Petrogenesis of Early Paleozoic Supracrustal Rocks in Southeastern Yunnan: Constraints on Intracontinental Orogeny in the South China Craton

Early Paleozoic sedimentary rocks and granitoids are widely distributed across the South China Craton, which provides crucial insights into crustal reconstitution. This study examines petrology, zircon U-Pb-Hf isotopes and whole-rock geochemistry of supracrustal rocks in southeastern Yunnan, China. Detrital zircons from the paraschists show ages of 2702-513 Ma, with two main peaks at 665 Ma and 517-514 Ma and a maximum protolith depositional age of ~514 Ma. The protoliths were deposited in a continental arc-related basin at the southwestern Yangtze Craton. The gneissic monzogranite, granodiorite and K-feldspar granite have zircon U-Pb ages of 436 ±3 Ma, 442 ±2 Ma and 441 ±2 Ma, respectively. All samples show A/CNK ratios greater than 1.1, negative εHf_(t) values of -4.87 to -0.38 and TDM2 model ages of 1738-1453 Ma, classifying them as peraluminous S-type granites. They were originated from the partial melting of Paleoproterozoic to Mesoproterozoic crustal materials within a collisional setting. Minor amphibolites and epidote-tremolite schists suggested that some mafic dikes intruded into the paraschists between 452-428 Ma. A 414-400 Ma tectono-thermal event led to the formation of widespread pegmatite veins. The crust in the southwestern South China Craton was thickened at 500-460 Ma to>50 km and remained stable at around 440-420 Ma with low temperatures below 800℃, indicating an early Paleozoic intracontinental orogeny in the South China Craton.