Recognition of trench basins in collisional orogens: Insights from the Yarlung Zangbo suture zone in southern Tibet
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cognition of trench basins in collisional orogens: Insights from the Yarlung Zangbo suture zone in southern Tibet 1*
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Xiumian HU , Wei AN , Eduardo GARZANTI & Qun LIU 1
Institute of Continental Geodynamics, State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, 2
Nanjing University, Nanjing 210023, China; School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China; 3 Department of Earth and Environmental Sciences, Università di Milano-Bicocca, Milano 20126, Italy
Received October 27, 2019; revised October 10, 2020; accepted October 14, 2020; published online November 10, 2020
Abstract Trench basin, as an important sedimentary repository in oceanic subduction zones, documents faithfully the evolution of paleodrainage and paleogeographic information. Because of the frequent intense deformation during and after deposition, the recognition of trench-basin strata in orogenic belts is quite challenging. Several trench-fill deposits have been identified from the Yarlung Zangbo suture in southern Tibet, which can be classified into two types based on major differences in formation timing and tectonic setting. The first type developed during subduction of the Neotethyan oceanic slab in the Cretaceous (e.g., the Jiachala, Rongmawa, and Luogangcuo formations), and the second type developed during the initial stage of the India-Asia collision in the Palaeogene (e.g., the Sangdanlin-Zheya formations). The former was originally deposited on the subducting oceanic crust and then accreted as tectonic slices into the subduction complex; the latter was deposited unconformably on the continental margin of the subducting Indian plate and then involved in the subduction complex during the continental collision. Typical lithologies of trench-basin fills include abyssal chert, siliceous shale, silty to sandy turbidites, debris flows deposits, and slump deposits without carbonate. Detritus feeding these basins were chiefly from the uplifted terrane in the upper plate. This paper summarizes the geological features of trench basins developed in southern Tibet and proposes criteria for recognizing trench-basins in collisional orogens. Keywords Trench basin, Provenance analysis, Yarlung Zangbo suture zone, Southern Tibet, Cretaceous-Paleocene, Himalayan orogen Citation:
Hu X, An W, Garzanti E, Liu Q. 2020. Recognition of trench basins in collisional orogens: Insights from the Yarlung Zangbo suture zone in southern Tibet. Science China Earth Sciences, 63, https://doi.org/10.1007/s11430-019-9687-x
1. Trench basins and their evolution Surveys of marine geology have shown that a trench basin develops at the site of subduction zone, on top of the downgoing plate and in front of the overlying plate, stretching over thousands of kilometers along the convergent plate boundary. The trench basin, together with the forearc basin developed between the volcanic arc and the trench, and trench-slope basin formed onto the subduction complex, deposit a major * Corre
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