从板缘造山到陆内变形的对称与非对称模式:岩石圈构造极性的形成机制OA

[Objective]Tectonic vergence records the geometric asymmetry and kinematic directionality of shortening during orogenic thickening and provides a key link between surface deformation and lithospheric-scale geodynamics.Although vergence is widely used in structural geology,its expression at the scale of entire orogenic belts remains insufficiently clarified,especially in intracontinental settings where stable plate-boundary subduction is absent.This study aims to compare vergence patterns from plate-margin orogens to intracontinental mountain belts and to identify the mechanisms controlling their formation,maintenance,weakening,and transformation.[Methods]We synthesize five representative orogenic systems:the Central Andes,Taiwan,the Alps,the Qilian Shan,and the Tian Shan.Surface structural styles,fold-thrust belt geometry,orogen-foreland basin coupling,geomorphic evolution,modern crustal deformation,seismicity,and lithospheric architecture—constrained by Moho/LAB geometry and geophysical imaging—are integrated to evaluate vergence at multiple scales.[Results]Plate-margin convergent systems commonly develop stable one-sided tectonic vergence.In the Central Andes,long-lived subduction of the Nazca slab provides persistent asymmetric forcing,causing shortening to be localized above the subduction interface and transmitted eastward toward the retroarc and foreland.The Altiplano Plateau,with crustal thickness locally reaching 60-75 km,records progressive Cenozoic crustal thickening,uplift,and eastward propagation of deformation.Taiwan,as a young arc-continent collision system,locally records early-stage bidirectional deformation around the Central Range and arc-side backthrusting near the Longitudinal Valley-Coastal Range system.However,foreland basin evolution,westward migration of the frontal fold-thrust belt,and modern shortening concentrated along the western Taiwan thrust system indicate that its long-term,orogen-scale,dominant vergence remains west-directed.The Alps demonstrate that tectonic vergence is time-dependent.During early subduction and continental collision,deformation was localized along a single subduction interface,producing a north-vergent simple-shear-dominated architecture.After collision,slab break-off,eclogitization of the orogenic root,and thermomechanical reorganization weakened the earlier interface-controlled deformation and promoted strain redistribution across both flanks of the orogen,leading to paired north-and south-vergent thrust systems and a more symmetric collisional structure.In intracontinental orogens,stable one-sided vergence is not guaranteed.The Qilian Shan and Tian Shan lack compelling evidence for a continuous,long-lived,single-sided lithospheric subduction interface.Their deformation is mainly expressed by distributed crustal thickening,high-angle reverse faulting on opposing flanks,and near-symmetric shortening.Recent studies from the Qilian Shan further show that lithospheric-scale tectonic wedges may develop along basin-mountain transition zones,where relatively rigid basin lithosphere wedges into the weakened lower crust of a thickened orogen.Such wedge structures are best interpreted as local expressions within a pure-shear,vertically coherent deformation framework rather than as large-scale simple-shear intracontinental subduction.[Conclusions]Lithospheric-scale tectonic vergence is controlled by the coupling among boundary conditions,negative-buoyancy forcing,and lithospheric strength-buoyancy structure.Persistent single-sided slabs or effective negative-buoyancy sources favor stable simple-shear vergence,whereas slab break-off,loss of one-sided forcing,and mechanically strong opposing blocks favor distributed pure-shear thickening and weak or near-symmetric vergence.[Significance]This study provides a unified framework for interpreting tectonic vergence from plate margins to continental interiors.It highlights vergence as a geometrically testable indicator for linking surface deformation,basin-orogen coupling,and lithospheric-scale geodynamic processes.