Chronology, geochemistry and geological significance of the Early Cretaceous intrusive rocks from the Tahe region, northeastern China

The Phanerozoic granites occur on a wide range of scales in northeastern China. The emphasis in this study is placed on the Early Cretaceous intrusive rocks from the Tahe region, NE Dahingganling region, where the research of the intrusive rocks may be highly helpful to the understanding of Mesozoic magmatic evolution and tectonic settings. The intrusive rocks in this region consist dominantly of quartz diorite, granodiorite, monzogranite, syenogranite and granodioritic porphyry. The LA-ICP-MS zircon U-Pb dating yields the age determinations of 131 ±1 Ma (MSWD=0.73) and 130 ±1 Ma (MSWD=2.2) for granodiorite and quartz diorite, respectively. The intrusive rocks cited above are enriched in SiO₂(61.32%-71.68%) and Al₂O₃(13.53%-15.62%), and have the ΣREE values between 152.28×10^-6 and 253.85×10^-6, indicating the metaluminous or peraluminous high-K calc-alkaline granitic rocks. Geochemically, these granitic rocks may be classified into two types:high-Sr and lowYb, and low-Sr and high-Yb types originated from different depths of the Earth's crust. It is inferred that the Early Cretaceous intrusive rocks in the study area were created by the processes of gradually eastward shear closure of the Mongolia-Ochotsk Sea basin, and probably related to the thickening of the lower crust caused by the continentcontinent collision along the Mongolia-Ochotsk orogenic belt.