Isotopic chronological characteristics and significance of intermediate-acid magmatic rocks in Yamansu area

Yamansu area stretched across multiple regional tectonic belts, and there was significant controversies about the formation of each tectonic zone, the form and scale of relative tectonic movement in previous researches. The petrology, geochemistry and zircon U-Pb isotopic chronology of the intermediate-acid magmatic rocks were investigated through collecting intermediate-acid magmatic rock samples from different tectonic belts. The results show that the granite porphyry (TW-1) in the Kushui melange zone was peraluminous and calc-alkaline I-type granite, and the other two tectonic belts are weak peraluminous high potassium calcium-alkaline S-type granite. All samples were relatively enriched in LREE and are relatively even in HREE. The trace element character istics shows the source of all samples was crust and TW-1 was mixed with some mantle materials. The U-Pb isotopic chronology shows that there were two magmatic intrusions in the study area in Early Permian (295.1 Ma and 285.1 Ma). Granites from these three tectonic belts were formed under the collision-related structural environment by structural discrimination diagrams, which reflects the process of collision subduction-uplift-collision subduction-intraplate extension. Combining with the regional geology of the study area, the energy level and influence range of the northward collision and subduction of the Paleo-Tethys Ocean are much larger than the southward collision of the Kangur Ocean.