Geochemistry and possible age of Gudongshan volcanic rocks, Tarim Basin

Abstract：There are 4 volcanic rock interlayers in the Permian strata of Gudongshan area, southern central Tarim Basin, but there exists no geochemical data and isotopic age constraint on the Gudongshan volcanic rock at present. Based on detailed field mapping and experiments, this paper reports field characteristics, geochemical characteristics, K-Ar dating results and zircon SHRIMP U–Pb dating results of Gudongshan volcanic rocks in the study area and also discusses the possible age and tectonic setting of Gudongshan volcanic rock. The preliminary results obtained by the authors indicate that igneous activities occurred repeatedly in Cretaceous. The youngest igneous activity age recorded by zircon SHRIMP U–Pb dating is Late Cretaceous (80.1 ± 4.3 Ma). The authors hold that the age of Gudongshan volcanic rock should be reconsidered, and is probably Cretaceous. Geochemical data show that Gudongshan volcanic rocks are rich in TiO2, FeO+Fe2O3 and P2O5, and poor in Al2O3, MgO and CaO. Both main elements and trace elements indicate that Gudongshan volcanic rocks are intraplate basalts (WPB) formed in an extensional intraplate setting.