Neoarchean Granitic Gneisses in the Kongling Complex, Yangtze Craton: Petrogenesis and Tectonic Implications

This study carries out systematical geochronological and whole-rock geochemical investigations for the Neoarchean granitic gneisses of the Kongling complex, and discusses the petrogenesis and ~3.0-2.6 Ga tectonic evolution of the nucleus of the Yangtze craton. The zircon LA-ICP-MS U-Pb dating reveals that the gneisses were crystallized at 2 673±39 Ma, and experienced high-pressure granulite-facies metamorphism at 2 042±27 Ma. The geochemical study illustrates an enrichment of Si and depletions of Mg, Cr and Ni, as well as negative anomalies of high field strength elements, Eu and Sr. The εNd(t) values of the gneisses vary between -1.9 to -0.1 and the corresponding two-stage Nd isotopic model ages range from 3.15-3.01 Ga, combined with their relatively high calculated zircon saturation temperature (789-825℃), indicating that the Kongling Neoarchean gneisses might have formed by partial melting of juvenile felsic crustal materials under a high-temperature condition in the post-collisional extensional tectonic setting. Combined with the documented work, it is suggested that the nucleus of the Yangtze craton, represented by the Kongling complex, may fully record an ~2.9-2.6 Ga orogenic-related event including earlier stage of oceanic slab subduction, middle stage of arc (or continent)-continent collision, and later stage of post-collisional extension. © 2019, Editorial Department of Earth Science. All right reserved.