Calcium isotopes of carbonate rocks can trace calcium cycles and record changes in the marine environment. As published calcium isotope profiles of carbonate rocks at the Permian-Triassic boundary are rare, comparative studies on deep-water profiles were lacking for the major extinction event that occurred during this time. We present sections of different water depths in the Chibi area of southern China that we have selected for a comparative study. We analyzed carbon isotopes, calcium isotopes, as well as major and trace elements of carbonates from two sections (Chibi North and Chibi West) to obtain information on the volcanic activity, ocean acidification, as well as sea level rise and fall in the Chibi area during the mass extinction period. All carbon and calcium isotopes of carbonates from both sections are all negative after the mass extinction boundary. Carbonates from the Chibi North section have higher δ44/40Ca values and lower Sr/Ca ratios than the rocks from the Chibi West section. We propose that the negative bias of the calcium isotopes in the two sections result from diagenesis. Diagenesis transforms primary aragonite into calcite, showing the characteristics of high δ44/40Ca value and low Sr/Ca. By comparing our data with three published profiles of shallow-water carbonate rock, we recognize that calcium isotopes record gradients at different water depths. In the slope environment, the enhancement of pore fluid action near the coast caused an increase of the fluid buffer alteration, and we propose that a regression event occurred in the Chibi region during the Late Permian.

Rechargeable zinc-ion batteries (ZIBs) are considered the most promising energy storage device to replace lithium-ion batteries (LIBs) due to their high security and environment-friendly feature. However, the synthesis of high-performance cathode materials usually requires harsh conditions (such as high temperature and high pressure), which limits the practical application of ZIBs. Herein, a facile large-scale preparation of H 2 O and Mg 2+ co-intercalated vanadium oxide is realized by heating vanadium pentoxide and magnesium sulfate solution in a water bath at low temperature. Through in-depth investigation, it is found that the introduced H 2 O and Mg 2+ not only expand the layer spacing of vanadium pentoxide but also improve the structural stability of V−O layers and ion diffusion. As a result, the obtained product displays an excellent specific capacity of 473 mAh g −1 at 0.1 A g −1 and superior cycle performance when used as the cathode material of ZIBs. Such a result indicates that H 2 O and Mg 2+ co-intercalated vanadium oxide shows a good application prospect.