Zinc isotope evidence for intensive magmatism immediately before the end-Permian mass extinction

The end-Permian extinction is typically ascribed to massive volcanic eruptions, but direct geochemical evidence linking the two independent events is generally lacking. Zinc is an important micronutrient of marine phytoplanktons, and Zn isotope (delta Zn-66) ratios of seawater are markedly higher than those of volcanic rocks and riverine waters. We conducted high-resolution Zn concentration and Zn isotope analyses on carbonate rocks across the Permian-Triassic boundary (PTB) in the Meishan section of south China. An abrupt increase of Zn concentration and a concomitant 0.5 parts per thousand decrease in delta Zn-66 occur similar to 35 k.y. before the mass extinction and carbon isotope (delta C-13) minima. Mass balance calculation demonstrates that a 0.5 parts per thousand negative shift in delta Zn-66 within thousands of years requires rapid and massive input of isotopically light Zn from volcanic ashes, hydrothermal inputs, and/or extremely fast weathering of large igneous provinces. A positive delta Zn-66 shift of as much as 1.0 parts per thousand following the mass extinction demonstrates that primary productivity recovered and reached a maximum in fewer than 360 k.y. Our finding provides insights into the marine Zn cycling across the PTB and clarifies the temporal relationship and duration of events, including intensive volcanism, carbon isotope excursion, mass extinction, and widespread ocean anoxia.