关键词: 辽西地区, 花岗质片麻岩, 锆石UPb年代学, EBSD, 流变学参数, 古太平洋板块

Abstract:  A large number of granitic rocks exposed in the Xingcheng area of western Liaoning have undergone strong ductile deformation, and their unique deformation patterns provide a unique perspective for unraveling the tectonic evolution of the northeastern margin of the North China craton during the Mesozoic. The granitic gneiss exposed in the Niangniangding area Xingcheng，displays significant ductile deformation characteristics, with the mineral stretching lineations consistently dipping towards NNE at low angles, indicative of toptoSSW thrust ductile shear deformation. Zircon UPb dating results show that the protolith of granitic gneiss was formed at Middle Jurassic (169.5±1.6 Ma). In addition, the quartz EBSD fabric and rheological analyses indicate that the paleostress is 13.817.7 MPa, the strain rate is 1.16×10-162.20×10-14 s-1, and the deformation temperature is 350450 ℃ for the deformed rocks. Comprehensive studies suggest that the observed deformation was characterized by a slow deformation process under the greenschist facies condition prevalent in the middle to shallow crust, which originated from the superposition of the closure of the MongolOkhotsk Ocean and the subduction of the PaleoPacific plate during the latest Late Jurassic to earliest Early Cretaceous.

Key words: western Liaoning, granitic gneiss, zircon UPb geochronology, EBSD, rheological parameters, PaleoPacific plate