Variations in antimony isotope and toxic metals across the Guadalupian-Lopingian (Permian) boundary at Penglaitan, China: Implications for the Emeishan volcanism and marine extinction

The Guadalupian-Lopingian (G-L) extinction event during the Permian stands a major diversity decline. The Emeishan Large Igneous Province (ELIP) has long been posited as the principal trigger, but direct geochemical evidence establishing a connection between these events has remained elusive. Here, we present antimony (Sb) concentration and isotope (delta 123Sb) analyses conducted across the G-L boundary at Penglaitan, South China. Our investigation reveals a large spike in Sb concentration concurrent with a significant decline in delta 123Sb values spanning the G-L boundary. The delta 123Sb values range from -0.49%o to +0.48%o with the lightest values occurring at the main extinction horizon of marine benthos. Other toxic metals (As, Hg, Pb, etc.) are enriched in the same horizons and are likely of volcanic origin. Our estimates based on mass balance calculations indicate that the ELIP increased oceanic toxic metal loading by an order of magnitude. Their toxic effects may have contributed to stressed regional marine environment and biodiversity loss in South China during the G-L transition.