Gondwana Research ( IF 6.174 ) Pub Date : 2020-10-03 , DOI: 10.1016/j.gr.2020.08.014 Xiao-Fei Qiu; Xi-Run Tong; Tuo Jiang; Nimat Ullah Khattak
Reworking or growth of the Hadean (>4.0 Ga) continental crust provides important hints in understanding the early evolution history of Earth. In this study, a comprehensive program of zircon U-Pb dating and Hf isotope analyses, as well as whole-rock major and trace element analyses, has been carried out on the Muzidian granitic gneisses from the northern Dabie orogen. The Muzidian gneisses are tonalite or granodiorite in composition, and have geochemical features resembling those typical of the tonalite-trondhjemite-granodiorite (TTG) suites. Zircon U-Pb dates range from ~2.5–2.4 Ga in the magmatic cores and from ~2.1–2.0 Ga in the metamorphic rims. Both the zircon cores and the rims have highly negative ɛHf(t) values of −25.2 to −19.9 and −31.0 to −28.1, respectively, corresponding to Tcrust of 4.25 Ga to 3.98 Ga, thereby, indicating that the protoliths of the orthogneisses in the northern Dabie orogen were formed by reworking of Hadean continental crust. This provides strong evidence for the presence of Hadean continental crust in the northern Yangtze block. These remnants of Hadean rocks resided in the continental crust of the Yangtze block for more than about 1700 Ma before being reworked. Compared to the ancient crustal components in the Kongling area of the Yangtze block, the Muzidian area along the northern margin of the Yangtze block seems to be more prospective for further occurrences of the Hadean zircon and/or rocks.