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1.
Michael R. W. Johnson 《地学学报》2003,15(1):46-51
ABSTRACT The nature of the Indian crust underthrusting the Himalaya may be studied in xenoliths within Ordovician granites in the external part of the Himalaya. These peraluminous S-type granites have travelled for c . 200 km in the Main Central (or related) thrust. The granites and xenoliths sample Indian basement now buried beneath the High Himalayan thrust pile. In low-strain granites the xenoliths reveal polyphase tectonite fabrics older than the fabrics in the country rocks. Most xenoliths show greenschist/lower amphibolite facies assemblages; none is typical granulite facies of the Indian Shield. Therefore, the portion of the Indian crust underthrusting the Himalaya may be early/middle Proterozoic reworked Indian Shield, as in peninsular India. Alternatively reworking may be assigned to the Pan-African (late Proterozoic) orogeny. This prospect is raised by recent work in East Antarctica but evidence in the Himalaya is rather ambiguous. If confirmed, a Pan-African event calls for reassessment of the geological history of the Himalayan region, particularly with respect to the placing of India in Gondwanaland. 相似文献
2.
James F Ni 《Journal of Earth System Science》1989,98(1):71-89
The Himalayan mountains are a product of the collision between India and Eurasia which began in the Eocene. In the early stage
of continental collision the development of a suture zone between two colliding plates took place. The continued convergence
is accommodated along the suture zone and in the back-arc region. Further convergence results in intracrustal megathrust within
the leading edge of the advancing Indian plate. In the Himalaya this stage is characterized by the intense uplift of the High
Himalaya, the development of the Tibetan Plateau and the breaking-up of the central and eastern Asian continent. Although
numerous models for the evolution of the Himalaya have been proposed, the available geological and geophysical data are consistent
with an underthrusting model in which the Indian continental lithosphere underthrusts beneath the Himalaya and southern Tibet.
Reflection profiles across the entire Himalaya and Tibet are needed to prove the existence of such underthrusting. Geodetic
surveys across the High Himalaya are needed to determine the present state of the MCT as well as the rate of uplift and shortening
within the Himalaya. Paleoseismicity studies are necessary to resolve the temporal and spatial patterns of major earthquake
faulting along the segmented Himalayan mountains. 相似文献
3.
GAO Rui ZHOU Hui GUO Xiaoyu LU Zhanwu LI Wenhui WANG Haiyan LI Hongqiang XIONG Xiaosong HUANG Xingfu XU Xiao 《地学前缘》2021,28(5):320-336
印度板块与亚洲板块的碰撞使喜马拉雅-青藏高原隆升,地壳增厚和生长扩展。探测青藏高原深部结构,揭露两个大陆如何碰撞,碰撞如何使大陆变形的过程,是全球关切的科学奥秘。深地震反射剖面探测是打开这个科学奥秘的最有效途径之一。20多年来,运用这项高技术探测到青藏高原巨厚地壳的精细结构,攻克了难以得到下地壳和Moho清晰结构的技术瓶颈,揭露了陆陆碰撞过程。本文在探测研究成果基础上,从青藏高原南北-东西对比,再到高原腹地,系统地综述了青藏高原之下印度板块与亚洲板块碰撞-俯冲的深部行为。印度地壳在高原南缘俯冲在喜马拉雅造山带之下,亚洲板块的阿拉善地块岩石圈在北缘向祁连山下俯冲,祁连山地壳向外扩展,塔里木地块与高原西缘的西昆仑发生面对面的碰撞,在高原东缘发现龙日坝断裂而不是龙门山断裂是扬子板块的西缘边界,高原腹地Moho 薄而平坦,岩石圈伸展垮塌。多条深反射剖面揭露了在雅鲁藏布江缝合带下印度板块与亚洲板块碰撞的行为,印度地壳不仅沿雅鲁藏布江缝合带存在由西向东的俯冲角度变化,而且其向北行进到拉萨地体内部的位置也不同。在缝合带中部,显示印度地壳上地壳与下地壳拆离,上地壳向北仰冲,下地壳向北俯冲,并在俯冲过程发生物质的回返与构造叠置,使印度地壳减薄,喜马拉雅地壳加厚。俯冲印度地壳前缘与亚洲地壳碰撞后沉入地幔,处于亚洲板块前缘的冈底斯岩基与特提斯喜马拉雅近于直立碰撞,冈底斯下地壳呈部分熔融状态,近乎透明的弱反射和局部出现的亮点反射,以及近于平的Moho都反映出亚洲板块南缘的伸展构造环境。 相似文献
4.
陆陆碰撞过程是板块构造缺失的链条。印度板块与亚洲板块的碰撞造就了喜马拉雅造山带和青藏高原的主体。然而,人们对印度板块在大陆碰撞过程中的行为尚不了解。如大陆碰撞及其碰撞后的大陆俯冲是如何进行的、印度板块是俯冲在青藏高原之下还是回转至板块上部(喜马拉雅造山带内)以及两者比例如何,这些仍是亟待解决的问题。印度板块低角度沿喜马拉雅主逆冲断裂(MHT)俯冲在低喜马拉雅和高喜马拉雅之下已经被反射地震图像很好地揭示。然而,关于MHT如何向北延伸,前人的研究仅获得了分辨率较低的接收函数图像。因而,MHT和雅鲁藏布江缝合带之间印度板块的俯冲行为仍是一个谜。喜马拉雅造山楔增生机制,也就是印度地壳前缘的变形机制,反映出物质被临界锥形逆冲断层作用转移到板块上部,或是以韧性管道流的样式向南溢出。在本次研究中,我们给出在喜马拉雅造山带西部地区横过雅鲁藏布江缝合带的沿东经81.5°展布的高分辨率深地震反射剖面,精细揭示了地壳尺度结构构造。剖面显示,MHT以大约20°的倾斜角度延伸至大约60 km深度,接近埋深为70~75 km的Moho面。越过雅鲁藏布江缝合带运移到北面的印度地壳厚度已经不足15 km。深地震反射剖面还显示中地壳逆冲构造反射发育。我们认为,伴随着印度板块俯冲,地壳尺度的多重构造叠置作用使物质自MHT下部的板块向其上部板块转移,这一过程使印度地壳厚度减薄了,同时加厚了喜马拉雅地壳。 相似文献
5.
Xue Guangqi Jiang Mei Qian Hui Wei Suhua Dong Yingjun Gerard Wittlinger Georges Poupinet Edi Kissling WT ”BX 《地学前缘》2000,(Z1)
SEISMIC STUDIES ON THE CRUST-MANTLE STRUCTURE ACROSS KARAMAY-KUCHA IN XINJIANG, CHINA 相似文献
6.
Richard L Brown 《Tectonophysics》1978,48(1-2)
The Shuswap metamorphic core complex of the southeast Canadian Cordillera, which is allochthonous with respect to a fixed reference frame beneath the Plains of the North American craton, evolved and became consolidated prior to major development of thrust faulting in the Rocky Mountains.Polyphase deformation of the infrastructure of the complex beneath a weakly compressed suprastructure is probably due to shear strains generated by underthrusting of marginal lithosphere rather than to gravitational upwelling and lateral spreading.Pre-metamorphic to early metamorphic strain of the complex may be related to eastward underthrusting from the west. Late metamorphic strain may be related to westward underthrusting of the North American craton from the east. Continued underthrusting of the craton led to uplift and northeastward translation of the consolidated metamorphic complex together with development of thrust faults in the Rocky Mountains. 相似文献
7.
《Gondwana Research》2015,28(4):1487-1493
Receiver function imaging along a temporary seismic array (ANTILOPE-2) reveals detailed information of the underthrusting of the Indian crust in southern Tibet. The Moho dips northward from ~ 50 km to 80 km beneath the Himalaya terrane, and locally reaches ~ 85 km beneath the Indus–Yalung suture. It remains at ~ 80 km depth across the Lhasa terrane, and shallows to ~ 70 km depth under the Qiangtang terrane. An intra-crustal interface at ~ 60 km beneath the Lhasa terrane can be clearly followed southward through the Main Himalaya Thrust and connects the Main Boundary Thrust at the surface, which represents the border of the Indian crust that is underthrusting until south of the Bangong–Nujiang Suture. A mid-crustal low velocity zone is observed at depths of 14–30 km beneath the Lhasa and Himalaya terranes probably formed by partial melt and/or aqueous fluids. 相似文献
8.
Focal-mechanism solutions of four earthquakes in the eastern Himalayas and northern Burma are determined using the first motion of compressional waves. Two possible solutions thus obtained for each event reveal steeply dipping fault with predominantly strike-slip motion. The stress directions inferred from the focal mechanism solutions are interpreted in the light of predictions of the plate tectonics theory, viz., the underthrusting of the Indian plate in the Burma region in an easterly direction.Dynamic parameters (seismic moment, apparent stress and average dislocations) are obtained using the corrected spectra of Love waves. The earthquakes are found to possess low seismic moment and apparent stress values. A comparison of these estimates with values for intraplate earthquakes is given. It is suggested that these earthquake might be a consequence of a nonhomogeneous rupture process. 相似文献
9.
Crustal structures of the Central and Eastern Pyrenees are compared with those of the Alps and Carpathians. By analogy, northward subduction/underthrusting in the Central and Eastern Pyrenees is proposed. Southward subduction/underthrusting is found along the North Iberian margin and Western Pyrenees. Hence, a flip—a change in the direction of subduction/underthrusting—is postulated between the Central and Western Pyrenees. 相似文献
10.
11.
《Gondwana Research》2014,26(4):1690-1699
The continental collision between the Indian and Asian plates plays a key role in the geologic and tectonic evolution of the Tibetan plateau. In this article we present high-resolution tomographic images of the crust and upper mantle derived from a large number of high-quality seismic data from the ANTILOPE project in western Tibet. Both local and distant earthquakes were used in this study and 35,115 P-wave arrival times were manually picked from the original seismograms. Geological and geochemical results suggested that the subducting Indian plate has reached northward to the Lhasa terrane, whereas our new tomography shows that the Indian plate is currently sub-horizontal and underthrusting to the Jinsha river suture at depths of ~ 100 to ~ 250 km, suggesting that the subduction process has evolved over time. The Asian plate is also imaged clearly from the surface to a depth of ~ 100 km by our tomography, and it is located under the Tarim Basin north of the Altyn Tagh Fault. There is no obvious evidence to show that the Asian plate has subducted beneath western Tibet. The Indian and Asian plates are separated by a prominent low-velocity zone under northern Tibet. We attribute the low-velocity zone to mantle upwelling, which may account for the warm crust and upper mantle beneath that region, and thus explain the different features of magmatism between southern and northern Tibet. But the upwelling may not penetrate through the whole crust. We propose a revised geodynamic model and suggest that the high-velocity zones under Lhasa terrane may reflect a cold crust which has interrupted the crustal flow under the westernmost Tibetan plateau. 相似文献
12.
印度板块与亚洲板块的碰撞使喜马拉雅-青藏高原隆升,地壳增厚并生长扩展。探测青藏高原深部结构,揭露两个大陆如何碰撞以及碰撞如何使大陆变形的过程,是对全球关切的科学奥秘的探索。深地震反射剖面探测是打开这个科学奥秘的最有效途径之一。二十多年来,运用这项高技术探测到青藏高原巨厚地壳的精细结构,攻克了难以得到下地壳和Moho面信息的技术瓶颈,揭露了陆-陆碰撞过程。本文在探测研究成果的基础上,从青藏高原南北-东西对比,再到高原腹地,系统地综述了青藏高原之下印度板块与亚洲板块碰撞-俯冲的深部行为。印度地壳在高原南缘俯冲在喜马拉雅造山带之下,亚洲板块的阿拉善地块岩石圈在北缘向祁连山下俯冲,祁连山地壳向外扩展,塔里木地块与高原西缘的西昆仑发生面对面的碰撞,在高原东缘发现龙日坝断裂(而不是龙门山断裂)是扬子板块的西缘边界,高原腹地Moho面厚度薄而平坦,岩石圈伸展垮塌。多条深反射剖面揭露了在雅鲁藏布江缝合带下印度板块与亚洲板块碰撞的行为,不仅沿雅鲁藏布江缝合带走向印度地壳俯冲行为存在东西变化,而且印度地壳向北行进到拉萨地体内部的位置也不同。在缝合带中部,研究显示印度地壳上地壳与下地壳拆离,上地壳向北仰冲,下地壳向北俯冲,并在俯冲过程中发生物质的回返与构造叠置,这导致印度地壳减薄,喜马拉雅地壳加厚。俯冲印度地壳前缘与亚洲地壳碰撞后沉入地幔,处于亚洲板块前缘的冈底斯岩基与特提斯喜马拉雅近于直立碰撞,冈底斯下地壳呈部分熔融状态,近乎透明的弱反射和局部出现的亮点反射以及近于平的Moho面都反映出亚洲板块南缘处于伸展构造环境。 相似文献
13.
Crustal shortening of the ocean floor in the eastern Mediterranean is recognized by a marked thickening of the sedimentary layer seaward of the Hellenic and Calabrian island arcs. Steep gradients and large negative free-air anomalies in the gravity field along with a highly uniform, low regional heat flow are manifestations of the thickened crust. Bodies of recently deformed sediment in and seaward of the Hellenic Trough reveal the style, polarity, and dynamics of the thickening mechanism.
A linear buried anticlinal structure, inferred from analysis of surface ship gravity profiles, may mark the site of contemporary intrabasinal underthrusting. The distribution of earthquakes beneath the Mediterranean Ridge supports the interpretation that the Anaximander, Ptolomy, and Strabo Mountains are features comparable to large basement nappes. Cyprus is one such structure, offset to the south, where the oceanic crust and part of the upper mantle have been involved in the décollement. 相似文献
14.
Rubn Díez Fernndez Ricardo Arenas Sonia Snchez Martínez Irene Novo‐Fernndez Richard Albert 《地学学报》2020,32(4):239-245
Within the Variscan Orogen, Early Devonian and Late Devonian high‐P belts separated by mid‐Devonian ophiolites can be interpreted as having formed in a single subduction zone. Early Devonian convergence nucleated a Laurussia‐dipping subduction zone from an inherited lithospheric neck (peri‐Gondwanan Cambrian back‐arc). Slab‐retreat induced upper plate extension, mantle incursion and lower plate thermal softening, favouring slab‐detachment within the lower plate and diapiric exhumation of deep‐seated rocks through the overlying mantle up to relaminate the upper plate. Upper plate extension produced mid‐Devonian suprasubduction ocean floor spreading (Devonian ophiolites), while further convergence resulted in plate coupling and intraoceanic ophiolite imbrication. Accretion of the remaining Cambrian ocean heralded Late Devonian subduction of inner sections of Gondwana across the same subduction zone and the underthrusting of mainland Gondwana (culmination of NW Iberian allochthonous pile). Oblique convergence favoured lateral plate sliding, and explained the different lateral positions along Gondwana of terranes separated by Palaeozoic ophiolites. 相似文献
15.
In the present paper integrated appraisals of landform evolution and their geomorphic features, drainage networks across the upper part of Yamuna river basin have been attempted by using various geomorphic indices such as watershed, drainage density (D), drainage texture, stream-gradient index (SL), hypsometric integral (HI), drainage basin asymmetry (AF), mountain front sinuosity (Smf), sinuosity index (SI), valley floor height and width ratio (Vf) and data of historical earthquakes in characterizing the basin in view of relative index of active tectonics (RIAT) on DEM in geographic information systems (GIS) environment to assess the influence of recent tectonics on geomorphologic growth of the basin.The substantiated RIAT classes through some field observations and corroborated by recent seismicity reveal the recent activation of Yamuna tear faults in the basin with delineation of four RIAT classes such as class-1 (inactive 9.8% of the area), class-2 (low active; 16.40% of the area), class-3 (moderately active; 42.38% of the area) and class-4 (very active; 31.62%). The results suggest that the Himalayan frontal thrust (HFT) and Yamuna tear (YT) located in the basin is morphogenic in nature and got activated several times as evidenced by number of seismic activities in the basin and adjoining regions. The incision, and sharp turning of rivers, crenulations and warping of cross beddings/laminations and silt/clay beds and lenses, megascopic and mesoscopic faulting in sediment sequences suggest a very active nature of the HFT and YT till date in association with three prolific microseismogenic weak zones These active discontinuities appear to support the formation and development of different deformational features in sediment sequences which may be indirectly related to subduction and underthrusting of Indian plate under Eurasian plate below the Himalayan mountain chain. 相似文献
16.
An overview is presented of the Indian apparent polar wander path (APWP) for the Phanerozoic and in particular for post-Late Palaeozoic times. This APWP is compiled on basis of data available at October 1981 from peninsular and extrapeninsular Indo-Pakistan and from DSDP cores from the Indian plate. One of the more important and newly recognized features of this APWP is a large-scale Triassic-Jurassic loop. This loop indicates a changeover from a Late Palaeozoic-Early Mesozoic northwards and counter-clockwise rotational movement, with Greater India reaching moderately low southern latitudes, into a southwards and clockwise rotational movement during the Early to Middle Jurassic. Recognizable likewise in APWP's from other Gondwana continents, this loop reflects the opening of the Neotethys.Studies of extrapeninsular regions up to and north of the Indus-Tsangpo suture zone have shown wide-spread presence of magnetic overprints, which delineate two regionally confined age groups. Younger overprints (20–40 m.y.) predominate in the more external thrust zones. Older overprints (50–60 m.y.), in contrast, are found in the more internal zones both north and south of the Indus-Tsangpo suture zone. The latter are interpreted to reflect a late phase of relaxation in the Early Tertiary collision of Greater India with south-central Asia or off-shore island arcs, which occurred at equatorial to low northern palaeolatitudes (0°–10°N). Subsequent northwards movement over 2500–3000 km or more and impingement of Greater India into southern Asia resulted into large-scale underthrusting of Greater India along the Main Central Thrust beneath southern Tibet, and to clockwise rotation of thrust units in the Western Himalaya. A discrepancy between Indian palaeomagnetic data and results available todate from southern Tibet is discussed. 相似文献
17.
Structural development of the Tso Morari ultra-high pressure nappe of the Ladakh Himalaya 总被引：2，自引：0，他引：2
A continental subduction-related and multistage exhumation process for the Tso Morari ultra-high pressure nappe is proposed. The model is constrained by published thermo-barometry and age data, combined with new geological and tectonic maps. Additionally, observations on the structural and metamorphic evolution of the Tso Morari area and the North Himalayan nappes are presented. The northern margin of the Indian continental crust was subducted to a depth of > 90 km below Asia after continental collision some 55 Ma ago. The underthrusting was accompanied by the detachment and accretion of Late Proterozoic to Early Eocene sediments, creating the North Himalayan accretionary wedge, in front of the active Asian margin and the 103–50 Ma Ladakh arc batholith. The basic dikes in the Ordovician Tso Morari granite were transformed to eclogites with crystallization of coesite, some 53 Ma ago at a depth of > 90 km (> 27 kbar) and temperatures of 500 to 600 °C. The detachment and extrusion of the low density Tso Morari nappe, composed of 70% of the Tso Morari granite and 30% of graywackes with some eclogitic dikes, occurred by ductile pure and simple shear deformation. It was pushed by buoyancy forces and by squeezing between the underthrusted Indian lithosphere and the Asian mantle wedge. The extruding Tso Morari nappe reached a depth of 35 km at the base of the North Himalayan accretionary wedge some 48 Ma ago. There the whole nappe stack recrystallized under amphibolite facies conditions of a Barrovian regional metamorphism with a metamorphic field gradient of 20 °C/km. An intense schistosity with a W–E oriented stretching lineation L1 and top-to-the E shear criteria and crystallization of oriented sillimanite needles after kyanite, testify to the Tso Morari nappe extrusion and pressure drop. The whole nappe stack, comprising from the base to top the Tso Morari, Tetraogal, Karzok and Mata–Nyimaling-Tsarap nappes, was overprinted by new schistosities with a first N-directed and a second NE-directed stretching lineation L2 and L3 reaching the base of the North Himalayan accretionary wedge. They are characterized by top-to-the S and SW shear criteria. This structural overprint was related to an early N- and a younger NE-directed underthrusting of the Indian plate below Asia that was accompanied by anticlockwise rotation of India. The warping of the Tso Morari dome started already some 48 Ma ago with the formation of an extruding nappe at depth. The Tso Morari dome reached a depth of 15 km about 40 Ma ago in the eastern Kiagar La region and 30 Ma ago in the western Nuruchan region. The extrusion rate was of about 3 cm/yr between 53 and 48 Ma, followed by an uplift rate of 1.2 mm/yr between 48 and 30 Ma and of only 0.5 mm/yr after 30 Ma. Geomorphology observations show that the Tso Morari dome is still affected by faults, open regional dome, and basin and pull-apart structures, in a zone of active dextral transpression parallel to the Indus Suture zone. 相似文献
18.
造山带地壳结构和成分的基本特征对于认识大陆地壳成分演化和区域成矿背景具有重要意义.综合青藏高原拉萨地体东南部地球物理、高温高压岩石物性和岩浆岩地球化学资料,分析该地区地壳整体成分特征,并探讨其可能成因.该地区平均地壳波速显著低于全球大陆和造山带地壳的平均值,表明地壳整体具有中酸性成分,下地壳特征也可由中性岩石(残余体性质的中性含石榴石麻粒岩)解释.拉萨地体东南部整体地壳成分特征应与多阶段长英质化有关,包括碰撞前大陆弧演化阶段(以堆晶或残余体下地壳拆沉为主)和碰撞后高原垮塌阶段(以加厚下地壳拆沉为主,伴随印度古老长英质陆壳物质的俯冲回返/构造底侵).拉萨地体是研究大陆地壳成分演化的绝佳区域,亟待进一步开展多学科综合研究. 相似文献
19.
Robert R. Loucks 《Contributions to Mineralogy and Petrology》1996,124(3-4):346-358
In polymineralic plutonic igneous and metamorphic rocks, slowly cooled crystals seldom retain their initial chemical compositions.
This paper introduces a new, simple and widely applicable material-balance method that recovers the former compositions of
minerals – regenerating in many rock types their chemical memory of the environment in which they formed – without a priori knowledge of temperature or pressure or diffusion kinetics. Restored stable-isotopic, trace-element, and/or major-element
compositions provide a basis for interpretations of petrogenetic processes and conditions, including recovery of peak temperature
and pressure, depth, and average diffusion distance during re-equilibration. Case studies illustrate applications of the mineral-restoration
technique to regional crustal dynamics, ore metallogeny, and igneous fluid dynamics and petrogenesis. The first illustrative
case addresses the controversial origin of decimetre-thick, modally graded rock layers in the Skaergaard intrusion. Layer-wide
mineral-chemistry gradients that previously were ascribed a primary origin are here shown to be due to sub-solidus diffusive
re-equilibration amongst minerals that initially were chemically uniform. This finding redefines the constraints to be satisfied
by fluid-dynamic models of chemical differentiation processes in the magma chamber, and eliminates the basis of prior interpretations
of the modally graded layers as products of in situ crystallization on the magma chamber's floor. In another case, lower crustal olivine-chromite cumulates underwent a long
two-stage history of mineral-composition readjustment spanning >500° C. The technique introduced here removes the effects
of the second-stage solid-state diffusion, recovering mineral compositions that represent the igneous solidus temperature at the termination of the metasomatic stage. The third example removes effects of retrograde diffusive ion-exchange
from garnet, hornblende, and clinopyroxene in order to restore the rock's chemical memory of its pressure and depth of crystallization.
The depth corresponds to a measure of extreme Cenozoic uplift and erosion (∼58 km) along the Main Mantle Thrust, which juxtaposes
the underthrusting Indian Plate and the over-riding Kohistan island-arc terrain in the Pakistani Himalayas.
Received: 28 March 1995 / Accepted: 11 April 1996 相似文献
20.
《Gondwana Research》2014,25(3-4):936-945
Body wave seismic tomography is a successful technique for mapping lithospheric material sinking into the mantle. Focusing on the India/Asia collision zone, we postulate the existence of several Asian continental slabs, based on seismic global tomography. We observe a lower mantle positive anomaly between 1100 and 900 km depths, that we interpret as the signature of a past subduction process of Asian lithosphere, based on the anomaly position relative to positive anomalies related to Indian continental slab. We propose that this anomaly provides evidence for south dipping subduction of North Tibet lithospheric mantle, occurring along 3000 km parallel to the Southern Asian margin, and beginning soon after the 45 Ma break-off that detached the Tethys oceanic slab from the Indian continent. We estimate the maximum length of the slab related to the anomaly to be 400 km. Adding 200 km of presently Asian subducting slab beneath Central Tibet, the amount of Asian lithospheric mantle absorbed by continental subduction during the collision is at most 600 km. Using global seismic tomography to resolve the geometry of Asian continent at the onset of collision, we estimate that the convergence absorbed by Asia during the indentation process is ~ 1300 km. We conclude that Asian continental subduction could accommodate at most 45% of the Asian convergence. The rest of the convergence could have been accommodated by a combination of extrusion and shallow subduction/underthrusting processes. Continental subduction is therefore a major lithospheric process involved in intraplate tectonics of a supercontinent like Eurasia. 相似文献