Geochronology and geochemistry of the Late Triassic adakitic granites and their geological implications in northern Liaoning province

This article conducted petrological, geochemical, zircon U-Pb dating, and Hf isotope research on the Gaojiadian granodiorite intrusion in the northern Liaoning, eastern section of the North edge of the North China Craton. The research provides new data for the study of Late Triassic magmatic activities in the northern margin of the North China plate. Zircon U-Pb dating research shows that it was formed during the Middle Triassic period (222~221Ma). The geochemical characteristics of granodiorite are high SiO2 (67.04-68.65 wt%), Al2O3 (16.25-16.78 wt%), Na2O (4.57-4.98 wt%), Sr (368.6-813.2×10-6), low Y (6.9-13.9×10-6), Yb (0.83-1.17×10-6), and high Sr/Y value (53.6-74.0), showing typical Adakite characteristics. Zircon Hf isotope analysis shows ε Hf (t) values between 9.51 and 12.24, reflecting the depleted source region characteristics. Based on the comprehensive geochemical characteristics and previous research results, the Gaojiadian adakite granodiorite in the northern Liaoning area formed during the extension environment after the closure of the Palaeo-Asian Ocean, with thinning of the crust and partial melting of the lower crust due to crustal thinning and extension.