Petrogenesis of the Early Paleozoic S-type granites within the Wuyi Terrane: Implications for the tectonic evolution of the South China Block

The Early Paleozoic tectonic evolution of the South China Block (SCB) remains a subject of considerable debate, particularly regarding whether it resulted from intracontinental orogeny or the subduction–collision process. The Wuyi Terrane (WYT), located at the center of the Wuyi–Yunkai orogen, plays a crucial role in understanding the petrogenesis of the Early Paleozoic magmatic products and tectonic evolution of the SCB. This study presents zircon U–Pb ages, geochemical analyses, and Lu–Hf isotopic data for the Fufang and Guixi granitic plutons located within the WYT. Zircon U–Pb dating results indicate that these granites were formed during the Early Paleozoic (ca. 437–436 Ma), and negative zircon ε Hf (t) values (-20.7 to -6.2) suggest an ancient crustal source for the granites. These contemporaneous granites, characterized by peraluminous to strongly peraluminous compositions, are classified as high-K calc-alkaline to shoshonitic series and are recognized as highly fractionated S-type granites. They exhibit enrichment in Rb, Th, U, K, and Pb, while showing depletions in Ba, Sr, Nb, Ta, P, and Ti. The observed variations in Eu anomalies suggest differing source compositions and magmatic processes between the two plutons. Based on the geochemical and isotopic evidence, we propose that the Fufang granites originated from the partial melting of crustal meta-sedimentary rocks, without the contribution of mantle-derived materials, whereas the Guixi granites resulted from the partial melting of a heterogeneous crustal source predominantly composed of meta-sedimentary rocks, with a minor contribution from meta-igneous rocks. The granites underwent varying degrees of feldspar-dominated fractional crystallization throughout their magmatic evolution. In conjunction with their post-collisional geochemical characteristics and the regional tectonic frameworks, we suggest that the Early Paleozoic tectonic evolution of the SCB was characterized by intracontinental orogeny, with the formation of the Fufang and Guixi granites occurring during the intracontinental lithospheric extensional phase that followed collisional compression. • Integrated study of emplacement age, source characteristics, genetic classification, and magmatic evolution of two granitic plutons in the Wuyi Terrane. • U-Pb dating indicates ages of ca. 437-436 Ma, marking key Early Paleozoic magmatic events. • The plutons are crustal-sourced, highly fractionated S-type granites, with varying degrees of fractional crystallization. • The Early Paleozoic tectonic evolution of the SCB is characterized as an intracontinental orogeny.