Confirmation of the granite during Neoproterozoic in Beishan of Gansu Province, and its constraints on the tectonic-evolutional pattern of Beishan orogen

Beishan is located in Central Asia Belt, and records sighificant information of the Neoproterozoic tectonic evolution. The Neoproterozoic monzogranite was newly confirmed by studying the 1:250 000 Devonian intrusive pluton in Xianshuigou area, Beishan, Gansu Province. LA-ICP-MS zircon U-Pb dating of the monzonitic granite was carried out, the weighted age of ²⁰⁶Pb/²³⁸U is (787±15 )Ma. The monzogranite is characterized by high SiO₂, low TiO₂ , high Al₂O₃ , rich alkali, and σ and A/CNK is higher than 1.05. LREE is high relative to HREE. (La/Yb)_N value is 15.20-23.28, which indicates LREE and HREE are highly differentiated, (La/Sm)_N value is 3.14-4.22, which indicates LREE fractionation is large, δEu is negative. Rb, Th, La are high, Nb,P,Ti,Sr are depleted, showing the characteristics of S-type granite. The Neoproterozoic monzonitic granite was formed in the continental collision tectonic environment and located on the edge of Rodinia supercontinent. This magmatic event reflects the continental collision during Neoproterozoic in Beishan.