Large Igneous Province and magmatic arc sourced Permian-Triassic volcanogenic sediments in China

Whole-rock geochemistry and zircon trace element and U-Pb age data for Late Permian-early Middle Triassic volcanogenic sedimentary rocks in SW China show a change from Large Igneous Province to subduction-related sources immediately before the Permian-Triassic boundary. Zircons from Late Permian samples give identical within-error ages to the adjoining Emeishan Large Igneous Province (LIP). The bulk-rock geochemistry of these Late Permian units shows no depletion in high field strength elements and is similar to the high-titanium basalts of the Emeishan. Six samples of latest Permian-earliest Triassic tuff and two earliest Middle Triassic tuffs samples yield U-Pb zircon ages at of similar to 252 Ma and similar to 247 Ma, respectively. These tuffs and interstratified volcanogenic sedimentary rocks show significant depletion in high field strength elements, akin to magmatic arc-related rocks. Zircons from the tuffs have Nb/Hf. Th/Nb and Hf/Th ratios similar to those from arc/orogenic-related settings and distinct from the zircons from the Late Permian samples which display within-plate/anorogenic characteristics. Our data demonstrate that there is a compositional change of the volcanogenic sediments across the Permian-Triassic boundary in South China. (C) 2012 Elsevier B.V. All rights reserved.