LA-MC-ICP-MS zircon U-Pb dating of garnet monzonitic granite in the Manhan Mountain of Liangcheng, Inner Mongolia, and its petrogenesis

The garnet monzonitic granite in the Liangcheng area of Inner Mongolia was classified as Early Archean intrusive rocks (γ₁¹⁽²⁾)by the 1:200000 regional geological survey in the early 1970s. The rock was named porphyroid medium-coarse granite and called Manhanshan pluton. 1:250000 regional geological survey divided it into weakly-gneissic garnet monzonitic granite, weaklygneissic porphyroblastic biotite-garnet monzonitic granite and other different geological units. To further study the formation age of the garnet-granite, the authors conducted zircon LA-MC-ICP-MS U-Pb dating of weakly-gneissic porphyritic biotite-garnet monzonitic granite, and the results yielded an age of (1933.3±9.8) Ma, which represents the magmatic crystallization ages of the garnet monzonitic granites. Geochemical analyses show that the garnet monzonitic granites resulted from partial melting of the Neoarchean khondalite series, with the features of strongly peraluminous S- type granites. Combined with existing age data, it is held that the North China Craton occurred in large- scale tectono- magmatic thermal events during 1 900- 2 000 Ma (Middle Paleoproterozoic).