Deformation Characteristics of Superposed Lineations in the Yanbian Group: Implications for Neoproterozoic Orogenesis Along the Western Yangtze Margin

ABSTRACT The western margin of the Yangtze Block preserves key geological records related to the assembly and breakup of the Rodinia supercontinent during the Mesoproterozoic–Neoproterozoic and thus constitutes an ideal window for deciphering global tectonic evolution during this interval. Based on geometric and kinematic analyses of superposed lineations, axial–planar cleavages and ductile shear zones within the Yanbian Group, this study identifies two independent tectonic deformation events. The early event (D 1 , ca. 835 Ma) is characterised by early folds, a steeply plunging lineation (L 1 ) and a steep axial‐planar cleavage (S 1 ). Combined with the regional evolution, it reflects a near E–W compressional stress field, interpreted as the tectonic response of a back‐arc basin to the prolonged subduction and magmatic activity of the Panxi–Hannan magmatic arc. The later event (D 2 , ca. 825 Ma) overprints this architecture and is marked by gently plunging, near–horizontal slickenside lineation (L 2 ), a crenulation lineation, refolding of earlier structures and an E–W striking dextral strike–slip ductile shear zone. These structures indicate a NW–SE oriented maximum compressive stress (). We interpret the brittle to brittle–ductile flexural slip along S 1 in the slates and phyllites, together with the deeper level dextral ductile shear zone, as the upper– and mid–crustal expressions of the same D 2 stress field, documenting vertical partitioning of strain during this phase. Taken together, D 1 and D 2 record a transition from sustained convergence during Rodinia amalgamation to stress‐field reorganisation in the waning stage of subduction, marking the kinematic switch from an active continental margin to an intracontinental extensional setting along the western Yangtze margin.