摘要
The origin of the Mesozoic high Ba-Sr(HBS)granitic magmatism in the Jiaodong Peninsula remains controversial in petrogenesis models and geodynamic settings.Here,we report zircon UPb age,trace element and oxygen isotope compositions,and whole-rock major-trace element and Sr-Nd isotope compositions of the HBS Yashan granodiorite.The zircon U-Pb age of~118 Ma denotes that the Yashan granodiorite belongs to the Weideshan-stage magmatic activity,which is consistent with the age of Mo mineralization in the Yashan intrusion.The low Sr/Y(48.8-115)and high(La/Yb)_(N)(23.8-50.4)ratios of the Yashan granodiorite are analogous to adakitic features derived from the lower-crust.This is also supported by the whole-rock initial^(87)Sr/^(86)Sr ratios(0.7096-0.7103)and zircon δ^(18) O values(6.79‰-8.03‰).Contemporaneous mantle-derived mafic microgranular enclaves indicate the involvement of the metasomatized lithospheric mantle.The high magma oxygen fugacity of the Yashan intrusion as indicated by high zircon Ce^(4+)/Ce^(3+) values suggests the involvement of plate subduction.The obviously lower Dy/Yb,La/Yb and Sr/Y ratios of magmatic rocks in the Weideshan-stage than those in the early-stage imply lithospheric thinning of the eastern North China Craton.We propose that the Yashan HBS granodiorite was formed by crust-mantle interactions during slab rollback.
基金
supported by the National Key R&D Program of China(No.2016YFC0600408)
the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42020203)。
