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Miocene Tectonic Evolution from Dextral‐Slip Thrusting to Extension in the Nyainqĉntanglha Region of the Tibetan Plateau

2007; Wiley; Volume: 81; Issue: 3 Linguagem: Inglês

10.1111/j.1755-6724.2007.tb00961.x

1755-6724

Zhenhan Wu, Patrick J. Barosh, Zhao Xun, Zhonghai Wu, HU Dao-gong, Qisheng Liu,

High-pressure geophysics and materials

Abstract: Dextral‐slip in the Nyainqĉntanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east‐west dextral‐slip Gangdise fault system merges eastward into the northeast‐trending, southeast‐dipping Nyainqĉntanglha thrust system that swings eastward farther north into the dextral‐slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqĉntanglha granitic batholith formed along the thrust system in 18.3–11.0 Ma as the western block drove under the eastern one. The dextral‐slip movement ended at ∼11 Ma and the batholith rose, as marked by gravitational shearing at 8.6–8.3 Ma, and a new fault system developed. Northwest‐trending dextral‐slip faults formed to the northwest of the raisen batholith, whereas the northeast‐trending South Damxung thrust faults with some sinistral‐slip formed to the southeast. The latter are replaced farther to the east by the west‐northwest‐trending Lhünzhub thrust faults with dextral‐slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north‐south grabens in the Late Miocene at ∼6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, Damxung‐Yangbajain and Angan graben systems that pass east of the Nyainqĉntanglha Mountains are locally controlled by the earlier northeast‐trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest‐trending dextral‐slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.