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Lothar Ratschbacher Christian Dingeldey Christine Miller Bradley R. Hacker Michael O. McWilliams 《Tectonophysics》2004,394(3-4):155-170
New 40Ar/39Ar geochronology places time constraints on several stages of the evolution of the Penninic realm in the Eastern Alps. A 186±2 Ma age for seafloor hydrothermal metamorphic biotite from the Reckner Ophiolite Complex of the Pennine–Austroalpine transition suggests that Penninic ocean spreading occurred in the Eastern Alps as early as the Toarcian (late Early Jurassic). A 57±3 Ma amphibole from the Penninic subduction–accretion Rechnitz Complex dates high-pressure metamorphism and records a snapshot in the evolution of the Penninic accretionary wedge. High-pressure amphibole, phengite, and phengite+paragonite mixtures from the Penninic Eclogite Zone of the Tauern Window document exhumation through ≤15 kbar and >500 °C at 42 Ma to 10 kbar and 400 °C at 39 Ma. The Tauern Eclogite Zone pressure–temperature path shows isothermal decompression at mantle depths and rapid cooling in the crust, suggesting rapid exhumation. Assuming exhumation rates slower or equal to high-pressure–ultrahigh-pressure terrains in the Western Alps, Tauern Eclogite Zone peak pressures were reached not long before our high-pressure amphibole age, probably at ≤45 Ma, in accordance with dates from the Western Alps. A late-stage thermal overprint, common to the entire Penninic thrust system, occurred within the Tauern Eclogite Zone rocks at 35 Ma. The high-pressure peak and switch from burial to exhumation of the Tauern Eclogite Zone is likely to date slab breakoff in the Alpine orogen. This is in contrast to the long-lasting and foreland-propagating Franciscan-style subduction–accretion processes that are recorded in the Rechnitz Complex. 相似文献
3.
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
4.
Alastair Robertson Osman Parlak Timur Ustaömer Kemal Taslı Nurdan İnan Paulian Dumitrica 《Geodinamica Acta》2013,26(3-4):230-293
This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedimentological, petrographic and structural data. The new information is synthesised with existing results from the study area and adjacent regions (Central Pontides and Lesser Caucasus) to produce a new tectonic model for the Mesozoic–Cenozoic tectonic development of this key Tethyan suture zone.The Tethyan suture zone in NE Turkey (Ankara–Erzincan–Kars suture zone) exemplifies stages in the subduction, suturing and post-collisional deformation of a Mesozoic ocean basin that existed between the Eurasian (Pontide) and Gondwanan (Tauride) continents. Ophiolitic rocks, both as intact and as dismembered sequences, together with an intrusive granite (tonalite), formed during the Early Jurassic in a supra-subduction zone (SSZ) setting within the ?zmir–Ankara–Erzincan ocean. Basalts also occur as blocks and dismembered thrust sheets within Cretaceous accretionary melange. During the Early Jurassic, these basalts erupted in both a SSZ-type setting and in an intra-plate (seamount-type) setting. The volcanic-sedimentary melange accreted in an open-ocean setting in response to Cretaceous northward subduction beneath a backstop made up of Early Jurassic forearc ophiolitic crust. The Early Jurassic SSZ basalts in the melange were later detached from the overriding Early Jurassic ophiolitic crust.Sedimentary melange (debris-flow deposits) locally includes ophiolitic extrusive rocks of boninitic composition that were metamorphosed under high-pressure low-temperature conditions. Slices of mainly Cretaceous clastic sedimentary rocks within the suture zone are interpreted as a deformed forearc basin that bordered the Eurasian active margin. The basin received a copious supply of sediments derived from Late Cretaceous arc volcanism together with input of ophiolitic detritus from accreted oceanic crust.Accretionary melange was emplaced southwards onto the leading edge of the Tauride continent (Munzur Massif) during latest Cretaceous time. Accretionary melange was also emplaced northwards over the collapsed southern edge of the Eurasian continental margin (continental backstop) during the latest Cretaceous. Sedimentation persisted into the Early Eocene in more northerly areas of the Eurasian margin.Collision of the Tauride and Eurasian continents took place progressively during latest Late Palaeocene–Early Eocene. The Jurassic SSZ ophiolites and the Cretaceous accretionary melange finally docked with the Eurasian margin. Coarse clastic sediments were shed from the uplifted Eurasian margin and infilled a narrow peripheral basin. Gravity flows accumulated in thrust-top piggyback basins above accretionary melange and dismembered ophiolites and also in a post-collisional peripheral basin above Eurasian crust. Thickening of the accretionary wedge triggered large-scale out-of-sequence thrusting and re-thrusting of continental margin and ophiolitic units. Collision culminated in detachment and northward thrusting on a regional scale.Collisional deformation of the suture zone ended prior to the Mid-Eocene (~45?Ma) when the Eurasian margin was transgressed by non-marine and/or shallow-marine sediments. The foreland became volcanically active and subsided strongly during Mid-Eocene, possibly related to post-collisional slab rollback and/or delamination. The present structure and morphology of the suture zone was strongly influenced by several phases of mostly S-directed suture zone tightening (Late Eocene; pre-Pliocene), possible slab break-off and right-lateral strike-slip along the North Anatolian Transform Fault.In the wider regional context, a double subduction zone model is preferred, in which northward subduction was active during the Jurassic and Cretaceous, both within the Tethyan ocean and bordering the Eurasian continental margin. 相似文献
5.
A. N. Filippov 《Lithology and Mineral Resources》2012,47(1):70-88
The composition of sandstones constituting different structural stages of the Jurassic accretionary wedge in the Samarka (upper and middle? structural levels in the Lyamfana Creek and Katen River basins, respectively) and Nadan’khada-Bikin (lower level in the Ulitka River basin) terranes of the Sikhote Alin region reflects changes in provenances and tectonic settings of the near-continental sedimentation basin in different periods of the wedge formation. In the terminal Middle Jurassic (Lyamfana Creek), the region was dominated by the subduction regime with sedimentary material transported from the eroded part of the continental-margin magmatic arc. During the Kimmeridgian-Tithonian (Katen River), erosion of granitoid batholiths of the arc exposed blocks of the crystalline basement along strike-slip faults. In the Tithonian-Berriasian period (Ulitka River), the role of these blocks increased, suggesting intensification of oblique subduction or development of transform faults during the accretion. 相似文献
6.
The Teplá–Barrandian unit (TBU) of Central Europe's Bohemian Massif exposes perhaps the best preserved fragment of an accretionary wedge in the Avalonian–Cadomian belt, which developed along the northern active margin of Gondwana during Late Neoproterozoic. In the central TBU, three NE–SW-trending lithotectonic units (Domains 1–3) separated by antithetic brittle faults differ in lithology, style and intensity of deformation, magnetic fabric (AMS), and degree of Cadomian regional metamorphism. The flysch-like Domain 1 to the NW is the most outboard (trenchward) unit which has never been significantly buried and experienced only weak deformation and folding. The central, mélange-like Domain 2 is characterized by heterogenous intense deformation developed under lower greenschist facies conditions, and was thrust NW over Domain 1 along a SE-dipping fault. To the SE, the most inboard (arcward) Domain 3 is lithologically monotonous (dominated by graywackes and slates), was buried to depths corresponding up to the lower greenschist facies conditions, where it was overprinted by a pervasive SE-dipping cleavage and then was exhumed along a major NW-dipping normal fault.We interpret these domains to represent allochtonous tectonic slices that were differentially buried and then exhumed from various depths within the accretionary wedge during Cadomian subduction. The NW-directed thrusting of Domain 2 over Domain 1 may have been caused by accretion at the wedge front, whereas the SE-dipping cleavage and SE-side-up exhumation of Domain 3 may record inclined pervasive shortening during tectonic underplating and subsequent horizontal extension of the rear of the wedge. The boundary faults were later reactivated during Cambro–Ordovician extension and Variscan compression.Compared to related terranes of the Cadomian belt, the TBU lacks exposed continental basement, evidence for regional strike-slip shearing, and extensive backarc magmatism and LP–HT metamorphism, which could be interpreted to reflect flat-slab Cadomian subduction. This, in turn, suggests that Cadomian accretionary wedges developed in a manner identical to those of modern settings, elevating the TBU to a key position for understanding the style, kinematics, and timing of accretionary processes along the Avalonian–Cadomian belt. 相似文献
7.
The Northern Calcareous Alps (NCA) of southern Bavaria and northern Tyrol constitute a carbonate-dominated polyphase fold-thrust wedge; together with its Grauwacken Zone Basement, it is the northernmost part of the far-travelled Upper Austroalpine thrust complex of the Eastern Alps. The present geometry developed in several kinematic stages. Jurassic extensional faults that affected large parts of the NCA and their basement originated when the main part of the NCA was still located southeast of the Central Alpine Ötztal-Silvretta complex. These faults and related facies transitions influenced the later style of detachment of the NCA thrust sheets. Mid to Late Cretaceous detachment, thrust-sheet stacking and motion over the Central Alpine complex are registered in clastic deposits of syntectonic basins. The latest Cretaceous to Cenozoic NNE- to N-directed motion of the NCA towards Europe in front of the Central Alpine complex created another set of significant contraction structures, which at depth overprinted all previous structures. During Cretaceous to Cenozoic deformation, the NCA experienced about 80 km of shortening, i.e., about 73% along the TRANSALP Profile. The European basement and autochthonous Mesozoic cover beneath the allochthonous NCA thrust sheets and flysch complexes seem to have remained relatively undeformed. 相似文献
8.
The Duguer area represents one of the few occurrences of high-grade metamorphic rocks in the ‘Central Uplift’ zone of the Qiangtang terrane, central Tibet. The metamorphic rocks consist mainly of orthogneiss, paragneiss, and schist. To better understand the formation of these rocks, seven samples of gneiss and schist from the Duguer area were selected for in situ zircon U–Pb analysis and Ar–Ar dating of metamorphic minerals. The results suggest two distinct metamorphic stages, during the Late Triassic (229–227 Ma) and Late Jurassic (150–149 Ma). These stages correspond to the closure of the Palaeo-Tethys Ocean and northward subduction of the Bangong–Nujiang Neo-Tethys oceanic crust, respectively. We suggest that the Late Triassic metamorphic rocks of the Duguer area in the central South Qiangtang subterrane provide evidence of continental collision between the North and South Qiangtang subterranes, following the subduction of oceanic crust. It is likely that deep subduction of oceanic crust occurred along the Longmu Co–Shuanghu–Lancangjiang suture zone (LSLSZ), which would have hindered exhumation owing to the high density of oceanic crust. Subsequent break-off and delamination of the subducted oceanic slab at ~220 Ma may have resulted in exhumation of high-pressure and high-grade metamorphic rocks in the South Qiangtang subterrane. The Late Jurassic ages of metamorphism and deformation obtained in this study indicate the occurrence of an Andean-type orogenic event within the South Qiangtang subterrane. This hypothesis is further supported by an apparent age gap in magmatic activity (150–130 Ma) along the magmatic arc, and the absence of Late Jurassic sediments. 相似文献
9.
The middle and eastern parts of the Northern Calcareous Alps (NCA) can be subdivided into two distinct units with a lateral boundary marked by abrupt changes in the conodont colour alteration index (CAI-values). The first of these is a northern unit (Tirolikum) with a relatively homogeneous distribution of no or low grade conodont alteration (CAI 1.0–2.0). The thermal overprint is thought to be relatively young and related to a heat flow from the Tauern crystallization. The second unit consists of the Juvavic nappe system (Juvavikum), which is distributed along the southern rim of the NCA but also covers some of the northern parts of the Tirolikum. With respect to its CAI-distribution the Juvavikum is more heterogeneous on a regional and local scale, with some local CAI-inversions. The Juvavikum additionally shows distinctly different sets of CAI-values one with weak (CAI 1.0–1.5) and another with strong alteration (CAI 5.5–7.0) — at present the highest known thermal overprint measured in the NCA. The metamorphism is relatively old as it predates the Late Jurassic—Early Cretaceous gravity tectonic emplacement of the Juvavikum onto the Tirolikum. The high CAI-values of parts of the Juvavic nappe system are though to be related to tectonic burial in an accretionary wedge formed parallel to the closure of the Vardar Ocean. The low CAI values of the Tirolikum apparently exclude a direct juxtaposition of the two units at the time of metamorphism. 相似文献
10.
Eastern Gondwana was subjected to subduction processes during the Middle-Late Jurassic, but how these processes affected intraplate deformation in eastern Australia is poorly understood. Here we present 40Ar/39Ar, K-Ar, and Rb-Sr geochronological data from illitic clay-bearing fault gouges associated with the northern part of the 200 km long, N-striking, dextral strike-slip, Demon Fault in eastern Australia. We show a major range of geochronological ages at 162.99 ± 0.74–152.1 ± 4.8 Ma, indicating that the Demon Fault was active during the Late Jurassic. This period partially coincides with the Middle-Late Jurassic deposition of widespread ash-fall tuffs in the Clarence-Moreton, Surat, and Eromanga basins. We propose that Middle-Late Jurassic intraplate tectonism in eastern Australia was influenced by subduction processes farther east, which produced extensive calc-alkaline magmatism in New Zealand from ~170 Ma. A global plate reorganisation event, related to the development of Early-Middle Jurassic sea-floor spreading of the Pacific Plate, possibly acted as the driving mechanism responsible for the intensification of magmatism and intraplate faulting in eastern Gondwana. 相似文献
11.
Late Cretaceous exhumation history of an extensional extruding wedge (Graz Paleozoic Nappe Complex, Austria) 总被引：1，自引：1，他引：0
Krenn Kurt Fritz Harald Mogessie Aberra Schaflechner Johannes 《International Journal of Earth Sciences》2008,97(6):1331-1352
Late Cretaceous structures within the eastern Graz Paleozoic Nappe Complex define an extruding wedge with north-eastward directed
thrusting in eastern portions and strike-slip shear along the margins. Stacking structures are overprinted by south-westward
directed extension with low-grade metamorphic rocks in the hangingwall and high-grade basement rocks in the footwall. Pressure–temperature
and structural data are obtained from successively opening quartz veins that record various stages of progressive deformation
and metamorphism. Fluid inclusion data and related structures show that during extension isothermal decompression from ca.
550°C and 8 kbar down to ca. 450°C and 2 kbar was related to exhumation of rocks from deep crustal levels. The data point
to a high geothermal gradient and explain condensed paleo-isotherms due to ductile normal faulting in the eastern areas of
the Graz Paleozoic Nappe Complex. The investigated Late Cretaceous structural elements suggest that the Graz Paleozoic Nappe
Complex decoupled from the surrounding basement units and operated as a large-scale extension–extrusion corridor that evolved
prior to Miocene extrusion tectonics in the Eastern Alps. 相似文献
12.
New data on ophiolite-bearing terranes of the Liguride Complex, together with some information on the terranes of the Sicilide Complex, result in a better understanding of the role and tectonic significance of these units in the construction of the Southern Apennines orogenic belt. The Liguride Complex is composed of two main tectonic units overlain by a thick turbiditic sequence of Late Oligocene-Middle Miocene age. The uppermost one (Frido Unit) is a polydeformed and polymetamorphosed sequence, composed of two tectonic subunits of shales and calc-schists, respectively, containing blocks of ophiolite, garnet gneiss, amphibolites and granitoids. This unit is thrust over the un-metamorphosed terranes (Calabro–Lucano Flysch Unit) consisting of a broken formation with blocks of Late Jurassic ophiolite and their sedimentary cover, Cretaceous-Eocene pelagic sediments and Late Oligocene volcaniclastic deposits. The Frido Unit underwent HP/LT metamorphism (P= 8–10 Kb; T= 400–500 °C) resulting in glaucophane and lawsonite assemblages in the ophiolitic rocks and aragonite in the meta-limestones and calc-schists, followed by greenschist fades metamorphism (P= 4 Kb; T= 300–350 °C). From a structural point of view units of the Liguride Complex comprise structures developed at different structural levels, indicating progressive non-coaxial deformation in response to tectonic transport towards the N-NE. The ophiolite-bearing terranes of the Liguride Complex can be considered as a remnant of an accretionary complex in which the Calabro Lucano Flysch Unit represents the toe of the wedge where frontal accretion processes occur and the Frido Unit is a deeper portion. Emplacement of the Frido Unit is explained as being due to formation of a deep duplex structure during the early stage of continental collision processes. The polarity of tectonic transport provides new evidence that the Liguride Complex represents a suture zone between the Apulian and the Calabrian blocks. The age of collision appears to be not older than late Oligocene. The allochtonous terranes of the Liguride and Sicilide Complexes, therefore, represent a complete accretionary wedge which records, first, subduction of the Neotethys ocean beneath the Calabrian (Europe) continental margin and, later, continental collision with the African block. 相似文献
13.
南祁连拉脊山口增生楔的结构与组成特征 总被引：2，自引：1，他引：1
造山带内增生楔/增生杂岩结构与组成的精细研究可为古洋盆演化和古板块构造格局重建提供最直接证据。北祁连构造带发育多条增生杂岩带,记录了阿拉善和中祁连地块之间原特提斯洋的俯冲和闭合过程,然而南祁连构造带大地构造演化长期存在争议。地质填图结果表明,南祁连构造带拉脊山口地区存在一套强烈片理化的玄武岩、灰黑色和红色硅质岩、砂岩和泥岩组合,它们与一套呈现"块体裹夹于基质"结构特征的混杂岩共同构成了增生杂岩,发育双重逆冲构造、逆冲断层、无根褶皱、紧闭褶皱和透入性面理。该增生杂岩与蛇绿岩之间为断层接触,并位于断层下盘。混杂岩是由斜长花岗岩(561Ma)、斜长岩(507Ma)、辉绿岩、玄武岩、硅质岩和砂岩等外来或原地岩块与浊流成因的细碎屑岩基质共同组成;基质和砂岩块体均发育同沉积构造,呈现出滑塌堆积典型特征。空间上,拉脊山口增生杂岩与上覆蛇绿岩被断层所分割且共同仰冲于中祁连南缘青石坡组浊积岩之上,具有与东侧昂思多地区增生杂岩和蛇绿岩相似的岩石组成、构造变形和时空结构特征。它们与南侧的岛弧带共同构成了南祁连构造带寒武纪-早奥陶世沟-弧体系,指示了寒武纪-早奥陶世时期南祁连洋盆向南俯冲。 相似文献
14.
台湾造山带是中新世晚期以来相邻菲律宾海板块往北西方向移动,导致北吕宋岛弧系统及弧前增生楔与欧亚大陆边缘斜碰撞形成的。目前该造山带仍在活动,虽然规模很小,但形成了多数大型碰撞造山带中的所有构造单元,是研究年轻造山系统的理想野外实验室,为理解西太平洋弧-陆碰撞过程和边缘海演化提供了一个独特的窗口。本文总结了二十一世纪以来对台湾造山带的诸多研究进展,讨论了其构造单元划分及演化过程。我们将台湾造山带重新划分为6个构造单元,由西至东分依次为:(1)西部前陆盆地;(2)中央山脉褶皱逆冲带;(3)太鲁阁带;(4)玉里-利吉蛇绿混杂岩带;(5)纵谷磨拉石盆地;(6)海岸山脉岛弧系统。其中,西部前陆盆地为6.5Ma以来伴随台湾造山带的隆升剥蚀形成沉积盆地。中央山脉褶皱逆冲带为新生代(57~5.3Ma)欧亚大陆东缘伸展盆地沉积物由于弧-陆碰撞受褶皱、逆冲及变质作用改造形成的。太鲁阁带是造山带中的古老陆块,主要记录中生代古太平洋俯冲在欧亚大陆活动边缘形成的岩浆、沉积和变质岩作用。玉里-利吉蛇绿混杂岩带和海岸山脉岛弧系统分别为中新世中期(~18Ma)以来南中国海板块向菲律宾海板块之下俯冲形成的岛弧和弧前增生楔,其中玉里混杂岩中有典型低温高压变质作用记录,变质年龄为11~9Ma;岛弧火山作用的主要时限为9.2~4.2Ma。纵谷磨拉石盆地记录1.1Ma以来的山间盆地沉积。台湾造山带的构造演化可划分为4个阶段:(a)古太平洋板块俯冲与欧亚大陆边缘增生阶段(200~60Ma);(b)欧亚大陆东缘伸展和南中国海扩张阶段(60~18Ma);(c)南中国海俯冲阶段(18~4Ma);(d)弧-陆碰撞阶段(<6Ma)。台湾弧-陆碰撞造山带是一个特殊案例,其弧-陆碰撞并不伴随着弧-陆之间的洋盆消亡,而是由于北吕宋岛弧及弧前增生楔伴随菲律宾海板块运动向西北方走滑,仰冲到欧亚大陆边缘,形成现今的台湾造山带。 相似文献
15.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(8):681-685
The paper reviews paleomagnetic data from the Central West Carpathians (CWC) of Poland and Slovakia. The CWC constitute an orogen deformed by pre-Tertiary and Tertiary events, situated on the internal side of the Pieniny Klippen Belt and the Tertiary Outer West Carpathian accretionary wedge. The CWC are regarded as the eastern prolongation of the Austroalpine series. There are paleomagnetic evidences for a counterclockwise rotation of the CWC after Oligocene. Having subtracted the effect of this rotation, Middle Cretaceous paleomagnetic poles from the CWC are brought into agreement with preGosau paleopoles from the Upper Austroalpine units of the Northern Calcareous Alps (NCA). It is inferred that a common clockwise rotation of the CWC and NCA had taken place between 90-60 Ma (Middle — Late Cretaceous) during the oblique convergence of the Austroalpine/Central Carpathian realm with the Penninic continental basement. 相似文献
16.
Summary The Cretaceous Eclogite-Gneiss unit and its tectonic overburden (Micaschist, Phyllite and Lower Magdalensberg units) and the
underlying Preims subunit of the Saualpe, Eastern Alps, have been investigated in order to constrain the mode of exhumation
of the type locality of eclogites. 40Ar/39Ar ages of white mica from the eclogite-bearing unit suggest rapid, uniform cooling and exhumation between 86 and 78 Ma (Santonian-Campanian).
Overlying units show upwards increasingly older ages with an age of 261.7 ± 1.4 Ma in the uppermost, low-grade metamorphic
unit (Lower Magdalensberg unit). We consider this Permian age as geologically significant and to record a Permian tectonic
event. Rocks of phyllite and micaschist units along western margins of the Saualpe block yield amphibole and white mica ages
ranging from 123 to 130 Ma. These are considered to closely date the age of nappe stacking, whereas a single biotite age of
66–68 Ma from a shear zone is interpreted to date retrogression during normal faulting. Biotite and amphibole of Micaschist
and Eclogite-Gneiss units show variable contents of extraneous argon. Consequently, their ages are in part geologically meaningless
whereas other samples yield meaningful ages. The white mica ages from the Eclogite-Gneiss unit range from 78 to 85 Ma and
argue for cooling through ca. 400 °C during the time as the westerly adjacent Upper Cretaceous Krappfeld collapse basin formed.
The Preims subunit with paragneiss and marbles is considered to represent a large synmetamorphic shear zone at the base of
the overthrusting Eclogite-Gneiss unit. The unit comprises a flat-lying foliation and a SE-trending lineation. This zone is
interpreted to represent a zone of top-NW thrusting. A major ductile low-angle normal fault with top to ESE shear has been
detected between the Eclogite-Gneiss and overlying units, and between the Micaschist and Phyllite units. The ductile thrust
at the base and the low-angle normal fault at the top are considered to confine a NW-ward extruding high-pressure wedge. The
new observations argue for rapid exhumation of a subducted high-pressure wedge within a subduction channel. Rapid surface
erosion of the exhuming wedge might have facilitated exhumation. Eroded sedimentary rocks are preserved within adjacent Gosau
basins, although only pebbles of low-grade metamorphic rocks of the uppermost tectonic unit can be found in these basins. 相似文献
17.
The age of the major geological units in Japan ranges from Cambrian to Quaternary. Precambrian basement is, however, expected, as the provenance of by detrital clasts of conglomerate, detrital zircons of metamorphic and sedimentary rocks, and as metamorphic rocks intruded by 500 Ma granites. Although rocks of Paleozoic age are not widely distributed, rocks and formations of late Mesozoic to Cenozoic can be found easily throughout Japan. Rocks of Jurassic age occur mainly in the Jurassic accretionary complexes, which comprise the backbone of the Japanese archipelago. The western part of Japan is composed mainly of Cretaceous to Paleogene felsic volcanic and plutonic rocks and accretionary complexes. The eastern part of the country is covered extensively by Neogene sedimentary and volcanic rocks. During the Quaternary, volcanoes erupted in various parts of Japan, and alluvial plains were formed along the coastlines of the Japanese Islands. These geological units are divided by age and origin: i.e. Paleozoic continental margin; Paleozoic island arc; Paleozoic accretionary complexes; Mesozoic to Paleogene accretionary complexes and Cenozoic island arcs. These are further subdivided into the following tectonic units, e.g. Hida; Oki; Unazuki; Hida Gaien; Higo; Hitachi; Kurosegawa; South Kitakami; Nagato-Renge; Nedamo; Akiyoshi; Ultra-Tamba; Suo; Maizuru; Mino-Tamba; Chichibu; Chizu; Ryoke; Sanbagawa and Shimanto belts.The geological history of Japan commenced with the breakup of the Rodinia super continent, at about 750 Ma. At about 500 Ma, the Paleo-Pacific oceanic plate began to be subducted beneath the continental margin of the South China Block. Since then, Proto-Japan has been located on the convergent margin of East Asia for about 500 Ma. In this tectonic setting, the most significant tectonic events recorded in the geology of Japan are subduction–accretion, paired metamorphism, arc volcanism, back-arc spreading and arc–arc collision. The major accretionary complexes in the Japanese Islands are of Permian, Jurassic and Cretaceous–Paleogene age. These accretionary complexes became altered locally to low-temperature and high-pressure metamorphic, or high-temperature and low-pressure metamorphic rocks. Medium-pressure metamorphic rocks are limited to the Unazuki and Higo belts. Major plutonism occurred in Paleozoic, Mesozoic and Cenozoic time. Early Paleozoic Cambrian igneous activity is recorded as granites in the South Kitakami Belt. Late Paleozoic igneous activity is recognized in the Hida Belt. During Cretaceous to Paleogene time, extensive igneous activity occurred in Japan. The youngest granite in Japan is the Takidani Granite intruded at about 1–2 Ma. During Cenozoic time, the most important geologic events are back-arc opening and arc–arc collision. The major back-arc basins are the Sea of Japan and the Shikoku and Chishima basins. Arc–arc collision occurred between the Honshu and Izu-Bonin arcs, and the Honshu and Chishima arcs. 相似文献
18.
《Gondwana Research》2014,25(3):1272-1286
The Mejillonia terrane, named after the Mejillones Peninsula (northern Chile), has been traditionally considered an early Paleozoic block of metamorphic and igneous rocks displaced along the northern Andean margin in the Mesozoic. However, U–Pb SHRIMP zircon dating of metasedimentary and igneous rocks shows that the sedimentary protoliths were Triassic, and that metamorphism and magmatism took place in the Late Triassic (Norian). Field evidence combined with zircon dating (detrital and metamorphic) further suggests that the sedimentary protoliths were buried, deformed (foliated and folded) and metamorphosed very rapidly, probably within few million years, at ca. 210 Ma. The metasedimentary wedge was then uplifted and intruded by a late arc-related tonalite body (Morro Mejillones) at 208 ± 2 Ma, only a short time after the peak of metamorphism. The Mejillones metamorphic and igneous basement represents an accretionary wedge or marginal basin that underwent contractional deformation and metamorphism at the end of a Late Permian to Late Triassic anorogenic episode that is well known in Chile and Argentina. Renewal of subduction along the pre-Andean continental margin in the Late Triassic and the development of new subduction-related magmatism are probably represented by the Early Jurassic Bólfin–Punta Tetas magmatic arc in the southern part of the peninsula, for which an age of 184 ± 1 Ma was determined. We suggest retaining the classification of Mejillonia as a tectonostratigraphic terrane, albeit in this new context. 相似文献
19.
晚侏罗世东亚多向汇聚构造体系的形成与变形特征 总被引：37，自引：2，他引：35
板块构造研究成果与同位素精确定年数据的积累,使我们对发生在中国东部的晚侏罗世-早白垩世东亚多向汇聚作用有了深刻的认识.全球三大洋在晚侏罗世(165±5)Ma近乎同时的开启,以及东亚周边占太平洋、新特提斯洋和蒙古-鄂霍茨克洋的俯冲消亡,在中国中东部和东亚地区形成了多向挤压汇聚的燕山期构造体系,即东业多向汇聚构造体系(简称东亚汇聚).东亚汇聚启动了经典的燕山运动,发育了独特的构造变形特征.东亚汇聚构造体系具有两个近乎稳定的刚性陆核,即鄂尔多斯地块和四川(盆地)地块,在它们的周缘形成了晚侏罗世-早白垩世陆内多向挤压变形和似前陆盆地,如大巴山晚侏罗世前陆.此外,东亚多向汇聚构造体系影响了东亚和中亚大部分地区的板内变形作用,在中国大陆及其周边形成了反映南北向挤压的蒙古弧共轭走滑断裂系统、燕山-阴山陆内造山带、大别山-大巴山侏罗纪陆内造山带等典型的燕山期构造带.东亚汇聚具有深刻的全球构造背景与动力来源,是重要的科学研究问题. 相似文献
20.
《地学前缘(英文版)》2022,13(2):101272
Polymetamorphic units are important constituents of continent–continent collisional orogens, and rift metamorphic assemblages are often overprinted by subsequent metamorphism during subduction and collision. This study reports the metamorphic conditions and evolution of the Dorud–Azna metamorphic units in the central part of the Sanandaj–Sirjan zone (SSZ), Iran. Here, new geothermobarometry results are integrated with 40Ar/39Ar mineral and Th–U–Pb monazite and thorite ages to provide new insight of polyphase metamorphism in the two different basement units of the SSZ, the lower Galeh-Doz orthogneiss and higher Amphibolite-Metagabbro units. In the Amphibolite-Metagabbro unit, staurolite micaschist underwent a prograde P–T evolution from 640 ± 20 °C/6.2 ± 0.8 kbar in garnet cores (M1) to 680 ± 20 °C/7.2 ± 1.0 kbar in garnet rims (M2). Three Th–U–Pb monazite ages of 306 ± 5 Ma, 322 ± 28 Ma and 336 ± 39 Ma from the garnet-micaschists testify the Carboniferous age of M1 metamorphism. In the same unit, the metagabbro records P–T conditions of 4.0 ± 0.8 kbar and 580 ± 50 °C in the (magmatic) amphibole core (Late Carboniferous intrusion) to 7.5 ± 0.7 kbar and 700 ± 20 °C in the amphibole rim indicating a prograde P–T path during subsequent burial (M1). New 40Ar/39Ar dating of white mica from the staurolite micaschist yielded a staircase pattern ranging from 36 ± 12 Ma to 170 ± 2 Ma. This implies polymetamorphism with a minimum Late Jurassic cooling age through the Ar retention temperature of ca. 425 ± 25 °C after M2 metamorphism and a Paleogene low-grade metamorphic overprint (M3), while 40Ar/39Ar white mica dating of garnet micaschist yielded a plateau age of 137.84 ± 0.65 Ma. We therefore interpret the amphibolite-grade metamorphism M2 to have predated 170 Ma and is likely between 180 and 200 Ma. Furthermore, it is overprinted at about 36 Ma under retrogressive low-grade M3 metamorphism (at temperatures of ~350–240 °C) during final shortening and exhumation. In the underlying Galeh-Doz unit, the Panafrican granitic orthogneiss intruded at P–T conditions of 3.2 ± 4 kbar and 700 ± 20 °C, then it was metamorphosed and deformed at 600 ± 50 °C and 2.0 ± 0.8 kbar (metamorphic stage M1) prior to Late Carboniferous intrusion of mafic dikes. 40Ar/39Ar dating of amphibole from the Galeh-Doz orthogneiss gave plateau-like steps between 260 and 270 Ma, representing the age of cooling through ca. 500 °C after the M1 metamorphic event. Interestingly, the results of this study demonstrate polyphase metamorphic histories in both the Galeh-Doz orthogneiss and Amphibolite-Metagabbro units at different P–T conditions and final thick-skinned Paleogene emplacement of these units over the underlying low-grade metamorphic June Complex. Our findings suggest that both units are affected by high-T/low-P Late Carboniferous orogenic metamorphism along with the bimodal magmatism, as result of rifting. We propose that the Early Jurassic amphibolite-grade M2 metamorphism of the SSZ is correlated with the initial subduction of the Neotethyan Ocean. Eventually, the investigated units reflect various stages of a Wilson cycle, from rifting to initiation of the subduction in final plate collision. 相似文献