Large-scale displacement along the Altyn Tagh Fault (North Tibet) since its Eocene initiation: Insight from detrital zircon U–Pb geochronology and subsurface data

Feng Cheng (1, 2) , Marc Jolivet (2) , Suotang Fu (3) , Changhao Zhang (3) , Qiquan Zhang (3) , Zhaojie Guo (1)

1 Key Laboratory for Orogenic Belts and Crustal Evolution
2 GR - Géosciences Rennes
3 Qinghai Oilfield Company

Marking the northern boundary of the Tibetan plateau, the Altyn Tagh fault plays a crucial role in accommodating the Cenozoic crustal deformation affecting the plateau. However, its initiation time and amount of offset are still controversial despite being key information for the understanding of Tibet evolution. In this study, we present 1122 single LA-ICP-MS detrital zircon U–Pb ages obtained from 11 Mesozoic to Cenozoic sandstone samples, collected along two sections in the northwestern Qaidam basin (Eboliang and Huatugou). These data are combined with new3D seismic reflection profiles to demonstrate that: (1) fromthe Paleocene to early Eocene, the Eboliang section was approximately located near the present position of Anxi, 360 ± 40 km southwest from its current location along the Altyn Tagh fault, and sediments were mainly derived from the Altyn Tagh Range. At the same period, the Huatugou section was approximately located near the present position of Tula, ca. 360 km southwest from its current location along the Altyn Tagh fault, and the Eastern Kunlun Range represented a significant sediment source. (2) Left-lateral strike-slip movement along the Altyn Tagh fault initiated during the early-middle Eocene, resulting in northeastward displacement of the two sections. (3) By early Miocene, the intensive deformation within the Altyn Tagh Range and northwestern Qaidam basin strongly modified the drainage system, preventing the materials derived fromthe Altyn Tagh Range to reach the Eboliang and the Huatugou sections. The post-Oligocene clastic material in the western Qaidam basin is generally derived fromlocal sources and recycling of the deformed Paleocene to Oligocene strata. From these data, we suggest enhanced tectonic activity within the Altyn Tagh Range and northwestern Qaidam basin since Miocene time, and propose an earlymiddle Eocene initiation of left-lateral strike-slip faulting leading to a 360 ± 40 km offset along the Altyn Tagh fault

Mots clés: Detrital zircon U–Pb geochronology; Cenozoic tectonics; North Tibet; Altyn Tagh fault; Qaidam basin

Domaines: Géochimie; Tectonique

Feng Cheng, Marc Jolivet, Suotang Fu, Changhao Zhang, Qiquan Zhang, et al.. Large-scale displacement along the Altyn Tagh Fault (North Tibet) since its Eocene initiation: Insight from detrital zircon U–Pb geochronology and subsurface data. Tectonophysics, 2016, 677-678, pp.261-279. ⟨10.1016/j.tecto.2016.04.023⟩. ⟨insu-01312745⟩