Structural Deformation Characteristics and Mechanisms of the Taihua Complex along the Southern Margin of the North China Craton:Key Constraints on the Tectonic Evolution of the Trans-North China Orogen
The Trans-North China Orogen(TNCO)serves as a crucial window for understanding the Paleoproterozoic tectonic evolution of the North China Craton.However,the lack of research on collision-related structures,particularly in the southern segment,significantly impedes a thorough understanding of the tectonic evolution of the TNCO.A systematic study of the structure and geochronology was conducted on the Taihua Complex in the southern part of the TNCO.The results indicate that the Taihua Complex underwent intense ductile deformation with widespread preservation of ductile shear zones and syn-shearing folds,notably sheath folds.The kinematics of ductile shear zones and syn-shearing folds exhibit consistent top-to-the-WNW sense of shear,with deformation temperatures ranging from 600 to 650℃.The evolution of syn-shearing folds and the rotation of syn-tectonic leucocratic veins within shear zones record the progressive deformation process.The zircon U-Pb ages of syntectonic migmatites within the shear zones constrain the timing of ductile deformation to between 1 890 and 1 843 Ma.A comprehensive analysis of the geometry,kinematics,geochronology,and deformation temperatures suggests that ductile shear zones and regionally scaled sheath folds represent the exhumation structures of the orogenic belt,supporting the orogenic model of SE-directed subduction polarity.Based on the new structural and chronological data,in conjunction with previous research,it is proposed that the TNCO experienced a protracted orogenic evolution process,with the interval from 1.97 to 1.89 Ga signifying the continental subduction stage,1.89 to 1.84 Ga corresponding to the subsequent exhumation stage,and 1.84 to 1.78 Ga corresponding to the post-orogenic extension phase.This protracted collisional orogeny process in the TNCO provides robust evidence for the sustained occurrence of a large-scale collisional orogeny for over 100 Mya.
Ductile shear zoneSheath foldZircon U-Pb datingXiaoqinling regionTrans-North China Orogen
NETL
NSTL
万方数据
