Tectonic evolution and plateau uplift around the Changma Basin in the Qilian Mountains, NE Tibetan Plateau

• Main Author: Vernon, Rowan Emma
• Other Authors: England, Richard ; Parrish, Randall
• Published: University of Leicester 2016
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.692497

The Qilian Mountains are one of the most actively uplifting regions of the Tibetan Plateau and may provide a type example for the early evolution of its older regions. The mountains form a 300 km wide, NW – SE trending fold-thrust belt which extends 1000 km along the northeast margin of the Plateau and over-thrust the Hexi Corridor to the northeast and the Qaidam Basin to the southwest. An early-mid Palaeozoic orogenic suture belt, composed of faulted terranes of Late Proterozoic to early-mid Palaeozoic meta-sedimentary and meta-volcanic strata, is exposed in the Qilian Mountains and has been previously suggested to be reactivated by Late Cenozoic deformation. NE-directed crustal shortening, associated with the far-field effects of the Indo-Asian collision, has been active in the Qilian Mountains since the early-mid Miocene. It is characterised by the uplift of high mountain ranges along crustal scale thrust faults which splay south-eastwards from the sinistral-slip, north-northeast trending Altyn Tagh Fault and are postulated to connect along a shallow-dipping decollement in the midlower crust. Initiation of uplift in the Qilian Mountains was associated with a considerable decrease in the slip rate along the eastern end of the Altyn Tagh Fault and coincides with a plateau-wide reorganisation of deformation. This project presents new field mapping and remote sensing analysis and integrates this with existing geophysical data to i) understand and constrain the tectonic evolution of the northeast corner of the Qilian Mountains and the northwest corner of the Hexi Corridor, ii) examine the structural and lithological control of the Palaeozoic accretionary crust over Late Cenozoic deformation within the mountain ranges, and iii) establish the spatial and temporal extent of different styles of deformation within the northeastern Qilian Mountains.