Unraveling driving mechanisms of late Neoarchean tectonics: Integrated structural, geochronological, and geochemical constraints from the Taishan Group, eastern North China Craton

Whether late Neoarchean tectonics was dominated by vertical crustal recycling or by horizontal plate interactions remains debated. The Eastern Block of the North China Craton (NCC) preserves both dome-and-keel structures and linear tectonic belts, providing a key region for evaluating the emergence of horizontal tectonics during the Neoarchean. This study investigates the structural evolution, deformation history, and geochemical characteristics of the Archean Taishan Group in the western Shandong Province (WSP) to evaluate the tectonic significance of late Neoarchean deformation in the eastern NCC. The ca. 2.7 Ga meta-basalts display ocean-island basalt–like geochemical affinities and locally preserve pillow lava structures, suggesting formation in an oceanic plateau or plume-related setting. In contrast, the ca. 2.5 Ga meta-andesites exhibit arc-like geochemical signatures characterized by large-ion lithophile element enrichment and high field strength element depletion. Importantly, both the ca. 2.7 Ga and ca. 2.5 Ga rock assemblages record intense horizontal shortening, including penetrative foliations, upright folding, thrusting, and regional ductile shearing. The deformation in the WSP can be divided into three stages. The D1 stage is characterized by the widespread development of the early S1 foliation and locally occurring rootless folds. The D2 stage is marked by upright folds (F2), S2 foliation, thrust faults, and deformation of pillow lavas. The D3 stage is dominated by regional ductile shearing, accompanied by a series of associated structural features. Quartz electron backscatter diffraction analyses indicate deformation temperatures of 500–700 °C, consistent with mid- to lower-crustal deformation conditions. Zircon U-Pb geochronology reveals a regional metamorphic event at ca. 2.51 Ga recorded in the meta-basalts. Combined with other geochronological and structural constraints, the deformation history of the Taishan Group is interpreted to have initiated at ca. 2.56 Ga, corresponding to the onset of regional horizontal convergence and possibly subduction-related tectonic activity. Deformation peaked during 2.53–2.51 Ga, representing the most intense stage of regional tectonic shortening and crustal reworking. Ductile shearing likely terminated before ca. 2.50 Ga, after which the orogenic belt may have entered a late-stage evolution characterized by differential uplift and progressive exhumation. Integrated structural and geochemical evidence suggests that the WSP records the coexistence of plume-related magmatism and localized horizontal convergence during the late Neoarchean. The tectonic evolution of the Taishan Group likely involved a transition from plume-influenced oceanic plateau magmatism to subduction-related tectonic reworking. These results indicate that horizontal plate interactions had likely emerged in the eastern NCC by the late Neoarchean, although the tectonic regime may still have differed from fully developed Phanerozoic-style plate tectonics.