Eastern Kunlun Range Research Articles

Two Phases of Crustal Shortening in Northeastern Tibet as a Result of a Stronger Qaidam Lithosphere During the Cenozoic India–Asia Collision

AbstractAlthough two phases of Cenozoic crustal deformation in the Qilian Shan thrust belt of northeastern Tibet has been documented, their dynamic causes remain unclear. To address this issue, we investigate whether the mechanical strength of the Qaidam Basin, which is located between the Eastern Kunlun Range and the Qilian Shan, was a controlling factor for the observed deformation history by performing 2‐D thermal–mechanical simulations. Our models consider the division of the Tibetan terranes (i.e., Qilian arc, Kunlun‐Qaidam, Songpan‐Ganzi, Qiangtang, and Lhasa, from north to south) bounded by suture zones. Simulation results show that weak suture zones in central Tibet can lead to peeling off and sinking of the mantle lithosphere beneath the Qiangtang and Songpan–Ganzi terranes. After lithospheric delamination, varying north‐south width, thickness and strength of the Qaidam crust creates three end‐member model results: (a) the mantle lithosphere of the Lhasa terrane delaminates while the mantle lithosphere beneath Eastern Kunlun‐Qaidam terrane and the Qilian Shan thrust belt (KQQ) remains undeformed, (b) the Lhasa mantle lithosphere moves northward while the KQQ mantle lithosphere subducts southward, and (c) the Lhasa mantle lithosphere moves northward while lithospheric thickening occurs north of the Qaidam Basin. Our simulations show that pre‐existing weaknesses in northeastern Tibet can be activated and deformed shortly after the onset of collision, and a second wave of deformation sweeps across northeastern Tibet after lithospheric delamination in northern Tibet.

Cenozoic deformation in the eastern domain of the North Qaidam thrust belt, northern Tibetan Plateau

Abstract The present topography of the northern Tibetan Plateau is characterized by the northwest-trending Eastern Kunlun Range, Qaidam Basin, and Qilian Shan, which figure importantly into the evolution and mechanism of Tibetan plateau development during Cenozoic Indo-Asian convergence. Understanding the Cenozoic deformation history and the source-to-sink relationship through time has significant implications for deciphering the growth history of the northern Tibetan Plateau. Despite decades of study, the timing, pattern, and mechanisms of deformation across the northern Tibetan Plateau are still vigorously debated. The North Qaidam thrust belt, located between the Qaidam Basin and Qilian Shan thrust belt, provides a valuable record of Cenozoic deformation in the northern Tibetan Plateau. Here, we present the results of new geologic mapping, structural and sedimentology analysis, and apatite fission track thermochronology to constrain the Cenozoic evolution history and reconstruct the paleogeomorphology of the eastern domain of the North Qaidam thrust belt and its foreland, the Wulan Basin. Our analyses reveal the North Qaidam thrust belt experienced multi-phase exhumation since the Cretaceous. A period of Eocene localized thrust-related uplift of the North Qaidam thrust belt initiated shortly after India-Asia collision, and lower erosion rates in the Oligocene allowed the thrust belt to expand along-strike eastward. Local uplift shed sediments to the southwest, directly into the Qaidam Basin. Reactivation of the proximal thrust faults and initiation of the northwest-striking right-slip Elashan fault at ca. 15–10 Ma drove the final accelerated mid-Miocene cooling and denudation to the surface. This phase of deformation established the overall framework morphology of the northeastern margin of the Tibetan Plateau, including the overall structure of the basins and ranges.

Proterozoic–Phanerozoic tectonic evolution of the Qilian Shan and Eastern Kunlun Range, northern Tibet

AbstractThe Proterozoic–Phanerozoic tectonic evolution of the Qilian Shan, Qaidam Basin, and Eastern Kunlun Range was key to the construction of the Asian continent, and understanding the paleogeography of these regions is critical to reconstructing the ancient oceanic domains of central Asia. This issue is particularly important regarding the paleogeography of the North China-Tarim continent and South China craton, which have experienced significant late Neoproterozoic rifting and Phanerozoic deformation. In this study, we integrated new and existing geologic field observations and geochronology across northern Tibet to examine the tectonic evolution of the Qilian-Qaidam-Kunlun continent and its relationships with the North China-Tarim continent to the north and South China craton to the south. Our results show that subduction and subsequent collision between the Tarim-North China, Qilian-Qaidam-Kunlun, and South China continents occurred in the early Neoproterozoic. Late Neoproterozoic rifting opened the North Qilian, South Qilian, and Paleo-Kunlun oceans. Opening of the South Qilian and Paleo-Kunlun oceans followed the trace of an early Neoproterozoic suture. The opening of the Paleo-Kunlun Ocean (ca. 600 Ma) occurred later than the opening of the North and South Qilian oceans (ca. 740–730 Ma). Closure of the North Qilian and South Qilian oceans occurred in the Early Silurian (ca. 440 Ma), whereas the final consumption of the Paleo-Kunlun Ocean occurred in the Devonian (ca. 360 Ma). Northward subduction of the Neo-Kunlun oceanic lithosphere initiated at ca. 270 Ma, followed by slab rollback beginning at ca. 225 Ma evidenced in the South Qilian Shan and at ca. 194 Ma evidenced in the Eastern Kunlun Range. This tectonic evolution is supported by spatial trends in the timing of magmatism and paleo-crustal thickness across the Qilian-Qaidam-Kunlun continent. Lastly, we suggest that two Greater North China and South China continents, located along the southern margin of Laurasia, were separated in the early Neoproterozoic along the future Kunlun-Qinling-Dabie suture.

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

AbstractSignals of uplift and deformation across the Tibetan Plateau associated with the Cenozoic India-Asia collision can be used to test debated deformation mechanism(s) and the growth history of the plateau. The spatio-temporal evolution of the Eastern Kunlun Range in northern Tibet provides a window for understanding the intracontinental tectonic evolution of the region. The Eastern Kunlun Range exposes the Cenozoic Kunlun left-slip fault and kinematically linked thrust belts. In this contribution, integrated field observations and apatite fission-track thermochronology were conducted to constrain the initiation ages of localized thrust faults and the exhumation history of the Eastern Kunlun Range. Our analyses reveal four stages of cooling of the Eastern Kunlun Range. We relate these four stages to the following interpreted tectonic evolution: (1) an initial period of early Cretaceous cooling and slow exhumation over the early Cenozoic, which is associated with the formation of a regional unconformity observed between Cretaceous strata and early Cenozoic sediments; (2) rapid Oligocene cooling that occurred at the eastern domain of the Eastern Kunlun Range related to the southern Qaidam thrusts; (3) extensive rapid cooling since the early-middle Miocene in most of the eastern-central domains and significant uplift of the entire range; and (4) a final pulse of rapid late Miocene-to-present cooling associated with the initiation of the Kunlun left-slip fault and dip-slip shortening at the western and eastern termination of the left-slip fault. Early Cenozoic deformation was distributed along the northern extent of the Tibetan Plateau, and overprinting out-of-sequence deformation migrated back to the south with the initiation of Miocene-to-present deformation in the Eastern Kunlun Range.

Late Mesozoic–Cenozoic cooling history of the northeastern Tibetan Plateau and its foreland derived from low-temperature thermochronology

AbstractThe growth history and formation mechanisms of the Cenozoic Tibetan Plateau are the subject of an intense debate with important implications for understanding the kinematics and dynamics of large-scale intracontinental deformation. Better constraints on the uplift and deformation history across the northern plateau are necessary to address how the Tibetan Plateau was constructed. To this end, we present updated field observations coupled with low-temperature thermochronology from the Qaidam basin in the south to the Qilian Shan foreland in the north. Our results show that the region experienced a late Mesozoic cooling event that is interpreted as a result of tectonic deformation prior to the India-Asia collision. Our results also reveal the onset of renewed cooling in the Eocene in the Qilian Shan region along the northern margin of the Tibetan Plateau, which we interpret to indicate the timing of initial thrusting and plateau formation along the plateau margin. The interpreted Eocene thrusting in the Qilian Shan predates Cenozoic thrust belts to the south (e.g., the Eastern Kunlun Range), which supports out-of-sequence rather than northward-migrating thrust belt development. The early Cenozoic deformation exploited the south-dipping early Paleozoic Qilian suture zone as indicated by our field mapping and the existing geophysical data. In the Miocene, strike-slip faulting was initiated along segments of the older Paleozoic suture zones in northern Tibet, which led to the development of the Kunlun and Haiyuan left-slip transpressional systems. Late Miocene deformation and uplift of the Hexi corridor and Longshou Shan directly north of the Qilian Shan thrust belt represent the most recent phase of outward plateau growth.

Jurassic evolution of the Qaidam Basin in western China: Constrained by stratigraphic succession, detrital zircon U-Pb geochronology and Hf isotope analysis

The formation and evolution of an intracontinental basin triggered via the subduction or collision of plates at continental margins can record intracontinental tectonic processes. As a typical intracontinental basin during the Jurassic, the Qaidam Basin in western China records how this extensional basin formed and evolved in response to distant subduction or collisional processes and tectonism caused by stresses transmitted from distant convergent plate margins. The Jurassic evolution of the Qaidam Basin, in terms of basin-filling architecture, sediment dispersal pattern and basin properties, remains speculative; hence, these uncertainties need to be revisited. An integrated study of the stratigraphic succession, conglomerates, U-Pb geochronology, and Hf isotopes of detrital zircons was adopted to elucidate the Jurassic evolutionary process of the Qaidam Basin. The results show that a discrete Jurassic terrestrial succession characterized by alluvial fan, braided stream, braided river delta, and lacustrine deposits developed on the western and northern margins of the Qaidam Basin. The stratigraphic succession, U-Pb age dating, and Hf isotope analysis, along with the reconstructed provenance results, suggest small-scale distribution of Lower Jurassic sediments deposited via autochthonous sedimentation on the western margin of the basin, with material mainly originating from the Altyn Tagh Range. Lower Jurassic sediments in the western segment of the northern basin were shed from the Qilian Range (especially the South Qilian) and Eastern Kunlun Range. And coeval sediments in the eastern segment of the northern basin were originated from the Quanji massif. During the Middle-Late Jurassic, the primary source areas were the Qilian Range and Eastern Kunlun Range, which fed material to the whole basin. The Jurassic sedimentary environment in the Qaidam Basin evolved from a series of small-scale, scattered, and rift-related depressions distributed on the western and northern margins during the Early Jurassic to a larger, extensive, and unified depression occupying the whole basin in the Middle Jurassic. The Altyn Tagh Range rose to a certain extent during the Early Jurassic but lacked large-scale strike-slip tectonism throughout the Jurassic. At that time, the North Qaidam tectonic belt had not yet been uplifted and did not shed material into the basin during the Jurassic. The Qaidam Basin experienced intracontinental extensional tectonism with a northeast-southwest trend throughout the Jurassic in response to far-field effects driven by the sequential northward or northeastward amalgamation of blocks to the southern margin of the Qaidam Block and successive accretion of the Qiangtang Block and Lhasa Block onto the southern Eurasian margin during the Late Triassic−Early Jurassic and Late Jurassic−Early Cretaceous, respectively.

Block motions and strain partition on active faults in Northeast Tibet and their geodynamic implications

AbstractAn updated GPS velocity field and set of focal mechanism solutions have allowed us to quantify the detailed tectonic deformation of Northeast Tibet. By employing block kinematic modelling, we show how the relative motion of modelled blocks is accommodated by deformation on major fault structures across the region, from the Eastern Kunlun Range to the Qilian Shan, with the slip rate decrease from the centre towards the east in the Kunlun, the Haiyuan and the Altyn Tagh Fault, as well as strain partitioning on these faults. The deflection of both the derived block strains and the focal stress from the west to the east also implies the strain transfer from the strike‐slip shearing to crustal shortening. Combining the different faulting regimes in each block with the distinctive distribution of the strain ratios, our results support a model of diffusive deformation associated with strain partition along tectonic boundary faults.

Cenozoic cooling history and fluvial terrace development of the western domain of the Eastern Kunlun Range, northern Tibet

The growth of the Tibetan Plateau resulted primarily from Cenozoic India-Asia collision and continued convergence, and thus the deformation timing and geomorphic evolution of northern Tibet are critical to understanding the dynamics of orogenic plateau growth. Although previous studies have suggested that the Altyn Tagh Shan and the Eastern Kunlun Range of northern Tibet have experienced differential faulting and exhumation history, our knowledge of the temporal and spatial distribution of the growth of the northwestern Tibetan Plateau is still lacking. In this study, we integrate new geologic mapping, low-temperature themochronometry (18 apatite-fission track ages), and Optically Stimulated Luminescence (OSL) dating to provide constraints on the Cenozoic cooling history of northwestern Tibet and late Quaternary fluvial terrace development. We focus on where Altyn Tagh Shan structures are juxtaposed against Eastern Kunlun Range structures. New fission-track cooling ages from one traverse along the Aksu River yielded three cooling age domains: Paleocene, Miocene, and early Pliocene. With this new knowledge of ~12–10 Ma initiation of Jianxiashan thrusting and exhumation, we suggest a refined N-S shortening rate of this thrust system of 2.0–2.4 mm/yr and strain rates of 8–9 × 10−16 s−1. Thermal history modeling suggests that the study area experienced two broad events, including slow cooling through the AFT PAZ since the early Eocene and rapid cooling during the late Miocene. Our OSL dating results from the Aksu drainage reflect two separate processes of aggradation and incision that occurred during the late Pleistocene and Holocene, respectively, which are interpreted to result from long-term forcing of incision by a constant rate of tectonic uplift modulated by late Quaternary climatic variations. We interpret that this incision occurred at a rate of ~1 mm/yr, which is faster than exhumation rates inferred from the AFT data (0.3–0.5 mm/yr). These Quaternary exhumation rates may reflect faster recent exhumation or uplift associated with the proximal Altyn Tagh fault. In accordance with previous studies, we present a refined Cenozoic tectonic model for the evolution history of northern Tibet. The deformation pattern of northern Tibet results from clockwise rotation of preexisting weaknesses and transpressional deformation along the Kunlun fault and the Haiyuan fault.

Early–Middle Jurassic paleogeography reconstruction in the Western Qaidam Basin: Insights from sedimentology and detrital zircon geochronology

The Western Qaidam Basin (WQB) is situated at the northeastern margin of the Tibetan Plateau. It is adjacent to the Altyn Tagh Range to the west and is bordered at the south and north by the Eastern Kunlun Range and Southern Qilian Range, respectively. Sporadic Jurassic outcrops are exposed along the Altyn Tagh Range. Although subsurface data have revealed that the Jurassic rocks also developed in the basin interior, little is known about their distribution and depositional characteristics. Hydrocarbon exploration has revealed that the Lower–Middle Jurassic strata are important source rocks and reservoirs in the WQB. However, due to post-depositional uplifting, exhumation or deep burial, the sediments provenance, paleogeography and the basin properties during the Early–Middle Jurassic in the whole WQB remain less understood. In this study, we examine the sedimentary records combined with detrital zircon U–Pb geochronology based on an analysis of post-depositional modification, to reveal the source-to-sink relationship between the WQB and surrounding potential source areas, and to further reconstruct the Early–Middle Jurassic paleogeography of the WQB. During the Early Jurassic, there were a series of small-scale, separated rift basins which were characterized by proximal sedimentation and rapid facies shift in the WQB. Specifically, the Lower Jurassic sediments in the southern WQB mainly originated from the Eastern Kunlun Range with minor supply from the Paleozoic intrusions that might have been exposed in the hinterland of the Qaidam Block; the provenance in the northern WQB was dominated by the uplift area to the west. There was a broader depression basin in the southern WQB. The Eastern Kunlun Range and the ancestral Altyn Mountains, served as the two dominant source areas for the clastic material of the southern WQB during the Middle Jurassic. Integrated analysis on sedimentology and provenance reveals that the southeastern Tarim Basin and the WQB were likely to have been interconnected or adjacent during Middle Jurassic period. We thus infer that no large-scale strike-slip displacement along the Altyn Tagh Fault occurred during that period. Combining regional tectonic settings, we tentatively suggest that the extensional setting following the orogenic movement in the eastern part of the Paleo–Tethys Ocean could have been responsible for the formation of the Early Jurassic rift basins. By the early Middle Jurassic, the Bangonghu–Nujiang Tethys Ocean and the Mongol–Okhotsk Ocean were subducted northward beneath the Qiangtang terrane and Siberian continent, respectively. These led to the presence of an extensional stress field and the formation of a broader depression basin in the southern WQB during the Middle Jurassic. Paleogeography reconstruction results indicate that the northern WQB should have much potential for hydrocarbon exploration.

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

The Eastern Kunlun arc activities were interrupted by repeated continent–continent collision followed by ocean opening along the older suture zones previous created in the Neoproterozoic. The first report of the later Devonian‐early Carboniferous arc magmatism has played a vital role in constraining the evolution of the Eastern Kunlun Orogen. We undertook zircon U–Pb dating, Hf isotopic compositions, whole‐rock geochemical and Nd–Sr isotopic analyses of the Jianxiashan pluton in the western end of the Eastern Kunlun Range. The pluton is composed of tonalite, granodiorite, and monzogranites. Our new data suggest that the pluton formed during the late Devonian‐early Carboniferous with ages of 339–358 Ma. These rocks have high A/CNK = 1.06–1.30, with 1.11–3.80% of normative corundum and are characterized by negative Eu anomalies and strong depletion in Ba, Nb, and Sr elements. The zircon Hf isotopic analyses give predominantly negative εHf(t) values (−9.25 to −2.80), whereas the values of inherited zircons are various from −25.84 to +8.80. The U–Pb age and Hf isotopic data of these inherited zircons are similar to the widespread meta‐sediments of Kuhai Group basement. The peraluminous granitoids have negative εNd(t) values (−7.1 to −5.1) and relatively high initial 87Sr/86Sr ratios (0.71009). These isotopic compositions suggest that the Kuhai Group could possibly be the source rocks of these peraluminous granitoids. We suggest the tonalite and granodiorite are I‐S transition type, whereas the monzogranite is highly fractionated S‐type formed in a back‐arc extensional tectonic setting, which was possibly related to the northern subduction of the Paleo‐Kunlun oceanic lithosphere.

Formation and evolution of the Eastern Kunlun Range, northern Tibet: Evidence from detrital zircon U-Pb geochronology and Hf isotopes

The Eastern Kunlun Range, as a high-elevation and granitoid-rich tectonic element in northern Tibet, records Paleozoic–Mesozoic amalgamation process of the East Asia continent and Cenozoic uplift of the Tibetan Plateau. However, Precambrian evolution of the Eastern Kunlun remains poorly understood and relations between Eastern Kunlun and adjacent terranes (e.g., Qaidam and Qilian) during the Phanerozoic accretion process are still highly controversial. We use detrital zircon U-Pb geochronological and Hf isotopic data of Proterozoic and Paleozoic metasedimentary rocks from the Eastern Kunlun Range, to reconstruct its origin and subsequent evolutionary history. Detrital zircons of the Proterozoic rocks are dominated by early–middle Neoproterozoic ages (700–1000 Ma), with two age peaks at ca. 800 Ma and ca. 920 Ma and εHf(t) values ranging from −10 to 5. The youngest detrital zircon ages (648–788 Ma) demonstrate that these investigated Proterozoic strata, which were previously mapped as Paleoproterozoic to Mesoproterozoic, were most likely deposited in the middle–late Neoproterozoic. Abundant 0.9–1.0 Ga detrital zircon crystals are consistent with those crystalline rocks of similar ages across the Kunlun-Qaidam and Qilian terranes, which are generally interpreted as the product of Grenvillian orogenesis. These findings support the hypothesis that these terranes were probably within a single continental landmass (named as KQQ block) during the Neoproterozoic. The high similarity of detrital zircon ages, Hf isotopes and Neoproterozoic lithostratigraphy between western Yangtze and KQQ blocks, supports a temporary connection of the KQQ block to western Yangtze in Rodinia supercontinent. Detrital zircons of the analyzed Paleozoic rocks are characterized by 390–490 Ma age populations. These results, in combination with published granitoids data of the northern Tibet, favor a scenario in which the Kunlun-Qaidam and Qilian terranes underwent separated subduction and accretion processes during the late Cambrian–Devonian, but together formed an upper plate to northward subduction of the Paleo-Tethys during the Permian–Triassic.

Cenozoic growth of the Eastern Kunlun Range (northern Tibetan Plateau): evidence from sedimentary records in the southwest Qaidam Basin

ABSTRACT The Cenozoic sedimentary infill of the Qaidam Basin in the northern Tibetan Plateau provide significant insights into the uplift history and the tectonic evolution of the basin-bounding mountain ranges. Along the SW basin margin, a continuous record is preserved in the ~3000-m-thick Cenozoic succession at the Changweitai area. An up-section switch from marginal and deep lacustrine sedimentation to lacustrine delta-alluvial fan deposition indicates progradation and increasingly basinward advance of sediment transportation systems. Provenance data from sandstone petrology, palaeocurrent analysis and zircon U-Pb geochronology suggest that the Eastern Kunlun Range has been consistently providing material to the SW Qaidam basin since the deposition of the upper Xiaganchaigou Formation, indicating its latest uplift episode prior to the Late Eocene (before 35.5 Ma). However, variation in depositional systems indicates a clear shift in sediment provenance between the deposition of the Xiayoushashan Formation and the Shangyoushashan Formation. We propose that the Cenozoic Eastern Kunlun Range experienced a northward encroachment of shortening into the Qaidam Basin. During the Early Miocene, extensive topographic growth of the Altyn Tagh Range caused by reactivation of the Altyn Tagh strike-slip fault, provided the main source of sediment for the western Qaidam basin. Subsequently, a new source for the basin was provided by the uplifting Qimen Tagh subrange since ~15 Ma.

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

AbstractThe 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.

Tectonics of the Eastern Kunlun Range: Cenozoic Reactivation of a Paleozoic‐Early Mesozoic Orogen

AbstractThe Eastern Kunlun Range in north Tibet, located along the northern margin of the eastern Tethyan orogenic system, records evidence for continental break‐up and ocean development in the Neoproterozoic, Paleozoic‐early Mesozoic subduction and continental collision, Mesozoic intracontinental extension, and Cenozoic contractional deformation. The Kunlun region is marked by active left‐lateral strike‐slip deformation of Kunlun fault system, one of the major intracontinental strike‐slip faults in Tibet that developed in response India‐Asia. To better constrain the tectonic evolution of the Eastern Kunlun Range and the closure of the various Kunlun oceans, we conducted detailed investigation integrating new geologic mapping, geochronology, and whole‐rock geochemistry with a synthesis of existing datasets across north Tibet. The Eastern Kunlun Range experienced three major deformation events in the Neoproterozoic, early Paleozoic, and Late Paleozoic‐early Mesozoic, which were associated with collision of the Proto‐, Paleo‐, and Neo‐Kunlun arcs, respectively. Our new detrital zircon analyses from Mesoproterozoic‐Cenozoic strata constrain stratigraphic age and sediment provenance and highlight the importance of three periods of arc activity. Our stratigraphic synthesis, including new field observations, provides new insights into connections between sediment dispersal and changes in tectonism and paleogeography. Miocene‐to‐present strike‐slip activity on the Kunlun fault and the associated strain pattern can be explained by clockwise rotation of the Kunlun fault and its wall rock as a bookshelf‐fault system, which has been proposed for northern Tibet as a result of distributed north‐south right‐lateral shear. The development of this fault system was facilitated by the presence of a Triassic suture that provided a preexisting weakness.

Mesozoic-Cenozoic evolution of the Eastern Kunlun Range, central Tibet, and implications for basin evolution during the Indo-Asian collision

Abstract The present-day Tibetan plateau, which is the largest highland on Earth, formed primarily due to the India-Asia collision since 50–60 Ma. The development of the plateau has been associated with the Cenozoic development of two large intra-plateau sedimentary basins in north-central Tibet: the Qaidam and Hoh Xil basins to the north and south of the Eastern Kunlun Range, respectively. We conducted an integrated study of these two basins and the Eastern Kunlun Range that separates them to understand the timing and mechanisms of their development in order to decipher the growth and uplift history of the plateau. Crustal shortening in the Fenghuoshan-Nangqian and Qilian Shan-Nan Shan thrust belts initiated no later than the early Eocene, which formed the northern and southern boundaries of the combined Hoh Xil and Qaidam basins in central Tibet. The distinct two-stage development of the Hoh Xil basin suggests emergence of a topographic barrier between the Hoh Xil basin in the south and Qaidam basin in the north in the early Neogene, which is supported by the existing and new apatite fission-track data from the Eastern Kunlun Range that suggest rapid cooling after ca. 20 Ma. Previous and newly collected geochronological, petrological, and thermochronological data are best interpreted in the context of the Paleogene Paleo-Qaidam hypothesis, which requires Hoh Xil and Qaidam basins to have been parts of a single integrated basin during the early stage of the Cenozoic Tibetan plateau development.

Cenozoic basin evolution of the central Tibetan plateau as constrained by U-Pb detrital zircon geochronology, sandstone petrology, and fission-track thermochronology

We conduct sandstone-composition analysis, U-Pb detrital-zircon dating, and apatite fission-track thermochronology to determine how basin development was associated with the Cenozoic deformation across central Tibet. Our results are consistent with a two-stage basin development model: first a single fluvial-lacustrine system formed (i.e., Paleo-Qaidam basin) in between two thrust belts (i.e., the Fenghuoshan and Qilian Shan thrust belts) in the Paleogene, which was later partitioned into two sub-basins in the Neogene by the Kunlun transpressional system and its associated uplift. The southern sub-basin (i.e., Hoh Xil basin) strata have detrital-zircon age populations at 210–300 Ma and 390–480 Ma for the Eocene strata and at 220–310 Ma and 400–500 Ma for the early Miocene strata; petrologic analysis indicates that the late Cretaceous-Eocene strata were recycled from the underlying Jurassic rocks. The northern sub-basin (i.e., Qaidam basin) strata yield detrital-zircon age clusters at 210–290 Ma and 370–480 Ma in the Eocene, 220–280 Ma and 350–500 Ma in the Oligocene, 250–290 Ma and 395–510 Ma in the Miocene, and 225–290 Ma and 375–480 Ma in the Pliocene. Proterozoic ages of the detrital zircon are most useful for determining provenance: the pre-Neogene Hoh Xil and Qaidam strata all contain the distinctive age peaks of ~1800 Ma and ~2500 Ma from the Songpan-Ganzi terrane south of the Kunlun fault, whereas detrital zircon of this age is absent in the Neogene Qaidam strata suggesting the emergence of a topographic barrier between the two basins. This inference is consistent with our fission-track thermochronological data from the Eastern Kunlun Range that suggest rapid cooling within the range did not start until after 30–20 Ma. Our new data support the Paleo-Qaidam hypothesis that requires the Hoh Xil and Qaidam basins were parts of a single Paleogene basin bounded by the Qilian Shan and Fenghuoshan thrust belts.

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

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 new 3D seismic reflection profiles to demonstrate that: (1) from the Paleocene to early Eocene, the Eboliang section was approximately located near the present position of Anxi, 360±40km 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. 360km 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 from the Altyn Tagh Range to reach the Eboliang and the Huatugou sections. The post-Oligocene clastic material in the western Qaidam basin is generally derived from local 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 early-middle Eocene initiation of left-lateral strike-slip faulting leading to a 360±40km offset along the Altyn Tagh fault.

Pre-Cenozoic geologic history of the central and northern Tibetan Plateau and the role of Wilson cycles in constructing the Tethyan orogenic system

In order to better constrain the evolution of the Tethyan orogenic system, we conducted an integrated investigation involving U-Pb dating of igneous and detrital zircon, geochemical analysis of igneous rocks, compositional analysis of sedimentary strata, and a synthesis of existing work across the Qilian Shan, Qaidam Basin, and the Eastern Kunlun Range of central and northern Tibet. This effort reveals five stages of arc magmatism at 1005–910 Ma, 790–720 Ma, 580–500 Ma, 490–375 Ma, and 290–195 Ma, respectively. Arc activities were interrupted by repeated continent-continent collision followed by ocean opening along the older suture zones first created in the Neoproterozoic. This suggests that Wilson cycles have played a controlling role in constructing the southern Asian continent. The magmatic history and regional geologic constraints allow us to construct a coherent tectonic model that has the following key features. (1) The linked South Qilian suture in the west and North Qinling suture in the east formed the northern boundary of the coherent Kunlun–Qaidam–North Qinling Terrane in the early Paleozoic. (2) The Songpan-Ganzi Terrane has been the western part of the Yangtze craton since the Neoproterozoic. (3) Development of the wide (>700 km) Permian–Triassic arc across the Kunlun-Qaidam Terrane was induced by flat subduction and rapid slab rollback, which also caused extreme extension of the Songpan-Ganzi Terrane. (4) The formation of the Anymaqen-Kunlun-Muztagh Ocean (= the Neo–Kunlun Ocean in this study) was created within Laurasia rather than being a preexisting ocean between Gondwana and Laurasia as postulated by most early studies.

Relief history and denudation evolution of the northern Tibet margin: Constraints from 40Ar/39Ar and (U–Th)/He dating and implications for far-field effect of rising plateau

How does the rising Tibetan Plateau affect its peripheral region? The current understanding of the mechanism of orogenic plateau development is incomplete and thus no consensus yet exists in this regard. However, our new 40Ar/39Ar and (U–Th)/He dataset presented in this study may shed some light on this issue. 40Ar/39Ar dating, on two vertical transects from the massif between Nuomuhong and Golmud, indicates that the Eastern Kunlun Range was built-up and exhumated during the later Triassic initially, and a minimum overburden of ~11.7–14.0km has been eroded since ~220Ma. (U–Th)/He age–elevation relationships (AERs) indicate a rapid exhumation event at ~40Ma following a long period of slow exhumation phase from late Mesozoic to early Eocene time. In this study, two scenarios – one assuming a single stage and the other assuming multiple stages of evolution history – are modeled. Modeling of a multiple stage scenario is reasonable and is able to reflect the “actual” situation, which reveals the entire denudation and relief history of the northern Tibet from late Mesozoic to the present time. After prolonged denudation before 50Ma, a low topography (~0.17 times the relief of the present) developed by 50Ma with an erosion rate of 0.013-0.013+0.025mm/yr. The highest relief (~1.82 times the relief of the present) of the Cenozoic time came into being at 40Ma with an erosion rate of 0.052±0.025mm/yr, which was possibly a result of the collision between India and Eurasia. Subsequently, the relief steadily decreased to the present level due to continued denudation. This suggests that deformation propagation from the continued convergence boundary between India and Eurasia was insignificant after the construction of the highest relief. This observation is broadly consistent with published accounts on the stratigraphic, cooling, and faulting histories of the northern Tibet margin.

Source to sink relation between the Eastern Kunlun Range and the Qaidam Basin, northern Tibetan Plateau, during the Cenozoic

Understanding the source to sink relationship through time between the Eastern Kunlun Range, one of the major mountain belts in the northern Tibetan Plateau, and the actively deforming Qaidam Basin to the north has important implications for unravelling the growth history of the Tibetan Plateau. In this study, U-Pb dating (laser-ablation–inductively coupled plasma–mass spectrometry) of detrital zircons from 22 sandstone samples (Paleocene to Holocene) collected from four sections within the southwestern Qaidam Basin is combined with provenance analysis and new seismic profile interpretation to investigate the mountain building of the Eastern Kunlun Range and its effects on the development of the Qaidam Basin. The U-Pb age distributions of detrital grains from Paleocene strata are characterized by a major component of Paleozoic to late Proterozoic ages. Furthermore, carbonate debris containing foraminifera have been recognized in the Paleocene conglomerate sequences. We thus suggest that the Eastern Kunlun Range was already exhumed prior to the Paleocene. The southward onlaps of Paleocene to Oligocene strata observed on seismic profiles and the appearance of a Mesozoic component in the detrital zircon age spectra of Eocene to Oligocene strata indicate that the Qaidam Basin was widening southward during that early Cenozoic period. Well-developed post-Oligocene growth strata and the increasing proportion of Mesozoic and Paleozoic U-Pb ages in detrital zircon grains from late Neogene strata demonstrate that the relief of the Eastern Kunlun and Altyn Tagh Ranges increased, leading to isolation and narrowing of the Qaidam Basin, from Miocene to the present. The inferred pulsed deformation in the Eastern Kunlun Range highlights the complex growth history of the Tibetan Plateau.