关键词: 华北克拉通, 辽东半岛, 克拉通破坏, 三叠纪, A型花岗岩, 锆石U-Pb 定年, Hf同位素, 地球化学

Abstract:  The timing of lithospheric thinning and cratonic destruction in the Eastern North China craton (NCC) during the Mesozoic remains controversial. This study investigates the petrogenesis and tectonic environment of the Linjiagou pluton in the Liaodong Peninsula using petrology, zircon U-Pb dating, zircon Hf isotopes, and geochemistry. The Linjiagou pluton, composed primarily of medium-fine grained biotite-bearing monzogranite, formed at (220.8±1.2) Ma. Geochemically, the granite exhibits high SiO2(w(SiO2) = 69.24%-71.33%) and total alkali (w(Na2O+K2O)=8.37%-8.64%) contents, low MgO contents (w(MgO)=0.45%-0.60%), enrichment in large ion lithophile elements (e.g.,Rb,K,Ba,Th), depletion in high field-strength elements (e.g.,Ta,Nb,P,Ti), right-inclined REE patterns ((La/Yb)N average= 20.12), and negative Eu anomalies (δEu=0.38-0.46). Zircon Lu-Hf isotopes reveal negative εHf(t) values (-18.1 to -12.7), suggesting a parental magma source from partial melting of ancient crust. These geochemical characteristics suggest a within-plate post-orogenic extension environment, potentially related to the collision between the Yangtze craton and the North China craton. The widespread Late Triassic magmatism in the Liaodong Peninsula suggests that the decratonization of the NCC may have begun during this period.

Key words:  , North China craton, Liaodong Peninsula, decratonization, Triassic, A-type granite, ziron U-Pb dating, Hf isotope, geochemistry