共查询到18条相似文献，搜索用时 140 毫秒
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藏东类乌齐地区辉长岩:冈瓦纳大陆北缘晚古生代裂解的记录 总被引：1，自引：0，他引：1
青藏高原处于冈瓦纳大陆与劳亚大陆的交汇部位,是研究冈瓦纳大陆裂解与聚合过程的关键地区。晚古生代伴随着特提斯洋的打开与扩张,冈瓦纳大陆北缘发生了广泛的裂解作用。大陆板内岩浆作用是超大陆裂解的重要证据。在青藏高原内部已有二叠纪大陆板内特征基性岩的报道,它们是该裂解事件的记录。然而,根据目前的相关报道,这些岩石主要出露在青藏高原的西部,以羌塘和潘伽地区为主,在其他地区尚无相关报道。首次报道的藏东类乌齐地区早二叠世辉长岩LA-ICP-MS锆石U-Pb定年结果显示,辉长岩的形成年龄为280±2Ma。全岩地球化学资料表明,辉长岩具有与典型大陆板内玄武岩类似的地球特征。辉长岩具有明显正的锆石εHf(t)值(5.1~11.5),暗示其岩浆起源于亏损的地幔源区。结合区域地质资料,认为类乌齐辉长岩是冈瓦纳大陆北缘早二叠世裂解的产物。因此,早二叠世大陆板内基性岩浆作用在青藏高原东部也有出露,它们是在羌塘-潘伽地幔柱活动的作用下,冈瓦纳大陆北缘裂解与班公湖-怒江洋打开和扩张的结果。 相似文献
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西藏西南部达巴-休古嘎布蛇绿岩带的形成与演化 总被引：16，自引：0，他引：16
:该蛇绿岩带的岩体由地幔橄榄岩组成,主要岩石类型是方辉橄榄岩和纯橄榄岩,缺少典型蛇绿岩剖面中的洋壳单元.微量元素和稀土元素特征显示蛇绿岩形成于类似洋中脊的构造环境.笔者提出该区蛇绿岩来源于印度大陆北缘洋盆的洋壳碎片,这个陆缘洋盆与新特提斯洋主体的形成和演化准同步.洋盆的演化模式是:早三叠世,随着印度(冈瓦纳)大陆向南漂移,其北部边缘因引张裂解产生裂谷,于晚三叠世向东开口与新特提斯洋主体连通,洋盆初具洋壳性质,北侧形成阿依拉-仲巴微陆块.侏罗-白垩纪为洋盆洋壳演化期,处于类似洋中脊的构造环境.晚白垩世末洋盆开始闭合.在新特提斯洋板块向北俯冲消减过程中,阿依拉-仲巴微陆块、陆缘洋盆和印度大陆一起随着向北漂移,在印度大陆向北挤压作用下洋盆逐渐收缩以致最终闭合. 相似文献
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全球早古生代造山带(Ⅳ):板块重建与Carolina超大陆 总被引：2，自引：0，他引：2
古元古代与显生宙的板块构造特征和旋回演化过程具有明显区别,反映出地质记录为两种不同的板块构造体制。早古生代为这两个时期的过渡阶段,其构造过程研究与板块重建是地球板块构造旋回机制和周期分析的关键。本文采用综合集成的方法,在总结对比罗迪尼亚超大陆裂解以来全球早古生代主要碰撞造山带的地质事件基础上,分析早古生代碰撞造山带的演化特征,总结出与冈瓦纳大陆拼合、劳俄大陆拼合、古中华陆块群增生相关的7期碰撞-增生造山事件群:Brasiliano、东非、Kuunga、东亚与原特提斯洋和古亚洲洋演化相关的的加里东期造山事件、经典加里东造山、中欧加里东造山、Appalachian造山。再在这7期造山事件群基础上,结合古地磁、古生物、古地理等资料,重建了新元古代-早古生代末全球板块的拼合过程:罗迪尼亚超大陆从新元古代的~950 Ma开始经历了3个阶段裂解,此时存在泛大洋、莫桑比克洋和古太平洋3个大洋,随后615~560 Ma Iapetus洋打开,~560 Ma波罗的陆块与西冈瓦纳裂离导致狭窄的Ran洋打开;~540 Ma南半球Brasiliano、东非和Kuunga造山运动导致冈瓦纳大陆分阶段最终完成拼贴;~500 Ma冈瓦纳大陆北缘西段的微陆块群局部向北裂离,导致Rheic洋和Tornquist洋打开,并于~420 Ma随经典加里东造山带和中欧缝合带形成导致Iapetus洋闭合,此时斯瓦尔巴特和英国可能位于格陵兰地盾东南缘,同时冈瓦纳大陆北缘东段华北为代表的微陆块基本拼合在冈瓦纳大陆北缘;此外,虽然425 Ma西伯利亚板块有远离聚合了的劳俄大陆的趋势,但晚奥陶世-早泥盆世南美和北美板块靠近,北美板块与环冈瓦纳北缘西段的地体拼合碰撞。在大约400 Ma时,南、北美洲的混合生物群和古地理重建显示两者非常接近,因此,推测此时存在一个初始的逐步稳定的超大陆的可能,本文称为Carolina超大陆,因为Carolina造山带是这个超大陆最终拼合的地带。并据此判断超大陆旋回为7亿年。 相似文献
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柴达木盆地北缘新元古代-早古生代大洋的形成、发展和消亡 总被引：4，自引：0，他引：4
柴达木盆地北缘构造带是一条典型的早古生代造山带,是由陆壳深俯冲形成的高压/超高压变质带,产于其中的高压/超高压变质岩石原岩形成时代普遍大于750Ma,原岩的性质为陆壳属性,但柴北缘东段都兰沙柳河地区出露的含柯石英榴辉岩原岩的形成时代为516Ma,原岩的性质为洋壳属性,证实柴北缘局部地段还存在洋壳深俯冲,柴北缘地区可能记录了从大洋俯冲到大陆俯冲再到碰撞造山这一完整的演化历史。本文主要从岩石学、年代学、地球化学以及同位素地球化学等方面对柴北缘地区陆壳深俯冲前新元古代-早古生代大洋发展与演化的岩石记录进行了系统总结,认为柴北缘地区在700~850Ma时受Rodinia超大陆裂解事件的影响发生了裂解;535~700Ma时在裂解事件的基础上形成了一个新元古代-早古生代的大洋,沿柴北缘连续分布的岩石记录表明该洋盆可能在早古生代已具有一定的规模;460~535Ma时该洋壳发生了俯冲消减作用;450~460Ma期间洋盆闭合消失。这一认识对全面深入了解柴北缘高压/超高压变质带早古生代构造演化历史具有重要意义。 相似文献
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青藏高原北部被认为是原特提斯洋闭合所形成的早古生代造山系，其中原特提斯洋演化的物质记录主要分布在东昆仑北部、西昆仑北部、阿尔金、祁连、柴北缘等，以出露典型的新元古代晚期-早古生代蛇绿岩、弧岩浆岩、俯冲增生杂岩、高压-超高压变质带等地质体为特征，并夹有前寒武纪微大陆块体。通过近20余年的研究，青藏高原北部早古生代造山系的研究取得了一些重要进展和基本共识，认为其经历了从原特提斯洋的开启、大洋俯冲增生、闭合到大陆俯冲碰撞造山的过程。然而，随着研究的不断深入，一些新的科学问题不断涌现，有的问题显得更加突出。本文通过横穿青藏高原东北部祁连-柴北缘造山带的两条地质廊带的解剖，对与原特提洋演化有关的岩石构造单元进行了重新划分；结合一些新发表的研究资料，梳理出青藏高原北部原特提斯造山系的研究新进展，并探讨了几个关键科学问题：(1)青藏高原北部与原特提斯洋演化有关的缝合带有几条?相关的问题是有几个原特提斯分支洋盆?(2)原特提斯洋的俯冲极性如何?单一向北、单一向南还是双向俯冲?(3)原特提斯洋中微陆块的性质和起源如何?虽然多数学者认为这些块体起源于冈瓦纳大陆，但何时从冈瓦纳大陆分离仍有很大争议，起源于冈... 相似文献
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藏北羌塘早古生代岩浆作用及其构造演化对研究青藏高原早期演化历史以及羌塘盆地基底性质结构等具有重要科学意义。本文在综述前人研究基础上,系统总结了藏北羌塘地区早古生代岩浆岩的时空分布特征及年代学格架,初步探讨了青藏高原早古生代构造-岩浆事件对冈瓦纳大陆北缘构造演化以及羌塘盆地基底属性的约束。羌塘地区早古生代岩浆岩主要分布在日湾茶卡、都古尔、戈木日、本松错等地区,岩性以变质辉长岩、变质玄武岩、安山岩、花岗岩、变质流纹岩以及花岗片麻岩等为主。基于区域地质调查和年代学研究结果,羌塘地区早古生代发生了多期岩浆作用,分别为~500 Ma、~482 Ma、~474 Ma、~455 Ma、~438 Ma。这些岩浆岩可能是泛非造山运动结束后,冈瓦纳大陆北缘岩石圈伸展减薄的产物,并构成了羌南-保山板块早古生代的结晶基底,但有关伸展减薄的机制问题仍需开展进一步的研究工作,这些地质记录对恢复和反演青藏高原冈瓦纳大陆北缘的陆缘性质具有重要约束意义。 相似文献
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《吉林大学学报(地球科学版)》2015,(Z1)
<正>冈瓦纳的裂解过程是地质学界的长久热点话题。正是冈瓦纳北缘从古生代以来持续的陆块北向裂离和汇聚形成的一系列俯冲带、洋盆残迹和造山带,构成了现今的亚洲大部。其中,冈瓦纳大陆北缘晚石炭—早二叠世裂解是其中最重要的阶段之一。古生物、地层学、古气候和古地磁等研究显示,本次裂解中南羌塘和Sibumasu地块作为东基梅里大陆的主体,在早二叠世时左右从冈瓦纳大陆北缘分离并向低纬度漂移。同期的玄武岩浆在印度冈瓦纳和周缘地区有广泛报道,如印度地块北缘的Panjal Traps、Abor、Bhote Kosi, 相似文献
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本文对超大陆、超大陆旋回、冈瓦纳及特提斯问题进行了论述，认为陆块是不断组合、拼接与裂解和扩散的，也就是超大陆演化．这种演化过程与威尔逊旋回相关．冈瓦纳大陆在元古宙并未构成统一的大陆体．而是在元古宙末一古生代初才拼合成统一的冈瓦纳大陆．特提斯洋的发生、发展和消亡都与中国大陆各块体的发展与演化有着密切的关系． 相似文献
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QIU Ruizhao CHEN Yuming CHEN Xiuf ZHAO Hongjun REN Xiaodong ZHAO Like ZHANG Cao WANG Liangliang 《《地质学报》英文版》2019,93(Z2):43-44
The Paleo‐Tethys Ocean was a Paleozoic ocean located between the Gondwana and Laurasia supercontinents. It was usually consider to opening in the early Paleozoic with the rifting of the Hun superterrane from Gondwana following the subduction of the Rheic Ocean/proto‐Tethys Ocean. However, the opening time and detailed evolutionary history of the Paleo‐Tethys Ocean are still unclear. The Paleozoic ophiolites have recently been documented in the middle of the Qiangtang terrane, northern Tibetan Plateau, and they mainly occur in the Gangma Co area. These ophiolites are composed of serpentinite, pyroxenite, isotropic and cumulate gabbros, basalt, hornblendite and plagiogranite. Whole‐rock geochemical data suggest that all mafic rocks were formed in an oceanic‐ridge setting. Furthermore, positive whole‐rock εNd(t) and zircon εHf(t) values suggest that these rocks were derived from a long‐term depleted mantle source. The data allow us to conform that these rocks represent an ophiolite suite. Zircon U‐Pb dating of gabbros and plagiogranites yielded weighted mean ages of 437‐501 Ma. The occurrence of the ophiolite suite suggests that a Paleozoic Ocean basin (Paleo‐Tethys) existed in middle of the Qiangtang terrane. We hypothesize that the ophiolite in the middle of the Qiangtang terrane represents the western extension of the Sanjiang Paleo‐Tethys ophiolite in the east margin of the Tibetan Plateau, and they mark the main Paleo‐Tethys Ocean. This is the oldest ophiolite from the Paleo‐Tethyan suture zones and the Paleo‐Tethys Ocean basin probably opened in the Middle Cambrian, and continued to grow throughout the Paleozoic. The ocean was finally closed in the Middle to Late Triassic as inferred from the metamorphic ages of eclogite and blueschist that occur nearby. The Paleo‐Tethys Ocean was probably formed by the breakup of the northern margin of Gondwana, with southward subduction of the proto‐Tethys oceanic lithosphere along the northern margin of the supercontinent. 相似文献
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Early Paleozoic evolution of the northern Gondwana margin is interpreted from integrated in situ U-Pb and Hf-isotope analyses on detrital zircons that constrain depositional ages and provenance of the Lancang Group, previously assigned to the Simao Block, and the Mengtong and Mengdingjie groups of the Baoshan Block. A meta-felsic volcanic rock from the Mengtong Group yields a weighted mean 206Pb/238U age of 462 ± 2 Ma. The depositional age for the previously inferred Neoproterozoic Lancang and Mengtong groups is re-interpreted as Early Paleozoic based on youngest detrital zircons and meta-volcanic age. Detrital U-Pb zircon analyses from the Baoshan Block define three distinctive age peaks at older Grenvillian (1200–1060 Ma), younger Grenvillian (~ 960 Ma) and Pan-African (650–500 Ma), with εHf(t) values for each group similar to coeval detrital zircons from western Australia and northern India. This suggests that the Baoshan Block was situated in the transitional zone between northeast Greater India and northwest Australia on the Gondwana margin and received detritus from both these cratons. The Lancang Group yields a very similar detrital zircon age spectrum to that of the Baoshan Block but contrasts with that for the Simao Block. This suggests that the Lancang Group is underlain by a separate Lancang Block. Similar detrital zircon age spectra suggest that the Baoshan Block and the Lancang Block share common sources and that they were situated close to one another along the northern margin of East Gondwana during the Early Paleozoic. The new detrital zircon data in combination with previously published data for East Gondwana margin blocks suggests the Early Paleozoic Proto-Tethys represents a narrow ocean basin separating an “Asian Hun superterrane” (North China, South China, Tarim, Indochina and North Qiangtang blocks) from the northern margin of Gondwana during the Late Neoproterozoic-Early Paleozoic. The Proto-Tethys closed in the Silurian at ca. 440–420 Ma when this “Asian Hun superterrane” collided with the northern Gondwana margin. Subsequently, the Lancang Block is interpreted to have separated from the Baoshan Block during the Early Devonian when the Paleo-Tethys opened as a back-arc basin. 相似文献
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Sebastián Oriolo Bernhard Schulz Silvana Geuna Pablo DGonzález Juan E.Otamendi JiíSláma Elena Druguet Siegfried Siegesmund 《地学前缘(英文版)》2021,12(1):109-130
Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension and back-arc basin development.The southwestern margin is represented by Famatinian and Pampean basement realms exposed in South America,both related to the protracted Paleozoic evolution of the Terra Australis Orogen,whereas the northwestern margin is mainly recorded in Cadomian domains of Europe and adjacent regions.However,no clear relationships between these regions were so far established.Based on a compilation and reevaluation of geological,paleomagnetic,petrological,geochronological and isotopic evidence,this contribution focuses on crustal-scale tectonic and geodynamic processes occurring in Western Gondwana accretionary orogens,aiming at disentangling their common Early Paleozoic evolution.Data show that accretionary orogens were dominated by high-temperature/lowpressure metamorphism and relatively high geothermal gradients,resulting from the development of extended/hyperextended margins and bulk transtensional deformation.In this sense,retreating-mode accretionary orogens characterized the Early Paleozoic Gondwana margin,though short-lived pulses of compression/transpression also occurred.The existence of retreating subduction zones favoured mantle-derived magmatism and mixing with relatively young(meta)sedimentary sources in a thin continental crust.Crustal reworking of previous forearc sequences due to trenchward arc migration thus took place through assimilation and anatexis in the arc/back-arc regions.Therefore,retreating-mode accretionary orogens were the locus of Early Paleozoic crustal growth in Western Gondwana,intimately associated with major flare-up events,such as those related to the Cadomian and Famatian arcs.Slab roll back,probably resulting from decreasing convergence rates and plate velocities after Gondwana assembly,was a key factor for orogen-scale geodynamic processes.Coupled with synchronous oblique subduction and crustal-scale dextral deformation,slab roll back might trigger toroidal mantle flow,thus accounting for bulk dextral transtension,back-arc extension/transtension and a large-scale anticlockwise rotation of Gondwana mainland. 相似文献
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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
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During the Early Paleozoic, transgressions and the distribution of sedimentary facies on the northern Gondwana margin were controlled by a regional NNW-SSE to almost north-south striking structural relief. In Early Silurian times, a eustatic highstand enabled the sea to reach its maximum southward extent.The counterclockwise rotation of Gondwana during the Cambrian and Early Ordovician caused the northern Gondwana margin to shift from intertropical to southern polar latitudes in Ordovician times. Glacial and periglacial deposits are reported from many localities in Morocco, Algeria, Niger, Libya, Chad, Sudan, Jordan and Saudi Arabia. The Late Ordovician glaciation phase was followed by a period of a major glacioeustatic sea-level rise in the Early Silurian due to the retreat of the ice-cap. As a consequence of the decreasing water circulation in the basin centers (Central Arabia, Murzuk- and Ghadames basins), highly bituminous euxinic shales were deposited. These shales are considered to be the main source rock of Paleozoic oil and gas deposits in parts of Saudi Arabia, Libya and Algeria.The following regression in the southern parts of the Early Silurian sea was probably caused by a second glacial advance, which was mainly restricted to areas in Chad, Sudan and Niger. Evidence for glacial activity and fluvioglacial sedimentation is available from rocks overlying the basal Silurian shale in north-east Chad and north-west Sudan. The Early Silurian ice advance is considered to be responsible for the termination of euxinic shale deposition in the basin centers. 相似文献
16.
东亚原特提斯洋(Ⅰ):南北边界和俯冲极性 总被引：1，自引：1，他引：0
原特提斯洋是从新元古代Rodinia裂解到早古生代发育于滇缅泰/保山微陆块以北、塔里木-华北陆块以南的一个复杂成因的洋盆。长期以来对原特提斯洋的南、北边界及其早古生代末俯冲极性还存在争论,而这是恢复重建Pangea超大陆聚合前构造背景的关键。本文综合利用野外地质、构造、岩浆、沉积学、地球化学、构造年代学和层析成像等最新成果,以期界定原特提斯域的南、北边界位置,确定原特提斯洋边界俯冲极性。集成分析结果表明,北界为古洛南-栾川缝合线(或宽坪缝合线)及其直至西昆仑的西延部分;南界为龙木措-双湖-昌宁-孟连缝合线。原特提斯洋北部在华北-阿拉善-塔里木陆块泥盆纪向南俯冲并与冈瓦纳大陆北缘拼合过程中,形成了一个巨型弯山构造,现保存在祁连-阿尔金-柴达木地区的中国中央造山带内。原特提斯洋南部分支也可能在泥盆纪闭合,使得包括羌北、若尔盖、扬子、华夏、布列亚-佳木斯等在内的大华南陆块、印支陆块等也向南俯冲与冈瓦纳北缘发生了聚合。 相似文献
17.
仲巴地体是雅鲁藏布江缝合带西段南北蛇绿岩带之间的重要构造单元,目前对其是否存在早古生代构造-热事件记录及构造属性判别尚不明确.通过野外观测、岩石地球化学研究和年代学分析,在仲巴地体中段的公珠错一带识别出一套侵入到黑云斜长片麻岩中的片麻状二长花岗岩,其锆石U-Pb年龄为~478 Ma,表明岩石形成时代为早奥陶世;该套花岗岩具有高Si、富Al和总碱含量较高的特点,铝饱和指数A/CNK=1.13~1.20,富集大离子亲石元素Rb、K,相对亏损Ba、Sr、Nb、Ti等,属于钙碱性强过铝质花岗岩.这是首次在雅鲁藏布江缝合带西段仲巴地体内部识别出代表早奥陶世构造-热事件的地质记录,该套花岗岩形成过程与原特提斯洋向冈瓦纳大陆北缘俯冲结束后的上地壳熔融相关,证明仲巴地体在早古生代应为东冈瓦纳大陆北缘的组成部分. 相似文献
18.
新疆古生代构造—生物古地理 总被引：4，自引：0，他引：4
通过6幅图表达了新疆古生代板块的构造－生物古地理区系。早古生代，包括劳伦，波罗的、西伯利亚和哈萨克斯坦4陆块的亚帕特斯古陆（Iapetusa)群，与由其余陆块构成的冈瓦纳古陆群隔原特提斯洋相对峙。石炭－二叠纪，欧美、安加拉、太平洋和冈瓦纳4古陆共存并立。西伯利亚和哈萨克斯担板块经历了早古生代亚伯特斯古陆、晚古生代安加拉古陆和早二叠世晚期以来欧亚大陆3个发展阶段。塔里木、中朝、华南－东南亚板块经历了早古生代冈瓦纳古陆、晚古生代太平洋古陆和早二叠世晚期以来欧亚大陆3个发展阶段。指出在中晚寒武世和晚奥陶世哈萨克斯坦板块靠近塔里木、中朝和华南－东南亚板块；在早古生代其余时期它接近西伯利亚板块。伊犁和托克逊－雅满苏地体是在中泥盆世之前裂解自塔里木板块，尔后在早二叠世晚期接近安加拉古陆。塔里木板块北东缘北山地区在早二叠世早期首先靠近安加拉古陆。塔里木与西伯利亚－哈萨克斯坦板块之间缝合时代大抵上和土耳其－中伊朗－冈底斯与华南－东南亚板块之间缝合时代一致。缝合事件发生在早二叠世早期，而相应的构造运动出现在早晚二叠世之交。 相似文献