Provenance of the Permian–Triassic boundary volcanic ash beds in South China

Abstract

Volcanism represented by the Permian–Triassic boundary (PTB) volcanic ash beds in South China plays a vital role in the PTB mass extinction. However, the probable provenance of the PTB volcanic ashes has not been exactly identified until now. In this study, the geochemical analysis was conducted on newly found five volcanic ash beds from the Mao'ershan and Tielukou sections in the northern part of the Yangtze platform. Volcanic ashes geochemistry indicates a felsic nature and negative Eu anomalies. Zircons selected from the five ash beds yield LA‐ICP‐MS U–Pb ages varying from ca. 255 to 248 Ma, and εHf(t) values of −8.6 to 1.1, which indicates the earlier stage volcanic ash beds in Mao'ershan are likely derived from mantle material and partial melting of crustal rocks, and the later stage volcanic ash beds in Tielukou are derived largely from ancient crustal rocks. Combined with previous U–Pb ages, εHf(t) values, trace elements of zircons, and geological setting, the PTB volcanic ash beds probably drift from the Jomda–Weixi volcanic belt in Sanjiang region of SE Asia, and that are represented by the volcanic rocks in Misha regions, eastern margin of the Lanping Basin. New data and discussion on the provenance of the PTB volcanic ashes provide important implications for the trigger of PTB mass extinction.