Abstract: The Solonker zone, Inner Mongolia is a key area in the evolution of the Central Asia Orogenic Belt (CAOB). It lies at the center of an ongoing debate on the PaleoAsian Ocean closure time and temporospatial relationship between the North China and Siberian Plates. It is therefore essential to study indepth the intermediaacid intrusive rock of this region. In this work, we carried out a systematic investigation on the petrology, chronology and geochemistry of the Haer Bogetuoer TTG rock. LAICPMS zircon UPb age dating 266.7±3.7 Ma indicated the TTG rock from Solonker was emplaced during the middle Permian. Geochemical analysis of major elements showed that the lithological series belonged to the highsodium calcalkali and metaluminous rock series. The overall content of rareearth elements (REEs) was low in the TTG rock, with light REEs slightly enriched without apparent Eu anomaly. Rock samples were enriched in large ionic lithophile elements including Rb, Ba, Th and U, and extremely depleted in high field strength elements such as Nb, Ta and Ti. These geochemical characteristics are similar to that of typical magmatite in an island arc setting. Integrating geological, tectonic, chronologic and geochemical characteristics of the TTG rock, we conclude that the TTG rock complex from Solonker formed in an island arc setting, and the subduction of the PaleoAsian Ocean plate beneath the North China plate continued during the middle Permain, implying the PaleoAsian Ocean did not close until the middle Permain. The Haer Bogetuoer TTG from the Solonker zone, Inner Mongolia serves as petrological record of ocean crust underthrusting. Our study provides new geological insight into the evolution of the Solonker suture zone and PaleoAsian Ocean tectonic domain.

Key words:  U-Pb age, zircon, LA-ICP-MS, TTG rock, island arc, Solonker, PaleoAsian Ocean