Abstract
The Micangshan-Dabashan tectonic belt, located in the southern Qinling-Dabie Orogen near the northeastern Tibetan Plateau, is a crucial area for understanding the processes and mechanisms of orogenesis. Previous studies have been focused on the cooling process via thermochronology and the mechanism and process of basement uplift have been investigated. However, the coupling process of basement exhumation and sedimentary cap cooling is unclear. The tectono-thermal history constrained by the detrital apatite fission track (AFT) results could provide valuable information for understanding crustal evolution and the coupling process. In this study, we provided new detrital AFT thermochronology results from the Micangshan-Dabashan tectonic belt and obtained nine high-quality tectono-thermal models revealing the Meso-Cenozoic cooling histories. The AFT ages and lengths suggest that the cooling events in the Micangshan area were gradual from north (N) to south (S) and different uplift occurred on both sides of Micangshan massif. The cooling in Dabashan tectonic zone was gradual from northeast (NS) to southwest (SW). The thermal histories show that a relatively rapid cooling since ca. 160 Ma occurred in the Micangshan-Dabashan tectonic belt, which was a response to the event of Qinling orogenic belt entered the intracontinental orogenic deformation. This cooling event may relate to the northeastward dextral compression of the Yangtze Block. The sedimentary cap of Cambriano-Ordovician strata responded positively to this rapid cooling event and entered the PAZ since ca. 63 Ma. The deep buried samples may be limited affected by climate and water erosion and the accelerated cooling was not obvious in the Late Cenozoic. Collectively, the cooling processes of basement and sedimentary cap in Micangshan-Dabashan tectonic belt were inconsistent. The uplift of the sedimentary area is not completely consistent with that of the basement under thrust and nappe action. The rigid basement was not always continuous and rapidly uplifted or mainly showed as lateral migration in a certain stage because of the different intensities and modes of thrust and nappe action, and the plastic sedimentary strata rapidly uplifted due to intense folding deformation.
Highlights
The Micangshan-Dabashan tectonic belt, located at the northeastern margin of the Tibetan Plateau, is a key “basinmountain coupling” transitional orogenic belt that separates the Qinling orogenic belt to the north and the Sichuan Basin to the south (Figure 1)
Micangshan-Dabashan tectonic belt formed after collision with the South China Block (SCB) and North China Block (NCB) in the Indochina period and intracontinental orogeny in the Yanshanian-Himalayan period (Zhang et al, 1989; Meng and Zhang, 2000; Meng et al, 2005; Tan et al, 2007; Xu et al, 2009; Tian et al, 2010; Tian et al, 2012)
The thermochronometry dating and thermal histories results above and others from the, TongbaiDabieshan (Webb et al, 1999; Reiners et al, 2003; Hu et al, 2006), Taibaishan (Wang et al, 2005) and Western Qinling (Zheng et al, 2004; Enkelmann et al, 2006) show that the regional uplift occurred from the Late Jurassic to the Early Cretaceous and an accelerated uplift since the Late Cenozoic which related to the growth of the northeastern Tibetan Plateau
Summary
The Micangshan-Dabashan tectonic belt, located at the northeastern margin of the Tibetan Plateau, is a key “basinmountain coupling” transitional orogenic belt that separates the Qinling orogenic belt to the north and the Sichuan Basin to the south (Figure 1). We present a lowtemperature thermochronology study of the Micangshan and Northern Dabashan, employing apatite fission track (AFT) data from nine detrital samples to assess the regional cooling history and providing information about the coupling relationship of uplift in basement and sedimentary areas. The South China Block subducted under the North China Block beginning in the late Caledonian, underwent full collision until the Late Triassic, and experienced continuous compression and reconstruction in the Yanshan-Himalayan Structural phenomena such as continuous fold deformation, differential uplift and thrust-slip faults are widely developed (Shi and Shi, 2014, Figures 2C,D). A GOF value greater than 0.05 indicates acceptable simulation results, while a GOF value greater than 0.5 indicates high-quality simulation results (Ketcham, 2005)
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