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1.
Paleozoic Accretion-Collision Events and Kinematics of Ductile Deformation in the Eastern Part of the Southern-Central Tianshan Belt, China 总被引：3，自引：0，他引：3
The Tianshan range could have been built by both late Early Paleozoic accretion and Late Paleozoic collision events. The late Early Paleozoic Aqqikkudug-Weiya suture is marked by Ordovician ophiolitic melange and a Silurian flysch sequence, high-pressure metamorphic relics, and mylonitized rocks. The Central Tianshan belt could principally be an Ordovician volcanic arc; whereas the South Tianshan belt, a back-arc basin. Macro- and microstructures, along with unconformities, provide some kinematic and chronological constraints on 2-phase ductile deformation. The earlier ductile deformation occurring at ca. 400 Ma was marked by north-verging ductile shearing, yielding granulite-bearing ophiolitic melange blocks and garnet-pyroxene-facies ductile deformation, and the later deformation, a dextral strike-slip tectonic process, occurred during the Late Carboniferous-Early Permian. Early Carboniferous molasses were deposited unconformably on pre-Carboniferous metamorphic and ductilely sheared rocks, implying t 相似文献
2.
Xu Shutong Jiang Laili Liu Yican Zhang Yong Institute of Geological Sciences of Anhui Province Hefei Anhui Sun Sheping 《《地质学报》英文版》1992,66(3):221-238
The Dabie Mountains are believed to be a collisional orogenic belt between the Yangtze amd Sino-Koreancontinental plates. It is composed of the foreland fold-thrust zone, the subducting cover and basement of theYangtze continental plate, the coesite- and diamond-bearing ultra-high pressure metamorphic zone and themeta-ophiolitic melange zone in the subducting basement, the fore-arc flysch nappe and the back thrust zoneoccurring respectively on the southern and northern margins of the Sino-Korean continental plate and the in-herited basin with molassic deposits on the northern margin. When the palaeo-Dabie oceanic plate subductednorthward in the Early Palaeozoic, volcanic arc and back arc basin probably formed on the southern margin ofthe Sino-Korean continental plate. The Sm / Nd isotopic dating of the strata and eclogite which were drawn in-to the foreland fold-thrust zone indicates that the intense collision of the two continental plates took place inthe Early Mesozoic. 相似文献
3.
DuYuansheng WangJiasheng HanXin ShiGR 《中国地质大学学报(英文版)》2003,14(1):1-7
The Late Caledonian to Early Hercynian North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. North Qiilan started in the latest Proterozoic to Cambrian as a rift basin an the southern mar-gin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a fardand basin from Silurian to the Early and Middle Devonian. The Early Silurian fly-sch and sulmmrine alluvial fan, the Middle to Late Silurian shallow marine to tidal flat deposits and the Early and Middle Devonian terrestrial.molasse are developed along the corridor Nansimn. The shallo-wing-upward succession from subabyssal flysch, shallow marine, tidal flat to terrestrial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stake to molasse stake during the Silurian and Devonian time. 相似文献
4.
The Central Tianshan belt in northwestern China is a small Precambrian block located in the southern part of the Central Asia Orogenic Belt （CAOB）, which is considered as ＂the most voluminous block of young continental crust in the world＂ that comprises numerous small continental blocks separated by Paleozoic magmatic arcs. The Precambrian basement of the central Tianshan Mountains is composed of volcanic rocks and associated volcano-sedimentary rocks that were intruded by granitic plutons. Geochemical analyses demonstrate that the granitic plutons and volcanic rocks were generated in the Andean-type active continental arc environment like today＇s Chile, and the zircon U-Pb SHRIMP dating indicates that they were developed at about 956 Ma, possibly corresponding to the subduction of the inferred Mozambique Ocean under the Baltic-African super-continent. 相似文献
5.
Tectonic Units and Their Fundamental Characteristics on the Northern Margin of the Alxa Block 总被引：6，自引：0，他引：6
Wu Tairan Geology Department China University of Geosciences Beijing He Guoqi Geology Department Peking University Jiang Minxi 《《地质学报》英文版》1993,67(4)
The northern margin of the Alxa block is the junction of a tectonic units. Four first-order tectonic units are distinguished: 1. the Yagan structural zone characteristic of an immature island arc; 2. the Zhusileng-Hangwula structural zone, which was a passive continental margin in the Early Palaeozoic and was transformed into an active continental margin in the Late Palaeozoic;3. the Shalazha structural zone characteristic of a mature island arc; 4. the Nuru-Langshan structural zone, which was a Proterozoic orogenic belt and later evolved into an extensional transtional crust in the Palaeozoic. The above-mentioned tectonic units differ remarkably in sedimentary formations, magmatic rock associations, metamorphism and geochemistry and are bounded by faults between one another. 相似文献
6.
Relationships Between the North China Plate and the Tarim Plate 总被引：3，自引：0，他引：3
Wang Tingyin Wang Jinrong Liu Jinkun D epartment of Geology Lanzhou U niversity Lanzhou GansuWang Shizheng Ningxia Bureau of Geology Mineral Resources Yinchuan Ningxiaand Wu Jiahong Shenyang Institute of Geology Mineral Resources Shenyang Liaoning 《《地质学报》英文版》1994,68(2)
The relationships and boundary between the North China and Tarim plates have been unclear for a long time ; however, the two plates occupy a prominent position in the formation and evolution of the continental lithosphere of China. It is proposed that the Engger Us ophiolitic melange zone discovered recently north of Alaxa is a typical suture between the two plates. The ophiolitic melange zone is composed mainly of a mixture of fragments of ancient oceanic crust and sedimentary rocks of active and passive continental margins. The melange may be divided into tectonic inclusions and matrix. The suture extends northeastwards into the Republic of Mongolia and probably westwards to meet the Altun fault. With the Engger Us ophiolitic melange zone as the boundary the Alaxa area may be divided into two parts: the northern part (AN ) belongs to the Tarim plate, while the southern part (AS) the North China plate. Geological evidence shows that the two plates were amalgamated in the Late Permian or a bit later. 相似文献
7.
Ultrabasic rocks in the Mianxian-Lueyang ophiolitic melange zone include harzburgite and dunite which exhibit LREE depletion with remarkable positive Eu anomaly.The diabase dike swarm shows LREE enrichment but slightly negative Eu anomaly.Metamorphosed volcanic rocks can be divided into two groups in terms of their REE geochemistry and trace element ratios of Ti/V,Th/Ta,Th/Yb and Ta/Yb.One is ths MORB-type basalt with LREE depletion,representing the fragments of oceanic crust and implying an association of the MORB-type ophiolite and an ancient ocean basin between the Qinling and Yangtze plates during the Middle Paleozoic-Early Mesozoic era.The oter comprises the island-arc volcanic rocks including tholeiitic basalt and a large amount of calc-alkaline intermediate-acic volcanic rock,which could not be the component of the ancient oceanic crust but the result of magmatism at the continental margin.This indicates that the Mianxian-Lueyang limited ocean basin had undergone a whole process of development,evolution and vanishing from Devonian-Cretaceous to Permian.And the Qinling area had becone an independent lithospheric microplate,on the southern side of which there were exhibited the tectonic characteristics of active continental margins during the Late Paleozoic-Early Mesozoic.That is to say.the Qinling cannot be simply considered as a result of collision between the Yangtze and North China plates. 相似文献
8.
Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma. 相似文献
9.
In northeastern Sanandaj-Sirjan structural zone, the Takab-Ghorveh belt comprises a volcanic province which related to the collision between the Eurasian and Arabian continents. It contains almost Quaternary andesitic basalt to alkali basalt. These alkali basaltes show Strombolian type eruptions. The volcanic rocks in Bijar area represent a range of mafic magmas, re-vealed by mingling and mixing textures. A variety of features suggest that the lava flows before eruption from magma chambers, contaminated by continental crust. 相似文献
10.
The Discovery of Late Ordovician Granodiorite in the Xiemisitai Area, Xinjiang and its Geological Significance 总被引：2，自引：0，他引：2
<正>Objective The Xiemisitai area located in the northern part of the West Junggar,Xinjiang is an important component of the central Asian metallogenic domain.Recent studies show that the formation age of acid volcanic and intrusive rocks in the Xiemisitai area mainly ranges from the Late Silurian to the Early Devonian,and the age of the mineralized dacite porphyry is Early Silurian.These rocks are the 相似文献
11.
中天山北缘大型右旋走滑韧剪带研究 总被引：22，自引：4，他引：18
中天山北缘是一个近 EW向的大型右旋走滑韧剪带。宏、微观构造尺度的运动学研究表明 ,该带经历过至少二期韧性变形作用。第一期为从南向北的逆冲推覆韧剪变形 ,时代为中—晚志留世 ,以米什沟剖面为代表 ,对应于早古生代洋壳从北向南俯冲及稍后吐哈陆块朝中天山岛弧的碰撞事件。第二期为沿 EW方向的右旋走滑韧性变形 ,其构造形迹广泛分布于中天山北缘带各个地段 ;北天山石炭纪火山岩已卷入该期构造活动 ,走滑时代为晚石炭世—早二叠世 ,对应于晚石炭世塔里木与西伯利亚两大板块碰撞造山诱发的陆内变形、走滑剪切。走滑带中新生白云母 4 0 Ar/39Ar年龄为 ( 2 69± 5) Ma。剪切面理、拉伸线理、矿物韧剪构造、石英 C轴组构提供了构造运动学证据 ;地层不整合及同位素测年值提供了变形时间证据。二叠纪以后的构造事件也影响到中天山北缘带 ,但只有脆性变形形迹 ,无韧性剪切。最后对本区古生代构造演化进行了讨论 相似文献
12.
甘肃北山地区古亚洲南缘古生代岛弧带位置的讨论 总被引：3，自引：1，他引：2
综合研究得出结论:"甘肃北山红石山断裂带以北的雀儿山-英安山地区为一种与俯冲洋壳板块相关的岛弧带,它记录了古亚洲大洋向南缘东天山古陆系统下俯冲消减的整个地史过程".主要依据:①该地区缺少古老基底陆壳;②发育于区内的中奥陶世-泥盆纪不同时代地层中的火山岩和石炭-三叠纪的中酸性侵入岩,主要以钙碱性或TTG或埃达克成分系列为主要标志,揭示深部有消减洋壳板片或岩源的存在;③从中奥陶世和志留纪火山岩的玄武岩、安山岩和英安岩组合,到泥盆纪以安山岩、英安岩为主的流纹岩、玄武岩组合,至三叠纪马鞍山、小草湖中酸性侵入岩序列的部分高钾钙碱性岩石类型组合,反映古亚洲大洋在南侧消减带之上从一种不成熟岛弧到成熟岛弧和大陆边缘弧发育演化的过程;文章提出代表古亚洲大洋南缘消减带的实际位置应在雀儿山-英安山一线以北的蒙古境内,而北山岛弧带实属南侧东天山古陆陆缘增生地体的一部分. 相似文献
13.
14.
New geological, geochronological and isotopic data reveal a previously unknown arc system that evolved south of the Kyrgyz Middle Tianshan (MTS) microcontinent during the Middle and Late Ordovician, 467–444 Ma ago. The two fragments of this magmatic arc are located within the Bozbutau Mountains and the northern Atbashi Range, and a marginal part of the arc, with mixed volcanic and sedimentary rocks, extends north to the Semizsai metamorphic unit of the southern Chatkal Range. A continental basement of the arc, indicated by predominantly felsic volcanic rocks in Bozbutau and Atbashi, is supported by whole-rock Nd- and Hf-in-zircon isotopic data. εNd(t) of + 0.9 to − 2.6 and εHf(t) of + 1.8 to − 6.0 imply melting of Neo- to Mesoproterozoic continental sources with Nd model ages of ca. 0.9 to 1.2 Ga and Hf crustal model ages of ca. 1.2 to 1.7 Ga. In the north, the arc was separated from the MTS microcontinent by an oceanic back-arc basin, represented by the Karaterek ophiolite belt. Our inference of a long-lived Early Palaeozoic arc in the southwestern MTS suggests an oceanic domain between the MTS microcontinent and the Tarim craton in the Middle Ordovician.The time of arc-continent collision is constrained as Late Ordovician at ca. 450 Ma, based on cessation of sedimentation on the MTS microcontinent, the age of an angular unconformity within the Karaterek suture zone, and the age of syncollisional metamorphism and magmatism in the Kassan Metamorphic Complex of the southern Chatkal Range. High-grade amphibolite-facies metamorphism and associated crustal melting in the Kassan Metamorphic Complex restricts the main tectonic activity in the collisional belt to ca. 450 Ma. This interpretation is based on the age of a synkinematic amphibolite-facies granite, intruded into paragneiss during peak metamorphism. A second episode of greenschist- to kyanite–staurolite-facies metamorphism is dated between 450 and 420 Ma, based on the ages of granitoid rocks, subsequently affected or not affected by this metamorphism. The latest episode is recorded by greenschist-facies metamorphism in Silurian sandstones and granodiorites and by retrogression of the older, higher-grade rocks. This may have occurred at the Silurian to Devonian transition and reflects reorganization of a Middle Palaeozoic convergent margin.Late Ordovician collision was followed by initiation of a new continental arc in the southern MTS. This arc was active in the Early Silurian, latest Silurian to Middle Devonian, and Late Carboniferous, whereas during the Givetian through Mississippian (ca. 385–325 Ma) this area was a passive continental margin. These arcs, previously well constrained west of the Talas-Ferghana Fault, continued eastwards into the Naryn and Atbashi areas and probably extended into the Chinese Central Tianshan. The disappearance of a major crustal block with transitional facies on the continental margin and too short a distance between the arc and accretionary complex suggest that plate convergence in the Atbashi sector of the MTS was accompanied by subduction erosion in the Devonian or Early Pennsylvanian. This led to a minimum of 50–70 km of crustal loss and removal of the Ordovician arc as well as the Silurian and Devonian forearcs in the areas east of the Talas-Ferghana Fault. 相似文献
15.
A mafic–ultramafic intrusive belt comprising Silurian arc gabbroic rocks and Early Permian mafic–ultramafic intrusions was recently identified in the western part of the East Tianshan, NW China. This paper discusses the petrogenesis of the mafic–ultramafic rocks in this belt and intends to understand Phanerozoic crust growth through basaltic magmatism occurring in an island arc and intraplate extensional tectonic setting in the Chinese Tianshan Orogenic Belt (CTOB). The Silurian gabbroic rocks comprise troctolite, olivine gabbro, and leucogabbro enclosed by Early Permian diorites. SHRIMP II U-Pb zircon dating yields a 427 ± 7.3 Ma age for the Silurian gabbroic rocks and a 280.9 ± 3.1 Ma age for the surrounding diorite. These gabbroic rocks are direct products of mantle basaltic magmas generated by flux melting of the hydrous mantle wedge over subduction zone during Silurian subduction in the CTOB. The arc signature of the basaltic magmas receives support from incompatible trace elements in olivine gabbro and leucogabbro, which display enrichment in large ion lithophile elements and prominent depletion in Nb and Ta with higher U/Th and lower Ce/Pb and Nb/Ta ratios than MORBs and OIBs. The hydrous nature of the arc magmas are corroborated by the Silurian gabbroic rocks with a cumulate texture comprising hornblende cumulates and extremely calcic plagioclase (An up to 99 mol%). Troctolite is a hybrid rock, and its formation is related to the reaction of the hydrous basaltic magmas with a former arc olivine-diallage matrix which suggests multiple arc basaltic magmatism in the Early Paleozoic. The Early Permian mafic–ultramafic intrusions in this belt comprise ultramafic rocks and evolved hornblende gabbro resulting from differentiation of a basaltic magma underplated in an intraplate extensional tectonic setting, and this model would apply to coeval mafic–ultramafic intrusions in the CTOB. Presence of Silurian gabbroic rocks as well as pervasively distributed arc felsic plutons in the CTOB suggest active crust-mantle magmatism in the Silurian, which has contributed to crustal growth by (1) serving as heat sources that remelted former arc crust to generate arc plutons, (2) addition of a mantle component to the arc plutons by magma mixing, and (3) transport of mantle materials to form new lower or middle crust. Mafic–ultramafic intrusions and their spatiotemporal A-type granites during Early Permian to Triassic intraplate extension are intrusive counterparts of the contemporaneous bimodal volcanic rocks in the CTOB. Basaltic underplating in this temporal interval contributed to crustal growth in a vertical form, including adding mantle materials to lower or middle crust by intracrustal differentiation and remelting Early-Paleozoic formed arc crust in the CTOB. 相似文献
16.
Ordovician Macquarie Arc and turbidite fan relationships,Lachlan Orogen,southeastern Australia: stratigraphic and tectonic problems 总被引：1，自引：1，他引：0
Ordovician rocks of the Lachlan Orogen consist of two major associations, mafic to intermediate volcanic and volcaniclastic rocks (Macquarie Arc), which aerially comprise several north–south-trending belts, and the quartz-rich turbidite succession. Relationships between these associations are integral to resolving their tectonic settings and opinions range between contacts being major thrusts, combinations of various types of faults, and stratigraphic contacts with structural complications. Stratigraphic contacts between these associations are found with volcaniclastic-dominant units overlying quartz-turbidite units along the eastern boundary of the eastern volcanic belt and along the southern boundary of the central volcanic belt. Mixing between these major associations is limited and reflects waning quartzose turbidite deposition along a gently sloping sea floor not penetrating steeper volcaniclastic aprons that were developing around the growing volcanic centres formed during late Middle Ordovician to early Silurian Macquarie Arc igneous activity. An island arc setting has been most widely supported for the Macquarie Arc, but the identification and polarity of the associated subduction zone remain a contentious issue particularly for the Early Ordovician phase of igneous activity. The Macquarie Arc initiated within a Cambrian backarc formed by sea-floor spreading behind a boninitic island arc and presumably reflects a renewed response to regional convergence as subduction ceased along the Ross–Delamerian convergent boundary at the East Gondwana continental margin. An extensional episode accompanied initiation of the late Middle Ordovician expansion in island arc development. A SSE-dipping subduction zone is considered to have formed the Macquarie Arc and underwent anticlockwise rotation about an Euler pole at the western termination of the island arc. This resulted in widespread deformation west of the Macquarie Arc in the Benambran Orogeny and development of subduction along the eastern margin of the orogenic belt. 相似文献
17.
18.
拉鸡山断裂带位于祁连山褶皱带内,呈北西-南东向延伸.后者构成青藏高原的东北边缘,由三个主要构造单元组成:北部是一条早古生代的板块缝合带,中部是一个元古代的结晶地块,南部由一套晚古生代到三叠纪的被动大陆边缘沉积物组成.对拉鸡山及其邻区的构造研究结果表明,祁连山褶皱带在古生代加里东期发生过大规模的缩短,北祁连的早古生代蛇绿岩和岛弧火山岩沿祁连山中央冲断层向南,陆内俯冲到中祁连元古界变质杂岩之下.由于发生在晚古生代和晚中生代的陆内变形,位于中祁连之下的北祁连的蛇绿岩和岛弧火山岩发生褶皱,并被抬升到地表.到新生代,由于印度板块和欧亚大陆之间的碰撞和陆内汇聚作用,拉鸡山断裂带再次活动,这些下古生界蛇绿岩和岛弧火山岩通过冲断作用快速抬升,将中祁连地块一分为二.因此,拉鸡山是一个抬升的构造窗,不是一个中祁连结晶地块中的早古生代大陆裂谷. 相似文献
19.
West Junggar (NW China) and East Kazakhstan are situated in the southwest of the Central Asian orogenic belt (CAOB). Tectonic entities in the two areas share the same tectonic evolution history and make up the famous horseshoe-shaped orocline in Central Asia. This paper presents a newly compiled cross-border tectonic sketch map of West Junggar and East Kazakhstan and proposes the extension of the Chingiz–Tarbagatai belt and the North Balkhash-West Junggar belt.The Chingiz–Tarbagatai Belt in East Kazakhstan consists mainly of Middle-Late Ordovician differentiated volcanic rocks, pyroclastic sediments and flysch; while in the Tarbagatai Mountain in China, Tarbagatai (Kujibai) ophiolite is newly found with zircon (gabbro) age of 478 ± 3 Ma and the Ordovician flysch metamorphosed to a greenschist facies is distinguished from Devonian–Carboniferous rock associations. Therefore, the Early Paleozoic Chingiz–Tarbagatai belt of East Kazakhstan evidently extends to the northern part of West Junggar along the Tarbagatai orogenic belt.The North Balkhash-West Junggar belt lying south to the Chingiz–Tarbagatai belt is separated by the EW-trending Baiyanghe–Heshituoluogai depression in West Junggar. Early Ordovician–Early Silurian ophiolitic fragments and related pyroclastic sediments are widely exposed in Tekturmas, North Balkhash and Agadyr of East Kazashtan. Similarly, Early Paleozoic ophiolites have also been verified in Tangbale, Mayile, Baerluke, Darbut and Karamay of West Junggar in recent years. Therefore, nearly all ophiolites in West Junggar and East Kazakhstan are proved to have formed in Early Paleozoic, which suggests that the evolution of the paleo-ocean in the two areas reached its peak in the Early Paleozoic. Based on the ages of the Tangbale, Karamay and Hongguleleng ophiolites, an Early Paleozoic continental accretionary belt extending from Tangbale to Hongguleleng is determined at the NW margin of the Junggar basin for the first time. According to spatiotemporal comparison, ophiolites exposed in West Junggar and East Kazakhstan might originate from the same paleo-ocean tectonic region, and then the North Balkhash in East Kazakhstan and the West Junggar were offset for a long distance with respect to each other by the major Junggar dextral fault.Because of the large-scale accretion of continental crust before Silurian, the Late Paleozoic ocean in West Junggar and East Kazakhstan became smaller with residual nature, and extensive arc-basin-trench systems might be absent during the closure of this residual ocean. 相似文献