Tectonic and Crustal Evolution in the Dabie Area:Constraints from U-Pb-Hf isotopes of river clastic zircons
[Objective and Methods]This study aimed to systematically reveal the magmatic tectonic thermal events and crustal growth processes experienced in the Dabie area,U-Pb Hf isotope studies were conducted on zircons from three different river debris sediments in the Dabie area.[Results]The results showed that zircon U-Pb ages can be di-vided into four groups:2 676-2 424 Ma,203-1 812 Ma,890-748 Ma,and 140-120 Ma.The zircon Hf two-stage model age(tDM2)can also be divided into four groups:3 371-3 241 Ma,2 470-2 329 Ma,1 858-1 751 Ma,and 1 132-1 072 Ma.[Conclusions](1)The magmatic activity records in the Dabie region can be roughly divided into nine stages.The"quiet periods"are 3.00-2.90 Ga,2.40-2.10 Ga,1.80-0.90 Ga,and 0.70-0.14 Ga respectively,and the"explosive periods"are 4.00-3.00 Ga,2.90-2.40 Ga,2.10-1.80 Ga,0.90-0.70 Ga,and 0.14-0.12 Ga.(2)The Dabie area has experienced four metamorphic events,which occurred in the Late Neoarchean(～2.50 Ga),Middle Paleoproterozoic(～2.00 Ga),Triassic(0.24-0.20 Ga),and Cretaceous(0.14-0.12 Ga).(3)The Dabie area mainly experienced four stages of crustal growth:the initial growth of the Earth's crust was approximately 4.4-4.1 Ga in the early stage of Earth formation;there was rapid growth and accumulation of crust from 4.0-2.8 Ga;2.6 Ga to 2.0 Ga ex-perienced long-term crustal growth,with strong the magmatic activity at 2.7 Ga to 2.4 Ga in the Dabie area,indicat-ing that crustal reconstruction events were also extremely common during this period;crust grew slowly after 2.0 Ga.(4)Before 2.0 Ga,there were significant differences in magma,metamorphism,and crustal growth events between the Dabie and Huangling areas,indicating that the two were more likely independent micro blocks before this.
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