India-Eurasia Collision Research Articles

The geology of the Shyok suture zone: evidence for Cretaceous extension of the southern Eurasian margin and Eocene India–Eurasia collision

This study discusses whether the Eurasian margin, before the onset of the India–Eurasia collision, was a Cordillera-style accretionary orogen or a more complex Japan–Mariana-style margin with extended back-arc basins and oceanic crust between the volcanic arc(s) and continental lithosphere. This distinction is critical to understanding the development of the India–Eurasia orogenic system because each of these scenarios has very different implications for the timing of the continental collision between India and Eurasia. We present new field mapping, U/Pb zircon dates and whole-rock geochemical results that constrain the tectonostratigraphic and structural development of the Shyok suture zone, which separates the Kohistan–Ladakh arc from the Karakoram terrane in northwestern India and Pakistan. Our results suggest that the Shyok suture comprises a Jurassic forearc ophiolite overlain by Eurasia-derived sedimentary strata interlayered with andesites, which accumulated throughout the Cretaceous in a back-arc basin that was under extension between 115 and 72 Myr ago. Closure of this back-arc basin post-dates the formation of the Indus suture zone between the Kohistan–Ladakh arc and India.

Comparison of Crustal Stress and Strain Fields in the Himalaya–Tibet Region: Geodynamic Implications

The Himalaya–Tibet region represents a complex region of active deformation related to the ongoing India–Eurasia convergence process. To provide additional constraints on the active processes shaping this region, we used a comprehensive dataset of GNSS and focal mechanisms data and derived crustal strain and stress fields. The results allow the detection of features such as the arc-parallel extension along the Himalayan Arc and the coexistence of strike-slip and normal faulting across Tibet. We discuss our findings concerning the relevant geodynamic models proposed in the literature. While earlier studies largely emphasized the role of either compressional or extensional processes, our findings suggest a more complex interaction between them. In general, our study highlights the critical role of both surface and deep processes in shaping the geodynamic processes. The alignment between tectonic stress and strain rate patterns indicates that the crust is highly elastic and influenced by present-day tectonics. Stress and strain orientations show a clockwise rotation at 31°N, reflecting deep control by the underthrusted Indian Plate. South of this boundary, compression is driven by basal drag from the underthrusting Indian Plate, while northward, escape tectonics dominate, resulting in eastward movement of the Tibetan Plateau. Localized stretching along the Himalaya is likely driven by the oblique convergence resulting from the India–Eurasia collision generating a transtensional regime over the Main Himalayan Thrust. In Tibet, stress variations appear mainly related to changes in the vertical axis, driven by topographically induced stresses linked to the uniform elevation of the plateau. From a broader perspective, these findings improve the understanding of driving crustal forces in the Himalaya–Tibet region and provide insights into how large-scale geodynamics drives surface deformation. Additionally, they contribute to the ongoing debate regarding the applicability of the stress–strain comparison and offer a more comprehensive framework for future research in similar tectonic settings worldwide.

Process and Mechanism of Exhumation in the Southern Altai Mountains, Northwest China

This study presents new fission track data from 40 apatite and 40 zircon samples in the Southern Altai Mountains (SAMs), revealing apatite fission track (AFT) ages of 110 ± 8 Ma to 54 ± 4 Ma and zircon fission track (ZFT) ages of 234 ± 24 Ma to 86 ± 7 Ma. The exhumation rates derived from three thermochronological methods range from 0.01 to 0.1 km/Ma (Age-Elevation method), 0.01 to 0.14 km/Ma (Half-Space thermal model), and 0.027 to 0.075 km/Ma (Age2exhume model). Thermal history modeling using HeFTy software reveals similar thermal histories on both sides of the Kangbutiebao Fault, with a notable cooling event and higher exhumation rates to the northeast. The Late Cretaceous (100–75 Ma) rapid cooling is associated with tectonic reactivation, likely linked to the collapse of the Mongol–Okhotsk Orogen and slab rollback in the southern Tethys Ocean. In the Late Cenozoic (10–0 Ma), cooling and uplift reflect the influence of tectonic stresses from the India–Eurasia collision, which also drove the reactivation of the Kangbutiebao Fault. These findings suggest a complex interplay of tectonic processes driving exhumation in the SAMs from the Late Jurassic to the Early Paleogene.

Oblique Rifting in the Southern Tibetan Plateau Revealed From 3‐D High‐Resolution Seismic Travel‐Time Tomography Around the India–Eurasia Continental Collision Zone

AbstractThe India–Eurasia continental collision zone (IECCZ) is an ideal setting for studying plate collision processes, plateau uplift mechanisms, and orogenic activities. Several models have attempted to explain the north–south (N‒S) collision and east–west (E‒W) extension based on geological and geophysical observations. Among them, the subduction of the subducted Indian lower crust (SILC) and the deep geometric shape of the southern Tibetan rifts are still controversial. To address these issues, we selected P‐ and S‐wave arrival times from 35,193 earthquakes recorded by 575 permanent and temporary stations and applied an improved double‐difference tomography method to obtain high‐resolution 3‐D P‐ and S‐wave velocity structures of the crust and uppermost mantle and relocated earthquake event locations around the IECCZ. The N‒S velocity profiles display a northward‐subducting high‐velocity layer stretching from the 20–40 km depth range in the Himalayan belt to the 50–60 km depth range beneath the northern Lhasa terrane (NL), suggesting that the eclogitized SILC extended beyond the Indus–Yarlung suture, reaching the NL. Additionally, the E‒W velocity profile at the SILC front reveals a discrete high‐velocity layer at depths of 40–60 km beneath the Longgar, Tingri–Nyima, Xianza‐Dinggye, and Yadong–Gulu rifts, implying that the SILC experienced tearing. Based on a comprehensive analysis of the seismicity, large‐earthquake source mechanisms near the Moho, and tomographic images of the study area, we proposed a new dynamic model of the India–Eurasia collision and N–S‐trending rifts. The significant characteristic of this model is that the rifts cut through the crust obliquely, not vertically.

Evidence from zircon and apatite thermochronology provides evidence for the tectonic-thermal evolution and denudational processes in Dulan, Eastern Kunlun Mountains, China

Since the Middle Jurassic, the East Kunlun orogenic belt in China has undergone significant denudation. This region offers crucial insights into the tectonic processes that have shaped the Tibetan Plateau. Moreover, the region boasts abundant mineral resources. This study uses techniques, such as zircon and apatite fission track (ZFT&AFT) analyses as well as citing several apatite (U-Th)-He (AHe) ages and FT ages data from the study areas, to unravel the tectonic-thermal evolution and denudation processes. The results reveal ZFT ages spanning from 167 ± 5 to 92 ± 4 Ma, and AFT ages spanning from 116 ± 6 to 64 ± 4 Ma. Based on the AFT, ZFT, and AHe data, this paper constructed a tectonic-thermal history model. In the first stage (ca. 170–120 Ma), rapid cooling at 2.00 ℃/Ma and denudation of 2.85 km occurred. The second stage (ca. 120–20 Ma) showed cooling rates of 0.60 ℃/Ma and denudation of 1.70 km. In the third stage (ca. 20–0 Ma), rapid cooling with rates of 1.50 ℃/Ma and denudation of 0.86 km were speculated. The first stage indicates the closure of the Paleo-Tethys Ocean in the Middle Jurassic, with the collision of the Lhasa and Qiangtang blocks with Eurasia along the Bangong-Nujiang suture zone in the Cretaceous. The second stage is mainly related to the northward subduction of the Neo-Tethys Ocean and the far-flung effects of the India-Eurasia collision. The uplift of the Tibetan plateau due to the Himalayan orogeny likely contributed to the third stage. The denuded thickness in the study area since 170 Ma is 5.41 km.

India–Eurasia convergence speed-up by passive-margin sediment subduction

The fast increase of convergence rate between India and Eurasia around 65 million years ago (Ma)—from approximately 8 cm yr−1 to a peak rate of approximately 18 cm yr−1—remains a complex geological event to explain1–8, given the inherent uncertainty surrounding the tectonic history and the intricate interplay of forces influencing plate speed9–11. Here we use a combination of geochemical analysis and geodynamic modelling to propose that this rapid convergence can be explained by sediment subduction derived from the northern Indian passive margin. Through isotope and trace element analysis, we find an enhanced contribution of terrigenous sediment melt to the mantle source of the Gangdese magmatic rocks around 65 Ma, concurrent with the acceleration of India–Eurasia convergence. Numerical experiments suggest that subduction of sediments more than 1 km thick covering an approximately 1,000-km-wide ocean basin abutting the northern Indian passive margin starting from 65 Ma could have spurred the increased convergence rate and further led to significant crustal extension, consistent with empirical observations. Our study implies that the acceleration of India–Eurasia convergence marks the arrival of passive-margin-derived sediments, constraining the initial India–Eurasia collision to be around 60 Ma. It further suggests that temporary accelerations in subduction rates might be a common feature at the final stage of continental assembly.

Chronology, structures and salt tectonics in the northern Kuqa Depression, NW China: Implications for the Cenozoic uplift of Tian Shan and foreland deformation

Foreland fold-and-thrust belts (FTBs) are shaped by the coupled influence of surface processes (e.g., erosion, sedimentation) and deep geological processes (e.g., plate rheology, flexure and kinematics) across various timescales. These processes record multiple phases of orogenic evolution and are crucial for understanding the interplay between mountain building and the sedimentary basin filling. In this paper, we conducted an integrated study including magnetostratigraphy of exposed strata, detailed field investigations and interpretations of subsurface seismic profiles in the northern Kuqa Depression. This study aims to elucidate the tectonic uplift of the Tian Shan by examining salt-related structures. The present findings reveal that diapirism in the study area commenced in the early Eocene and continued at least into the late Miocene. Notably, the Tuzimaza diapir has been significantly squeezed due to regional contraction since ∼5.3 Ma. The exposed growth strata were primarily compressional, rather than halokinetic, suggesting the lateral expansion of the Tuzimaza anticline since the latest Miocene (∼5.3 Ma). This expansion was a response to the far-field effects of the Indian-Eurasian collision. We propose that the local activation of the Tian Shan likely initiated in the early Oligocene (∼34 Ma), with three subsequent episodes of deformation occurring ∼24 Ma, ∼10 Ma and ∼ 5.3 Ma. The earlier episodes can be attributed to basement uplift in the northern Kuqa Depression, whereas the later episode starting at ∼5.3 Ma reflects more intensive deformation across the entire foreland, indicative of the steady outward growth of the Tian Shan. Collectively, all these tectonic events have contributed to the formation of the modern Tian Shan.

Earthquake Sequence Simulation and Hazard Analysis in the Tianshan Orogenic Belt and Adjacent Areas

ABSTRACT The Tianshan orogenic belt is located in central Eurasia. Its tectonic deformation and seismicity are primarily influenced by the far-field effect of the India–Eurasia collision. It is one of the regions with the most intensive seismicity in China. Understanding the mechanisms of earthquake nucleation in this region is a hot topic in the seismicity community. The numerical simulation of earthquake sequences is an efficient measure for comprehensively exploring earthquake occurrence characteristics, tectonic loading, and subsequence patterns. It is also an important method for predicting and mitigating earthquake disasters. This study utilized a finite-element model to investigate the evolution of regional historical earthquakes via the split-node method. Coulomb failure stress analyses from interactions of simulated historical earthquakes since 1900 indicate that the Taxkorgan fault may be prone to the next significant earthquake event.

The Miocene Acceleration of Strike-Slip Deformation in the Northern Tian Shan, Central Asia

Abstract The Tian Shan has been deformed during the Cenozoic as a far-field response to the India–Eurasia collision. This contribution reports new apatite fission-track (AFT) and apatite (U-Th)/He data from the northern Tian Shan, including areas along the southern margin of the Junggar Basin and adjacent to the western segment of the Bolokenu-Aqikekuduk Fault (BAF). Thermal history modeling of the presented data suggests that the Cenozoic exhumation along the basin margin started >20 Ma, and the oblique-slip BAF could have been active since at least ~10 Ma with a total exhumation magnitude of ~2 km during the late Cenozoic. Since then, the mean exhumation rate on southern wall of the BAF is comparable to the Quaternary uplift rate previously measured on the same segment of the fault. To examine the extent of the Miocene acceleration of the transpressional deformation pattern, an exhumation model since 50 Ma was established by inverse modeling >1000 published and new AFT and (U-Th)/He ages from the Tian Shan and the northeastern Tibetan Plateau. The model suggests that after the initial unroofing, a significant acceleration in exhumation occurred during 15–10 Ma, in regions including the interiors of northern and southwestern Tian Shan near major strike-slip structures. This change coincided with the northward propagation of the Pamir and the eastward expansion of the northeastern Tibetan Plateau along the west and south margins of the Tarim Basin, respectively.

The Miocene Acceleration of Strike-Slip Deformation in the Northern Tian Shan, Central Asia

Abstract The Tian Shan has been deformed during the Cenozoic as a far-field response to the India–Eurasia collision. This contribution reports new apatite fission-track (AFT) and apatite (U-Th)/He data from the northern Tian Shan, including areas along the southern margin of the Junggar Basin and adjacent to the western segment of the Bolokenu-Aqikekuduk Fault (BAF). Thermal history modeling of the presented data suggests that the Cenozoic exhumation along the basin margin started >20 Ma, and the oblique-slip BAF could have been active since at least ~10 Ma with a total exhumation magnitude of ~2 km during the late Cenozoic. Since then, the mean exhumation rate on southern wall of the BAF is comparable to the Quaternary uplift rate previously measured on the same segment of the fault. To examine the extent of the Miocene acceleration of the transpressional deformation pattern, an exhumation model since 50 Ma was established by inverse modeling >1000 published and new AFT and (U-Th)/He ages from the Tian Shan and the northeastern Tibetan Plateau. The model suggests that after the initial unroofing, a significant acceleration in exhumation occurred during 15–10 Ma, in regions including the interiors of northern and southwestern Tian Shan near major strike-slip structures. This change coincided with the northward propagation of the Pamir and the eastward expansion of the northeastern Tibetan Plateau along the west and south margins of the Tarim Basin, respectively.

Miocene adakitic monzogranites in the Northeast Pamir: Evidence for post India-Eurasia collisional evolution

The Pamir Plateau contains critical information on the tectonic evolution of the Tethys domain. In this study, we report geochronology, geochemistry, and Sr-Nd-Hf isotopic compositions of the Cenozoic adakitic monzogranite in the Reskam and Taxkorgan areas, NE Pamir, to provide new insights into the post-collisional tectonic evolution following the India-Eurasian collision. Zircon UPb ages reveal these granitoids were emplaced at ca 12–8 Ma. Geochemically, they exhibit relatively uniform whole-rock major and trace element compositions, and share typical adakitic signatures with high SiO2 (68.55–73.30 wt%), moderate Al2O3 (14.11–15.84 wt%), elevated Sr (399–1710 ppm) and La (34–182 ppm), but low Y (5.53–15.10 ppm) and Yb (0.39–1.26 ppm), and thus in high Sr/Y (32−200) and (La/Yb)N ratios (20–236). Isotopically, these adakitic rocks show significantly enriched whole-rock SrNd (εNd(t) = −7.97 to −5.76; 87Sr/86Sr(t) = 0.7072–0.7110) and zircon Hf (mostly εHf(t) -5 to −2) isotopic compositions. Elemental and isotope signatures indicate their origin from partial melting of mafic-intermediate sources under high pressure, with a residuum of negligible feldspar but dominant garnet. Integrating the new findings with reported data of granitoids in the Pamir, we estimate the crustal thickness variations from the Cretaceous to Miocene. The crustal thickness in the Pamir region largely remained no more than 45 km before India-Asia collision, after which a significant increase in crustal thickness occurred, reaching a peak of 80–100 km around 10 Ma. We propose that the break-off of the subducted Neo-Tethys oceanic slab (ca. 40 Ma) and lithospheric delamination (ca. 25 Ma) led to two-stage rapid continental uplift events in Pamir Syntax.

Paleolatitude of Mafic Dykes in the Xiugugabu ophiolite: Implications for the intraoceanic Trans-Tethyan subduction zone and multistage India-Eurasia collision

An intraoceanic Trans-Tethyan subduction zone has been identified in both the Kohistan-Ladakh arc and the West Burma Terrane. This has significant implications for the India-Eurasia collision. Concurrently, the dismembered ophiolites within the Yarlung-Tsangpo Suture Zone likely originated from the intraoceanic Trans-Tethyan subduction zone or the Andean-type southern Eurasian continental margin. A paleomagnetic study was conducted on the Lower Cretaceous (∼120–130 Ma) mafic dykes in the Xiugugabu ophiolite to resolve the uncertainty of its origin. The characteristic remanent magnetization (ChRM) obtained through stepwise thermal demagnetization successfully passed consistency/fold and reversal tests. After tilt correction, the overall mean direction of the ChRM was D = 296.9°, I = −25.5°, k = 47.6, α95 = 4.5°, and N = 22, indicating a paleolatitude of 13.4°N/S and a paleopole at 15.0° N, 326.6°E with A95 = 3.8°. Compared with previous paleomagnetic data from the Trans-Tethyan subduction zone, our findings strongly support the involvement of the Xiugugabu ophiolite in the intraoceanic Trans-Tethyan subduction zone. This finding reinforces the hypothesis that there were two distinct subduction zones in the Neotethyan Ocean during the Early Cretaceous. One subduction zone was situated on the southern margin of the Gangdese Arc. The second was the intraoceanic subduction zone, located approximately 3500 km from the southern margin of Eurasia, in the southern hemisphere. Our results also support a multistage India–Eurasia collision process involving continental plates, intraoceanic arcs, and terranes within the Neo-Tethyan Ocean.

Late Miocene Oroclinal Bending of the Mazatagh Thrust Belt in the Central Tarim Basin and Its Tectonic Implications

AbstractThe arcuate Mazatagh thrust belt (MTB) in the central Tarim Basin is one of the key regions for understanding the Cenozoic intracontinental deformation in response to the India–Eurasia collision. However, whether it was formed due to oroclinal bending and its kinematic processes remain unclear. Here, we present a detailed paleomagnetic rotation study at Hongbaishan in the middle MTB to shed new light on the deformation in this region. Positive fold and reversal tests of 50 site means suggest primary magnetizations. The paleomagnetic declinations indicate ∼14.6 ± 8.5° absolute clockwise rotation at Hongbaishan since the late Miocene (∼7.6 Ma). Together with the rotation results calculated from Hongbaishan‐1 and Mazatagh magnetostratigraphic data sets in the southeastern MTB, these results reveal an increasing magnitude of clockwise rotation along the belt toward its southeastern tip. Positive oroclinal tests along the MTB suggest the occurrence of oroclinal bending that curved the originally straight MTB before and during the deposition of its lower part, and nearly half of the bending had occurred during the deposition of its upper part. This oroclinal bending is mostly attributed to the northward indentation of the West Kunlun Mountains along the décollement salt‒gypsum layers and further implies ∼7.9° absolute clockwise rotation of the Tarim Basin since the late Miocene. Integrating these findings with other lines of geological evidence around the Tarim Basin, we propose that episodic widespread tectonic deformation with basinward propagation occurred since the late Miocene due to the far‐field effect of the continuous northward indentation of the Indian Plate into Eurasia.

Active Tectonic Deformation of the Qilian Shan, Northeastern Tibetan Plateau

Abstract —The Qilian Shan (or Qilian Mountains), located on the northeastern margin of the Tibetan Plateau, is an actively growing orogenic belt resulting from the far-field impact of the India–Eurasia collision. The northward penetration of the Indian Plate is responsible for intense crustal shortening in the Qilian Shan. However, the tectonic deformation pattern in response to the crustal shortening remains unclear. In this study, we present the regional seismicity, fault activity, and GPS crustal movement velocity field to characterize the active tectonic deformation of the Qilian Shan based on historical data over the past two decades. The results suggest that the western Qilian Shan is characterized by distributed north–south crustal shortening, while the eastern Qilian Shan is dominated by blocklike eastward extrusion of crust along major strike-slip faults coupled with clockwise rotation. North–south crustal shortening and east–west lateral extrusion, two deformation modes responding to the India–Eurasia convergence, match the crustal deformation in the Qilian Shan. The tectonic deformation of the western Qilian Shan is largely in agreement with the former, while the eastern Qilian Shan corresponds closely to the latter. Lower crustal flow beneath the central Tibetan Plateau provides the potential driving force to induce the eastward extrusion of crustal material out of the plateau and the growth of some boundary mountain ranges, such as the Qilian Shan.

Identification of carbonated eclogitic source for Cenozoic intraplate alkaline basalts from western Central Asia and its geodynamic implication

Carbonated eclogite has been identified as a significant component in the formation of intraplate alkaline basalts, typically attributed to stagnated subducted oceanic slabs, such as the Pacific plate beneath eastern China. However, it is unclear whether this component exists in other tectonic settings. Here, we present new zircon UPb geochronology, mineral chemistry, and geochemical analyses of Cenozoic Tuoyun basanites and alkaline basalts from western Central Asia, where stagnated subducted oceanic slabs are absent, to elucidate the source properties and associated geodynamic processes. Olivine compositions (e.g., moderate Ni concentrations, low Mn/Fe and Ni/(Mg/Fe) ratios) and whole-rock chemistry (e.g., high Fe/Mn, Ca/Al, and Zr/Hf ratios, TiO2 contents, and weak anomalies of Zr-Hf-Ti) suggest a carbonated eclogite in the mantle source of the Tuoyun basanites. Trace elements (positive NbTa anomalies and absence of positive Eu anomaly) and depleted to slightly enriched Sr-Nd-Hf isotopic compositions indicate that the basanites originated from mantle sources composed of variable proportions of altered oceanic crust (AOC) and carbonates. Synthesizing regional geochemical, geophysical studies and tectonic history, we propose that the continuous India-Eurasia collision triggered mantle upwelling, leading to the formation of a widespread carbonated eclogitic mantle source beneath western Central Asia. Our findings suggest that carbonate-rich mantle sources may also be present in areas without stagnated subduction slabs.

Stress regimes in the Himalaya–Karakoram–Tibet, the western part of India–Eurasia collision: stress field implications based on focal mechanism solution data

SUMMARY The stress regime patterns of high-seismically active regions within the western part of the India–Eurasia collision, spanning from 67° E to 83° E and 27° N to 39° N, are elucidated through analysis of 684 Focal Mechanism Solutions from 1962 to 2021. Eighteen seismically active zones used for the stress tensor inversion, are defined based on the spatial extent of the seismicity, the depth distribution of seismic events, focal mechanism studies, and seismotectonics of the region. The defined regimes are: (1) Sulaiman Ranges and Lobe Region, (2) Hindukush, (3) Pamir, (4) Nanga Parbat Syntaxis, (5) Hazara Syntaxis, (6) Kashmir–Zanskar region, (7) Kangra–Chamba, (8) Kinnaur and Kaurik–Chango fault zone (KCFZ), (9) Garhwal, (10) Kumaon, (11) Karakoram fault zone, and (12) Gozha–Ashikule fault zone. Seismicity is reported only in the crust or up to mid-crust in most of the regions, except for the Pamir and Hindukush, where the seismicity can be observed down to 160 and 280 km, respectively. We report a clockwise rotation of the maximum horizontal stress (SHmax) of about 42° and 21° in the Hindukush and Pamir regions, respectively. with increasing focal depths from north west to north. The region where major and strong earthquakes occur indicates pure compressive regimes. Most of the zones support transpressive and transtensional tectonics with a few zones by normal and strike-slip fault regimes. Regions like Nanga Parbat syntaxis, Kinnaur, KCFZ, and Zanskar are exceptions, where extensional and transformational tectonic features dominate. Plate convergence force has less effect on defining the stress regime in the Karakoram fault zone and Gozha–Ashikule regions, which display transtensional and pure extensional regimes, respectively. Underthrusting of the Indian plate through complex tectonics is indicated by dominant compression stresses with evidences of normal, strike-slip, and oblique fault mechanisms.

Development of major unconformities in the forearc regions: A signal of west Myanmar−Asia assemblage before the late Paleocene

It has long been debated whether the India-Eurasia collision was a single-stage event that began 60-55 million years ago, or whether it was a two-stage process that involved a collision between India and the Trans-Tethyan Arc before the early Paleocene, and the collision of India with Eurasia during the middle Eocene. Here, we report a late Paleogene angular unconformity (ca. 40-28 Ma) in western Myanmar. This angular unconformity developed around the same time as the Assam unconformity (NE India) but is younger than those found in northern Myanmar. Development of these unconformities indicates that an oblique convergence margin in western Myanmar formed before the middle Eocene, with a major dextral strike-slip fault (proto-Sagaing/Shan Scarp Fault) in the backarc. We interpret this oblique convergence margin to be partial continental collision between the West Myanmar Terrane (WMT) and NE India. In backarc regions, syn-rift successions of the Shwebo sub-basin have formed as a consequence of transtensional tectonics along the proto-Sagaing/Shan Scarp Fault since at least the late Paleocene. The syn-rift successions consist of Asian-derived materials that were not identified in the forearc because of the Wuntho-Popa Arc served as a geographical barrier. The presence of the unconformities and tectonic configuration of the Myanmar backarc sub-basins are inconsistent with the scenario inferred from paleomagnetic data, in which the WMT was part of an intra-oceanic arc at near-equatorial latitudes before the late Oligocene. Instead, we propose that the WMT has been part of continental SE Asia since at least the Paleocene (ca. 60-58 Ma). We reconsider the paleomagnetic data and suggest that the Mawgyi Arc, rather than the WMT, is the oceanic fragment that rifted from the northern Gondwana margin during the Late Jurassic. The Mawgyi Arc collided with continental SE Asia (WMT) during the Late Cretaceous, and then with India during the early Eocene (ca. 51-49 Ma). Our results support the collision between India and Eurasia is a multistage event.

Geodetic constraints on three-component motion of the Ordos block (China) and their implications for lithospheric dynamics

Abstract The Ordos block is a rigid portion of the North China Craton lying within the India-Eurasia collision zone that experiences little internal deformation, but is surrounded by active faulting, extensional grabens, and seismicity. In the surrounding region, geodetic studies have imaged complex crustal deformation, while seismic studies have suggested that the lithosphere is encountering regional modification by mantle convection. The Ordos block thus presents a valuable opportunity to compare seismic and geodetic constraints and investigate geodynamic processes affecting the region’s lithosphere. We here robustly image vertical land motion and horizontal strain rates using observations from the geographically extensive Global Navigation Satellite System and leveling networks in and around the Ordos block. Our results indicate that the Ordos block uplifts with some lateral variability at 0.5–2.0 mm/yr. In the northeastern Ordos block and Datong volcanic area, the crustal uplift rates are 2.0–4.0 mm/yr on average, much faster than those elsewhere on the block. We correct for non-tectonic vertical motion from surface hydrological loading and glacial isostatic adjustment, finding that these do not explain the vertical rate anomalies. Horizontal crustal extension and uplift are accompanied by a pattern of crustal contraction at the Datong volcanic field. Additionally, we find uplift west of and subsidence east of the Qinling Orogenic Belt, which are inconsistent with eastward crustal extrusion along it, suggesting instead a negligible migration of crustal materials especially to the east of 106°E. Comparing the geodetic measurements to evidence from seismic velocity anomalies and numerical simulation, we argue that the motions are consistent with lithospheric re-equilibration resulting from the heterogeneous thinning of the lithosphere by convective mantle upwelling and radial flow as well as shortening from the India-Eurasia collision.

Reconstruction of the thermal evolution since the late paleozoic in the Ounan Sag, Eastern Qaidam Basin, NW China: New constraints from vitrinite reflectance data and (U–Th)/He thermochronology

Reconstructing the thermal evolution of the eastern Qaidam Basin is important for gaining a deeper understanding of its lithospheric geodynamics and for more accurate hydrocarbon evaluation and prediction. This article presents a set of new apatite and zircon (U–Th)/He thermochronological ages. Combined with 336 vitrinite reflectance (Ro) data, the thermal history of the Ouanan Sag in the eastern Qaidam Basin has been reconstructed using inversion models. Three detrital samples from the Ounan Sag shows that the apatite (U–Th)/He ages are primarily concentrated in the range of 17.0 Ma to 76.5 Ma and that the zircon (U–Th)/He ages range from 200 Ma to 289.3 Ma. The time-temperature models demonstrate that the Ounan Sag experienced rapid subsidence and heating from the Carboniferous to late Permian, and exhumation/cooling events from the end of Permian to the Triassic. This thermal evolution was influenced by the widespread intrusion of plutons, and the collision and orogenesis caused by asthenosphere upwelling below the Qaidam arc, and slab rollback of the Southern Kunlun oceanic lithosphere, respectively. Additionally, our models depict the main exhumation/cooling stages since the Paleogene and a reheating event in the Miocene as a result of the intensifying growth of the Qinghai–Tibet Plateau and local sedimentary loading, followed by the initial India–Eurasia collision. Furthermore, the eastern Qaidam Basin experienced consistent heating during the late Paleozoic, reaching the maximum paleotemperature and geothermal gradient in the late Permian, with values of ∼230 °C and ∼43–44 °C/km, respectively. This study suggests that the source rocks in the most upper member of upper Carboniferous Keluke (C2k) Formations in the Ounan Sag reached the gas generation stage in the late Permian.

Sluggish rise of the western Gangdese mountains after India-Eurasia collision

With the most prominent topography on Earth, the Tibetan Plateau has profound influences on the hydrologic cycle and climate dynamics in Asia. However, the regional uplift history of the Tibetan Plateau remains highly debated. Here, we use europium anomalies and LREE/HREE ratio in detrital zircon, combined with whole-rock La/YbN ratio, to constrain the crustal thickness and topographic evolution of the Gangdese mountains in southern Tibet. Europium anomaly, controlled by pressure-sensitive minerals plagioclase and garnet, has been shown to correlate with crustal thickness. Our results reveal contrasting crustal thickening histories of the eastern (east of ∼88°E) and western (west of ∼88°E) parts of the Gangdese. Prior to the India-Eurasia collision (∼60–55 Ma), the crust of the eastern Gangdese thickened continuously from ∼40 km to nearly 60 km, while the western Gangdese maintained a mildly thickened crust of ∼50 km. Both parts underwent substantial thinning (to 40–45 km) immediately before the India-Eurasia collision, but the eastern Gangdese re-thickened rapidly afterwards. In the western Gangdese, post-collisional thickening was delayed until ∼40–20 Ma, which resulted in a mild elevation of ∼2000 m for most areas of southern Tibet until the late Oligocene. This diachronous uplift of the Gangdese after collision may have resulted from more mantle-derived magma additions in the eastern Gangdese before collision, which could rheologically weaken its lithosphere. We suggest that the diachronous uplift of the Gangdese after the India-Eurasia collision may have dominated the moisture transfer pattern across southern Tibet through the late Eocene and intensified the South Asian monsoon through the Oligocene-Miocene boundary (∼25–20 Ma).