Original paper

Geochemistry and U-Pb zircon age of Late Triassic volcanogenic sediments in the central Yangtze Block: Origin and tectonic implications

Qiu, Liang; Yan, Dan-Ping; Zhou, Mei-Fu; Gao, Jian-Feng; Tang, Shuang-Li; Barnes, Michael


A Triassic tuffaceous layer occurs in the central Yangtze Block. The altered tuffaceous rocks are composed of tuffite, rhyolitic tuff and andesitic/basaltic tuff. The tuffaceous rocks have similar flat REE patterns with light REE fractionation and strongly negative Ti and Eu anomalies (δEu = 0.48–0.83). The samples show low εNd(t) values of –12.0 to –6.8 and relatively high (87Sr/86Sr)i ratios (0.705961–0.708771). U–Pb age data yield a younger and prominent age population of eruption at ca.212 Ma. Proterozoic to Permian inherited zircons that were found in these samples have subordinate age peaks at ca.800, 1850 and 2450 Ma. The geochemical and isotopic compositions of the Late Triassic tuffaceous rocks suggest that they derived from melting of enriched mantle with crustal contamination in a syncollisional extensional setting of the Indosinian Orogeny during the closure of the eastern branch of the Paleo-Tethyan Ocean.


crustal contaminationsyncollisional extensiontuffaceous rocksindosinian orogenyyangtze block