The Early-Middle Triassic Supervolcano in the Yangtze Block, South China and associated obstacles to biotic recovery

The end-Permian mass extinction was one of the major global crises spanning the entire Early Triassic or longer. Eruptions of volcanos were one of the factors that delayed the biotic recovery after this event. Supervolcano eruptions can cause catastrophic effects on global environment, climate, and life. Here we investigate the tuff layers from Early-Middle Triassic boundary in the Yangtze Block and identify a supervolcano eruption event. The zircon U-Pb ages of the section-Langdai, section-Daijiagou and section-Longmendong tuff samples are 247.1 ±1.9 Ma, 247.6 ±2.0 Ma and 247.7 ±1.7 Ma, respectively. These ages mark the Olenekian-Anisian boundary. The zircon grains from the tuff layers have negative ε_Hf(t) (-15.3 to -0.8), two-stage Hf model (T_DM2) ages (1.7 to 2.2 Ga) and display high-δ¹⁸O values (mostly > 10‰). Clay minerals and quartz dominate the rock composition. The whole rock compositions show that the tuff layers were derived from magma of intermediate to felsic composition, which formed by the remelting of Paleoproterozoic materials of continental crust. The volcanic eruption site is located in the Jinshajiang-Ailaoshan-Song Ma suture zone in the southwestern margin of the Yangtze Block. A combination of the closure of the Paleo-Tethys Ocean Basin and the collision of the Indochina Block and South China contributed to the eruption, which was a supervolcano eruption under the active continental margin arc settings. We speculate that this supervolcano eruption might have contributed to the delayed biotic recovery after the end-Permian mass extinction.