Coexistence of episodic and prolonged magmatism during the exhumation of subducted continental crust revealed by multi-method chronology of Early Paleozoic granites in South Altyn, western China

This study presents a comprehensive multi-method chronology, integrating zircon, titanite, and monazite dating, combined with detailed field geological investigations, petrology, and whole-rock geochemical analyses of granodiorite, diorite enclave, and monzogranite in the South Altyn Tatelekebulake area. The granodiorite yields a zircon age of 483 Ma and two episodic monazite age of 488 ± 3 Ma and 430 ± 1 Ma. In contrast, the monzogranite, with a zircon age of 451 Ma, exhibits a continuous monazite age range of 491 Ma – 431 Ma. The diorite enclave shows a titanite age of 444 ± 11 Ma. Geochemical features suggest that both the granodiorite and diorite enclave originated from the partial melting of mafic rocks within the middle and lower crust during the exhumation stage of subducted continental crust, characterized by low pressure (<1.0 GPa) and a gradual decrease in temperature over time (850°C – 700°C). The trace elements characteristics of all samples implies potential influence from fluid flux within the subduction zone during magma emplacement and ascent. In conjunction with accessory mineral dating, these ages reflect coexistence of both episodic and prolonged magmatic activity within the study area. This prolonged magmatic activity provides evidence that partial melting of Early Paleozoic continental crust rocks in the South Altyn area may have undergone complete continental crust subduction, subsequent exhumation, and post-collisional extension processes. This study emphasizes the importance of multi-method chronology in unraveling the magmatic and tectonic evolution of orogenic belts and provides new insights into the Early Paleozoic tectonic evolution of the South Altyn orogenic belt.