Convergent continental margin volcanic source for ash beds at the Permian-Triassic boundary, South China : constraints from trace elements and Hf-isotopes

This study is supported by NSFC grants (41473006, 41272025, 41673011, 40972003, 41272023, 41572091). PAC acknowledges support from the Australian Research Council grant FL160100168.Volcanic activity around the time of the Permian-Triassic boundary (PTB) has been proposed as a trigger for the associated biocrisis. Multiple claystone beds are prominent near the PTB sections in South China. Twenty one PTB ash beds from three sections at Shangsi, Jianshi and Meishan in South China were sampled and analyzed. Volcanic ash geochemistry indicate dacite and rhyolite compositions. Zircons from the ash layers yield comparatively low Nb/Hf and high Th/Nb ratios, falling in the range of arc/orogenic-related settings. Zircon Hf-isotope compositions show that εHf(t) values vary from −11.7 to 1.8, indicating involvement of both juvenile and ancient crustal components. The ash beds (SS27a, JS129, JS130, JS133,MS25, MS26) near the biotic extinction horizon display a large variation in εHf (t) and relatively positive average values, indicating input of juvenile mantle or crust, and implying rapid transit through the older basement of the South China Craton. Spatial and temporal distribution of ash beds from thirty one PTB sections worldwide reveal that volcanic ash beds occur mainly in, or proximal to, the Tethys region and were sourced locally. Integration of Hf-isotope and trace-element compositions from magmatic zircons suggests that the PTB volcanism occurred along the convergent continent margin in, or near, southwestern South China as a result of the closure of the Paleo-Tethys Ocean.PostprintPeer reviewe

Resilience of infaunal ecosystems during the Early Triassic greenhouse Earth

The Permian-Triassic mass extinction severely depleted biodiversity, primarily observed in the body fossil of well-skeletonized animals. Understanding how whole ecosystems were affected and rebuilt following the crisis requires evidence from both skeletonized and soft-bodied animals; the best comprehensive information on soft-bodied animals comes from ichnofossils. We analyzed abundant trace fossils from 26 sections across the Permian-Triassic boundary in China and report key metrics of ichnodiversity, ichnodisparity, ecospace utilization, and ecosystem engineering. We find that infaunal ecologic structure was well established in the early Smithian. Decoupling of diversity between deposit feeders and suspension feeders in carbonate ramp-platform settings implies that an effect of trophic group amensalism could have delayed the recovery of nonmotile, suspension-feeding epifauna in the Early Triassic. This differential reaction of infaunal ecosystems to variable environmental controls thus played a substantial but heretofore little appreciated evolutionary and ecologic role in the overall recovery in the hot Early Triassic ocean

Calcium isotope evidence of Late Permian-Upper Triassic ocean acidification from Kamura, Japan

The end-Permian mass extinction (EPE; ca. 251.9 Ma) is the largest biological disaster in the Phanerozoic and has been hypothesized to be caused by ocean acidification due to large amount of CO2 (\u3e10,000 Pg C) emitted through Siberian Traps volcanism. The marine ecosystem, however, did not recover until several million years after the EPE. The continued deterioration of the environment is suggested to be responsible for the delayed recovery of life. To understand the causes and consequence of the end-Permian extinction event, we performed detailed geochemical analysis (δ44/40Ca, δ13C, 87/86Sr and trace elements) on carbonate from the Kamura section in Japan. The Kamura section analyzed spans the Uppermost Permian and Upper Triassic, deposited as shallow water successions in a seamount in the central Panthalassic ocean. The age framework of the Kamura section was determined based on conodont zonation and carbonate carbon isotope stratigraphy. Both δ44/40Ca and δ13Ccarb exhibit negative excursions across the PTB, exhibiting closely coupled relationship. We suggest that CO2-driven global ocean acidification best explains the coincidence of the negative excursions in both δ44/40Ca and δ13Ccarb. During the Middle and Late Triassic, strong coupling between δ44/40Cacarb and δ13Ccarb is collapsed, suggesting a recovery to normal marine pH. 87Sr/86Sr suggest the Siberian Trap volcanism played a significant role on the δ44/40Ca records during the Early Triassic

A Review on Recent Progress Achieved in Boron Carbon Nitride Nanomaterials for Supercapacitor Applications

Supercapacitors are regarded as reliable energy storage devices to alleviate the energy crisis and environmental pollution. However, the relatively low capacitance and low energy density limit the practical application of supercapacitors. In this context, boron carbon nitride (BCN) nanomaterials have been extensively studied in the past decade due to their chemical and thermal stability, high mechanical strength, as well as tunable bandgap. The specific capacitance and energy density of supercapacitors can be significantly improved by fabricating nanostructured BCN-based electrode materials. In this review, the recent advances in the application of BCN-based materials in supercapacitors is presented. Strategies such as structure design, porosity/defect engineering, and hybrid nanostructure construction to boost the electrochemical performance of BCN-based materials are provided and, finally, promising research directions for novel energy storage materials are proposed

Cathode materials for calcium‐ion batteries: Current status and prospects

Abstract In the post‐lithium‐ion battery era, calcium‐ion batteries (CIBs) have aroused extensive attention because of their strong cost competitiveness, low standard redox potentials, and high safety. However, the related research is progressing slowly due to the constraints of the development of electrode materials. The large ionic radius of Ca2+ especially increases the challenge to design cathode materials for reversible Ca2+ uptake/removal. Despite the inspiring achievements, various challenges still need to be further resolved. Here, this review systematically summarizes the recent advances in CIB cathode materials, including Prussian blue and its analogues, metal oxides, metal chalcogenides, polyanionic compounds, and organic materials. We first provide a brief introduction to CIBs and compare their advantages with other battery technologies. Then, preparation methods are introduced, and breakthrough investigations are highlighted. Finally, some possible research directions are discussed to promote the development of this emerging battery technology