Emeishan felsic volcanism lasted until the Changhsingian? New evidence from volcanic ash in the northern South China block

• The waning stage of Emeishan felsic volcanism probably continued until the middle Changhsingian (ca. 253 Ma). • Arc volcanism related to the subduction of Paleo-Tethys may have occurred in the middle Wuchiapingian stage (ca.256 Ma). • The Permian-Triassic boundary (ca.252 Ma) volcanic ashes in the South China block were derived from “magmatic arc volcanoes”. • The main cause that led to the Permian-Triassic boundary extinction was the eruption of arc volcanoes , not the Emeishan large igneous province eruption. The main episode of volcanism in the Emeishan large igneous province (ELIP) occurred ca. 260 Ma. However, the ending period of volcanism has not been well established. We present the SHRIMP and LA-ICP-MS zircon U–Pb geochronology, zircon Hf isotopes, and geochemistry of ashes in the Shuanghe and Xintang sections, northern South China block (SCB). The results show that the Al/Ti ratio and high field strength elements content of Changsingian ashes (253.5–253.0 Ma) are consistent with those of alkaline ashes in the Wuchiapingian coal measure of the western SCB. These volcanic rocks contain zircon grains with high ε Hf (t) values (mean + 2.53) and low Th/Nb ratios (mostly < 10), consistent with the origin from mantle-derived magmas within the plate. These magmas are interpreted to be related to the Emeishan felsic volcanism. Furthermore, the zircon grains separated from ashes at the Permian-Triassic boundary (PTB) (ca. 252 Ma) and the upper Longtan Formation (256.8 Ma), have low ε Hf (t) values (mean − 7.04) and high Th/Nb ratios (mostly greater than 40). These features are consistent with a magmatic arc source, and the arc was likely related to the subduction of Paleo-Tethys in the middle Wuchiapingian. Therefore, we propose that the waning stage of the Emeishan felsic volcanism continued until the middle Changhsingian (253 Ma), which is not a previously suggested older age of 257 Ma. However, the ashes near the PTB on the SCB should have come from the magmatic arc. The Emeishan volcanism may not be the main cause of the PTB extinction.