| Abstract: | The Langshan area is located in the west of Inner Mongolia, southwest of the Solonker ophiolite belt, which is the ideal workplace to study tectonic-magmatic evolution and geodynamics background in Late Paleozoic because of the intense magmatism. LA-ICP-MS Zircon U-Pb ages yielded the formation time of granodiorite of Sharichulu and Moruogu granitic pluton (278.07±0.66) Ma and (278.05±0.69) Ma, respectively, forming in the latest early Permian. Geochemical characteristics showed that the Zhalashan granites were high-K calc-alkaline (SiO2：63.76%～67.88%；K2O：2.74%～4.02%) and weak peraluminous rocks (A/CNK：0.94～1.07) with moderate Mg# values (38.98～47.53). In addition，it exhibited LILE and LREEs enriched, HFSE and HREEs depleted with slight Eu anomaly, and all of the above-mentioned indicated the characteristics of I-type granites and arc-related. Zircon Hf isotope showed that the scatter εHf（t）values varied from -0.6～-7.5, which suggests a mixed magma source of old continental crust with a small involvement of mantle components. Together with regional geological background，the authors hold that the Latest early Permian granodiorite of Langshan area formed in an active continental margin setting under the background of southward subduction of the Paleo-Asian Ocean which were not close at that time. |
