松辽盆地东南缘早白垩世营城组玄武粗安岩年代学、岩石地球化学和Sr-Nd-Hf同位素特征OA

This paper is the result of lithogeochemstry study. [Objective]The volcanic rocks associated with the Songliao Basin are of great significance to the study of the formation and evolution of the basin,and also provide important information for studying the Mesozoic magmatic activity and tectonic evolution in Northeast Asia.[Methods]In this study,the LA-ICP-MS zircon U-Pb dating,whole rock major and trace element compositions,Sr-Nd isotope and zircon in situ Hf isotope were analyzed on the basaltic trachyandesite from the early Cretaceous Yingcheng Formation in the southeastern margin of Songliao Basin.[Results]The zircon U-Pb dating yielded the age of 119.1±0.7 Ma for basaltic trachyandesite.The basaltic trachyandesite belongs to the alkaline rock series,total alkali(Na2O+K2O)=6.21%～6.41%,moderate MgO(3.16%～3.97%)and high Al2O3(16.21%～16.90%),relatively enriched in LILE(such as Rb,Ba、Th and K),and depleted in HFSE(such as Nb,Ta and Ti);The fractionation between LREE and HREE is obvious(La/Yb)N=9.37～10.05,and slight negative Eu anomalies(δEu=0.84～0.96).The basaltic trachyandesite have positive whole-rocks εNd(t)values(+2.12 to+2.65)and zircon εHf(t)values(+6.51 to+14.93),and low(87Sr/86Sr)i(0.704 569～0.704 896).[Conclusions]Isotope and elemental geochemical evidences studies indicate that the basaltic trachyandesite derived from the partial melting of the newly formed lithospheric mantle,and suffered a certain degree of crustal contamination,and formed in an intraplate extension setting.The extension mechanism is relate to the rapid subduction and retreat of the ancient Pacific plate.