{"paper_id":"4401abc5-fd61-4de9-ae25-55ca8cd4df9c","body_text":"Endogenic mantle-driven orogenic evolution: Slab rollback dynamics as the architect of retreating accretionary systems | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Endogenic mantle-driven orogenic evolution: Slab rollback dynamics as the architect of retreating accretionary systems Guochun Zhao, Xing Cui, Liangliang Wang, Ian Cawood, Peter Cawood, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6210811/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Retreating accretionary orogens exhibit a paradoxical capacity to sustain crustal shortening and growth contemporaneous with dominant upper plate extension. Deciphering the dynamic coupling between mantle flow and crustal evolution is critical in understanding orogenic mechanisms within such retreating systems, with profound implications for subduction zone dynamics and continental growth processes. Here we integrate high-resolution 2D numerical simulations, with quantitative geological boundary conditions from the Paleozoic Altaides archetype, to establish an endogenic orogenic mechanism driven by slab rollback-induced mantle circulation during retreating subduction. Our models demonstrate that spontaneous mantle upwelling and convections could systematically govern (1) progressive trench-directed arc migration, (2) crustal growth through intense bimodal magmatism with juvenile isotopic signatures, (3) self-organized forearc-arc-backarc-intraplate tectonic zoning, and (4) crustal thickening-extension cycles and diachronous coexistence, all of which characterize the Altaides and other archetypal retreating accretionary orogens. This intrinsic interplay between slab rollback, mantle upwelling, and upper plate response supersedes previous models dependent on external orogenic forcing, offering a unified framework to interpret accretionary orogens via deep Earth-surface interactions. Earth and environmental sciences/Solid Earth sciences/Geology Earth and environmental sciences/Planetary science/Geodynamics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Mountain belts (orogens) are traditionally classified into collisional and accretionary endmembers 1 . Collisional orogens follow terminal ocean closure and continental collisions, accompanied by crustal stacking and remelting of preexisting crustal material (for example, Himalayan-Karakoram-Tibetan orogen 2 ). In contrast, accretionary orogens develop at convergent margins during protracted oceanic subduction, like modern circum-Pacific orogenic belts, where crustal growth occurs via accretion of exotic terranes or emplacement of mantle-derived magmas 1 , 3 – 5 . A challenge in understanding accretionary orogenesis is identifying the mechanism of crustal shortening and uplift during the ongoing subduction without continental collision. Current paradigms attribute compression in \"advancing\" accretionary orogens to enhanced plate coupling either through attempted subduction of buoyant lithosphere or plate reorganizations resulting in transient adjustments in the relative convergence rate across the accretionary plate boundary 1 , 6 , 7 (Fig. 1 a and b ). Such mechanisms well explain features like inboard foreland thrust belt and basin, and narrow and long-lived magmatic belt (for example, the Mesozoic Canadian Cordillera accretionary orogen 8 ). Crustal growth, if any, occurs through lateral amalgamation of multiple terranes. However, these mechanisms fail to explain features specific to \"retreating\" accretionary systems, where overriding plate extension dominates despite continuous convergence (Fig. 1 c). These systems usually exhibit back-arc spreading, yet paradoxically record transient orogenesis (mountain-building) and crustal growth, without significant terrane accretion 9 – 13 . Deciphering the evolutionary pathways of such systems is essential to unraveling the continuum of accretionary orogenesis and the mechanisms driving continental crustal growth. Numerous 2D and 3D numerical as well as analogue modelings have demonstrated how slab-mantle interactions modulate the balance between compressional and extensional deformations within the overriding plate (for example, refs. 14 – 19 ). Indeed, mantle processes, particularly those associated with slab rollback and the consequent reorganization of mantle wedge convection, may play a critical, but yet underexplored, role in the formation and evolution of retreating accretionary systems 16 , 19 – 21 (Fig. 1 c). In this study, we synthesize the major characteristics of retreating accretionary orogens and integrate multiscale geological data from an archetypal example, the Paleozoic Altai Orogen in Altaides (also named Central Asian Orogenic Belt; one of the largest accretionary orogen with significant Phanerozoic continental growth 22 – 24 ). We then apply a novel 2D thermo-mechanical modeling based on geological calibration to unravel the interplay of slab retreat, induced mantle wedge convection, and the resulting tectonothermal responses. The numerical model successfully reproduces the dominant features of retreating accretionary systems, and captures the whole lithosphere- and asthenosphere-scale observed geological record of the Altai Orogen. Specifically, it replicates the migration history of the magmatic arc, pervasive and sustained magmatism, back-arc extension, and diachronous crustal deformation. Our study proposes a new endogenic orogenic model, which highlights the pivotal role of retreat-modulated reorganization of mantle flow and its coupling with the crust in shaping retreating accretionary orogens. Geological characteristics of retreating accretionary systems In addition to the prominent extensional features, as exemplified by modern Western Pacific subduction systems, detailed geological investigations of ancient retreating-type orogens have revealed a comprehensive suite of diagnostic characteristics. Notable examples include the Paleozoic Lachlan and New England segments of the Terra Australis Orogen in eastern Australia 6 , 9 , Mesozoic-Cenozoic Western Pacific subduction systems 25 , Proterozoic southwestern United States terranes 13 , and specific components of the Altaides 26 . These accretionary systems, generally, though not universally, exhibit the following characteristics across spatial and temporal scales: (1) deposition of quartz-rich turbidites in low-grade sedimentary basins; (2) prolonged trench retreat accompanied by progressive arc migration; (3) intensive syn-tectonic granitic magmatism; (4) presence of rift basins associated with lithospheric thinning; and (5) regional metamorphic gradients ranging from greenschist to amphibolite facies. Crucially, prolonged extensional phases are intermittently interrupted by short-lived compressional events. Despite shared traits, each orogen follows a unique evolutionary path shaped by boundary conditions, necessitating focused studies on well-preserved systems to refine geodynamic models. The early-middle Paleozoic Altai Orogen, located in the western Mongolia Collage of the Altaides 24 , preserves many of the characteristic attributes of retreating orogens, and its exceptional preservation of geological records and minimal post-orogenic modification make it a premier natural laboratory under this paradigm. The Altai Orogen consists of Precambrian microcontinents in the east, acting as the tectonic nuclei around which younger arcs and associated accretionary complex in the west accreted 27 (Fig. 2 a). The Lake Zone represents a Neoproterozoic island arc 28 and docked with the continental basement in the late Cambrian 29 . The Altai Zone lacks evidence for an underlying Precambrian basement related to the westward extension of the microcontinents beneath the zone 7 , 30 – 34 . Integrating data from detrital zircon provenance statistics, high-precision geochronology (zircon U-Pb, Ar-Ar thermochronology), quantitative P-T-t reconstructions via phase equilibrium modeling and strain analysis (see Methods ) of the studied region has revealed a lengthy retreating accretionary history over 150 Myr, summarized in Fig. 2 b and as follows. 1. Trench retreat and mantle-crust interactions The Altai Orogen chronicles a long history of westward trench retreat (> 300 km), marked by systematic migration of magmatic arcs from the Ikh-Mongol Arc to the current Chinese Altai (ca. 520–370 Ma; Fig. 2 b). Calc-alkaline granites and bimodal volcanism delineate arc progression, whereas backarc basin basalts and intraplate alkaline granites and OIB-type basalts signal asthenospheric upwelling under extensional regimes (see Supplementary Section S2; Fig. S4 ). This magmatic evolution aligns with models of stagnant slab dynamics and big mantle wedge formation, where enriched asthenospheric components derived from the stagnant slab could contribute to the intraplate-like magmatism (for example, refs. 10 , 35 ). Geochemical and isotopic data (e.g., positive zircon εHf(t) values; Table S2 and Fig. S5 ) reveal juvenile crustal growth dominated by mantle-derived melts, with minimal input from Precambrian basement rocks. The enhanced asthenosphere engagement and thermal input sustained low-pressure/high-temperature metamorphism (3–6 kbar, 570–750°C; Table S3 ) over ca. 80 Myr. 2. Sedimentary dynamics and crustal maturation Rapid trench retreat generated forearc basins filled with immature turbidites sourced from arc erosion (see Section S1 ). These sedimentary sequences, characterized by low compositional maturity, evolved into permeable crustal reservoirs prone to remelting and anatexis (e.g., S- and I-type granites; see Section S2 ). This process drove self-maturation of the crust, transforming rheologically weak sedimentary packages into magmatic plutons and localized fold-thrust belts during episodic compression. The interplay between extension-driven magmatism and sedimentary recycling emphasises a feedback mechanism that facilitates crustal maturation and stabilization in retreating systems. 3. Spatiotemporal stress field partitioning and thermal legacy The Altai Orogen exhibits diachronous compression-extension cycles, reflecting tectonic decoupling across its domains (Fig. 2 b; see Section S3 ). The Hovd Zone records late Ordovician (ca. 460–440 Ma) compression transitioning to prolonged extension, while the Altai Zone experienced Silurian (ca. 435–415 Ma) compression followed by > 50 Myr of extension. These two deformational events were not correlated with terrane addition, whereas the successive east to west compression and exhumation since the late Devonian occurred concurrently with the vertical frontal collision of the peri-Siberian complex from the north 36 , which is not considered in the east-west directed subduction process. The thermal anomalies, preserved in metamorphic gradients from Barrovian belts to rift-related assemblages (Fig. 2 b), provide critical constraints for modeling lithospheric thinning and heat transfer in retreating systems. Numerical modeling for retreating accretionary systems To decipher the first-order geodynamic process governing retreating orogens, we developed 2D thermo-mechanical simulations constrained by the diagnostic characteristics of the Altai Orogen. Model parameters, boundary conditions, and methodological details are described in Methods . Firstly, a series of parametric numerical experiments were conducted to test the influence of convergence duration, oceanic plate age, and initial subduction angle on orogenic styles, revealing a spectrum of tectonothermal responses with details provided in Section S5 . A reference model, selected for its optimal representation of observational constraints, forms the basis of our detailed analysis (Fig. 3 ). Although calibrated against the Altai Orogen, our simulations transcend regional complexity to reveal dynamics applicable to retreating accretionary systems globally. In the reference model (Model B in Section S5 ), the oceanic plate is initially driven to subduct beneath the continental lithosphere by an exerted external pushing force, forming the shallow dipping subduction zone within the first 20 Myr. As subduction transitioned into a self-sustaining mode, the negatively buoyant slab immediately steepens and undergoes rapid rollback (Fig. 3 a), resulting in the slab retreating some 300 km, from around 2750 km to 2450 km, by approximately 40 Myr (Fig. 3 b). Concurrently with trench retreat, the overriding plate shows strong extension and significant lithospheric thinning inboard of the trench, potentially driving formation of new oceanic crust. This process results in toroidal mantle flows, including asthenospheric upwelling in the mantle wedge (indicated by the white arrows) and small-scale convection cells in the back-arc (~ 2850 km; Fig. 3 b) that develop bilateral lithospheric underflow. As slab rollback continues, the subducting slab flattens as it encounters the mantle transition zone at ~ 600 km depth, forming a big mantle wedge structure. By approximately 56 Myr, the trench has retreated to ~ 2300 km, and another significant area of mantle upwelling emerges at the rear of the extended region (~ 2600 km). This upwelling zone coincides with the extreme overlying lithosphere thinning area, where the mantle flows horizontally and downward on both sides (Fig. 3 c and g ). The process persists until around 70 Myr, by which time the subducting slab angle increasingly shallows, with concomitant expansion of the big mantle wedge (Fig. 3 d). Under the influence of the upwelling asthenosphere, the lithosphere at the former accretionary wedge exhibits variable thickness and coexisiting compression and extension, while zones of mantle upwelling and downwelling occur inboard from the trench (> 3100 km) that corresponds to intraplate areas. Linking numerical simulations to geological constraints While 2-D numerical modelings are unable to fully encapsulate the inherent multiscale complexity of natural subduction zones and precisely replicate spatiotemporal geological relationships, they effectively reproduce the observed crustal kinematics, deformation, and magmatic evolution of retreating orogens, typified by the Altai Orogen. Integrating the numerical simulations with geological constraints shows a fundamental linkage between slab rollback mantle dynamics and the tectonothermal responses of retreating accretionary systems during the prolonged evolution: During the initial subduction phase, trench-directed corner flow establishes compressive stresses at the accretionary front (Fig. 4 ) while possible hydrous flux melting beneath the Ihk-Mongol arc generates calc-alkaline magmas (Fig. 2 ). As soon as the slab rollback begins (Fig. 3 a), the mantle corner flow could have impinged and heated the upper plate inboard of the trench location, which may explain the late Cambrian crustal anatexis in the Chinese Altai (Fig. 2 b). As the convergent plate margin evolved, the trench steadily retreats and the stress field of the upper plate shifts from compression to extension by around 40 Myr (Figs. 3 b and 4 ). This transition is marked by rapid rollback of the subducting slab and upwelling of the asthenosphere. As a result, the mantle wedge exhibits relatively low viscosity (η < 10¹⁹ Pa·s) and weaker rheological properties (Fig. 3 f). Concurrently, a reorganization of the mantle flow pattern occurs with flow vectors bifurcated into trench-parallel and slab-perpendicular components. The enhanced trench-directed mantle flow accelerates wedge extension, whereas the slab-perpendicular mantle flow in turn further promotes rollback of the slab. The thermal weakening effect (ΔT > 200°C) exerted by the upwelling asthenosphere on the overlying lithosphere facilitates further mantle upwelling and sustains adiabatic decompression melting, with possible resultant juvenile crustal addition and thickening. As slab retreat stabilizes, the thermal maturation of the mantle wedge establishes expansive high-temperature domains (> 1200°C) that sustain the Devonian magmatic surges (Fig. 2 b). The diversity of I-type, S-type, and hybrid granitoids emerges naturally from this high-heat regime with mantle and crustal melting 37 . Significant partial melting of the overriding crust decreases the overall lithospheric strength and facilitates the formation of a wide back-arc basin (for example, ref. 38 ; Figs. 2 b and 3 c). In intraplate regions, extensive lithospheric extension above the stagnant slab creates the conditions for the generation of alkaline magmatism (Figs. 3 and 4 ). Notably, the modeled stress regime during evolution mirrors the field-observed juxtaposition of thrust belts and rift basins in the upper plate (Figs. 2 b, 3 , and 4 ), which emerges from mantle flow velocity gradients. The horizontal viscosity profile reveals complex rheological variations within the upper plate ( Fig. S9a ), where the low-viscosity channels (η < 10¹⁹ Pa·s) enable vertical mantle upwelling/downwelling through Moho-level ( Fig. S9a ) and lateral redistribution via crustal-scale shear zones. The input of magma reduces the bulk lithospheric strength, diminishing the viscosity contrast at the lithosphere-asthenosphere boundary shown in the vertical profile ( Fig. S9b ). This rheological transformation enhances asthenosphere-lithosphere coupling, allowing efficient horizontal velocity transfer from the laterally migrating asthenosphere to the overriding plate (Fig. 5 ). The deformation of the overriding plate should primarily depend on the relative velocity differences between adjacent crustal blocks. In distant inland areas, where the model's right boundary is fixed, the overriding slab exhibits motion driven by and consistent with the direction of the underlying mantle flow, while continuous trench retreat creates sufficient accommodation space for material displacement, resulting in an overall extensional stress regime (Figs. 4 and 5 ). At the pull-out region (denoted as the newly accreted complex in Fig. 4 ), the crustal surface exhibits temporally and spatially variable stress states. For example, at the localized small convection position (plume in Figs. 3 b and 4 ), the maximum surface extension occurs due to divergent mantle flow on both sides. At the forearc adjacent to the trench, while mantle flow toward the trench direction drives plate motion, compressional stress could develop when this velocity exceeds the trench retreat rate (Figs. 4 and 5 ). Our reference model reveals that mantle flow patterns demonstrate significant spatial complexity, while the plate deformation represents a transient response to evolving mantle flow configurations rather than a steady-state condition. Such mantle-lithospheric coupling explains the juxtaposition of extensional and compressional regions within the Altai Orogen, as well as the alternating stress between extension and compression at a single region over time (Fig. 2 b). Endogenic orogenic mechanism for retreating accretionary systems Our integrated geological and numerical model reveals an endogenic orogenic mechanism for retreating accretionary orogens, operating through feedback loops between slab rollback kinematics and intrinsic mantle flows. Under this regime, the upwelling asthenosphere simultaneously acts as the thermal perturbator, rheological modifier, and material supplier, governing its evolution through three interlinked processes. First, evolving mantle flow geometries govern magmatic proliferation by steering melt generation, transport pathways, and emplacement loci, directly shaping forearc-arc-backarc-intraplate configurations. Second, lithospheric deformation results from a combination of slab rollback and trench migration, as well as basal shear tractions imposed by the mantle flow, supporting the hypothesis that mantle flow can influence surface deformation 39 . Third, unlike continental growth through crustal amalgamation, orogenic growth and maturation for such systems occur through juvenile crust production via decompression melting of upwelling mantle, and cratonization through melt-mediated thermal reworking of continental lithosphere. Although broader plate reorganization may modulate convergence rates (Fig. 1 b), our findings demonstrate that such external forces do not necessarily need to be active during, nor serve as the ultimate driver of, accretionary orogenesis. However, equally, potential coupling with other processes as shown in Fig. 1 merits consideration. Evaluating the timescales of synchronicity and cyclicity in orogenic processes on a global scale provides insights into their broader-scale effects 1 . Methods Geological data compilation We interpret the evolution of the western Mongolia Collage through a detailed evaluation of geological data on sedimentation, magmatism, deformation and metamorphism. All the detailed descriptions can be found in Supplementary Information , which includes three sections. Section S1 describes analyses of sedimentary phases and detrital zircon age patterns of the Altai Zone. Section S2 summarized geochronological and geochemical data of magmatic rocks from the western Mongolia Collage. Section S3 is deformation and metamorphism history. Supplementary Tables S1–S3 and Figures S1 –S5 are displayed as well. Numerical model Model geometry and initial and boundary conditions The model domain is 1000 km deep and 4000 km wide, resolved with 513 × 129 grid points. The computational domain has a uniform grid spacing, with the same resolution throughout the model. The reference model includes a 60 Myr-year-old subducting plate, a continental plate, and the asthenosphere mantle. To mimic the free surface in a finite difference code, we impose a 15-km-thick sticky air on the top boundary 40 , 41 . The subducting plate comprises oceanic crust and oceanic lithosphere, with a total thickness of 80 km. The continental plate comprises the upper crust, lower crust, and continental lithosphere, with a total thickness of 120 km. A 10-km-thick weak layer with an imposed constant viscosity separates the transition between the continental plate and the subducting plate. The temperature and density structures are shown in Figure S6 . The initial temperature structure of the model varies from 0°C at the surface to 1,300°C at the bottom of the lithosphere 42 , 43 . The temperature of the overriding plate increases linearly, and the half-space cooling model is used to calculate the temperature of the subducting slab. The initial temperature gradient of the asthenospheric mantle is ~ 0.5°C/km 42 . The initial stage of the modeling involves pushing an oceanic plate beneath a continental plate at a velocity of 5 cm/yr for 20 Myr to establish the initial subducting slab. The pushing force is then removed, and the system evolves self-consistently. The thermo-mechanical modeling of lithospheric deformation, mantle flow, and thermal evolution is conducted using a finite-difference numerical code, LaMEM 44 . This code employs a staggered grid combined with a marker-in-cell approach. We utilize the Boussinesq approximation to model incompressible flow, enforcing conservation of mass, momentum, and energy 45 : $$\\:\\begin{array}{c}\\frac{\\partial\\:{v}_{i}}{\\partial\\:{x}_{i}}=0\\:\\#（1）\\end{array}$$ $$\\:\\begin{array}{c}\\frac{\\partial\\:{\\tau\\:}_{ij}}{\\partial\\:{x}_{j}}-\\frac{\\partial\\:P}{\\partial\\:{x}_{i}}+\\rho\\:{g}_{i}=0\\#（2）\\end{array}$$ $$\\:\\begin{array}{c}\\rho\\:{C}_{p}\\frac{DT}{Dt}=\\frac{\\partial\\:}{\\partial\\:{x}_{i}}（\\lambda\\:\\frac{\\partial\\:T}{\\partial\\:{x}_{i}}）+{H}_{s}+{H}_{a}\\#\\left(3\\right)\\end{array}$$ where \\(\\:{\\text{x}}_{\\text{i}}\\) is Cartesian coordinates, \\(\\:{\\text{v}}_{\\text{i}}\\) represents the velocity component, \\(\\:{{\\tau\\:}}_{\\text{i}\\text{j}}\\) represents the deviatoric stress, \\(\\:\\text{T}\\) represents temperature, \\(\\:\\text{P}\\) represents the total pressure and \\(\\:{\\text{g}}_{\\text{i}}\\) represents gravitational acceleration. \\(\\:{\\text{C}}_{\\text{p}}\\) , \\(\\:{\\lambda\\:}\\) , \\(\\:{\\text{H}}_{\\text{s}}\\) , \\(\\:{\\text{H}}_{\\text{a}}\\) are heat capacity, thermal conductivity, shear heating, and adiabatic heating, respectively, while \\(\\:{\\rho\\:}\\) is density, which depends on temperature and pressure. For density calculations in the model, we use Perple_X to compute the densities of asthenosphere and oceanic lithosphere over a pressure-temperature range of 1–30 GPa and 300–1800°C. Other phases follow the relationship: $$\\:\\rho\\:={\\rho\\:}_{0}[1-\\alpha\\:(T-{T}_{0}\\left)\\right(1+\\beta\\:(P-{P}_{0})]$$ where \\(\\:{{\\rho\\:}}_{0}\\) is the reference density at the reference temperature \\(\\:{\\text{T}}_{0}\\) = 298 K and reference pressure \\(\\:{\\text{P}}_{0}\\) = 105 Pa, and \\(\\:{\\alpha\\:}\\) and \\(\\:{\\beta\\:}\\) are thermal expansivity and compressibility coefficients. The model assumes a visco-elasto-plastic rheology, with the constitutive equation for the deviatoric strain rate tensor describing nonlinear deformation in rocks as follows: $$\\:\\begin{array}{c}{\\dot{\\epsilon\\:}}_{ij}={\\dot{\\epsilon\\:}}_{ij}^{el}+{\\dot{\\epsilon\\:}}_{ij}^{vs}+{\\dot{\\epsilon\\:}}_{ij}^{pl}=\\frac{{\\stackrel{◇}{\\tau\\:}}_{ij}}{2G}+{\\dot{\\epsilon\\:}}_{Ⅱ}^{vs}\\frac{{\\tau\\:}_{ij}}{{\\tau\\:}_{Ⅱ}}+{\\dot{\\epsilon\\:}}_{Ⅱ}^{pl}\\frac{{\\tau\\:}_{ij}}{{\\tau\\:}_{Ⅱ}}\\:\\#\\left(4\\right)\\end{array}$$ where \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{i}\\text{j}}\\) is the deviatoric strain rate tensor, \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{i}\\text{j}}^{\\text{e}\\text{l}}\\) , \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{i}\\text{j}}^{\\text{v}\\text{s}}\\) , \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{i}\\text{j}}^{\\text{p}\\text{l}}\\) are the elastic, viscous and plastic components, respectively, \\(\\:{\\stackrel{\\text{◇}}{{\\tau\\:}}}_{\\text{i}\\text{j}}=\\frac{\\partial\\:{{\\tau\\:}}_{\\text{i}\\text{j}}}{\\partial\\:\\text{t}}+{{\\tau\\:}}_{\\text{i}\\text{k}}{{\\omega\\:}}_{\\text{k}\\text{j}}-{{\\omega\\:}}_{\\text{i}\\text{k}}{{\\tau\\:}}_{\\text{k}\\text{j}}\\) is the Jaumann objective stress rate, \\(\\:{{\\omega\\:}}_{\\text{i}\\text{j}}=\\frac{1}{2}\\left(\\frac{\\partial\\:{\\text{v}}_{\\text{i}}}{\\partial\\:{\\text{x}}_{\\text{j}}}-\\frac{\\partial\\:{\\text{v}}_{\\text{j}}}{\\partial\\:{\\text{x}}_{\\text{i}}}\\right)\\) is the spin tensor, \\(\\:\\text{G}\\) is the elastic shear modulus. The viscous strain rate takes into account both diffusion ( \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{l}}\\) ) and dislocation ( \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{n}}\\) ) creep: $$\\:\\begin{array}{c}{\\dot{\\epsilon\\:}}_{ij}^{vs}={\\dot{\\epsilon\\:}}_{l}+{\\dot{\\epsilon\\:}}_{n}={A}_{diff}{\\tau\\:}_{Ⅱ}+{A}_{disl}{\\left({\\tau\\:}_{Ⅱ}\\right)}^{n}\\#\\left(5\\right)\\end{array}$$ where n > 1 is the stress exponent of the dislocation creep (n = 1 when diffusion creep), and the pre-exponential factor \\(\\:{\\text{A}}_{\\text{d}\\text{i}\\text{f}\\text{f}}\\) and \\(\\:{\\text{A}}_{\\text{d}\\text{i}\\text{s}\\text{l}}\\) of each creep mechanism is defined by: $$\\:\\begin{array}{c}{A}_{diff}={B}_{diff}{exp}\\left[-\\frac{{H}_{diff}}{RT}\\right]\\#\\left(6\\right)\\end{array}$$ $$\\:\\begin{array}{c}{A}_{disl}={B}_{disl}\\left[-\\frac{{H}_{disl}}{RT}\\right]\\#\\left(7\\right)\\end{array}$$ where B, H = E + pV, E, and V denote the creep constant, enthalpy, activation energy, and activation volume, respectively, of the corresponding creep mechanism, and R is the gas constant. Diffusive creep describes the deformation caused by the absence of microscopic motion in the crystal lattice under external stress. In this type of deformation, the strain rate is linearly related to the stress, resulting in Newtonian rheological properties with other constant parameters. Dislocation creep is a non-Newtonian rheological creep, which is related to the deformation caused by the absence of linear motion in the crystal. The viscosity parameters for the model in this article are set as shown in Tables S4 and S5 44 . Plastic deformation occurs when differential stresses exceed the Drucker-Prager yield criterion: $$\\:\\begin{array}{c}{\\tau\\:}_{yield}=Psin\\left(\\phi\\:\\right)+Ccos\\left(\\phi\\:\\right)\\#\\left(8\\right)\\end{array}$$ where \\(\\:\\text{P}\\) , \\(\\:\\text{C}\\) , and \\(\\:{\\phi\\:}\\) are the pressure, cohesion, and friction angle, respectively. The effective viscosity is determined using the following expression: $$\\:\\begin{array}{c}{\\eta\\:}_{eff}={min}\\left[{\\left(\\frac{1}{G\\varDelta\\:t}+\\frac{1}{{\\eta\\:}_{creep}}\\right)}^{-1},{\\eta\\:}_{plastic}\\right]\\#\\left(9\\right)\\end{array}$$ The plastic viscosity is given by: $$\\:\\begin{array}{c}{\\eta\\:}_{plastic}=\\:\\frac{{\\tau\\:}_{yield}}{2{\\dot{\\epsilon\\:}}_{Ⅱ}}\\#\\left(10\\right)\\end{array}$$ where \\(\\:{{\\tau\\:}}_{\\text{y}\\text{i}\\text{e}\\text{l}\\text{d}}\\) is the yield stress and \\(\\:{\\dot{{\\epsilon\\:}}}_{\\text{Ⅱ}}\\) the second invariant of the strain rate tensor. Mantle density phase transition To enhance the geological accuracy of mantle density distribution in the model and improve the precision of the simulation results, this study uses Perple_X 46 to generate a mantle density phase diagram ( Fig. S7 ). The details of these calculations are provided in Section S4 . Declarations Acknowledgments We appreciate the helpful discussion with R. Chang. Funding: Project (JLFS/P-702/24) of Hong Kong RGC Co-funding Mechanism on Joint Laboratories with the Chinese Academy of Science, National Science Foundation of China (Grants 424B2048, 42176064), and Australian Research Council (FL160100168). Author contributions: Conceptualization: XC, LW; Methodology: XC, LW; Investigation: XC, LW, IC; Supervision: LD, PC, GZ; Writing—original draft: XC, LW; Writing—review & editing: all authors. Competing interests: Authors declare that they have no competing interests. Data and materials availability: All data are available in the main text or the Supplementary Information. References Cawood, P. A. et al. Accretionary orogens through Earth history. SP 318, 1–36 (2009). Yin, A. & Harrison, T. M. Geologic Evolution of the Himalayan-Tibetan Orogen. Annu. Rev. Earth Planet. Sci. 28, 211–280 (2000). Condie, K. C. 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Reviews of Geophysics 40, (2002). Nakakuki, T. & Mura, E. Dynamics of slab rollback and induced back-arc basin formation. Earth and Planetary Science Letters 361, 287–297 (2013). Jahn, B., Wu, F. & Chen, B. Granitoids of the Central Asian Orogenic Belt and continental growth in the Phanerozoic. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, 181–193 (2000). Windley, B. F. et al. Neoproterozoic to Paleozoic Geology of the Altai Orogen, NW China: New Zircon Age Data and Tectonic Evolution. The Journal of Geology 110, 719–737 (2002). Xiao, W. et al. A Tale of Amalgamation of Three Permo-Triassic Collage Systems in Central Asia: Oroclines, Sutures, and Terminal Accretion. Annu. Rev. Earth Planet. Sci. 43, 477–507 (2015). Tang, J., Wang, F., Wang, Y.-N., Long, X.-Y. & Xu, W.-L. Age, formation mechanisms, spatial extent, and geodynamic effects of the eastern and northeastern Asian big mantle wedges. Earth-Science Reviews 237, 104324 (2023). Li, P. et al. Evolution of the Central Asian Orogenic Belt along the Siberian margin from Neoproterozoic-Early Paleozoic accretion to Devonian trench retreat and a comparison with Phanerozoic eastern Australia. Earth-Science Reviews 198, 102951 (2019). Xiao, W. et al. Palaeozoic accretionary and convergent tectonics of the southern Altaids: implications for the growth of Central Asia. JGS 161, 339–342 (2004). Rudnev, S. N. et al. Early Paleozoic magmatism in the Bumbat-Hairhan area of the Lake Zone in western Mongolia ( geological , petrochemical , and geochronological data ). Russian Geology and Geophysics 53, 425–441 (2012). Lehmann, J. et al. Structural constraints on the evolution of the Central Asian Orogenic Belt in SW Mongolia. American Journal of Science 310, 575–628 (2010). Soejono, I. et al. A reworked Lake Zone margin: Chronological and geochemical constraints from the Ordovician arc-related basement of the Hovd Zone (western Mongolia). Lithos 294–295, 112–132 (2017). Hanžl, P. et al. Making continental crust: origin of Devonian orthogneisses from SE Mongolian Altai. Jour. Geosci. 25–50 (2016) doi: 10.3190/jgeosci.206 . Cui, X. et al. An early Paleozoic active continental margin basin along the southern Chinese Altai: Evidence from high-grade paragneisses in the Fuyun region. Am J Sci 322, 190–224 (2022). Broussolle, A. et al. Polycyclic Palaeozoic evolution of accretionary orogenic wedge in the southern Chinese Altai: Evidence from structural relationships and U–Pb geochronology. Lithos 314–315, 400–424 (2018). Jiang, Y. et al. Precambrian detrital zircons in the Early Paleozoic Chinese Altai: Their provenance and implications for the crustal growth of central Asia. Precambrian Research 189, 140–154 (2011). Zhao, D., Lei, J. & Tang, R. Origin of the Changbai intraplate volcanism in Northeast China: Evidence from seismic tomography. Chin. Sci. Bull. 49, 1401–1408 (2004). Buslov, M. M. et al. Late Paleozoic faults of the Altai region, Central Asia: tectonic pattern and model of formation. Journal of Asian Earth Sciences 23, 655–671 (2004). Cui, X., Sun, M., Zhao, G., Zhang, Y. & Yao, J. Two-Stage Mafic‐Felsic Magma Interactions and Related Magma Chamber Processes in the Arc Setting: An Example From the Enclave‐Bearing Calc‐Alkaline Plutons, Chinese Altai. Geochem Geophys Geosyst 22, e2021GC009939 (2021). Gerya, T. V. & Meilick, F. I. Geodynamic regimes of subduction under an active margin: effects of rheological weakening by fluids and melts. Journal Metamorphic Geology 29, 7–31 (2011). Sternai, P., Jolivet, L., Menant, A. & Gerya, T. Driving the upper plate surface deformation by slab rollback and mantle flow. Earth and Planetary Science Letters 405, 110–118 (2014). Crameri, F. et al. A comparison of numerical surface topography calculations in geodynamic modelling: an evaluation of the ‘sticky air’ method: Modelling topography in geodynamics. Geophysical Journal International 189, 38–54 (2012). Kaus, B. J. P., Mühlhaus, H. & May, D. A. A stabilization algorithm for geodynamic numerical simulations with a free surface. Physics of the Earth and Planetary Interiors 181, 12–20 (2010). Li, Z.-H., Gerya, T. & Connolly, J. A. D. Variability of subducting slab morphologies in the mantle transition zone: Insight from petrological-thermomechanical modeling. Earth-Science Reviews 196, 102874 (2019). Wang, L. et al. Subduction Initiation at the Solomon Back-Arc Basin: Contributions From Both Island Arc Rheological Strength and Oceanic Plateau Collision. Geophysical Research Letters 49, e2021GL093369 (2022). Pusok, A. E. & Kaus, B. J. P. Development of topography in 3-D continental-collision models. Geochemistry, Geophysics, Geosystems 16, 1378–1400 (2015). Turcotte, D. L. & Schubert, G. Geodynamics . (Cambridge University Press, 2002). Connolly, J. A. D. Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation. Earth and Planetary Science Letters 236, 524–541 (2005). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformation.docx Supplementary Information SupplementaryTables.xlsx SupplementaryTables S1-S3 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6210811\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":443428445,\"identity\":\"60539250-0918-4eef-9ea0-41c9e649fb73\",\"order_by\":0,\"name\":\"Guochun Zhao\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAn0lEQVRIiWNgGAWjYFACHiCuOGAAZDCTouUMyVoY20jRIu9/9uCHj/PuGBsc4D1sQJQWwwPnkiVnbntmZnCALzmBOC2NPQbSvNsO2xgc4DE+QJyWZh7j37xzSNEiz8ZjJs3bcNgMpIU4hxnw8JhZzjh22FjyMI8xcd6X7z9jfONDzWHDvuM9xhLE2XIAxiI6IuUbiFU5CkbBKBgFIxcAAESdLh1NdntHAAAAAElFTkSuQmCC\",\"orcid\":\"\",\"institution\":\"University of Hong Kong\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Guochun\",\"middleName\":\"\",\"lastName\":\"Zhao\",\"suffix\":\"\"},{\"id\":443428446,\"identity\":\"150ad065-0f4c-415f-ad0f-cfd3c311f8a1\",\"order_by\":1,\"name\":\"Xing Cui\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"The University of Hong Kong\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Xing\",\"middleName\":\"\",\"lastName\":\"Cui\",\"suffix\":\"\"},{\"id\":443428447,\"identity\":\"a00bc66e-5cc6-4bba-bef7-3138acbd7e57\",\"order_by\":2,\"name\":\"Liangliang Wang\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-3955-1064\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Liangliang\",\"middleName\":\"\",\"lastName\":\"Wang\",\"suffix\":\"\"},{\"id\":443428448,\"identity\":\"2c258766-7cd1-422c-982a-cc4ee3327893\",\"order_by\":3,\"name\":\"Ian Cawood\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"The University of Hong Kong\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Ian\",\"middleName\":\"\",\"lastName\":\"Cawood\",\"suffix\":\"\"},{\"id\":443428449,\"identity\":\"c1222b13-d663-4b0f-a9ed-26c770ba3bf2\",\"order_by\":4,\"name\":\"Peter Cawood\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-1200-3826\",\"institution\":\"Monash University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Peter\",\"middleName\":\"\",\"lastName\":\"Cawood\",\"suffix\":\"\"},{\"id\":443428450,\"identity\":\"ec8191a7-ceed-4b9a-9de3-035a8bccc71a\",\"order_by\":5,\"name\":\"Liming Dai\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-3713-1971\",\"institution\":\"Ocean university of China\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Liming\",\"middleName\":\"\",\"lastName\":\"Dai\",\"suffix\":\"\"},{\"id\":443428451,\"identity\":\"c93e0fc5-8229-4b1b-be1a-3e2db87c71ce\",\"order_by\":6,\"name\":\"Jinlong Yao\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-0433-4991\",\"institution\":\"Northwest University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Jinlong\",\"middleName\":\"\",\"lastName\":\"Yao\",\"suffix\":\"\"},{\"id\":443428452,\"identity\":\"04ce2f34-fe7f-4c43-8a25-48c059a79527\",\"order_by\":7,\"name\":\"Di Wang\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Ocean University of China\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Di\",\"middleName\":\"\",\"lastName\":\"Wang\",\"suffix\":\"\"},{\"id\":443428453,\"identity\":\"10936564-49ad-431c-9c6b-cc74deb499cb\",\"order_by\":8,\"name\":\"Min Sun\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"The Univesity of Hong Kong\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Min\",\"middleName\":\"\",\"lastName\":\"Sun\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2025-03-12 09:40:29\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-6210811/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-6210811/v1\",\"draftVersion\":[],\"editorialEvents\":[],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":80802091,\"identity\":\"b262b27e-a69e-4480-b5bd-1ae99d208fe8\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"png\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":1031465,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eSimplified schematic model\\u003c/strong\\u003e \\u003cstrong\\u003eillustrating mantle flow-induced stress perturbations in the overlying lithospheric plate, based on our geodynamic simulations. \\u003c/strong\\u003eV\\u003csub\\u003etrench\\u003c/sub\\u003e refers to the velocity of trench retreat, which is related to slab rollback and mantle flow. V\\u003csub\\u003ea\\u003c/sub\\u003e and V\\u003csub\\u003eb\\u003c/sub\\u003e respectively denote velocities of the upper plate at forearc and intraplate positions coupled with the underlying mantle flow. Compression is observed at a location when V\\u003csub\\u003etrench\\u003c/sub\\u003e \\u0026lt; V\\u003csub\\u003ea\\u003c/sub\\u003e near the trench. A-L coupling refers to asthenosphere and lithosphere coupling.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/4e7b8fcb6dbcab1235ac1bfd.png\"},{\"id\":80802095,\"identity\":\"e0f8d112-16b7-49aa-8b69-3ae960f20cb7\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":9316311,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eGeology of the western Mongolia Collage. \\u003c/strong\\u003e(a) Simplified schematic map of part of the Altaides, showing the subdivision of major tectonic units of the western Mongolia Collage. The green dotted line shows the transect position of (b). For a more detailed regional geological map, please refer to \\u003cstrong\\u003eFigure S1\\u003c/strong\\u003e. (b) Schematic time-space diagram for the western Mongolia Collage, showing the sedimentation, magmatism, and deformation and metamorphism during the early-middle Paleozoic period.\\u003cstrong\\u003e \\u003c/strong\\u003eThe granitoid and volcanic rock sample numbers and ages are listed in \\u003cstrong\\u003eTable S2\\u003c/strong\\u003ewith references therein. BABB: back-arc basin basalt; MP-MT: medium-pressure/medium-temperature; LP-HT: low-pressure/high-temperature.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/aeb5b85863386d98b907d2a5.png\"},{\"id\":80802093,\"identity\":\"3ca50edc-7e03-473e-88c5-e97dd7ec8fbe\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":3137086,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eTemporal evolution of mantle dynamics and lithospheric deformation for the reference model. \\u003c/strong\\u003ePanels (a–h) present numerical simulation results depicting the geodynamic evolution of stress, temperature, and viscosity over time. (a–d): The upper graph in each panel shows the stress fields across the lithosphere. The lower graph is temperature fields at different time intervals, with white arrows indicating the mantle flow directions. (e–h): Corresponding viscosity fields (logarithmic scale) at the same time intervals. The upper portion of each panel contains two color bars indicating the temperature and viscosity scales.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/0cd544d448bd94dab62191fa.png\"},{\"id\":80802094,\"identity\":\"33108705-6f71-468a-868b-2312a91b7721\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":1184324,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eTime-distance evolution of stress field in the reference model. \\u003c/strong\\u003eThe color map overlays the horizontal stress field (MPa), with red hues indicating compressional stress and blue hues representing tension stress. The model evolution can be divided into the initial convergence stage (0–20 Myr) and the self-sustaining stage (after 20 Myr). The trench retreat induces prominent tension-extension cycles and diachronous coexistence in the newly arrected area while permanent extension in continental inland. The red triangles schematically represent potential magmatic activity, inferred from the location of mantle upwelling hotspots in the model.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/9de78e61d0d83ac2cc8072d6.png\"},{\"id\":80802096,\"identity\":\"11f764f6-df9e-4035-81c1-d07e7b35b266\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"png\",\"order_by\":5,\"title\":\"Figure 5\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":1091925,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eSimplified schematic model\\u003c/strong\\u003e \\u003cstrong\\u003eillustrating mantle flow-induced stress perturbations in the overlying lithospheric plate, based on our geodynamic simulations. \\u003c/strong\\u003eV\\u003csub\\u003etrench\\u003c/sub\\u003e refers to the velocity of trench retreat, which is related to slab rollback and mantle flow. V\\u003csub\\u003ea\\u003c/sub\\u003e and V\\u003csub\\u003eb\\u003c/sub\\u003e respectively denote velocities of the upper plate at forearc and intraplate positions coupled with the underlying mantle flow. Compression is observed at a location when V\\u003csub\\u003etrench\\u003c/sub\\u003e \\u0026lt; V\\u003csub\\u003ea\\u003c/sub\\u003e near the trench. A-L coupling refers to asthenosphere and lithosphere coupling.\\u0026nbsp;\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"floatimage5.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/ed3ea42ee3b03661b623b69c.png\"},{\"id\":94612536,\"identity\":\"261ad169-e674-4065-9480-fa4f88460764\",\"added_by\":\"auto\",\"created_at\":\"2025-10-29 02:10:45\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":16791487,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/a2e45a40-eeba-44f4-8cab-95736892df65.pdf\"},{\"id\":80802099,\"identity\":\"5318e0c2-e5bd-4358-aba1-8ee08acc72bd\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:35\",\"extension\":\"docx\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":3599125,\"visible\":true,\"origin\":\"\",\"legend\":\"Supplementary Information\",\"description\":\"\",\"filename\":\"SupplementaryInformation.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/c1d693f5fd20a6f3d4860a11.docx\"},{\"id\":80802092,\"identity\":\"031e6a14-8cf1-4b81-b137-32cf0e061c87\",\"added_by\":\"auto\",\"created_at\":\"2025-04-17 08:47:34\",\"extension\":\"xlsx\",\"order_by\":2,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":37975,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eSupplementaryTables S1-S3\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"SupplementaryTables.xlsx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6210811/v1/4687c9d7d4862fdcc411dc60.xlsx\"}],\"financialInterests\":\"There is \\u003cb\\u003eNO\\u003c/b\\u003e Competing Interest.\",\"formattedTitle\":\"Endogenic mantle-driven orogenic evolution: Slab rollback dynamics as the architect of retreating accretionary systems\",\"fulltext\":[{\"header\":\"Introduction\",\"content\":\"\\u003cp\\u003eMountain belts (orogens) are traditionally classified into collisional and accretionary endmembers\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e. Collisional orogens follow terminal ocean closure and continental collisions, accompanied by crustal stacking and remelting of preexisting crustal material (for example, Himalayan-Karakoram-Tibetan orogen\\u003csup\\u003e\\u003cspan citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2\\u003c/span\\u003e\\u003c/sup\\u003e). In contrast, accretionary orogens develop at convergent margins during protracted oceanic subduction, like modern circum-Pacific orogenic belts, where crustal growth occurs via accretion of exotic terranes or emplacement of mantle-derived magmas\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR4\\\" citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e\\u003c/sup\\u003e. A challenge in understanding accretionary orogenesis is identifying the mechanism of crustal shortening and uplift during the ongoing subduction without continental collision. Current paradigms attribute compression in \\\"advancing\\\" accretionary orogens to enhanced plate coupling either through attempted subduction of buoyant lithosphere or plate reorganizations resulting in transient adjustments in the relative convergence rate across the accretionary plate boundary\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ea \\u003cb\\u003eand b\\u003c/b\\u003e). Such mechanisms well explain features like inboard foreland thrust belt and basin, and narrow and long-lived magmatic belt (for example, the Mesozoic Canadian Cordillera accretionary orogen\\u003csup\\u003e\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e\\u003c/sup\\u003e). Crustal growth, if any, occurs through lateral amalgamation of multiple terranes. However, these mechanisms fail to explain features specific to \\\"retreating\\\" accretionary systems, where overriding plate extension dominates despite continuous convergence (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ec). These systems usually exhibit back-arc spreading, yet paradoxically record transient orogenesis (mountain-building) and crustal growth, without significant terrane accretion\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR10 CR11 CR12\\\" citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003e. Deciphering the evolutionary pathways of such systems is essential to unraveling the continuum of accretionary orogenesis and the mechanisms driving continental crustal growth.\\u003c/p\\u003e \\u003cp\\u003eNumerous 2D and 3D numerical as well as analogue modelings have demonstrated how slab-mantle interactions modulate the balance between compressional and extensional deformations within the overriding plate (for example, refs.\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR15 CR16 CR17 CR18\\\" citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e\\u003c/sup\\u003e). Indeed, mantle processes, particularly those associated with slab rollback and the consequent reorganization of mantle wedge convection, may play a critical, but yet underexplored, role in the formation and evolution of retreating accretionary systems\\u003csup\\u003e\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR20\\\" citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003ec). In this study, we synthesize the major characteristics of retreating accretionary orogens and integrate multiscale geological data from an archetypal example, the Paleozoic Altai Orogen in Altaides (also named Central Asian Orogenic Belt; one of the largest accretionary orogen with significant Phanerozoic continental growth\\u003csup\\u003e\\u003cspan additionalcitationids=\\\"CR23\\\" citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e\\u003c/sup\\u003e). We then apply a novel 2D thermo-mechanical modeling based on geological calibration to unravel the interplay of slab retreat, induced mantle wedge convection, and the resulting tectonothermal responses. The numerical model successfully reproduces the dominant features of retreating accretionary systems, and captures the whole lithosphere- and asthenosphere-scale observed geological record of the Altai Orogen. Specifically, it replicates the migration history of the magmatic arc, pervasive and sustained magmatism, back-arc extension, and diachronous crustal deformation. Our study proposes a new endogenic orogenic model, which highlights the pivotal role of retreat-modulated reorganization of mantle flow and its coupling with the crust in shaping retreating accretionary orogens.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e\"},{\"header\":\"Geological characteristics of retreating accretionary systems\",\"content\":\"\\u003cp\\u003eIn addition to the prominent extensional features, as exemplified by modern Western Pacific subduction systems, detailed geological investigations of ancient retreating-type orogens have revealed a comprehensive suite of diagnostic characteristics. Notable examples include the Paleozoic Lachlan and New England segments of the Terra Australis Orogen in eastern Australia\\u003csup\\u003e\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e\\u003c/sup\\u003e, Mesozoic-Cenozoic Western Pacific subduction systems\\u003csup\\u003e\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e\\u003c/sup\\u003e, Proterozoic southwestern United States terranes\\u003csup\\u003e\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e\\u003c/sup\\u003e, and specific components of the Altaides\\u003csup\\u003e\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e\\u003c/sup\\u003e. These accretionary systems, generally, though not universally, exhibit the following characteristics across spatial and temporal scales: (1) deposition of quartz-rich turbidites in low-grade sedimentary basins; (2) prolonged trench retreat accompanied by progressive arc migration; (3) intensive syn-tectonic granitic magmatism; (4) presence of rift basins associated with lithospheric thinning; and (5) regional metamorphic gradients ranging from greenschist to amphibolite facies. Crucially, prolonged extensional phases are intermittently interrupted by short-lived compressional events.\\u003c/p\\u003e \\u003cp\\u003eDespite shared traits, each orogen follows a unique evolutionary path shaped by boundary conditions, necessitating focused studies on well-preserved systems to refine geodynamic models. The early-middle Paleozoic Altai Orogen, located in the western Mongolia Collage of the Altaides\\u003csup\\u003e\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e\\u003c/sup\\u003e, preserves many of the characteristic attributes of retreating orogens, and its exceptional preservation of geological records and minimal post-orogenic modification make it a premier natural laboratory under this paradigm. The Altai Orogen consists of Precambrian microcontinents in the east, acting as the tectonic nuclei around which younger arcs and associated accretionary complex in the west accreted\\u003csup\\u003e\\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e\\u003c/sup\\u003e (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003ea). The Lake Zone represents a Neoproterozoic island arc\\u003csup\\u003e\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e\\u003c/sup\\u003e and docked with the continental basement in the late Cambrian\\u003csup\\u003e\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e\\u003c/sup\\u003e. The Altai Zone lacks evidence for an underlying Precambrian basement related to the westward extension of the microcontinents beneath the zone\\u003csup\\u003e\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e,\\u003cspan additionalcitationids=\\\"CR31 CR32 CR33\\\" citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e30\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e\\u003c/sup\\u003e. Integrating data from detrital zircon provenance statistics, high-precision geochronology (zircon U-Pb, Ar-Ar thermochronology), quantitative P-T-t reconstructions via phase equilibrium modeling and strain analysis (see \\u003cb\\u003eMethods\\u003c/b\\u003e) of the studied region has revealed a lengthy retreating accretionary history over 150 Myr, summarized in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb and as follows.\\u003c/p\\u003e \\u003cp\\u003e1. Trench retreat and mantle-crust interactions\\u003c/p\\u003e \\u003cp\\u003eThe Altai Orogen chronicles a long history of westward trench retreat (\\u0026gt;\\u0026thinsp;300 km), marked by systematic migration of magmatic arcs from the Ikh-Mongol Arc to the current Chinese Altai (ca. 520\\u0026ndash;370 Ma; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb). Calc-alkaline granites and bimodal volcanism delineate arc progression, whereas backarc basin basalts and intraplate alkaline granites and OIB-type basalts signal asthenospheric upwelling under extensional regimes (see \\u003cb\\u003eSupplementary Section S2; Fig. S4\\u003c/b\\u003e). This magmatic evolution aligns with models of stagnant slab dynamics and big mantle wedge formation, where enriched asthenospheric components derived from the stagnant slab could contribute to the intraplate-like magmatism (for example, refs.\\u003csup\\u003e\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e\\u003c/sup\\u003e). Geochemical and isotopic data (e.g., positive zircon εHf(t) values; \\u003cb\\u003eTable S2\\u003c/b\\u003e and \\u003cb\\u003eFig. S5\\u003c/b\\u003e) reveal juvenile crustal growth dominated by mantle-derived melts, with minimal input from Precambrian basement rocks. The enhanced asthenosphere engagement and thermal input sustained low-pressure/high-temperature metamorphism (3\\u0026ndash;6 kbar, 570\\u0026ndash;750\\u0026deg;C; \\u003cb\\u003eTable S3\\u003c/b\\u003e) over ca. 80 Myr.\\u003c/p\\u003e \\u003cp\\u003e2. Sedimentary dynamics and crustal maturation\\u003c/p\\u003e \\u003cp\\u003eRapid trench retreat generated forearc basins filled with immature turbidites sourced from arc erosion (see \\u003cb\\u003eSection S1\\u003c/b\\u003e). These sedimentary sequences, characterized by low compositional maturity, evolved into permeable crustal reservoirs prone to remelting and anatexis (e.g., S- and I-type granites; see \\u003cb\\u003eSection S2\\u003c/b\\u003e). This process drove self-maturation of the crust, transforming rheologically weak sedimentary packages into magmatic plutons and localized fold-thrust belts during episodic compression. The interplay between extension-driven magmatism and sedimentary recycling emphasises a feedback mechanism that facilitates crustal maturation and stabilization in retreating systems.\\u003c/p\\u003e \\u003cp\\u003e3. Spatiotemporal stress field partitioning and thermal legacy\\u003c/p\\u003e \\u003cp\\u003eThe Altai Orogen exhibits diachronous compression-extension cycles, reflecting tectonic decoupling across its domains (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb; see \\u003cb\\u003eSection S3\\u003c/b\\u003e). The Hovd Zone records late Ordovician (ca. 460\\u0026ndash;440 Ma) compression transitioning to prolonged extension, while the Altai Zone experienced Silurian (ca. 435\\u0026ndash;415 Ma) compression followed by \\u0026gt;\\u0026thinsp;50 Myr of extension. These two deformational events were not correlated with terrane addition, whereas the successive east to west compression and exhumation since the late Devonian occurred concurrently with the vertical frontal collision of the peri-Siberian complex from the north\\u003csup\\u003e\\u003cspan citationid=\\\"CR36\\\" class=\\\"CitationRef\\\"\\u003e36\\u003c/span\\u003e\\u003c/sup\\u003e, which is not considered in the east-west directed subduction process. The thermal anomalies, preserved in metamorphic gradients from Barrovian belts to rift-related assemblages (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb), provide critical constraints for modeling lithospheric thinning and heat transfer in retreating systems.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eNumerical modeling for retreating accretionary systems\\u003c/h2\\u003e \\u003cp\\u003eTo decipher the first-order geodynamic process governing retreating orogens, we developed 2D thermo-mechanical simulations constrained by the diagnostic characteristics of the Altai Orogen. Model parameters, boundary conditions, and methodological details are described in \\u003cb\\u003eMethods\\u003c/b\\u003e. Firstly, a series of parametric numerical experiments were conducted to test the influence of convergence duration, oceanic plate age, and initial subduction angle on orogenic styles, revealing a spectrum of tectonothermal responses with details provided in \\u003cb\\u003eSection S5\\u003c/b\\u003e. A reference model, selected for its optimal representation of observational constraints, forms the basis of our detailed analysis (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e). Although calibrated against the Altai Orogen, our simulations transcend regional complexity to reveal dynamics applicable to retreating accretionary systems globally.\\u003c/p\\u003e \\u003cp\\u003eIn the reference model (Model B in \\u003cb\\u003eSection S5\\u003c/b\\u003e), the oceanic plate is initially driven to subduct beneath the continental lithosphere by an exerted external pushing force, forming the shallow dipping subduction zone within the first 20 Myr. As subduction transitioned into a self-sustaining mode, the negatively buoyant slab immediately steepens and undergoes rapid rollback (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea), resulting in the slab retreating some 300 km, from around 2750 km to 2450 km, by approximately 40 Myr (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb). Concurrently with trench retreat, the overriding plate shows strong extension and significant lithospheric thinning inboard of the trench, potentially driving formation of new oceanic crust. This process results in toroidal mantle flows, including asthenospheric upwelling in the mantle wedge (indicated by the white arrows) and small-scale convection cells in the back-arc (~\\u0026thinsp;2850 km; Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb) that develop bilateral lithospheric underflow.\\u003c/p\\u003e \\u003cp\\u003eAs slab rollback continues, the subducting slab flattens as it encounters the mantle transition zone at ~\\u0026thinsp;600 km depth, forming a big mantle wedge structure. By approximately 56 Myr, the trench has retreated to ~\\u0026thinsp;2300 km, and another significant area of mantle upwelling emerges at the rear of the extended region (~\\u0026thinsp;2600 km). This upwelling zone coincides with the extreme overlying lithosphere thinning area, where the mantle flows horizontally and downward on both sides (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec \\u003cb\\u003eand g\\u003c/b\\u003e). The process persists until around 70 Myr, by which time the subducting slab angle increasingly shallows, with concomitant expansion of the big mantle wedge (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ed). Under the influence of the upwelling asthenosphere, the lithosphere at the former accretionary wedge exhibits variable thickness and coexisiting compression and extension, while zones of mantle upwelling and downwelling occur inboard from the trench (\\u0026gt;\\u0026thinsp;3100 km) that corresponds to intraplate areas.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"Linking numerical simulations to geological constraints\",\"content\":\"\\u003cp\\u003eWhile 2-D numerical modelings are unable to fully encapsulate the inherent multiscale complexity of natural subduction zones and precisely replicate spatiotemporal geological relationships, they effectively reproduce the observed crustal kinematics, deformation, and magmatic evolution of retreating orogens, typified by the Altai Orogen. Integrating the numerical simulations with geological constraints shows a fundamental linkage between slab rollback mantle dynamics and the tectonothermal responses of retreating accretionary systems during the prolonged evolution:\\u003c/p\\u003e \\u003cp\\u003eDuring the initial subduction phase, trench-directed corner flow establishes compressive stresses at the accretionary front (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e) while possible hydrous flux melting beneath the Ihk-Mongol arc generates calc-alkaline magmas (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e). As soon as the slab rollback begins (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ea), the mantle corner flow could have impinged and heated the upper plate inboard of the trench location, which may explain the late Cambrian crustal anatexis in the Chinese Altai (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb). As the convergent plate margin evolved, the trench steadily retreats and the stress field of the upper plate shifts from compression to extension by around 40 Myr (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb and \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e). This transition is marked by rapid rollback of the subducting slab and upwelling of the asthenosphere. As a result, the mantle wedge exhibits relatively low viscosity (η\\u0026thinsp;\\u0026lt;\\u0026thinsp;10\\u0026sup1;⁹ Pa\\u0026middot;s) and weaker rheological properties (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ef). Concurrently, a reorganization of the mantle flow pattern occurs with flow vectors bifurcated into trench-parallel and slab-perpendicular components. The enhanced trench-directed mantle flow accelerates wedge extension, whereas the slab-perpendicular mantle flow in turn further promotes rollback of the slab. The thermal weakening effect (ΔT\\u0026thinsp;\\u0026gt;\\u0026thinsp;200\\u0026deg;C) exerted by the upwelling asthenosphere on the overlying lithosphere facilitates further mantle upwelling and sustains adiabatic decompression melting, with possible resultant juvenile crustal addition and thickening. As slab retreat stabilizes, the thermal maturation of the mantle wedge establishes expansive high-temperature domains (\\u0026gt;\\u0026thinsp;1200\\u0026deg;C) that sustain the Devonian magmatic surges (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb). The diversity of I-type, S-type, and hybrid granitoids emerges naturally from this high-heat regime with mantle and crustal melting\\u003csup\\u003e\\u003cspan citationid=\\\"CR37\\\" class=\\\"CitationRef\\\"\\u003e37\\u003c/span\\u003e\\u003c/sup\\u003e. Significant partial melting of the overriding crust decreases the overall lithospheric strength and facilitates the formation of a wide back-arc basin (for example, ref.\\u003csup\\u003e\\u003cspan citationid=\\\"CR38\\\" class=\\\"CitationRef\\\"\\u003e38\\u003c/span\\u003e\\u003c/sup\\u003e; Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb and \\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003ec). In intraplate regions, extensive lithospheric extension above the stagnant slab creates the conditions for the generation of alkaline magmatism (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e and \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eNotably, the modeled stress regime during evolution mirrors the field-observed juxtaposition of thrust belts and rift basins in the upper plate (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb, \\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e, and \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e), which emerges from mantle flow velocity gradients. The horizontal viscosity profile reveals complex rheological variations within the upper plate (\\u003cb\\u003eFig. S9a\\u003c/b\\u003e), where the low-viscosity channels (η\\u0026thinsp;\\u0026lt;\\u0026thinsp;10\\u0026sup1;⁹ Pa\\u0026middot;s) enable vertical mantle upwelling/downwelling through Moho-level (\\u003cb\\u003eFig. S9a\\u003c/b\\u003e) and lateral redistribution via crustal-scale shear zones. The input of magma reduces the bulk lithospheric strength, diminishing the viscosity contrast at the lithosphere-asthenosphere boundary shown in the vertical profile (\\u003cb\\u003eFig. S9b\\u003c/b\\u003e). This rheological transformation enhances asthenosphere-lithosphere coupling, allowing efficient horizontal velocity transfer from the laterally migrating asthenosphere to the overriding plate (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e). The deformation of the overriding plate should primarily depend on the relative velocity differences between adjacent crustal blocks. In distant inland areas, where the model's right boundary is fixed, the overriding slab exhibits motion driven by and consistent with the direction of the underlying mantle flow, while continuous trench retreat creates sufficient accommodation space for material displacement, resulting in an overall extensional stress regime (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e and \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e). At the pull-out region (denoted as the newly accreted complex in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e), the crustal surface exhibits temporally and spatially variable stress states. For example, at the localized small convection position (plume in Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003eb and \\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e), the maximum surface extension occurs due to divergent mantle flow on both sides. At the forearc adjacent to the trench, while mantle flow toward the trench direction drives plate motion, compressional stress could develop when this velocity exceeds the trench retreat rate (Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e and \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e). Our reference model reveals that mantle flow patterns demonstrate significant spatial complexity, while the plate deformation represents a transient response to evolving mantle flow configurations rather than a steady-state condition. Such mantle-lithospheric coupling explains the juxtaposition of extensional and compressional regions within the Altai Orogen, as well as the alternating stress between extension and compression at a single region over time (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003eb).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e\"},{\"header\":\"Endogenic orogenic mechanism for retreating accretionary systems\",\"content\":\"\\u003cp\\u003eOur integrated geological and numerical model reveals an endogenic orogenic mechanism for retreating accretionary orogens, operating through feedback loops between slab rollback kinematics and intrinsic mantle flows. Under this regime, the upwelling asthenosphere simultaneously acts as the thermal perturbator, rheological modifier, and material supplier, governing its evolution through three interlinked processes. First, evolving mantle flow geometries govern magmatic proliferation by steering melt generation, transport pathways, and emplacement loci, directly shaping forearc-arc-backarc-intraplate configurations. Second, lithospheric deformation results from a combination of slab rollback and trench migration, as well as basal shear tractions imposed by the mantle flow, supporting the hypothesis that mantle flow can influence surface deformation\\u003csup\\u003e\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e\\u003c/sup\\u003e. Third, unlike continental growth through crustal amalgamation, orogenic growth and maturation for such systems occur through juvenile crust production via decompression melting of upwelling mantle, and cratonization through melt-mediated thermal reworking of continental lithosphere.\\u003c/p\\u003e \\u003cp\\u003eAlthough broader plate reorganization may modulate convergence rates (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003eb), our findings demonstrate that such external forces do not necessarily need to be active during, nor serve as the ultimate driver of, accretionary orogenesis. However, equally, potential coupling with other processes as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e merits consideration. Evaluating the timescales of synchronicity and cyclicity in orogenic processes on a global scale provides insights into their broader-scale effects\\u003csup\\u003e\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u003c/sup\\u003e.\\u003c/p\\u003e\"},{\"header\":\"Methods\",\"content\":\"\\u003cdiv id=\\\"Sec7\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eGeological data compilation\\u003c/h2\\u003e \\u003cp\\u003eWe interpret the evolution of the western Mongolia Collage through a detailed evaluation of geological data on sedimentation, magmatism, deformation and metamorphism. All the detailed descriptions can be found in \\u003cb\\u003eSupplementary Information\\u003c/b\\u003e, which includes three sections. \\u003cb\\u003eSection S1\\u003c/b\\u003e describes analyses of sedimentary phases and detrital zircon age patterns of the Altai Zone. \\u003cb\\u003eSection S2\\u003c/b\\u003e summarized geochronological and geochemical data of magmatic rocks from the western Mongolia Collage. \\u003cb\\u003eSection S3\\u003c/b\\u003e is deformation and metamorphism history. Supplementary \\u003cb\\u003eTables S1\\u0026ndash;S3\\u003c/b\\u003e and \\u003cb\\u003eFigures \\u003cspan refid=\\\"MOESM1\\\" class=\\\"InternalRef\\\"\\u003eS1\\u003c/span\\u003e\\u0026ndash;S5\\u003c/b\\u003e are displayed as well.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec8\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eNumerical model\\u003c/h2\\u003e \\u003cdiv id=\\\"Sec9\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003eModel geometry and initial and boundary conditions\\u003c/h2\\u003e \\u003cp\\u003eThe model domain is 1000 km deep and 4000 km wide, resolved with 513 \\u0026times; 129 grid points. The computational domain has a uniform grid spacing, with the same resolution throughout the model. The reference model includes a 60 Myr-year-old subducting plate, a continental plate, and the asthenosphere mantle. To mimic the free surface in a finite difference code, we impose a 15-km-thick sticky air on the top boundary\\u003csup\\u003e\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR41\\\" class=\\\"CitationRef\\\"\\u003e41\\u003c/span\\u003e\\u003c/sup\\u003e. The subducting plate comprises oceanic crust and oceanic lithosphere, with a total thickness of 80 km. The continental plate comprises the upper crust, lower crust, and continental lithosphere, with a total thickness of 120 km. A 10-km-thick weak layer with an imposed constant viscosity separates the transition between the continental plate and the subducting plate. The temperature and density structures are shown in \\u003cb\\u003eFigure S6\\u003c/b\\u003e. The initial temperature structure of the model varies from 0\\u0026deg;C at the surface to 1,300\\u0026deg;C at the bottom of the lithosphere\\u003csup\\u003e\\u003cspan citationid=\\\"CR42\\\" class=\\\"CitationRef\\\"\\u003e42\\u003c/span\\u003e,\\u003cspan citationid=\\\"CR43\\\" class=\\\"CitationRef\\\"\\u003e43\\u003c/span\\u003e\\u003c/sup\\u003e. The temperature of the overriding plate increases linearly, and the half-space cooling model is used to calculate the temperature of the subducting slab. The initial temperature gradient of the asthenospheric mantle is ~\\u0026thinsp;0.5\\u0026deg;C/km\\u003csup\\u003e42\\u003c/sup\\u003e. The initial stage of the modeling involves pushing an oceanic plate beneath a continental plate at a velocity of 5 cm/yr for 20 Myr to establish the initial subducting slab. The pushing force is then removed, and the system evolves self-consistently.\\u003c/p\\u003e \\u003cp\\u003eThe thermo-mechanical modeling of lithospheric deformation, mantle flow, and thermal evolution is conducted using a finite-difference numerical code, LaMEM\\u003csup\\u003e\\u003cspan citationid=\\\"CR44\\\" class=\\\"CitationRef\\\"\\u003e44\\u003c/span\\u003e\\u003c/sup\\u003e. This code employs a staggered grid combined with a marker-in-cell approach. We utilize the Boussinesq approximation to model incompressible flow, enforcing conservation of mass, momentum, and energy\\u003csup\\u003e\\u003cspan citationid=\\\"CR45\\\" class=\\\"CitationRef\\\"\\u003e45\\u003c/span\\u003e\\u003c/sup\\u003e:\\u003cdiv id=\\\"Equa\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equa\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}\\\\frac{\\\\partial\\\\:{v}_{i}}{\\\\partial\\\\:{x}_{i}}=0\\\\:\\\\#（1）\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003cdiv id=\\\"Equb\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equb\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}\\\\frac{\\\\partial\\\\:{\\\\tau\\\\:}_{ij}}{\\\\partial\\\\:{x}_{j}}-\\\\frac{\\\\partial\\\\:P}{\\\\partial\\\\:{x}_{i}}+\\\\rho\\\\:{g}_{i}=0\\\\#（2）\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003cdiv id=\\\"Equc\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equc\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}\\\\rho\\\\:{C}_{p}\\\\frac{DT}{Dt}=\\\\frac{\\\\partial\\\\:}{\\\\partial\\\\:{x}_{i}}（\\\\lambda\\\\:\\\\frac{\\\\partial\\\\:T}{\\\\partial\\\\:{x}_{i}}）+{H}_{s}+{H}_{a}\\\\#\\\\left(3\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{x}}_{\\\\text{i}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is Cartesian coordinates, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{v}}_{\\\\text{i}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e represents the velocity component, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{{\\\\tau\\\\:}}_{\\\\text{i}\\\\text{j}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e represents the deviatoric stress, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{T}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e represents temperature, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{P}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e represents the total pressure and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{g}}_{\\\\text{i}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e represents gravitational acceleration. \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{C}}_{\\\\text{p}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\lambda\\\\:}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{H}}_{\\\\text{s}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{H}}_{\\\\text{a}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e are heat capacity, thermal conductivity, shear heating, and adiabatic heating, respectively, while \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\rho\\\\:}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is density, which depends on temperature and pressure.\\u003c/p\\u003e \\u003cp\\u003eFor density calculations in the model, we use Perple_X to compute the densities of asthenosphere and oceanic lithosphere over a pressure-temperature range of 1\\u0026ndash;30 GPa and 300\\u0026ndash;1800\\u0026deg;C. Other phases follow the relationship:\\u003cdiv id=\\\"Equd\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equd\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\rho\\\\:={\\\\rho\\\\:}_{0}[1-\\\\alpha\\\\:(T-{T}_{0}\\\\left)\\\\right(1+\\\\beta\\\\:(P-{P}_{0})]$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{{\\\\rho\\\\:}}_{0}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the reference density at the reference temperature \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{T}}_{0}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e = 298 K and reference pressure \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{P}}_{0}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e = 105 Pa, and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\alpha\\\\:}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\beta\\\\:}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e are thermal expansivity and compressibility coefficients.\\u003c/p\\u003e \\u003cp\\u003eThe model assumes a visco-elasto-plastic rheology, with the constitutive equation for the deviatoric strain rate tensor describing nonlinear deformation in rocks as follows:\\u003cdiv id=\\\"Eque\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Eque\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{\\\\dot{\\\\epsilon\\\\:}}_{ij}={\\\\dot{\\\\epsilon\\\\:}}_{ij}^{el}+{\\\\dot{\\\\epsilon\\\\:}}_{ij}^{vs}+{\\\\dot{\\\\epsilon\\\\:}}_{ij}^{pl}=\\\\frac{{\\\\stackrel{◇}{\\\\tau\\\\:}}_{ij}}{2G}+{\\\\dot{\\\\epsilon\\\\:}}_{Ⅱ}^{vs}\\\\frac{{\\\\tau\\\\:}_{ij}}{{\\\\tau\\\\:}_{Ⅱ}}+{\\\\dot{\\\\epsilon\\\\:}}_{Ⅱ}^{pl}\\\\frac{{\\\\tau\\\\:}_{ij}}{{\\\\tau\\\\:}_{Ⅱ}}\\\\:\\\\#\\\\left(4\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{i}\\\\text{j}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the deviatoric strain rate tensor, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{i}\\\\text{j}}^{\\\\text{e}\\\\text{l}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{i}\\\\text{j}}^{\\\\text{v}\\\\text{s}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{i}\\\\text{j}}^{\\\\text{p}\\\\text{l}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e are the elastic, viscous and plastic components, respectively, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\stackrel{\\\\text{◇}}{{\\\\tau\\\\:}}}_{\\\\text{i}\\\\text{j}}=\\\\frac{\\\\partial\\\\:{{\\\\tau\\\\:}}_{\\\\text{i}\\\\text{j}}}{\\\\partial\\\\:\\\\text{t}}+{{\\\\tau\\\\:}}_{\\\\text{i}\\\\text{k}}{{\\\\omega\\\\:}}_{\\\\text{k}\\\\text{j}}-{{\\\\omega\\\\:}}_{\\\\text{i}\\\\text{k}}{{\\\\tau\\\\:}}_{\\\\text{k}\\\\text{j}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the Jaumann objective stress rate, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{{\\\\omega\\\\:}}_{\\\\text{i}\\\\text{j}}=\\\\frac{1}{2}\\\\left(\\\\frac{\\\\partial\\\\:{\\\\text{v}}_{\\\\text{i}}}{\\\\partial\\\\:{\\\\text{x}}_{\\\\text{j}}}-\\\\frac{\\\\partial\\\\:{\\\\text{v}}_{\\\\text{j}}}{\\\\partial\\\\:{\\\\text{x}}_{\\\\text{i}}}\\\\right)\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the spin tensor, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{G}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the elastic shear modulus.\\u003c/p\\u003e \\u003cp\\u003eThe viscous strain rate takes into account both diffusion (\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{l}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e) and dislocation (\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{n}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e) creep:\\u003cdiv id=\\\"Equf\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equf\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{\\\\dot{\\\\epsilon\\\\:}}_{ij}^{vs}={\\\\dot{\\\\epsilon\\\\:}}_{l}+{\\\\dot{\\\\epsilon\\\\:}}_{n}={A}_{diff}{\\\\tau\\\\:}_{Ⅱ}+{A}_{disl}{\\\\left({\\\\tau\\\\:}_{Ⅱ}\\\\right)}^{n}\\\\#\\\\left(5\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere n\\u0026thinsp;\\u0026gt;\\u0026thinsp;1 is the stress exponent of the dislocation creep (n\\u0026thinsp;=\\u0026thinsp;1 when diffusion creep), and the pre-exponential factor \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{A}}_{\\\\text{d}\\\\text{i}\\\\text{f}\\\\text{f}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{A}}_{\\\\text{d}\\\\text{i}\\\\text{s}\\\\text{l}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e of each creep mechanism is defined by:\\u003cdiv id=\\\"Equg\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equg\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{A}_{diff}={B}_{diff}{exp}\\\\left[-\\\\frac{{H}_{diff}}{RT}\\\\right]\\\\#\\\\left(6\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003cdiv id=\\\"Equh\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equh\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{A}_{disl}={B}_{disl}\\\\left[-\\\\frac{{H}_{disl}}{RT}\\\\right]\\\\#\\\\left(7\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere B, H\\u0026thinsp;=\\u0026thinsp;E\\u0026thinsp;+\\u0026thinsp;pV, E, and V denote the creep constant, enthalpy, activation energy, and activation volume, respectively, of the corresponding creep mechanism, and R is the gas constant. Diffusive creep describes the deformation caused by the absence of microscopic motion in the crystal lattice under external stress. In this type of deformation, the strain rate is linearly related to the stress, resulting in Newtonian rheological properties with other constant parameters. Dislocation creep is a non-Newtonian rheological creep, which is related to the deformation caused by the absence of linear motion in the crystal. The viscosity parameters for the model in this article are set as shown in \\u003cb\\u003eTables S4 and S5\\u003c/b\\u003e\\u003csup\\u003e44\\u003c/sup\\u003e.\\u003c/p\\u003e \\u003cp\\u003ePlastic deformation occurs when differential stresses exceed the Drucker-Prager yield criterion:\\u003cdiv id=\\\"Equi\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equi\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{\\\\tau\\\\:}_{yield}=Psin\\\\left(\\\\phi\\\\:\\\\right)+Ccos\\\\left(\\\\phi\\\\:\\\\right)\\\\#\\\\left(8\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{P}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{C}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e, and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\phi\\\\:}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e are the pressure, cohesion, and friction angle, respectively. The effective viscosity is determined using the following expression:\\u003cdiv id=\\\"Equj\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equj\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{\\\\eta\\\\:}_{eff}={min}\\\\left[{\\\\left(\\\\frac{1}{G\\\\varDelta\\\\:t}+\\\\frac{1}{{\\\\eta\\\\:}_{creep}}\\\\right)}^{-1},{\\\\eta\\\\:}_{plastic}\\\\right]\\\\#\\\\left(9\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003eThe plastic viscosity is given by:\\u003cdiv id=\\\"Equk\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equk\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:\\\\begin{array}{c}{\\\\eta\\\\:}_{plastic}=\\\\:\\\\frac{{\\\\tau\\\\:}_{yield}}{2{\\\\dot{\\\\epsilon\\\\:}}_{Ⅱ}}\\\\#\\\\left(10\\\\right)\\\\end{array}$$\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{{\\\\tau\\\\:}}_{\\\\text{y}\\\\text{i}\\\\text{e}\\\\text{l}\\\\text{d}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e is the yield stress and \\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\dot{{\\\\epsilon\\\\:}}}_{\\\\text{Ⅱ}}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e the second invariant of the strain rate tensor.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e\\n\\u003ch3\\u003eMantle density phase transition\\u003c/h3\\u003e\\n\\u003cp\\u003eTo enhance the geological accuracy of mantle density distribution in the model and improve the precision of the simulation results, this study uses Perple_X\\u003csup\\u003e\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e\\u003c/sup\\u003e to generate a mantle density phase diagram (\\u003cb\\u003eFig. S7\\u003c/b\\u003e). The details of these calculations are provided in \\u003cb\\u003eSection S4\\u003c/b\\u003e.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eAcknowledgments\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eWe appreciate the helpful discussion with R. Chang.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFunding:\\u003c/strong\\u003e\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003eProject (JLFS/P-702/24) of Hong Kong RGC Co-funding Mechanism on Joint Laboratories with the Chinese Academy of Science, National Science Foundation of China (Grants 424B2048, 42176064), and Australian Research Council (FL160100168).\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAuthor contributions:\\u003c/strong\\u003e Conceptualization: XC, LW; Methodology: XC, LW; Investigation: XC, LW, IC; Supervision: LD, PC, GZ; Writing\\u0026mdash;original draft: XC, LW; Writing\\u0026mdash;review \\u0026amp; editing: all authors.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCompeting interests:\\u003c/strong\\u003e Authors declare that they have no competing interests.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eData and materials availability:\\u003c/strong\\u003e All data are available in the main text or the Supplementary Information.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003eCawood, P. A. \\u003cem\\u003eet al.\\u003c/em\\u003e Accretionary orogens through Earth history. SP 318, 1\\u0026ndash;36 (2009).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eYin, A. \\u0026amp; Harrison, T. M. Geologic Evolution of the Himalayan-Tibetan Orogen. Annu. Rev. Earth Planet. Sci. 28, 211\\u0026ndash;280 (2000).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eCondie, K. C. Accretionary orogens in space and time. in \\u003cem\\u003eGeological Society of America Memoirs\\u003c/em\\u003e vol. 200 145\\u0026ndash;158 (Geological Society of America, 2007).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eKr\\u0026ouml;ner, A. \\u003cem\\u003eet al.\\u003c/em\\u003e Reassessment of continental growth during the accretionary history of the Central Asian Orogenic Belt. Gondwana Research 25, 103\\u0026ndash;125 (2014).\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eKemp, A. I. S., Hawkesworth, C. 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Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation. Earth and Planetary Science Letters 236, 524\\u0026ndash;541 (2005).\\u003c/span\\u003e\\u003c/li\\u003e\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":true,\"hideJournal\":true,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true},\"keywords\":\"\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-6210811/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-6210811/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eRetreating accretionary orogens exhibit a paradoxical capacity to sustain crustal shortening and growth contemporaneous with dominant upper plate extension. Deciphering the dynamic coupling between mantle flow and crustal evolution is critical in understanding orogenic mechanisms within such retreating systems, with profound implications for subduction zone dynamics and continental growth processes. Here we integrate high-resolution 2D numerical simulations, with quantitative geological boundary conditions from the Paleozoic Altaides archetype, to establish an endogenic orogenic mechanism driven by slab rollback-induced mantle circulation during retreating subduction. Our models demonstrate that spontaneous mantle upwelling and convections could systematically govern (1) progressive trench-directed arc migration, (2) crustal growth through intense bimodal magmatism with juvenile isotopic signatures, (3) self-organized forearc-arc-backarc-intraplate tectonic zoning, and (4) crustal thickening-extension cycles and diachronous coexistence, all of which characterize the Altaides and other archetypal retreating accretionary orogens. This intrinsic interplay between slab rollback, mantle upwelling, and upper plate response supersedes previous models dependent on external orogenic forcing, offering a unified framework to interpret accretionary orogens via deep Earth-surface interactions.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Endogenic mantle-driven orogenic evolution: Slab rollback dynamics as the architect of retreating accretionary systems\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2025-04-17 08:47:30\",\"doi\":\"10.21203/rs.3.rs-6210811/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"81484d05-0e35-4523-b7ef-fcdd7628875f\",\"owner\":[],\"postedDate\":\"April 17th, 2025\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"posted\",\"subjectAreas\":[{\"id\":47211725,\"name\":\"Earth and environmental sciences/Solid Earth sciences/Geology\"},{\"id\":47211726,\"name\":\"Earth and environmental sciences/Planetary science/Geodynamics\"}],\"tags\":[],\"updatedAt\":\"2025-10-28T23:55:31+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2025-04-17 08:47:30\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-6210811\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-6210811\",\"identity\":\"rs-6210811\",\"version\":[\"v1\"]},\"buildId\":\"8U1c8b4HqxoKbykW_rLl7\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}