Structural analysis and tectonic evolution of the western domain of the Eastern Kunlun Range, northwest Tibet

Abstract

The Tibetan Plateau, the largest highland on Earth, formed due to the collision of India-Asia over the past 50–60 m.y., and the evolution of the Tibetan Plateau impacts our knowledge of continental tectonics. Examination of the northernmost margin of the Tibetan Plateau is key to unravelling the deformation mechanisms acting in northern Tibet. The left-slip Altyn Tagh fault system defines the northwest margin of the Tibetan Plateau, separating the Western and Eastern Kunlun Ranges in the southwest. Both Cenozoic and pre-Cenozoic crustal deformation events at this junction between the Altyn Tagh and Kunlun Ranges were responsible for the construction of northwestern Tibet, yet the relative contribution of each phase remains unconstrained. The western domain of the Eastern Kunlun Range is marked by active NE-trending, left-slip deformation of the Altyn Tagh fault and an E-striking Cenozoic thrust system developed in response India-Asia collision. To better constrain the Paleozoic Altyn Tagh and Kunlun orogens and establish the Cenozoic structural framework, we conducted an integrated investigation involving detailed geologic mapping (∼1:50,000 scale), U-Pb zircon geochronology, and synthesis of existing data sets across northwestern Tibet. Our new zircon analyses from Paleoproterozoic–Cretaceous strata constrain stratigraphic age and sediment provenance and highlight Proterozoic–Paleozoic arc activity. We propose a tectonic model for the Neoproterozoic–Mesozoic evolution of northwestern Tibet wherein restoration of an ∼56-km-long balanced cross section across the western domain of the Eastern Kunlun suggests that Cenozoic minimum shortening strain was ∼30% (∼24 km shortening). Field evidence suggests this shortening commenced after ca. 25–20 Ma, which yields an average long-term shortening rate of 1.2–0.9 mm yr–1 and strain rates of 4.7 × 10–16 s–1 to 2.3 × 10–16 s–1. Geometric considerations demonstrate that this contractional deformation did not significantly contribute to left-slip offset on the Altyn Tagh fault, which has ∼10 mm/yr slip rates.

Petrogenesis and tectonic significance of the late Devonian‐early Carboniferous Jianxiashan pluton in the western domain of the eastern Kunlun Orogen, northern Tibetan Plateau

“…Most of the thrust faults are southwest‐dipping. The faults are clearly described by Wu, Liu, et al, () and Wu, Zuza, et al, ().…”

“…555–420 Ma) (e.g., Qi, ; Wang et al, ; Yao et al, ) and Permian–Triassic (ca. 270–220 Ma) plutons (e.g., Wu et al, ; Dong et al, ; Wu et al, ; Wu, Liu, et al, ) and a large number of discontinuous thrust nappes (e.g., Wu et al, , ; Yin & Harrison, ). The Paleoproterozoic basement of the South Kunlun Belt is composed of the Late Paleoproterozoic Kuhai Group and the Meso‐Neoproterozoic Wanbaogou Group.…”

“…The Mesozoic strata (J 1–2 , J 3 and K 1 ; Figure ) are exposed in the northern portion of our study area and consist of polymictic conglomerate arkosic sandstones and coal‐bearing shale. The study area includes numerous Cenozoic thrust faults and potential strike‐slip faults (Yin, Dang, Wang, et al, ; Yin, Dang, Zhang, Chen, & McRivette, ; Zuza et al, Zuza & Yin, , Zuza et al, ; Wu, Liu, et al, ; Wu, Zuza, et al, ). Most of the thrust faults are southwest‐dipping.…”

“…Its east–west extent is nearly 90 km, and it has a width of 3–15 km (Figure ). The pluton intrudes the late Paleoproterozoic Kuhai Group amphibolite‐facies gneiss and the pillow lavas of the Carboniferous Tuokuzidaban Group (Wu, Liu, et al, ; Xu et al, ). The wall rock xenoliths are widespread in the pluton (Figure a) and are mainly composed of gneisses and schists.…”

Low-temperature thermochronology constraints on the evolution of the Eastern Kunlun Range, northern Tibetan Plateau

“…The Kunlun arcs, which intruded Precambrian gneiss and Neoproterozoic to early Mesozoic low-grade metasedimentary rocks, are associated with the evolution and closure of the Kunlun ocean(s) (e.g., Pan et al, 2004;Wu et al, 2016Wu et al, , 2017Wu et al, , 2019a. Proterozoic metamorphic basement is exposed along the eastern segment of the range, where it is thrust over the early Paleozoic arc sequences (e.g., Qinghai BMGR, 1991;Pan et al, 2004;Wu et al, 2019aWu et al, , 2020a. Unconformably overlying this unit is an upper Paleozoic passive continental margin sedimentary sequence (e.g., Qinghai BMGR, 1991;Yin and Harrison, 2000;Pan et al, 2004;Wu et al, 2019a).…”