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1.
Accretionary wedge is the typical product of subduction-zone processes at shallow depths.Determining the location,composition and mechanism of accretionary wedge has important implications for understanding the tectonism of plate subduction.The Central Asian Orogenic Belt(CAOB) is one of the world's largest accretionary orogenic belts,and records the bulk evolution of Paleo-Asian Ocean from opening to closure,with multi-stages and multi-types of crust-mantle interaction in the Paleozoic.West Junggar(western part of Junggar Basin),located in the core area of CAOB,is characterized by a multiple intra-oceanic subduction system during the Paleozoic.In its eastern part crop out Devonian-Carboniferous marine sedimentary rocks,Darbut and Karamay ophiolitic melanges,alkali oceanic island basalts,island arc volcanic rocks and thrusted nappe structure.Such lithotectonic associations indicate the occurrence of accretionary wedge at Karamay.In order to decipher its formation mechanism,this paper presents a synthesis of petrography,structural geology and geochemistry of volcanic rocks.In combination with oceanic subduction channel processes,itis suggested that the accretionary wedge is acomposite melange with multiple stages of formation.The application of oceanic subduction channel model to the Karamay accretionary wedge provides new insights into the accretion and orogenesis of CAOB.  相似文献   

2.
Cretaceous episodic growth of the Japanese Islands   总被引：1，自引：0，他引：1  
G. Kimura 《Island Arc》1997,6(1):52-68
Abstract The Japanese Islands formed rapidly in situ along the eastern Asian continental margin in the Cretaceous due to both tectonic and magmatic processes. In the Early Cretaceous, huge oceanic plateaus created by the mid-Panthalassa super plume accreted with the continental margin. This tectonic interaction of oceanic plateau with continental crust is one of the significant tectonic processes responsible for continental growth in subduction zones. In the Japanese Islands, Late Cretaceous-Early Paleogene continental growth is much more episodic and drastic. At this time the continental margin uplifted regionally, and intra-continent collision tectonics took place in the northern part of the Asian continent. The uplifting event appears to have been caused by the subduction of very young oceanic crust (i.e. the Izanagi-Kula Plate) along the continental margin. Magmatism was also very active, and melting of the young oceanic slab appears to have resulted in ubiquitous plutons in the continental margin. Regional uplift of the continental margin and intra-continent collision tectonics promoted erosion of the uplifted area, and a large amount of terrigenous sediment was abruptly supplied to the trench. As a result of the rapid supply of terrigenous detritus, the accretionary complexes (the Hidaka Belt in Hokkaido and the Shimanto Belt in Southwest Japan) grew rapidly in the subduction zone. The rapid growth of the accretionary complexes and the subduction of very young, buoyant oceanic crust caused the extrusion of a high-P/T metamorphic wedge from the deep levels of the subduction zone. Episodic growth of the Late Cretaceous Japanese Islands suggests that subduction of very young oceanic crust and/or ridge subduction are very significant for the formation of new continental crust in subduction zones.  相似文献   

3.
Geodynamic evolution of Korea: A view   总被引：2，自引：0，他引：2  
Abstract Evidence for South Korean Palaeozoic geodynamic evolution is restricted to the Ogcheon Belt, which is a complex polycyclic domain forming the boundary between the Precambrian Gyeonggi Block to the northwest and the Ryeongnam Block to the southeast. Two independent sub-zones can be distinguished: the Taebaeksan Zone to the northeast and the Ogcheon Zone sensu stricto. The Taebaeksan Zone and Ryeongnam Block display characteristic features of the North China palaeocontinent. This domain remained relatively stable during the Palaeozoic. In contrast, the Ogcheon Belt s. s. is a highly mobile zone that belongs to the South China palaeocontinent and corresponds to a rift that opened during the Early Palaeozoic. In lowermost Devonian times, the rift basin was closed and the Ogcheon Belt was structured in a pile of nappes. From the lack of suture in the Ogcheon Belt it can be inferred that the Gyeonggi Block belongs to the South China palaeocontinent. Thus, the boundary between the North China and South China blocks should be located to the north of Gyeonggi Block, that is, in the Palaeozoic Imjingang Belt. From the Middle Carboniferous, sedimentation started again on a weakly subsiding paralic platform located in the hinterland of the Late Palaeozoic orogen of southwest Japan. In the Late Carboniferous, increasing subsidence recorded extensional tectonics related to the opening of the Yakuno Oceanic Basin (southwest Japan). In the Middle Permian, the end of marine influences in the platform and emplacement of terrestrial coal measures, may be correlated with the closure of the oceanic area and subsequent ophiolite obduction. In Late Permian to Early Triassic times, the Honshu Block (the eastern palaeomargin of the Yakuno Basin) collided with Sino-Korea. Post-collisional intracontinental tectonics reached the Ogcheon Belt in the Middle Triassic (Songnim tectonism). Ductile dextral shear zones associated with synkinematic granitoids were emplaced in the southwest of the belt. In the Upper Triassic, the late stages of the intracontinental transcurrent tectonics generated narrow intramontane troughs (Daedong Supergroup). The Daedong basins were deformed during two tectonic events, in the Middle (?) and Late Jurassic. The Upper Jurassic to Lower Cretaceous basins (Gyeongsang Supergroup), that are controlled by left-lateral faults, may have resulted from the same tectonic event.  相似文献   

4.
Placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models. Distinct metallogenic associations across the Palaeozoic Lachlan Orogen in SE Australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an oceanic back-arc setting. In the Ordovician, significant orogenic gold deposits formed within a developing accretionary wedge along the Pacific margin of Gondwana. At the same time, major porphyry Cu-Au systems formed in an oceanic island arc outboard of an evolved magmatic arc that, in turn, gave rise to granite-related Sn-W deposits in the Early Silurian. During the ongoing evolution of the orogen in the Late Silurian to Early Devonian, sediment-hosted Cu-Au and Pb-Zn deposits formed in short-lived intra-arc basins, whereas a developing fore-arc system provided the conditions for the formation of several volcanogenic massive sulphide deposits. Inversion of these basins and accretion to the Australian continental margin triggered another pulse of orogenic gold mineralisation during the final consolidation of the orogenic belt in the Middle to Late Devonian.  相似文献   

5.
Abstract Mesozoic accretionary complexes of the southern Chichibu and the northern Shimanto Belts, widely exposed in the Kanto Mountains, consist of 15 tectonostratigraphic units according to radiolarian biochronologic data. The units show a zonal arrangement of imbricate structure and the age of the terrigenous clastics of each unit indicates successive and systematic southwestward younging. Although rocks in these complexes range in age from Carboniferous to Cretaceous, the trench-fill deposits corresponding to the Hauterivian, the Aptian to Middle Albian and the Turonian are missing. A close relationship between the missing accretionary complexes and the development of strike-slip basins is recognizable. The tectonic nature of the continental margin might have resulted from a change from a convergent into a transform or oblique-slip condition, so that strike-slip basins were formed along the mobile zones on the ancient accretionary complexes. Most terrigenous materials were probably trapped by the strike-slip basins. Then, the accretion of the clastic rock sequence occurred, probably as a result of the small supply of terrigenous materials in the trench. However, in the case of right-angle subduction, terrigenous materials might have been transported to the trench through submarine canyons and deposited there. Thus, the accretionary complexes grew rapidly and thickened. Changes both in oceanic plate motion and in the fluctuation of terrigenous supply due to the sedimentary trap caused pulses of accretionary complex growth during Jurassic and Cretaceous times. In the Kanto Mountains, three tectonic phases are recognized, reflecting the changes of the consuming direction of the oceanic plates along the eastern margin of the Asian continent. These are the Early Jurassic to early Early Cretaceous right-angle subduction of the Izanagi Plate, the Early to early Late Cretaceous strike-slip movement of the Izanagi and Kula Plates, and the late Late Cretaceous right-angle subduction of the Kula Plate.  相似文献   

6.
Abstract In this paper, a summary of the tectonic history of the Mirdita ophiolitic nappe, northern Albania, is proposed by geological and structural data. The Mirdita ophiolitic nappe includes a subophiolite mélange, the Rubik complex, overlain by two ophiolite units, referred to as the Western and Eastern units. Its history started in the Early Triassic with a rifting stage followed by a Middle to Late Triassic oceanic opening between the Adria and Eurasia continental margins. Subsequently, in Early Jurassic time, the oceanic basin was affected by convergence with the development of a subduction zone. The existence of this subduction zone is provided by the occurrence of the supra‐subduction‐zone‐related magmatic sequences found in both the Western and Eastern units of the Mirdita ophiolitic nappe. During the Middle Jurassic, continuous convergence resulted in the obduction of the oceanic lithosphere, in two different stages – the intraoceanic and marginal stages. The intraoceanic stage is characterized by the westward thrusting of a young and still hot section of oceanic lithosphere leading to the development of a metamorphic sole. In the Late Jurassic, the marginal stage developed by the emplacement of the ophiolitic nappe onto the continental margin. During this second stage, the emplacement of the ophiolites resulted in the development of the Rubik complex. In the Early Cretaceous, the final emplacement of the ophiolites was followed by the unconformable sedimentation of the Barremian–Senonian platform carbonate. From the Late Cretaceous to the Middle Miocene, the Mirdita ophiolitic nappe was translated westward during the progressive migration of the deformation front toward the Adria Plate. In the Middle to Late Miocene, a thinning of the whole nappe pile was achieved by extensional tectonics, while the compression was still active in the westernmost areas of the Adria Plate. On the whole, the Miocene deformations resulted in the uplift and exposition of the Mirdita ophiolites as observed today.  相似文献   

7.
History and modes of Mesozoic accretion in Southeastern Russia   总被引：8，自引：1，他引：8  
Boris  Natal'in 《Island Arc》1993,2(1):15-34
Abstract The history of Mesozoic accretion and growth of the Asia eastern margin, occupied by Southeastern Russia, includes five main events; two main tectonic regimes were responsible for the growth of the continent. In the Triassic-Jurassic, Early Cretaceous and Late Cretaceous-Paleogene, the subduction of the oceanic lithosphere resulted in the formation of wide accretionary wedges of the Mongol-Okhotsk, Khingan-Okhotsk and Eastern Sikhote-Alin active continental margins, respectively. These stages of the comparatively slow growth of the continent were broken by stages of rapid growth and drastic changes in the shape of the continent, since at these stages large terranes of various tectonic nature collided with active continental margins. At the end of the Early-Middle Jurassic, the Bureya terranes collided with the Mongol-Okhotsk active margin, and at the beginning of the Late Cretaceous there was collision of the Central and Southern Sikhote-Alin terranes with the Khingan-Okhotsk active margin.
Collision-related structural styles in all cases are indicative of oblique collision and great strike-slip motions along the main sutures. The peculiarities of the terrane's geological structure show that prior to collision with the Mongol-Okhotsk and Khingan-Okhotsk active margins, they had already accreted to Asia and then migrated along its margins along the strike-slip faults. The Bureya terranes were squeezed out of the compression zone between Siberia and North China. This compression zone originated after the Paleozoic oceans which divided these cratons had closed. The Khanka terranes and Mesozoic accretionary wedge terranes of the Sikhote-Alin shifted along the strike-slip faults subparallel to the Asia Pacific margin. Strike-slip motions resulted in duplication of the primary tectonic zonation.  相似文献   

8.
Yukio  Isozaki 《Island Arc》1996,5(3):289-320
Abstract The Japanese Islands represent a segment of a 450 million year old subduction-related orogen developed along the western Pacific convergent margin. The geotectonic subdivision of the Japanese Islands is newly revised on the basis of recent progress in the 1980s utilizing microfossil and chronometric mapping methods for ancient accretionary complexes and their high-P/T metamorphic equivalents. This new subdivision is based on accretion tectonics, and it contrasts strikingly with previous schemes based on‘geosyncline’tectonics, continent-continent collision-related tectonics, or terrane tectonics. Most of the geotectonic units in Japan are composed of Late Paleozoic to Cenozoic accretionary complexes and their high-PIT metamorphic equivalents, except for two units representing fragments of Precambrian cratons, which were detached from mainland Asia in the Tertiary. These ancient accretionary complexes are identified using the method of oceanic plate stratigraphy. The Japanese Islands are comprised of 12 geotectonic units, all noted in southwest Japan, five of which have along-arc equivalents in the Ryukyus. Northeast Japan has nine of these 12 geotectonic units, and East Hokkaido has three of these units. Recent field observations have shown that most of the primary geotectonic boundaries are demarcated by low-angle faults, and sometimes modified by secondary vertical normal and/or strike-slip faults. On the basis of these new observations, the tectonic evolution of the Japanese Islands is summarized in the following stages: (i) birth at a rifted Yangtze continental margin at ca 750–700 Ma; (ii) tectonic inversion from passive margin to active margin around 500 Ma; (iii) successive oceanic subduction beginning at 450 Ma and continuing to the present time; and (iv) isolation from mainland Asia by back-arc spreading at ca 20 Ma. In addition, a continent-continent collision occurred between the Yangtze and Sino-Korean cratons at 250 Ma during stage three. Five characteristic features of the 450 Ma subduction-related orogen are newly recognized here: (i) step-wise (not steady-state) growth of ancient accretionary complexes; (ii) subhorizontal piled nappe structure; (iii) tectonically downward-younging polarity; (iv) intermittent exhumation of high-P/T metamorphosed accretionary complex; and (v) microplate-induced modification. These features suggest that the subduction-related orogenic growth in Japan resulted from highly episodic processes. The episodic exhumation of high-P/T units and the formation of associated granitic batholith (i.e. formation of paired metamorphic belts) occurred approximately every 100 million years, and the timing of such orogenic culmination apparently coincides with episodic ridge subduction beneath Asia.  相似文献   

9.
This paper presents a review on the rock associations, geochemistry, and spatial distribution of Mesozoic-Paleogene igneous rocks in Northeast Asia. The record of magmatism is used to evaluate the spatial-temporal extent and influence of multiple tectonic regimes during the Mesozoic, as well as the onset and history of Paleo-Pacific slab subduction beneath Eurasian continent. Mesozoic-Paleogene magmatism at the continental margin of Northeast Asia can be subdivided into nine stages that took place in the Early-Middle Triassic, Late Triassic, Early Jurassic, Middle Jurassic, Late Jurassic, early Early Cretaceous, late Early Cretaceous, Late Cretaceous, and Paleogene, respectively. The Triassic magmatism is mainly composed of adakitic rocks, bimodal rocks, alkaline igneous rocks, and A-type granites and rhyolites that formed in syn-collisional to post-collisional extensional settings related to the final closure of the Paleo-Asian Ocean. However, Triassic calc-alkaline igneous rocks in the Erguna-Xing’an massifs were associated with the southward subduction of the Mongol-Okhotsk oceanic slab. A passive continental margin setting existed in Northeast Asia during the Triassic. Early Jurassic calc-alkaline igneous rocks have a geochemical affinity to arc-like magmatism, whereas coeval intracontinental magmatism is composed of bimodal igneous rocks and A-type granites. Spatial variations in the potassium contents of Early Jurassic igneous rocks from the continental margin to intracontinental region, together with the presence of an Early Jurassic accretionary complex, reveal that the onset of the Paleo- Pacific slab subduction beneath Eurasian continent occurred in the Early Jurassic. Middle Jurassic to early Early Cretaceous magmatism did not take place at the continental margin of Northeast Asia. This observation, combined with the occurrence of low-altitude biological assemblages and the age population of detrital zircons in an Early Cretaceous accretionary complex, indicates that a strike-slip tectonic regime existed between the continental margin and Paleo-Pacific slab during the Middle Jurassic to early Early Cretaceous. The widespread occurrence of late Early Cretaceous calc-alkaline igneous rocks, I-type granites, and adakitic rocks suggests low-angle subduction of the Paleo-Pacific slab beneath Eurasian continent at this time. The eastward narrowing of the distribution of igneous rocks from the Late Cretaceous to Paleogene, and the change from an intracontinental to continental margin setting, suggest the eastward movement of Eurasian continent and rollback of the Paleo- Pacific slab at this time.  相似文献   

10.
马尼拉俯冲带北段增生楔前缘构造变形和精细结构   总被引：1，自引：0，他引：1       下载免费PDF全文
马尼拉俯冲带是南海的东部边界,记录了南海形成演化的关键信息,同时也是地震和海啸多发区域.本文利用过马尼拉俯冲带北段的高分辨率多道地震剖面,分析了研究区内海盆和海沟的沉积特征,精细刻画了区内增生楔前缘的构造变形、结构以及岩浆活动特征.研究区内增生楔下陆坡部分由盲冲断层、构造楔和叠瓦逆冲断层构成,逆冲断层归并于一条位于下中新统的滑脱面上,滑脱面向海方向的展布明显受到增生楔之下埋藏海山和基底隆起的影响;上陆坡的反射特征则因变形强烈和岩浆作用而难以识别;岩浆活动开始于晚中新世末期并持续至第四纪.马尼拉俯冲带北段增生楔的形成时间早于16.5 Ma,并通过前展式逆冲向南海方向扩展;马尼拉俯冲带的初始形成时间可能在晚渐新世,而此时南海海盆扩张仍在持续.南海东北缘19°N-21°N区域为南海北部陆坡向海盆的延伸,高度减薄的陆壳的俯冲造成马尼拉海沟北段几何形态明显地向东凹进.  相似文献   

11.
伴随洋壳的俯冲,驼伏其上的海山会导致上覆板块的强烈变形.为解释该构造变形特征,本文运用物理模拟实验的方法,着重分析海山的斜向俯冲对上覆板块变形的影响,并将模拟结果与正向俯冲过程进行对比.实验结果显示:海山开始进入俯冲,前缘楔体的增生会被阻止,同时楔体被抬升并出现脱顶构造,未被海山破坏的楔体会出现后冲断层的激活,后冲断层轴平行于海山的俯冲方向.海山进一步俯冲,突起项部发育一系列张扭性质的微断裂和走滑性质的共轭断裂,尾随突起之后的楔体由于重力会产生正断层系统.比起正向俯冲,斜向俯冲过程中所产生的后逆冲体、海山两侧的叠瓦状逆冲推覆构造都出现不对称分布,断裂和微断裂束的走向不规则散开,后冲断层的轴向及海山俯冲过后在楔体上产生的凹槽的轨迹都不断斜向迁移,且凹槽两侧的地势不一致等.最后利用文中的物理模拟结果,很好的解释了马尼拉海沟中段俯冲构造的构造特征,同时对其他俯冲大陆边缘的构造解释具有指导意义.  相似文献   

12.
The early stages of southern Apennine development have been unraveled by integrating the available stratigraphic record provided by synorogenic strata (of both foredeep and wedge-top basin environments) with new structural data on the Liguride accretionary wedge cropping out in the Cilento area, southern Italy. Our results indicate that the final oceanic subduction stages and early deformation of the distal part of the Apulian continental margin were controlled by dominant NW–SE shortening. Early Miocene subduction-accretion, subsequent wedge emplacement on top of the Apulian continental margin and onset of footwall imbrication involving detached Apulian continental margin carbonate successions were followed by extensional deformation of the previously ‘obducted’ accretionary wedge. Wedge thinning also enhanced the development of accommodation space, filled by the dominantly siliciclastic Cilento Group deposits. The accretionary wedge units and the unconformably overlying wedge-top basin sediments experienced renewed NW–SE shortening immediately following the deposition of the Cilento Group (reaching the early Tortonian), confirming that the preceding wedge thinning represented an episode of synorogenic extension occurring within the general framework of NW–SE convergence. The documented Early to the Late Miocene steps of southern Apennine development are clearly distinct with respect to the subsequent (late Tortonian-Quaternary) stages of fold and thrust belt evolution coeval with Tyrrhenian back-arc extension, which were characterized by NE-directed thrusting in the southern Apennines.  相似文献   

13.
The NE- to NNE-striking Tan-Lu Fault Zone (TLFZ) is the largest fault zone in East China, and a typical representative for the circum-Pacific tectonics. Its late Mesozoic evolution resulted from subduction of the Paleo-Pacific Plate, and can be used for indication to the subduction history. The TLFZ reactivated at the end of Middle Jurassic since its origination in Middle Triassic. This phase of sinistral motion can only be recognized along the eastern edge of the Dabie-Sulu orogenis, and indicates initiation of the Paleo-Pacific (Izanagi) Plate subduction beneath the East China continent. After the Late Jurassic standstill, the fault zone experienced intense sinistral faulting again at the beginning of Early Cretaceous under N-S compression that resulted from the NNW-ward, low-angle, high-speed subduction of the Izanagi Plate. It turned into normal faulting in the rest of Early Cretaceous, which was simultaneous with the peak destruction of the North China Craton caused by backarc extension that resulted from rollback of the subducting Izanagi Plate. The TLFZ was subjected to sinistral, transpressive displacement again at the end of Early Cretaceous. This shortening event led to termination of the North China Craton destruction. The fault zone suffered local normal faulting in Late Cretaceous due to the far-field, weak backarc extension. The late Mesozoic evolution of the TLFZ show repeated alternation between the transpressive strike-slip motion and normal faulting. Each of the sinistral faulting event took place in a relatively short period whereas every normal faulting event lasted in a longer period, which are related to the subduction way and history of the Paleo-Pacific Plates.  相似文献   

14.
It is now generally accepted that Southeast Asia is composed of continental blocks which separated from Gondwana with the formation of oceanic crust during the Paleozoic, and were accreted to Asia in the Late Paleozoic or Early Mesozoic, with the subduction of the intervening oceanic crust. From east to west the Malay peninsula and Sumatra are composed of three continental blocks: East Malaya with a Cathaysian Permian flora and fauna; Sibumasu, including the western part of the Malay peninsula and East Sumatra, with Late Carboniferous–Early Permian 'pebbly mudstones' interpreted as glaciogenic diamictites; and West Sumatra, again with Cathaysian fauna and flora. A further unit, the Woyla nappe, is interpreted as an intraoceanic arc thrust over the West Sumatra block in the mid Cretaceous. There are varied opinions concerning the age of collision of Sibumasu with East Malaya and the destruction of Paleotethys. In Thailand, radiolarites have been used as evidence that Paleotethys survived until after the Middle Triassic. In the Malay peninsula, structural evidence and the ages of granitic intrusions are used to support a Middle Permian to Early Triassic age for the destruction of Paleotethys. It is suggested that the West Sumatra block was derived from Cathaysia and emplaced against the western margin of Sibumasu by dextral transcurrent faulting along a zone of high deformation, the Medial Sumatra Tectonic Zone. These structural units can be traced northwards in Southeast Asia. The East Malaya block is considered to be part of the Indochina block, Sibumasu can be traced through Thailand into southern China, the Medial Sumatra Tectonic Zone is correlated with the Mogok Belt of Myanmar, the West Burma block is the extension of the West Sumatra block, from which it was separated by the formation of the Andaman Sea in the Miocene, and the Woyla nappe is correlated with the Mawgyi nappe of Myanmar.  相似文献   

15.
The Cretaceous accretionary complexes of the Idonnappu Zone in the Urakawa area are divided into five lithological units, four of which contain greenstone bodies. The Lower Cretaceous Naizawa Complex consists of two lithologic units. The Basaltic Unit (B‐Unit) is a large‐scale tectonic slab of greenstone, consisting of depleted tholeiite similar to that of the Lower Sorachi Ophiolite (basal forearc basin ophiolite) in the Sorachi‐Yezo Belt. The Mixed Unit of Naizawa Complex (MN‐Unit) contains oceanic island‐type alkaline greenstones which occur as slab‐like bodies and faulted blocks with tectonically dismembered trench‐fill sediments. Repeated alternations of the two units in the Naizawa Complex may have been formed by the collision of seamounts with forearc ophiolitic body (Lower Sorachi Ophiolite) in the trench. The Upper Cretaceous Horobetsugawa Complex structurally underlies the Naizawa Complex in its original configuration, and it also contains greenstone bodies. Greenstones in the MH‐Unit occur as blocks and sedimentary clasts in a clastic matrix, and exhibit depleted tholeiite and oceanic‐island alkaline basalt/tholeiite chemistry. This unit is interpreted as submarine slide and debris flow deposits. Greenstones in the PT‐Unit occur at the base of several chert‐clastic successions. Most of the greenstones are severely sheared and show normal‐type mid‐ocean ridge basalt composition. The PT‐Unit greenstones are considered to have been derived from abyssal basement peeled off during accretion. The different accretion mechanism of the greenstones in the Naizawa and Horobetsugawa complexes reflects temporal changes in subduction zone conditions. Seamount accretion and tectonic erosion were dominant in the Early Cretaceous, due to highly oblique subduction of the old oceanic crust and minimal sediment supply. Whereas, thick sediments with minor mid‐ocean ridge basalt and olistostrome accreted in the Late Cretaceous, due to near‐orthogonal subduction of young oceanic crust with voluminous sediment supply.  相似文献   

16.
Collision, subduction and accretion events in the Philippines: A synthesis   总被引：7，自引：0，他引：7  
Abstract The Philippines preserves evidence of the superimposition of tectonic processes in ancient and present‐day collision and subduction zone complexes. The Baguio District in northern Luzon, the Palawan–Central Philippine region and the Mati–Pujada area in southeastern Mindanao resulted from events related to subduction polarity reversal leading to trench initiation, continent‐arc collision and autochthonous oceanic lithosphere emplacement, respectively. Geological data on the Baguio District in Northern Luzon reveal an Early Miocene trench initiation for the east‐dipping Manila Trench. This followed the Late Oligocene cessation of subduction along the west‐dipping proto‐East Luzon Trough. The Manila Trench initiation, which is modeled as a consequence of the counter‐clockwise rotation of Luzon, is attributed to the collision of the Palawan microcontinental block with the Philippine Mobile Belt. In the course of rotation, Luzon onramped the South China Sea crust, effectively converting the shear zone that bounded them into a subduction zone. Several collision‐related accretionary complexes (e.g. Romblon, Mindoro) are present in the Palawan–Central Philippine region. The easternmost collision zone boundary is located east of the Romblon group of islands. The Early Miocene southwestward shift of the collision boundary from Romblon to Mindoro started to end by the Pliocene. Continuous interaction between the Palawan microcontinental block and the Philippine Mobile Belt is presently taken up again along the collisional boundary east of the Romblon group of islands. The Mati–Pujada Peninsula area, on the other hand, is underlain by the Upper Cretaceous Pujada Ophiolite. This supra‐subduction zone ophiolite is capped by chert and pelagic limestones which suggests its derivation from a relatively deep marginal basin. The Pujada Ophiolite could be a part of a proto‐Molucca Sea plate. The re‐interpretation of the geology and tectonic settings of the three areas reaffirm the complex geodynamic evolution of the Philippine archipelago and addresses some of its perceived geological enigmas.  相似文献   

17.
Di  Zhou  Zhen  Sun  Han-zong  Chen  He-hua  Xu  Wan-yin  Wang  Xiong  Pang  Dong-sheng  Cai  Deng-ke  Hu 《Island Arc》2008,17(2):186-207
Abstract   During the Mesozoic era, the South China Sea and its environs were located at the south-eastern margin of the Eurasian continent. There has been hot debate on the influences of Tethyan and Paleo-Pacific tectonics to the Mesozoic evolution of the area. This paper compiles lithofacies maps of six time slices and discusses the paleogeographic and tectonic evolution of the area based on this compilation and other data on structural deformation and magmatism. In the Early Triassic, the Paleotethys Ocean extended eastward to the study area through the Song Da passage. Then a significant east–west differential evolution began. In the Late Triassic, the western area uplifted as a result of the collision between the Indosinian and South China blocks during the Indosinian orogeny, and the Song Da passage has closed since then. Meanwhile, a transgression of Paleo-Pacific waters occurred in the eastern and south-eastern portions of the area, forming the 'East Guangdong–North-west Borneo Sea'. In the Early Jurassic, seawater transgression was even more pronounced, resulting into the connection of this sea with the Mesotethys Ocean to the west. Large quantities of Tethyan water carrying Tethyan organisms entered the area. In the Middle Jurassic, a short-lived transgression occurred in the eastern Mesotethys and resulted in the formation of the 'Yunnan–Burma Sea'. The Late Jurassic to Early Cretaceous was the climax of the subduction of both the Mesotethys and Paleo-Pacific towards the Eurasian continent. This led to the formation of the great 'Circum South-east Asia Subduction–Accretion Zone' in the Middle or Late Cretaceous. This paper also presents various lines of evidence for a newly recognized segment of this Mesozoic subduction–accretion zone buried under Cenozoic sediments in the north-eastern South China Sea.  相似文献   

18.
Abstract Seismic reflections across the accretionary prism of the North Sulawesi provide excellent images of the various structural domains landward of the frontal thrust. The structural domain in the accretionary prism area of the North Sulawesi Trench can be divided into four zones: (i) trench area; (ii) Zone A; (iii) Zone B; and (iv) Zone C. Zone A is an active imbrication zone where a decollement is well imaged. Zone B is dominated by out‐of‐sequence thrusts and small slope basins. Zone C is structurally high in the forearc basin, overlain by a thick sedimentary sequence. The subducted and accreted sedimentary packages are separated by the decollement. Topography of the oceanic basement is rough, both in the basin and beneath the wedge. The accretionary prism along the North Sulawesi Trench grew because of the collision between eastern Sulawesi and the Bangai–Sula microcontinent along the Sorong Fault in the middle Miocene. This collision produced a large rotation of the north arm of Sulawesi Island. Rotation and northward movement of the north arm of Sulawesi may have resulted in southward subduction and development of the accretionary wedge along North Sulawesi. Lateral variations are wider in the western areas relative to the eastern areas. This is due to greater convergence rates in the western area: 5 km/My for the west and 1.5 km/My for the east. An accretionary prism model indicates that the initiation of growth of the accretionary prism in the North Sulawesi Trench occurred approximately 5 Ma. A comparison between the North Sulawesi accretionary prism and the Nankai accretionary prism of Japan reveals similar internal structures, suggesting similar mechanical processes and structural evolution.  相似文献   

19.
Southern Central America is a Late Mesozoic/Cenozoic island arc that evolved in response to the subduction of the Farallón Plate beneath the Caribbean Plate in the Late Cretaceous and, from the Oligocene, the Cocos and Nazca Plates. Southern Central America is one of the best studied convergent margins in the world. The aim of this paper is to review the sedimentary and structural evolution of arc‐related sedimentary basins in southern Central America, and to show how the arc developed from a pre‐extensional intra‐oceanic island arc into a doubly‐vergent, subduction orogen. The Cenozoic sedimentary history of southern Central America is placed into the plate tectonic context of existing Caribbean Plate models. From regional basin analysis, the evolution of the southern Central American island arc is subdivided into three phases: (i) non‐extensional stage during the Campanian; (ii) extensional phase during the Maastrichtian‐Oligocene with rapid basin subsidence and deposition of arc‐related, clastic sediments; and (iii) doubly‐vergent, compressional arc phase along the 280 km long southern Costa Rican arc segment related to either oblique subduction of the Nazca plate, west‐to‐east passage of the Nazca–Cocos–Caribbean triple junction, or the subduction of rough oceanic crust of the Cocos Plate. The Pleistocene subduction of the Cocos Ridge contributed to the contraction but was not the primary driver. The architecture of the arc‐related sedimentary basin‐fills has been controlled by four factors: (i) subsidence caused by tectonic mechanisms, linked to the angle and morphology of the incoming plate, as shown by the fact that subduction of aseismic ridges and slab segments with rough crust were important drivers for subduction erosion, controlling the shape of forearc and trench‐slope basins, the lifespan of sedimentary basins, and the subsidence and uplift patterns; (ii) subsidence caused by slab rollback and resulting trench retreat; (iii) eustatic sea‐level changes; and (iv) sediment dispersal systems.  相似文献   

20.
Detrital zircon multi‐chronology combined with provenance and low‐grade metamorphism analyses enables the reinterpretation of the tectonic evolution of the Cretaceous Shimanto accretionary complex in Southwest Japan. Detrital zircon U–Pb ages and provenance analysis defines the depositional age of trench‐fill turbidites associated with igneous activity in provenance. Periods of low igneous activity are recorded by youngest single grain zircon U–Pb ages (YSG) that approximate or are older than the depositional ages obtained from radiolarian fossil‐bearing mudstone. Periods of intensive igneous activity recorded by youngest cluster U–Pb ages (YC1σ) that correspond to the younger limits of radiolarian ages. The YC1σ U–Pb ages obtained from sandstones within mélange units provide more accurate younger depositional ages than radiolarian ages derived from mudstone. Determining true depositional ages requires a combination of fossil data, detrital zircon ages, and provenance information. Fission‐track ages using zircons estimated YC1σ U–Pb ages are useful for assessing depositional and annealing ages for the low‐grade metamorphosed accretionary complex. These new dating presented here indicates the following tectonic history of the accretionary wedge. Evolution of the Shimanto accretionary complex from the Albian to the Turonian was caused by the subduction of the Izanagi plate, a process that supplied sediments via the erosion of Permian and Triassic to Early Jurassic granitic rocks and the eruption of minor amounts of Early Cretaceous intermediate volcanic rocks. The complex subsequently underwent intensive igneous activity from the Coniacian to the early Paleocene as a result of the subduction of a hot and young oceanic slab, such as the Kula–Pacific plate. Finally, the major out‐of‐sequence thrusts of the Fukase Fault and the Aki Tectonic Line formed after the middle Eocene, and this reactivation of the Shimanto accretionary complex as a result of the subduction of the Pacific plate.  相似文献   

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