying an extensional setting.