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1.
Eisei Ikesawa Gaku Kimura Katsushi Sato Kotoe Ikehara-Ohmori Yujin Kitamura Asuka Yamaguchi Kohtaro Ujiie Yoshitaka Hashimoto 《Tectonophysics》2005,401(3-4):217-230
A tectonic mélange exposed on land is examined to reveal relationships between mélange formation, underplating, and deformation mechanisms, focusing on the deformation of basaltic rocks. The studied Mugi Mélange of the Shimanto Belt is composed of a shale matrix surrounding various blocks of sandstone, pelagic sediments, and basalts. The mélange was formed during Late Cretaceous to early Tertiary times in a subduction zone under P–T conditions of 150–200 °C and 6–7 km depth as estimated from vitrinite reflectance and quartz veins fluid inclusions. The mélange represents a range of deformation mechanisms; pressure solution with micro-scale cataclasis in the shale matrix, brittle tension cracking in the blocks, and ubiquitous strong cataclasis in the basal portion of basaltic layers. The cataclastic deformation in the basalts suggests a breakage of a topographic high in the seismogenic depth. 相似文献
2.
Hidetoshi Hara Koji Wakita Katsumi Ueno Yoshihito Kamata Ken-ichiro Hisada Punya Charusiri Thasinee Charoentitirat Pol Chaodumrong 《Gondwana Research》2009,16(2):310
We reconstructed the accretion process related to Paleo-Tethys subduction recorded in northern Thailand, based on mélange and thrust structures, and metamorphic temperatures derived from illite crystallinity data. Mélange formation was characterized by hydrofracturing and cataclastic deformation, with mud injection under semi-lithified conditions followed by shear deformation and pressure solution. Illite crystallinity data suggest metamorphic temperatures below 250 °C during mélange formation. The combined structural and metamorphic data indicate that during mélange formation, the accretionary complex related to Paleo-Tethys subduction developed at shallow levels within an accretionary prism. Asymmetric shear fabrics in mélange indicate top-to-south shear. After correction for rotation associated with collision between the Indian and Eurasian continents, the trend of the Paleo-Tethys subduction zone is estimated to have been N80 °E. We conclude that the Paleo-Tethys was subducted northward beneath the Indochina Block from the Permian to Triassic. 相似文献
3.
The Bay of Islands Ophiolite was emplaced onto the continental margin of North America during the mid-Ordovician Taconic orogeny, when tectonic slices of continental margin sediments were accreted to the moving allochthon. Tectonic slices grade into and are surrounded by mélange. Early fracture in sandstones formed without grain breakage and allowed penetration of liquid petroleum along fracture planes. Other fractures involved cataclastic flow and were sometimes re-activated during formation of later pressure solution cleavage. Shear-fracture and extension-fracture boudinage affect competent strata; extensional veins cut cement in limestone beds and are filled by shale, quartz, calcite and bitumen. Folds also formed, at a time when siltstone and sandstone were at least partially lithified. Mélange matrix shows abundant shear and extension fractures in a variety of orientations.Coaxial extension responsible for disruption of bedding can be explained by a brittle accretionary wedge model in which high fluid pressures resulted from tectonic dewatering of shales. Surface slope decreased as fluid pressure rose beneath the ophiolite, causing horizontal extension of the wedge. After escape of excess water the surface slope steepened again as renewed stacking occurred. 相似文献
4.
Ocean Plate Stratigraphy in East and Southeast Asia 总被引：10，自引：1，他引：10
Ancient accretionary wedges have been recognised by the presence of glaucophane schist, radiolarian chert and mélange. Recent techniques for the reconstruction of disrupted fragments of such wedges by means of radiolarian biostratigraphy, provide a more comprehensive history of ocean plate subduction and successive accretion of ocean floor materials from the oceanic plate through offscraping and underplating.Reconstructed ocean floor sequences found in ancient accretionary complexes in Japan comprise, from oldest to youngest, pillow basalt, limestone, radiolarian chert, siliceous shale, and shale and sandstone. Similar lithologies also occur in the mélange complexes of the Philippines, Indonesia, Thailand and other regions. This succession is called ‘Ocean Plate Stratigraphy’ (OPS), and it represents the following sequence of processes: birth of the oceanic plate at the oceanic ridge; formation of volcanic islands near the ridge, covered by calcareous reefs; sedimentation of calcilutite on the flanks of the volcanic islands where radiolarian chert is also deposited; deposition of radiolarian skeletons on the oceanic plate in a pelagic setting, and sedimentary mixing of radiolarian remains and detrital grains to form siliceous shale in a hemipelagic setting; and sedimentation of coarse-grained sandstone and shale at or near the trench of the convergent margin.Radiolarian biostratigraphy of detrital sedimentary rocks provides information on the time and duration of ocean plate subduction. The ages of detrital sediments becomes younger oceanward as younger packages of OPS are scraped off the downgoing plate.OPS reconstructed from ancient accretionary complexes give us the age of subduction and accretion, direction of subduction, and ancient tectonic environments and is an important key to understanding the paleoenvironment and history of the paleo-oceans now represented only in suture zones and orogenic belts. 相似文献
5.
The Aladag region of eastern Taurides, Turkey, is characterized by an imbricated thrust structure developed during late stage emplacement of the Pozanti-Karsanti ophiolite onto the Menderes-Taurus block in the late Cretaceous. The mid to late Cretaceous dynamothermal metamorphic sole and the underlying unmetamorphosed mélange, here named the Aladag accretionary complex, were accreted to the base of the Pozanti-Karsanti ophiolite during intra-oceanic subduction, transport and final obduction of the ophiolite onto the Menderes-Taurus block.In the dynamothermal metamorphic sole, intensity of deformation and degree of metamorphism increase from the base to the top, and at least three episodes of foliation, lineation and fold development are recognized. The asymmetry of quartz c-axis fabrics, tightness and asymmetry of folds of the same generation, and curvature of fold hinge lines increase from base to top, indicating that non-coaxial progressive deformation prevailed during the development of the metamorphic sole. The mélange is divided into three major thrust fault-bounded tectonic slivers, each of which is characterized by distinctive types of matrix and block lithologies, structures and deformation style. Kinematic analyses of the dynamothermal metamorphic sole and the mélange reveal that the tectonic transport direction of the Pozanti-Karsanti ophiolite during its emplacement was from north-northwest to south-southeast, suggesting that the Pozanti-Karsanti ophiolite was derived from a Neo-Tethyan ocean to the north of the Menderes-Taurus block. 相似文献
6.
The Huaiyu and Jiuling terranes in the central Jiangnan belt, south China, are separated by the Dongxiang-Shexian shear zone. An Upper Proterozoic ophiolite-bearing mélange is dispersed along the contact. Isotopic ages of mafic and ultramafic rocks within the mélange cluster around 1000 Ma (Sm-Nd method). Glaucophanes from blueschist yield an isotopic age of 866 Ma (K-Ar method), interpreted to date the timing of collision. The mélange and terranes underwent regional metamorphism during the Late Proterozoic. The resulting foliation was later crosscut by a Late Proterzoic sinistral oblique normal shear along the suture zone. Clastic sediments were unconformably deposited over both terranes during the Sinian (latest Proterozoic). 相似文献
7.
Permian to Cretaceous mélange of the McHugh Complex on the Kenai Peninsula, south-central Alaska includes blocks and belts of graywacke, argillite, limestone, chert, basalt, gabbro, and ultramafic rocks, intruded by a variety of igneous rocks. An oceanic plate stratigraphy is repeated hundreds of times across the map area, but most structures at the outcrop scale extend lithological layering. Strong rheological units occur as blocks within a matrix that flowed around the competent blocks during deformation, forming broken formation and mélange. Deformation was noncoaxial, and disruption of primary layering was a consequence of general strain driven by plate convergence in a relatively narrow zone between the overriding accretionary wedge and the downgoing, generally thinly sedimented oceanic plate. Soft-sediment deformation processes do not appear to have played a major role in the formation of the mélange. A model for deformation at the toe of the wedge is proposed in which layers oriented at low angles to σ1 are contracted in both the brittle and ductile regimes, layers at 30–45° to σ1 are extended in the brittle regime and contracted in the ductile regime, and layers at angles greater than 45° to σ1 are extended in both the brittle and ductile regimes. Imbrication in thrust duplexes occurs at deeper levels within the wedge. Many structures within mélange of the McHugh Complex are asymmetric and record kinematic information consistent with the inferred structural setting in an accretionary wedge. A displacement field for the McHugh Complex on the lower Kenai Peninsula includes three belts: an inboard belt of Late Triassic rocks records west-to-east-directed slip of hanging walls, a central belt of predominantly Early Jurassic rocks records north–south directed displacements, and Early Cretaceous rocks in an outboard belt preserve southwest–northeast directed slip vectors. Although precise ages of accretion are unknown, slip directions are compatible with inferred plate motions during the general time frame of accretion of the McHugh Complex. The slip vectors are interpreted to preserve the convergence directions between the overriding and underriding plates, which became more oblique with time. They are not considered indicative of strain partitioning into belts of orogen-parallel and orogen-perpendicular displacements, because the kinematic data are derived from the earliest preserved structures, whereas fabrics related to strain partitioning would be expected to be superimposed on earlier accretion-related fabrics. 相似文献
8.
A.H.G. Mitchell 《Tectonophysics》1986,125(1-3)
Ophiolites in different tectonic settings are underlain and overlain by characteristic rock units which bear similar relationships to each other and to the ophiolite. Consideration of these relationships in three settings, an active arc (Burma), a continental margin (Oman) and an island ridge-basin system (Cyprus) suggests that in all three settings they resulted from ophiolite detachment at a spreading ridge in a narrow oceanic basin with passive margins. In Burma and possibly in Oman and Cyprus, detachment was related to regional compressive stress associated with an earlier collision. Following detachment and loss of the spreading system, perhaps accompanied by deposition of stratiform sulphides, the rock relationships can be explained by subduction of the remnant oceanic basin beneath the ophiolite forming an island arc, accretion of continent-derived turbidites in front of and beneath the ophiolite, and collision of the ophiolite and overlying volcanic arc with a passive continental margin. Subsequent collision-related events include emplacement of serpentinite diapirs, rise of mud matrix melange and its extrusion as debris flows, elevation of a foreland ridge, and subsidence of a basin on the internal side of the ridge. In Taiwan, olistostromes with local ophiolite clasts in the Lichi mélange could be explained as debris flows of extruded mud-matrix mélange diapirs, generated by tectonic burial of wet sediments during collision-related back-thrusting. 相似文献
9.
俯冲增生杂岩带是造山带重要的组成单元,它记录了从俯冲到碰撞以及碰撞后陆内的演化历史,具有重要的研究价值。由于增生楔形成过程复杂,而后期的碰撞以及陆内变形又会强烈改造俯冲期的变形,因此如何区分增生杂岩中俯冲期间和碰撞阶段的变形就非常重要,但明确的区分两者又是非常困难的工作。我国几乎所有地区发育的俯冲-增生杂岩都经历了后期强烈的改造,因而正确合理地筛分俯冲阶段和碰撞阶段的变形,在我国的造山带研究中日益突出。本文在详细介绍俯冲期间相关变形及其机制的基础上,从不同构造要素的分布、发育特征、形成环境、成因机制等方面综合对比了俯冲阶段和碰撞阶段以及之后构造变形的异同,提出了区别不同阶段变形的主要原则。相比碰撞阶段变形,俯冲阶段的变形主要集中在俯冲隧道中,以简单剪切或一般剪切为主(逆冲断层多见),底板垫托以及双冲构造是变形的重要特征,变形呈弥散性,断层和面理以及褶皱等具有优势的构造极性,但缺少区域尺度的大型褶皱;纯剪变形少见,主要发育在俯冲隧道上方的增生楔中。流体作用以及水岩反应强烈,直接控制变形行为,发育有从显微尺度到区域尺度的变形分解现象。而碰撞阶段主要是在陆上环境进行,主要变形集中在接触带以及大型断裂/剪切带附近。断层和面理的构造极性不明显,增生楔整体变形,出现区域尺度的大型褶皱;流体作用虽有,但不如俯冲阶段明显和强烈,以逆冲和走滑断层多见。然而很多指标和依据并不是某种环境下唯一的,因此在实际工作中需要综合各方面信息和要素进行判断,合理区分不同阶段的变形。 相似文献
10.
SHRIMP U–Pb zircon dating of gabbro, anorthosite, trondhjemite and granodiorite from the Jinshajiang ophiolitic mélange of southwestern China provides geochronological constraints on the evolution of Paleo-Tethys. The ophiolitic mélange is exposed for about 130 km along the Jinshajiang River where numerous blocks of serpentinite, ultramafic cumulate, gabbro, sheeted dikes, pillow lavas and radiolarian chert are set in a greenschist matrix. A cumulate gabbro-anorthosite association and an amphibole gabbro have ages of 338 ± 6 Ma, 329 ± 7 Ma and 320 ± 10 Ma, respectively, which constrain the time of formation of oceanic crust. An ophiolitic isotropic gabbro dated at 282–285 Ma has the same age as a trondhjemite vein (285 ± 6 Ma) cutting the gabbro. These ages probably reflect a late phase of sea-floor spreading above an intra-oceanic subduction zone. At the southern end of the Jinshajiang belt, a granitoid batholith (268 ± 6 Ma), a gabbro massif (264 ± 4 Ma), and a granodiorite (adakite) intrusion (263 ± 6 Ma) in the ophiolitic mélange constitute a Permian intra-oceanic plutonic arc complex. A trondhjemite dike intruded serpentinite in the mélange at 238 ± 10 Ma and postdates the arc evolution of the Jinshajiang segment of Paleo-Tethys. 相似文献
11.
Gweltaz Maho Xavier Fayoux Stphane Guillot Eduardo Garzanti Paul Capiez Georges Mascle 《Journal of Asian Earth Sciences》2006,26(6):695-707
In the Ladakh–Zanskar area, relicts of both ophiolites and paleo-accretionary prism have been preserved in the Sapi-Shergol mélange zone. The paleo-accretionary prism, related to the northward subduction of the northern Neo-Tethys beneath the Ladakh Asian margin, mainly consists of tectonic intercalations of sedimentary and blueschist facies rocks. Whole rock chemical composition data provide new constraints on the origin of both the ophiolitic and the blueschist facies rocks. The ophiolitic rocks are interpreted as relicts of the south Ladakh intra-oceanic arc that were incorporated in the accretionary prism during imbrication of the arc. The blueschist facies rocks were previously interpreted as oceanic island basalts (OIB), but our new data suggest that the protolith of some of the blueschists is a calc-alkaline igneous rock that formed in an arc environment. These blueschists most likely originated from the south Ladakh intra-oceanic arc. This arc was accreted to the southern margin of Asia during the Late Cretaceous and the buried portion was metamorphosed under blueschist facies conditions. Following oceanic subduction, the external part of the arc was obducted to form the south Ladakh ophiolites or was incorporated into the Sapi-Shergol mélange zone. The incorporation of the south Ladakh arc into the accretionary prism implies that the complete closure of the Neo-Tethys likely occurred by Eocene time. 相似文献
12.
The Talaud Islands lie at the northern margin of the collision zone between the Sangihe and Halmahera island arc systems. Rock units on Talaud are Neogene marine strata, basalt and andesite, tectonic mélange, and ophiolite. The units are exposed in N–S trending belts that are commonly separated by faults. The marine strata consist of tuffaceous siltstone, sandstone, shale and marl. They are strongly deformed by west-verging folds with wavelengths of 20–500 m. Volcanic rocks of island arc affinity are exposed on the east coast of Karakelang Island and appear to be interbedded with the lowermost marine strata. Tectonic mélanges contain blocks of serpentinite, gabbro, basalt, red middle Eocene chert and limestone, and greywacke turbidites. The blocks range in length from a few millimetres to hundreds of metres, and are enclosed in a scaly clay matrix. Several mappable slabs of ophiolite are separated by Tertiary strata or mélange. The dismembered ophiolites consist of serpentized peridotite, gabbro, spilites and cherts. Locally, the mélanges and ophiolites are thrust over the younger sedimentary rocks along east-dipping faults. The dominant eastward dips of mélange foliation, the westward vergence of structures in the Neogene strata, the Eocene ages of the cherts, and the Miocene age of the strata overlying the ophiolite slabs suggest that the ophiolites are pieces of Eocene or older oceanic crust (derived from a mid-ocean ridge or back-arc basin) and upper mantle that were emplaced as thrust slices into the lower slope of a west-facing arc during the Miocene and have been uplifted during arc—arc collision. 相似文献
13.
The Ballantrae ophiolite in southern Scotland includes a NEE–SWW-trending serpentinite mélange that contains blocks of mafic blueschist and high-pressure, granulite facies, metapyroxenite (Sm–Nd metamorphic age: 576 ± 32 and 505 ± 11 Ma). Tectonic blocks of mafic schist are less than 3 × 3 m in size, and have greenschist, blueschist or epidote amphibolite facies assemblages corresponding to the high-pressure intermediate-type metamorphic facies series.Adjacent rocks of the serpentinite mélange are hydrothermally-altered MORB-like ophiolitic basalt (prehnite–pumpellyite facies), dolerite (actinolite–oligoclase sub-facies) and gabbro (amphibolite facies), all with assemblages that are diagnostic of the low-pressure metamorphic facies series.The difference in metamorphic facies series and parageneses of minerals between the high-pressure mafic blocks and the adjacent, low-pressure ophiolitic meta-basic rocks suggests that the former were exhumed from > 25 km depth within a cold subducted slab, and were juxtaposed with the latter, the bottom of a MORB-like ophiolite in the hanging wall of a trench. An ENE–WSW-trending, 501 ± 12 Ma volcanic arc belt extends for 3 km south of the serpentinite mélange. We suggest that ridge subduction associated with a slab window created arc-related gabbro (483 ± 4 Ma) at Byne Hill and within-plate gabbro (487 ± 8 Ma) at Millenderdale. Final continental collision created the duplex structure of the Ballantrae complex that includes the HP blocks and serpentinite mélange. These relations define diapiric exhumation in the Caledonian orogen of SW Scotland. 相似文献
14.
The Cammazes orthogneissic massif in the western Montagne Noire (France) has been affected by numerous tectonic phases during the Hercynian orogeny. The principal deformation, synchronous with a mesozonal metamorphism, is represented by different structural features such as foliation, ‘augen’ structures and deformation of megacrystals. These structural features are essentially varied with the concentration of feldspar megacrystals in the gneisses. The structural studies of these gneisses have allowed the recognition of the nature and the orientation of the principal deformation. To determine the intensity of this deformation, large undeformed feldspar crystals have been used as markers. These crystals have been assimilated to rigid ellipsoidal elements disposed in a random fashion in the initial stage of the mesostase which is considered as a viscous Newtonian fluid. The statistical studies of the orientation of these crystals with reference to the plane of flattening (foliation) has caused the appearance of an anisotropy in the final deformed state. This anisotropy, when compared to that obtained theoretically from a population of rigid elements included in a Newtonian fluid flowing at a slow speed, could evaluate the rate of the finite strain.
Résumé
Dans la Montagne Noire occidentale (France) le massif orthogneissique des Cammazes a été affecté lors de l'orogénèse hercynienne par une tectonique polyphasée. La déformation majeure, synchrone d'un métamorphisme mésozonal, se traduit par différents caractères structuraux (foliation, structure oeillée, déformations des mégacristaux) variant essentiellement avec la concentration des mégacristaux feldspathiques dans les gneiss. L'étude structurale a permis de définir la nature et l'orientation de cette déformation majeure. Pour préciser son intensité les grands cristaux indéformés de feldspaths, utilisés comme marqueurs, ont été assimilés à des éléments rigides ellipsoi'daux disposés dans l'état initial de façon aléatoire dans la mésostase considérée comme un fluide visqueux newtonien. L'étude statistique de leur orientation par rapport au plan d'aplatissement (foliation) fait apparaitre dans l'état final (déformé) une anisotropie. Cette anisotropie comparée à celle obtenue par voie théorique, d'une population d'éléments rigides inclus dans un fluide newtonien s'écoulant à faible vitesse, permet d'évaluer le taux de déformation finie. 相似文献15.
南祁连拉脊山口增生楔的结构与组成特征 总被引：2，自引：1，他引：1
造山带内增生楔/增生杂岩结构与组成的精细研究可为古洋盆演化和古板块构造格局重建提供最直接证据。北祁连构造带发育多条增生杂岩带,记录了阿拉善和中祁连地块之间原特提斯洋的俯冲和闭合过程,然而南祁连构造带大地构造演化长期存在争议。地质填图结果表明,南祁连构造带拉脊山口地区存在一套强烈片理化的玄武岩、灰黑色和红色硅质岩、砂岩和泥岩组合,它们与一套呈现"块体裹夹于基质"结构特征的混杂岩共同构成了增生杂岩,发育双重逆冲构造、逆冲断层、无根褶皱、紧闭褶皱和透入性面理。该增生杂岩与蛇绿岩之间为断层接触,并位于断层下盘。混杂岩是由斜长花岗岩(561Ma)、斜长岩(507Ma)、辉绿岩、玄武岩、硅质岩和砂岩等外来或原地岩块与浊流成因的细碎屑岩基质共同组成;基质和砂岩块体均发育同沉积构造,呈现出滑塌堆积典型特征。空间上,拉脊山口增生杂岩与上覆蛇绿岩被断层所分割且共同仰冲于中祁连南缘青石坡组浊积岩之上,具有与东侧昂思多地区增生杂岩和蛇绿岩相似的岩石组成、构造变形和时空结构特征。它们与南侧的岛弧带共同构成了南祁连构造带寒武纪-早奥陶世沟-弧体系,指示了寒武纪-早奥陶世时期南祁连洋盆向南俯冲。 相似文献
16.
北阿尔金恰什坎萨依沟地区早古生代构造变形特征及构造演化启示 总被引：1，自引：0，他引：1
出露在青藏高原北缘的红柳沟-拉配泉蛇绿混杂岩带一直以来为深入研究北阿尔金早古生代构造格架及演化提供了宝贵信息。经详细的野外地质填图和构造解析,文章针对红柳沟-拉配泉蛇绿混杂岩带内的构造样式、变形特征及形成时限进行研究,将北阿尔金蛇绿混杂岩带进一步细分为北侧混杂单元、中间层序单元和南侧混杂单元三个次级构造单元,南、北两侧混杂单元内以发育一系列复杂褶皱和逆冲断层为典型构造特征。卷入褶皱变形的最年轻地层岩石为中-晚奥陶世硅质岩,并被（416.8±3.7）Ma未变形的正长斑岩脉所截切;卷入逆冲断层的混杂岩中辉长岩和斜长花岗岩年龄为479~521 Ma和512.1~518.5 Ma,随后也被410.7~418.5 Ma未变形的冰沟岩体所侵位。这些基本事实表明,褶皱构造与逆冲断层均形成于中奥陶世-早泥盆世,推测其成因与北阿尔金洋俯冲作用导致的洋壳强烈缩短变形有关。在南侧混杂单元,褶皱构造样式自北向南逐渐由直立褶皱转变为斜歪褶皱,最后转变为倒转褶皱,显示出递进变形特征。褶皱所对应的应变椭球体也发生了旋转,表现出顶端指向北北东向的剪切作用,与混杂单元内逆冲断层所具有的向北北东方向逆冲、推覆特征相一致,从而推测它们与北阿尔金洋南南西向俯冲消减有密切联系。另外,在北侧混杂单元内还发育有同时期向南南东方向逆冲的断层以及轴面倾向北北东的斜歪褶皱,暗示北阿尔金洋在早古生代可能还发育有北北东方向的俯冲极性,整个北阿尔金洋俯冲消减模式可能具有双向性。 相似文献
17.
造山带内蛇绿混杂岩带结构与组成的精细研究可为古板块构造格局重建和古洋盆演化提供最直接证据。北山造山带内存在多条蛇绿混杂岩带,记录了古亚洲洋古生代以来的俯冲和闭合过程,然而其大地构造演化长期存在争议。红石山—百合山蛇绿混杂岩带位于北山造山带北部,主要由蛇绿(混杂)岩和增生杂岩组成,具典型的"块体裹夹于基质"的混杂岩结构特征,发育紧闭褶皱、无根褶皱、透入性面理和双重逆冲构造。蛇绿混杂岩带中岩块主要由超镁铁质-镁铁质岩(变质橄榄岩、辉石橄榄岩、异剥辉石岩、蛇纹岩)、辉长岩、玄武岩、斜长花岗岩、硅质岩等洋壳残块以及奥陶纪火山岩、灰岩等外来岩块组成,基质则主要为蛇纹岩、砂板岩及少量的绿帘绿泥片岩;在蛇绿混杂岩带北侧发育有台地相灰岩与深水浊积岩组成的沉积混杂块体,具滑塌堆积特征。蛇绿混杂岩带内发育三期构造变形,前两期为中深构造层次下形成的透入性变形,第三期为浅表层次的脆性变形,未形成区域性面理。空间上,由增生杂岩和蛇绿(混杂)岩组成的百合山蛇绿混杂岩带共同仰冲于绿条山组浊积岩之上,具有与红石山地区蛇绿混杂岩带相似的岩石组成、构造变形和时空结构特征。百合山蛇绿混杂岩带南侧发育同期的明水岩浆弧,由晚石炭世石英闪长岩-花岗闪长岩-二长花岗岩以及白山组岛弧火山岩组成,其与百合山蛇绿混杂岩带共同构成了北山造山带北部石炭—二叠纪的沟-弧体系,指示了红石山—百合山洋盆向南俯冲的极性。 相似文献
18.
John A. Katili 《Tectonophysics》1978,45(4):289-322
Sulawesi with its peculiar K-shaped pattern is situated in an area where the Eurasian, Indian—Australian and Pacific plates interact and collide.Complex geological processess in this area resulted in the transformation of a normal island-arc structure into an inverted one, deformation of an already tectonized belt, sweeping of fragments against unrelated terrain, thrusting of oceanic and mantle material over the island arc, closing of deep-sea basins behind the arc, trapping of old oceanic crust caused by the rolling up of an island arc, formation of a marginal basin by the spreading of the sea floor behind the arc, development of small subduction zones with reverse polarities etc.Small deep-sea basins surrounding Sulawesi such as the Gulf of Bone and the Gulf of Gorontalo originally formed the arc—trench gap of the Sulawesi island arc.The Banda Sea is considered as an oceanic crust trapped by the bending of the east—west trending Banda arc due to the northward drift of Australia combined with the westward movement of the Pacific plate. Similarly the Sulawesi Sea consists of an old Pacific crust trapped by the westward bending of the Sulawesi island arc, caused by the spearheading westward thrust along the Sorong transform-fault system, in which later a minor spreading center became active in its central part. The Molucca Sea comprises tectonic mélange in which presumably a small spreading center developed between the two colliding arcs of northern Sulawesi and western Halmahera. While the Benioff zones dip under the northern Sulawesi and Halmahera arcs in normal fashion, the mélange thrusts over them. The Strait of Makassar is a marginal basin which was brought into existence by the spreading of the sea floor between Kalimantan and Sulawesi.The evolution of Sulawesi started in Miocene time or even earlier when 800 km east of Kalimantan a north—south trending east-facing island arc came into existence, originating from a spreading center located in the Pacific Ocean. Volcanism and plutonism accompanied this subduction process.Collision between Sulawesi and the Australian—New Guinea plate which occurred in early Pliocene time severely transformed Sulawesi into an island with its convex side turned towards the continent, at the same time causing obduction of ophiolite in the eastern arc of this island.The movement of the Pacific plate continued and gradually pushed Sulawesi towards the Asian continent, resulting in the closing of the sea between Kalimantan and Sulawesi islands separated by small straits and deep seas resembling the complicated pattern of the Philippine Archipelago, in which the original double island-arc structure can no longer be recognized. 相似文献
19.
I. Metcalfe 《Journal of Asian Earth Sciences》2000,18(6)
It is proposed that the Bentong–Raub Suture Zone represents a segment of the main Devonian to Middle Triassic Palaeo-Tethys ocean, and forms the boundary between the Gondwana-derived Sibumasu and Indochina terranes. Palaeo-Tethyan oceanic ribbon-bedded cherts preserved in the suture zone range in age from Middle Devonian to Middle Permian, and mélange includes chert and limestone clasts that range in age from Lower Carboniferous to Lower Permian. This indicates that the Palaeo-Tethys opened in the Devonian, when Indochina and other Chinese blocks separated from Gondwana, and closed in the Late Triassic (Peninsular Malaysia segment). The suture zone is the result of northwards subduction of the Palaeo-Tethys ocean beneath Indochina in the Late Palaeozoic and the Triassic collision of the Sibumasu terrane with, and the underthrusting of, Indochina. Tectonostratigraphic, palaeobiogeographic and palaeomagnetic data indicate that the Sibumasu Terrane separated from Gondwana in the late Sakmarian, and then drifted rapidly northwards during the Permian–Triassic. During the Permian subduction phase, the East Malaya volcano-plutonic arc, with I-Type granitoids and intermediate to acidic volcanism, was developed on the margin of Indochina. The main structural discontinuity in Peninsular Malaysia occurs between Palaeozoic and Triassic rocks, and orogenic deformation appears to have been initiated in the Upper Permian to Lower Triassic, when Sibumasu began to collide with Indochina. During the Early to Middle Triassic, A-Type subduction and crustal thickening generated the Main Range syn- to post-orogenic granites, which were emplaced in the Late Triassic–Early Jurassic. A foredeep basin developed on the depressed margin of Sibumasu in front of the uplifted accretionary complex in which the Semanggol “Formation” rocks accumulated. The suture zone is covered by a latest Triassic, Jurassic and Cretaceous, mainly continental, red bed overlap sequence. 相似文献
20.
The Gulf of Cadiz spans the plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. A narrow east dipping subduction zone descends beneath the Gulf of Cadiz and the straits of Gibraltar. The deep crustal structure of the Gulf and the adjacent SW Iberian and Moroccan margins is constrained by numerous multi-channel seismic reflection and wide-angle seismic surveys. A compilation of these existing studies is presented in the form of depth to basement, sediment thickness, depth to Moho and crustal thickness maps. These structural maps image an E-W trending trough, with thin (< 10 km) crust beneath the Gulf of Cadiz. This trough is filled by an eastward thickening wedge of sediments, reaching a thickness of 10-15 km in the eastern Gulf. These sediments are tectonically deformed, primarily along a series of westward-vergent thrust faults and represent a 200-250 km wide accretionary wedge. The northern and especially the southern limits of the accretionary wedge are marked by sharp morphological lineaments showing evidence of recent deformation. These tectonic limits are situated in an internal position with respect to the Miocene deformation front (external Betic and Rif allocthons), which has been abandoned. At the western boundary of the accretionary wedge, near the adjacent Seine and Horseshoe abyssal plains, an E-W trending basement high (Coral Patch Ridge) can be seen indenting the deformation front in an asymmetric manner. Analog modeling is performed using granular materials accreted against a semicircular backstop (representing the basement of the Rif and Betic mountain belts). The modeling initially produces a symmetric, arcuate accretionary wedge. The ensuing collision of an oblique rigid indenter retards accretion on one side, resulting in an embayment and a locally steeper deformation front. The deformation pattern observed in morphology and high-resolution seismic profiles suggests the accretionary wedge and underlying subduction system is still active. The implications of active subduction for the source region of the 1755 Lisbon earthquake and the regional seismic hazard assessment are discussed. 相似文献