Petrogenesis of Late Cambrian granite in Luoguhe district of the northern Great Xing'an Range and its constrain on the tectonic evolution of the Xing-Meng Orogenic Belt

The Early Paleozoic granites in the northern part of the Great Xing'an Range are mainly distributed along the Mohe-Tahe.In this paper, geochronological and geochemical characteristics of the Luoguhe monzonite in the north of Mohe are studied.Zircons in the monzogranite is of magmatic origin, and LA-ICP-MS U-Pb dating indicates that it was formed in the Late Cambrian (486±3 Ma).The monzonite are characterized by high silicon (SiO₂=62.75%~73.32%), rich alkali (AlK=8.30%~9.45%), high aluminum (Al₂O₃=13.97%~16.53%), low magnesium, low calcium and low titanium, with A/CNK value ranging from 0.91 to 1.10, indicating that monzonite belongs to aluminous and high potassium calc-alkaline rock series.The SiO₂ content has a negative correlation with Al₂O₃ and P₂O₅.Rb, Th, U, K, Zr, Hf elements are enriched, while Ba, Nb, Ta, Sr, P and Ti are strongly depleted.In the chondrite normalized REE partition curves, LREE is enriched and HREE is depleted, which shows the characteristics of Ⅰ-type granites.Comprehensive analysis shows that the Luoguhe pluton was formed in a post-collisional tectonic setting during the late period of the orogeny between the southern margin of the Siberian plate and the Erguna micro landmass, which was transformed from compression system to extension system.