Provenance of Late Permian volcanic ash beds in South China: Implications for the age of Emeishan volcanism and its linkage to climate cooling

Whole-rock geochemistry and zircon trace element, U-Pb and Hf isotopic data for Upper Permian volcanic ash at Shangsi show a significant change in source from the Emeishan Large Igneous Province (LIP) to a convergent plate margin magmatic arc. The lower stratigraphic samples display high Al2O3/TiO2 ratios, strong negative Eu anomalies, and no depletion in high field strength elements. Zircons with ages of ca. 260 Ma from these ashes have a geochemical affinity to within-plate-type magmas and with felsic ignimbrites from the uppermost part of the Emeishan volcanic succession at Binchuan. These features, combined with relatively high epsilon(Hf)(t) values and low Th/Nb ratios in the zircons, imply a late-stage felsic volcanic origin related to Emeishan LIP. The upper stratigraphic samples at Shangsi display significant depletion in Nb and Ti; zircons separated from these volcanic ashes are chemically similar to those from arc-related/orogenic rocks, indicative of a magmatic arc source. Combined with published high-precision CA-TIMS data for these volcanic ash layers, the Emeishan volcanism can be constrained to between ca. 260-257.8 Ma. The age of Emeishan volcanism is consistent with the Wuchiapingian climate cooling event, supporting a potential linkage between these two phenomena. (C) 2018 Elsevier B.V. All rights reserved.