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The Dabie–Sulu Orogen hosts the largest province of ultrahigh-pressure (UHP) rocks in the world. The post-collisional extension eroded and transported volumes of rocks from the Dabie Orogen to adjacent basins, causing a lack of information about the orogen and thus obstructing our understanding of the exhumation process of UHP rocks. In addition, the mechanisms that triggered the post-collisional extension and affected the petrological-tectonic units of the orogen are still unclear. This study is focused on the time in which the present tectonic framework in the Dabie Orogen took place, selecting Early Cretaceous plutons in the eastern part of the orogen and carrying out detailed zircon LA-ICP-MS U-Pb dating and crystallization depth calculation. The zircon dating results show that the emplacement time of the Meichuan and Luannitan plutons and the Penghe superunit of the Zhubuyuan pluton are all ~128 Ma, while the Huangbai superunit of the Zhubuyuan pluton and the Longmianzhai pluton formed at ~125 Ma. The emplacement time and later anatexis of the Baimajian pluton occurred at ~128 and ~122 Ma, respectively. The results of the Al-in-hornblende geobarometer show that plutons of ~128 Ma have a similar crystallization depth, while plutons of ~125 Ma range from 7.6 to 9.5 km. The Baimajian pluton has a greater crystallization depth. Combined with the existing achievements, a conclusion can be drawn that the present tectonic framework of the Dabie Orogen began to form from ~128 Ma.
Wang et al. (Wed,) studied this question.