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1.
A comparison of late Mesoproterozoic palaeomagnetic poles from the Kalahari craton and its correlative Grunehogna craton in East Antarctica shows that the Kalahari–Grunehogna craton straddled the palaeo-Equator and underwent no azimuthal rotation between ca. 1130 and 1105 Ma. Comparison of the Kalahari palaeopoles with the Laurentia APWP between 1130 and 1000 Ma shows that there was a latitudinal separation of 30±14° between Kalahari and the Llano–West Texas margin of Laurentia at ca. 1105 Ma. The Kalahari craton could have converged with southwestern Laurentia between 1060 and 1030 Ma to become part of Rodinia by 1000 Ma. In Rodinia, the Kalahari craton lay near East Antarctica with the Namaqua–Natal orogenic belt facing outboard and away from the Laurentian craton.  相似文献   

2.
The geological, structural and tectonic evolutions of the Yenisey Ridge fold-and-thrust belt are discussed in the context of the western margin of the Siberian craton during the Neoproterozoic. Previous work in the Yenisey Ridge had led to the interpretation that the fold belt is composed of high-grade metamorphic and igneous rocks comprising an Archean and Paleoproterozoic basement with an unconformably overlying Mesoproterozoic–Neoproterozoic cover, which was mainly metamorphosed under greenschist-facies conditions. Based on the existing data and new geological and zircon U–Pb data, we recognize several terranes of different age and composition that were assembled during Neoproterozoic collisional–accretional processes on the western margin of the Siberian craton. We suggest that there were three main Neoproterozoic tectonic events involved in the formation of the Yenisey Ridge fold-and-thrust belt at 880–860 Ma, 760–720 Ma and 700–630 Ma. On the basis of new geochronological and petrological data, we propose that the Yeruda and Teya granites (880–860 Ma) were formed as a result of the first event, which could have occurred in the Central Angara terrane before it collided with Siberia. We also propose that the Cherimba, Ayakhta, Garevka and Glushikha granites (760–720 Ma) were formed as a result of this collision. The third event (700–630 Ma) is fixed by the age of island-arc and ophiolite complexes and their obduction onto the Siberian craton margin. We conclude by discussing correlation of these complexes with those in other belts on the margin of the Siberian craton.  相似文献   

3.
We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton, including recently published U–Pb and 40Ar–39Ar dates. These new precise ages suggest that at least some of the previously published K–Ar ages of Siberian mafic bodies should be ignored. The time–space geochronological chart, or the ‘barcode’ of mafic magmatic events shows significant differences between northern and southern Siberia. Both are characterized by ∼1900–1700 Ma magmatic events, but then there was an almost 1 Ga mafic magmatic ‘pause’ in south Siberia until ∼800 Ma. Meanwhile there are indications of multiple mafic magmatic events in North Siberia (Anabar shield and Olenek uplift) between ∼1600 and 1000 Ma. A series of magmatic events probably related to the breakup of Rodinia occurred in southern Siberia after ∼800 Ma. So far, there are no indications of late Neoproterozoic mafic magmatism in North Siberia. Ca. 1000–950 Ma mafic sills were reported from Meso- to Neo-Proterozoic sedimentary successions in the Sette-Daban area on the east side of the Siberian craton, but their tectonic setting is debated. Recent Ar–Ar dates of ∼1750 Ma for NW-trending dykes in the Aldan and Anabar shields, together with similar-age NNE-trending Baikal uplift dykes in south-eastern Siberia suggest the existence of a giant radial dyke swarm possibly related to a mantle plume centred in the Vilyui River area.  相似文献   

4.
The paper summarizes paleomagnetic results obtained from the Neoproterozoic rocks of the western margin of the Siberian craton. On the basis of the obtained paleomagnetic poles and available paleomagnetic data for the Precambrian of Siberia, a new version of the Neoproterozoic segment of the apparent polar wandering path (APWP) is proposed for the craton and is compared with the Laurentian APWP. The superposition of these paths suggests that in the Neoproterozoic the southern margin of the Siberian craton (in modern coordinates) faced the Canadian margin of Laurentia. Most likely, in the end of the Mesoproterozoic and during the Neoproterozoic the Siberian craton and Laurentia were connected to form the supercontinent Rodinia. At 1 Ga the western margin of the Siberian craton was a northern (in modern coordinates) continuation of the western margin of Laurentia. The available paleomagnetic data on Laurentia and continental blocks of Eastern Gondwana (Australia, Antarctica, India, South China) and the proposed APWP trend allowed a new model for the breakup of this segment of Rodinia. Analysis of a total of the data available suggests that strike-slip movements on the background of the progressive opening of the oceanic basin between Siberia and Laurentia were predominant in the south of the Siberian craton during the Neoproterozoic. Similar kinematics is typical of the western margin of Laurentia, where strike-slip motions are probably associated with the progressive opening of the ocean basin between Laurentia and eastern Gondwana.  相似文献   

5.
We present the synthesis of new data on detrital zircon geochronology of the Neoproterozoic strata of the southern part of the Siberian craton as well as a comprehensive analysis of previously published stratigraphic, sedimentological and geochronological (LA-ICP-MS) data obtained for key sections in this area that allows us to trace the process of birth and early stages of development of the Paleo-Asian Ocean (PAO). Before the break-up of Rodinia and opening of PAO, Tonian – Cryogenian intracontinental sedimentary basin existed between southern Siberia and northern Laurentia. The detachment of the southern flank of the Siberian craton from northern Laurentia and opening of the PAO between these cratons took place in Cryogenian. The detrital zircon ages from lower parts of Neoproterozoic successions suggest the Siberian craton as the sole provenance area right after the opening of the PAO. The age constraints on the lower parts of the studied Neoproterozoic successions, which are based on correlation of their tillite horizons with the Marinoan glaciation, suggest the late Cryogenian age for these sedimentary rocks. A clear change in the age spectra of detrital zircons from “unimodal” (Early Precambrian only) in older sedimentary rocks to “bimodal” (Early Precambrian as well as Neoproterozoic) in younger sequences of the studied successions marks the next stage of the PAO evolution. The abundance of youngest (630–610 Ma) detrital zircons in the upper parts of the studied sequences reflects a shrinkage of the oceanic basin as a result of the convergence of the craton with the microcontinents and island arcs within the Paleo-Asian Ocean. We suggest that a passive oceanic margin along the southern margin of the Siberian craton has been transformed into a series of foreland basins at ~610 Ma.  相似文献   

6.
Revision of crustal architecture and evolution of the Central Asian Orogenic Supercollage (CAOS) between the breakup of Rodinia and assembly of Pangea shows that its internal pattern cannot be explained via a split of metamorphic terranes from and formation of juvenile magmatic arcs near the East European and Siberian cratons, followed by zone-parallel complex duplication and oroclinal bending of just one or two magmatic arcs/subduction zones against the rotating cratons. Also, it cannot be explained by breakup of multiple cratonic terranes and associated magmatic arcs from Gondwana and their drift across the Paleoasian Ocean towards Siberia. Instead, remnants of early Neoproterozoic oceanic lithosphere at the southern, western and northern periphery of the Siberian craton, as well as Neoproterozoic arc magmatism in terranes, now located in the middle of the CAOS, suggest oceanic spreading and subduction between Eastern Europe and Siberia even before the breakup of Rodinia at 740–720 Ma. Some Precambrian terranes in the western CAOS and Alai-Tarim-North China might have acted as a bridge between Eastern Europe and Siberia.The CAOS evolution can be rather explained by multiple regroupings of old and juvenile crust in eastern Rodinia in response to: 1) 1000–740 Ma propagation of the Taimyr-Paleoasian oceanic spreading centres between Siberian and East European cratons towards Alai-Tarim-North China; 2) 665–540 Ma opening and expansion of the Mongol-Okhotsk Ocean, collision of Siberian and East European cratons with formation of the Timanides and tectonic isolation of the Paleoasian Ocean; 3) 520–450 Ma propagation of the Dzhalair-Naiman and then Transurals-Turkestan oceanic spreading centres, possibly from the Paleotethys Ocean, between Eastern Europe and Alai-Tarim, essentially rearranging all CAOS terranes into a more or less present layout; and 4) middle to late Paleozoic expansion of the Paleotethys Ocean and collision of Alai-Tarim-North China cratons with CAOS terranes and Siberian craton to form the North Asian Paleoplate prior to its collision with Eastern Europe along the Urals to form Laurasia. Two to five subduction zones, some stable long-term and some short-living or radically reorganized in time, can be restored in the CAOS during different phases of its evolution.  相似文献   

7.
We suggest new age constraints for regional stratigraphic units and a model of the Neoproterozoic geodynamic evolution of the southern Siberian craton proceeding from our data on genesis and lithology of sedimentary and volcanosedimentary complexes and their correlation combined with published geochronological and chemostratigraphic evidence. Large-scale rifting events in the region may have occurred between 1000 and 850 Ma in the east and between 780 and 730 Ma in the west. The latter time span correlates with the breakup of the Rodinia supercontinent. The interval of 780–680 Ma corresponding to the deposition of the Dalnyaya Taiga regional stratigraphic unit was marked by the onset of collision and the development of an island arc and a back-arc basin in the eastern part of the territory. The basal strata of the Baikal and Oselok Groups and their equivalents presumably deposited at about 730 Ma, and their signature of glacial events correlates with the global Sturtian Glacial. The deposition of the Zhuya unit between 680 and 630 Ma was associated with development of a foreland basin which gave way to a system of orogenic foredeeps in the Early Vendian (since 630 Ma). Our studies furnish new data on the stratigraphy of the Baikal Group and shed more light on its complex structure and ambiguously interpreted deposition sequence.  相似文献   

8.
Reappraisal of the palaeomagnetic data previously published about the West African Craton and their comparison with the most recent information obtained on doleritic dykes and stromatolite-bearing formations allow us to propose, after a critical examination of the old geochronological data, a new path for the West African Craton between 2200 and 700 Ma. This path has been compared with that of eastern China (which can be simply divided into a northern and a southern China block) between 1400 and 700 Ma. We can observe that these two blocks show a common path before their accretion to the Rodinia super-continent. These two blocks, which were located close the equator and at the outboard of Rodinia at about 1000 Ma, were also characterized by identical stromatolitic assemblages. This result shows that West Africa and Eastern China represented the antipodal continental margins of Rodinia. One can also deduce from our data that the accretion of Rodinia mainly resulted from north–south-oriented displacements. To cite this article: J.-P. Lefort et al., C. R. Geoscience 336 (2004).  相似文献   

9.
Studies of gneisses from the Yenisei regional shear zone (YRSZ) provide the first evidence for Mesoproterozoic tectonic events in the geologic history of the South Yenisei Ridge and allowed the recognition of several stages of deformation and metamorphism spanning from Late Paleoproterozoic to Vendian. The first stage (~ 1.73 Ga), corresponding to the period of granulite-amphibolite metamorphism at P = 5.9 kbar and T = 635 °C, marks the final amalgamation of the Siberian craton to the Paleo-Mesoproterozoic Nuna supercontinent. During the second stage, corresponding to a hypothesized breakup of Nuna as a result of crustal extension, these rocks underwent Mesoproterozoic dynamic metamorphism (P = 7.4 kbar and T = 660 °C) with three peaks at 1.54, 1.38, and 1.25 Ga and the formation of high-pressure blastomylonite rocks in shear zones. Late-stage deformations during the Mesoproterozoic tectonic activity in the region, related to the Grenville-age collision processes and assembly of Rodinia, took place at 1.17-1.03 Ga. The latest pulse of dynamic metamorphism (615–600 Ma) marks the final stage of the Neoproterozoic evolution of the Yenisei Ridge, which is associated with the accretion of island-arc terranes to the western margin of the Siberian craton. The overall duration of identified tectonothermal processes within the South Yenisei Ridge during the Riphean (~ 650 Ma) is correlated with the duration of geodynamic cycles in the supercontinent evolution. A similar succession and style of tectonothermal events in the history of both the southern and the northern parts of the Yenisei Ridge suggest that they evolved synchronously within a single structure over a prolonged time span (1385–600 Ma). New data on coeavl events identified on the western margin of the Siberian craton contradict the hypothesis of a mantle activity lull (from 1.75 to 0.7 Ga) on the southwestern margins of the Siberian craton during the Precambrian. The synchronous sequence and similar style of tectonic events on the periphery of the large Precambrian Laurentia, Baltica, and Siberia cratons suggest their spatial proximity over a prolonged time span (1550–600 Ma). The above conclusion is consistent with the results of modern paleomagnetic reconstructions suggesting that these cratons represented the cores of Nuna and Rodinia within the above time interval.  相似文献   

10.
The Verkhoyansk–Kolyma belt (VK) forms the western part of the Verkhoyansk–Chukotka Mesozoic orogen (NE Asia) and lies between the Siberian craton on the western side, the Mesozoic–Cenozoic Koryak–Kamchatka accretionary orogen on the eastern side, and the Arctic Alaskan craton to the north. The VK results from the collision of the Siberian craton and the Kolyma–Omolon composite terrane (KO), which acted as an indentor resulting the Kolyma orocline. The KO is made up of ophiolite and olistostromal and schistose units that were amalgamated during the Middle–Late Jurassic by thrust and nappe tectonics under greenschist facies metamorphism. This was followed in Latest Jurassic by thrusting and strike-slip faulting related to the collision of the KO composite terrane with the Siberian craton. This collision also produced the Verkhoyansk fold-and-thrust belt in the Siberian continental margin. In the earliest Cretaceous, collision of the Alaskan and Siberian margins resulted in further thrust and strike-slip tectonism.  相似文献   

11.
Geochronological data obtained in this work and previously known results of U-Pb geochronology suggest that principal metamorphic events, which took place in eastern part of the Irkut block (the Sharyzhalgai marginal ledge of the Siberian platform basement), correspond in age to (1) about 2.8 Ga, (2) 2649 ± 6 to 2562 ± 20 Ma, and (3) 1865 ± 4 to 1855 ± 5 Ma. Structural and metamorphic reworking of the earliest event originated under conditions of the granulite facies, whereas conditions of granulite and amphibolite facies were characteristic of the second and third events. Metasomatites after carbonate rocks originated in eastern part of the Sharyzhalgai ledge during the Early Proterozoic metamorphic event that lasted approximately 20 m.y. Being combined with age data, which are known at present for the reference syn-and post-collision granitoids in the Siberian platform basement and flanking foldbelts, new geochronological results show that accretion of basement blocks to the Siberian craton progressed from the east to the west between 1900 and 1840 Ma. To a first approximation, this geochronological interval characterizes time span of the Paleoproterozoic ocean closure and ultimate time, when the craton and supercontinent Columbia became amalgamated.  相似文献   

12.
中元古代晚期—新元古代早期的华北克拉通与塔里木、扬子克拉通存在明显差异,那里没有十分强烈的与罗迪尼亚超大陆汇聚及裂解有关的热-构造事件的地质记录,因此对华北克拉通与罗迪尼亚超大陆的关联存在不同的推测。近年来,在郯庐断裂带两侧新元古代碎屑岩地层中,从辽宁的榆树砬子群,经山东烟台蓬莱群至土门群,陆续测得众多具经典格林威尔期的碎屑锆石年龄。这一信息与西伯利亚东南缘上里菲碎屑岩中的碎屑锆石年龄谱十分相似。这些碎屑锆石的时代均不是华北或西伯利亚本土所具有的特点,说明华北东缘、西伯利亚东南缘与劳伦大陆东南缘格林威尔造山带存在某种亲缘关系。根据这种推测,笔者等提出了劳伦大陆格林威尔造山带、西伯利亚东南缘和华北东部(GOSEN)连接的假设。  相似文献   

13.
康滇地轴元古代重大地质事件与拉拉IOCG矿床成矿响应   总被引：2，自引：0，他引：2  
有关IOCG最新研究成果建议,将IOCG矿床限定于资源量大于1 Mt的大型/超大型矿床。对世界上已知的大型/超大型IOCG矿床的成矿背景和成矿作用进行分析对比,发现前寒纪大型/超大型IOCG矿床均位于前寒纪超大陆的边缘、形成于非造山期,与壳幔相互作用有关,与板底垫托、地幔柱等相关的重大地质事件关系密切。通过对康滇地轴元古代地质体岩石/矿物的同位素年龄数据分析研究,同时对拉拉IOCG矿床成矿特征及同位素测龄分析,认为扬子地台西缘康滇地轴存在早元古代早期(2 486～1 884 Ma BP)古陆壳,是Kenorland超大陆的一部分。在中元古代发育了康滇陆缘裂谷(1 725～1 466 Ma BP),与Columbia超大陆非造山期同时。新元古代的晋宁运动使该裂谷产物变质,及形成康定杂岩,成为康滇地轴的上层结晶基底(1 100～721 Ma BP)。其是Rodinia超大陆的拼贴与裂解事件的响应。拉拉矿床具有2期成矿作用。第一期火山喷发成矿期(1 712～1 680 Ma BP),是康滇裂谷事件的产物。第二期变质热液成矿期主成矿阶段(1 000～900Ma BP),是Rodinia超大陆的拼贴作用的响应。康滇地轴元代地层中具有形成IOCG矿床的巨大潜力。  相似文献   

14.
Rodinia was initially defined as a long‐lived supercontinent that assembled all the continental fragments around Laurentia and remained stable from 1000 up to 750 Ma. Nonetheless, recent work has cast doubt on the Rodinia palaeogeography and even on the timing of its assembly and break‐up. The geochronological and palaeomagnetic databases accumulated for South America and Africa in the last decade show that most of these continental fragments were not part of Rodinia. A wide Brasiliano Ocean separated most of the South American and African cratons from the Laurentia ? Amazonia ? Rio Apa ?West Africa margin. This ocean was closed between 940 and 630 Ma along the Pampean–Paraguay–Araguaia–Pharusian mobile belts. Moreover, accretion along the South American and African platforms was a diachronous and long‐lived process that involved several intra‐oceanic and continental magmatic arcs and microcontinents. This evolution started at around 1000 Ma and ended at around 520 Ma with the final assembly of Gondwana.  相似文献   

15.
The east margin of the Siberian craton is a typical passive margin with a thick succession of sedimentary rocks ranging in age from Mesoproterozoic to Tertiary. Several zones with distinct structural styles are recognized and reflect an eastward-migrating depocenter. Mesozoic orogeny was preceded by several Mesoproterozoic to Paleozoic tectonic events. In the South Verkhoyansk, the most intense pre-Mesozoic event, 1000–950 Ma rifting, affected the margin of the Siberian craton and formed half-graben basins, bounded by listric normal faults. Neoproterozoic compressional structures occurred locally, whereas extensional structures, related to latest Neoproterozoic–early Paleozoic rifting events, have yet to be identified. Devonian rifting is recognized throughout the eastern margin of the Siberian craton and is represented by numerous normal faults and local half-graben basins.Estimated shortening associated with Mesozoic compression shows that the inner parts of ancient rifts are now hidden beneath late Paleozoic–Mesozoic siliciclastics of the Verkhoyansk Complex and that only the outer parts are exposed in frontal ranges of the Verkhoyansk thrust-and-fold belt. Mesoproterozoic to Paleozoic structures had various impacts on the Mesozoic compressional structures. Rifting at 1000–950 Ma formed extensional detachment and normal faults that were reactivated as thrusts characteristic of the Verkhoyansk foreland. Younger Neoproterozoic compressional structures do not display any evidence for Mesozoic reactivation. Several initially east-dipping Late Devonian normal faults were passively rotated during Mesozoic orogenesis and are now recognized as west-dipping thrusts, but without significant reactivation displacement along fault surfaces.  相似文献   

16.
The Altaids are an orogenic collage of Neoproterozoic–Paleozoic rocks located in the center of Eurasia. This collage consists of only three oroclinally bent Neoproterozoic–Early Paleozoic magmatic arcs (Kipchak, Tuva–Mongol, and Mugodzhar–Rudny Altai), separated by sutures of their former backarc basins, which were stitched by new generations of overlapping magmatic arcs. In addition, the Altaids host accreted fragments of the Neoproterozoic to Early Paleozoic oceanic island chains and Neoproterozoic to Cenozoic plume-related magmatic rocks superimposed on the accreted fragments. All these assemblages host important, many world-class, Late Proterozoic to Early Mesozoic gold, copper–molybdenum, lead–zinc, nickel and other deposits of various types.In the Late Proterozoic, during breakup of the supercontinent Rodinia, the Kipchak and Tuva–Mongol magmatic arcs were rifted off Eastern Europe–Siberia and Laurentia to produce oceanic backarc basins. In the Late Ordovician, the Siberian craton began its clockwise rotation with respect to Eastern Europe and this coincides with the beginning of formation of the Mugodzhar–Rudny Altai arc behind the Kipchak arc. These earlier arcs produced mostly Cu–Pb–Zn VMS deposits, although some important intrusion-related orogenic Au deposits formed during arc–arc collision events in the Middle Cambrian and Late Ordovician.The clockwise rotation of Siberia continued through the Paleozoic until the Early Permian producing several episodes of oroclinal bending, strike–slip duplication and reorganization of the magmatic arcs to produce the overlapping Kazakh–Mongol and Zharma-Saur–Valerianov–Beltau-Kurama arcs that welded the extinct Kipchak and Tuva–Mongol arcs. This resulted in amalgamation of the western portion of the Altaid orogenic collage in the Late Paleozoic. Its eastern portion amalgamated only in the early Mesozoic and was overlapped by the Transbaikal magmatic arc, which developed in response to subduction of the oceanic crust of the Paleo-Pacific Ocean. Several world-class Cu–(Mo)-porphyry, Cu–Pb–Zn VMS and intrusion-related Au mineral camps, which formed in the Altaids at this stage, coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs. Major Pb–Zn and Cu sedimentary rock-hosted deposits of Kazakhstan and Central Asia formed in backarc rifts, which developed on the earlier amalgamated fragments. Major orogenic gold deposits are intrusion-related deposits, often occurring within black shale-bearing sutured backarc basins with oceanic crust.After amalgamation of the western Altaids, this part of the collage and adjacent cratons were affected by the Siberian superplume, which ascended at the Permian–Triassic transition. This plume-related magmatism produced various deposits, such as famous Ni–Cu–PGE deposits of Norilsk in the northwest of the Siberian craton.In the early Mesozoic, the eastern Altaids were oroclinally bent together with the overlapping Transbaikal magmatic arc in response to the northward migration and anti-clockwise rotation of the North China craton. The following collision of the eastern portion of the Altaid collage with the Siberian craton formed the Mongol–Okhotsk suture zone, which still links the accretionary wedges of central Mongolia and Circum-Pacific belts. In the late Mesozoic, a system of continent-scale conjugate northwest-trending and northeast-trending strike–slip faults developed in response to the southward propagation of the Siberian craton with subsequent post-mineral offset of some metallogenic belts for as much as 70–400 km, possibly in response to spreading in the Canadian basin. India–Asia collision rejuvenated some of these faults and generated a system of impact rifts.  相似文献   

17.
中国新元古代大陆拼合与Rodinia超大陆   总被引：46，自引：0，他引：46  
在对前人研究成果分析的基础上,结合对中祁连块块前寒武纪基底的研究,认为新元古代（1000－9000Ma）中国各主要克拉通地块（包括华夏地块、扬子地块、华北地块、阿拉善－祁连－柴达木地块、塔里木地块）曾经通过晋宁期碰撞拼合带发生过一次全面的多块体复杂拼贴。这次拼贴过程是全球性新元古代格林威尔碰撞造山作用和Rodinia超大陆形成过程的一个组成部分。新元古代拼合的古中国地块在当时位于Rodinia超大陆中北部澳大利亚、劳伦提亚和西伯利亚克拉通地块之同。中国的各主要克拉通地块只不过是巨型格林威尔碰撞带之中夹裹的一些小型地块,且都处于新元古代晚期Rodinia超大陆破裂的中心部位,这些正是中国大陆上克拉通地块活动性大的早期地质背景。  相似文献   

18.
The analysis of the basement of the Andes shows the strong Grenville affinities of most of the inliers exposed in the different terranes from Colombia to Patagonia. The terranes have different histories, but most of them participated in the Rodinia supercontinent amalgamation during the Mesoproterozoic between 1200 and 1000 Ma. After Rodinia break-up some terranes were left in the Laurentian side such as Cuyania and Chilenia, while others stayed in the Gondwanan side. Some of the terranes once collided with the Amazon craton remained attached, experiencing diverse rifting episodes all along the Phanerozoic, as the Arequipa and Pampia terranes. Some other basement inliers were detached in the Neoproterozoic and amalgamated again to Gondwana in the Early Cambrian, Middle Ordovician or Permian times. A few basement inliers with Permian metamorphic ages were transferred to Gondwana after Pangea break-up from the Laurentian side. Some of them were part of the present Middle America terrane. An exceptional case is the Oaxaquia terrane that was detached from the Gondwana margin after the Early Ordovician and is now one of the main Mexican terranes that collided with Laurentia. These displacements, detachments, and amalgamations indicate a complex terrane transfer between Laurentia and Gondwana during Paleozoic times, following plate reorganizations and changes in the absolute motion of Gondwana.  相似文献   

19.
Geological data on the Precambrian basic complexes of the Siberian Craton and their isotopic age are considered. The three main episodes of Precambrian basic magmatism of Siberia correspond to certain stages of the geodynamic evolution of the craton and the Earth as a whole. In the Late Paleoproterozoic, largely in the south and the north of the craton, the basic rocks were emplaced against the background of post-collision extension, which followed the preceding collision-accretion stage responsible for the formation of the craton. In the Mesoproterozoic, primarily in the north of the craton, basic magmatism was controlled by dispersed within-plate extension apparently caused by the impact of a mantle plume. Neoproterozoic basic magmatism widespread in the southern and southeastern parts of the craton was caused by rifting, which accompanied breakdown of the Rodinia supercontinent and opening of the Paleoasian ocean along the southern margin of the Siberian Craton.  相似文献   

20.
A study of gneisses and schists from the Yenisey regional shear zone (Garevka complex) at the western margin of the Siberian Craton has provided important constraints on the tectonothermal events and geodynamic processes in the Yenisey Ridge during the Riphean. In situ U-Th-Pb geochronology of monazite and xenotime from different garnet growth zones and the calculation of P-T path derived from chemical zoning pattern in garnet were used to distinguish three metamorphic events with different ages, thermodynamic regimes and metamorphic field gradients. The first stage occurred as a result of the Grenville orogeny during late Meso-early Neoproterozoic (1050–850 Ma) and was marked by low-pressure zoned metamorphism at ～4.8–5.0 kbar and 565–580°C and a metamorphic field gradient with dT/dH = 20–30°C/km typical of orogenic belts. At the second stage, the rocks experienced Late Riphean (801–793 Ma) collision-related medium-pressure metamorphism at ～7.7–7.9 kbar and 630°C with dT/dH ≤ 10°C/km. The final stage evolved as a syn-exhumation retrograde metamorphism (785–776 Ma) at ～4.8–5.4 kbar and 500°C with dT/dH ≤ 12°C/km and recorded a relatively fast uplift of the rocks to upper crustal levels in shear zones. The range of exhumation rates at the post-collisional stage (500–700 m/Ma) correlates with the duration of exhumation and the results of thermophysical numerical modeling of metamorphic rocks within orogenic belts. The final stages of collisional orogeny are marked by the development of rift-related bimodal dyke swarms associated with Neoproterozoic extension (797 ± 11 and 7.91 ± 6 Ma; U-Pb SHRIMP II zircon data) along the western margin of the Siberian craton and the beginning of the breakup of Rodinia. Post-Grenville metamorphic episodes of regional evolution are correlated with the synchronous succession and similar style of the later tectono-metamorphic events within the Valhalla orogen along the Arctic margin of Rodinia and support the spatial proximity of Siberia and North Atlantic cratons at about 800 Ma, as indicated by the latest paleomagnetic reconstructions.  相似文献   

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