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1.
The Anglona and SW Gallura regions represent key places to investigate the tectonic evolution of medium‐ and high‐grade metamorphic rocks cropping out in northern Sardinia (Italy). From south to north we distinguish two different metamorphic complexes recording similar deformation histories but different metamorphic evolution: the Medium Grade Metamorphic Complex (MGMC) and the High Grade Metamorphic Complex (HGMC). After the initial collisional stage (D1 deformation phase), both complexes were affected by three contractional deformational phases (D2, D3 and D4) followed by later extensional tectonics. The D2 deformation phase was the most significant event producing an important deformation partitioning that produced localized shearing and folding domains at the boundary between the two metamorphic complexes. We highlight the presence of two previously undocumented systems of shear belts with different kinematics but analogous orientation in the axial zone of Sardinia. They became active at the boundary between the MGMC and HGMC from the beginning of D2. They formed a transpressive regime responsible for the exhumation of the medium‐ and high‐grade metamorphic rocks, and overall represent a change from orthogonal to orogen‐parallel tectonic transport. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

2.
G. Musumeci 《Geodinamica Acta》2013,26(1-2):119-133
Abstract

The Monte Grighini Complex (Central-Western Sardinia) is a NW-SE trending metamorphic complex of Hereynian age made up of a medium grade Lower tectonic unit with mylonitie granitoids and a low grade Upper tectonic unit exposed in the westernmost and southernmost portions of this complex. The Lower Unit shows a prograde metamor phism from garnet to sillimanite zone and the transition from MP/MT to LP/HT metamorphism. The metamorphic climax was reached at the end of the main deformative phase 1)2 (600° C. 6 kbar). After the main tectonic and metamorphic phase. the Lower Unit was affected by a wide NW-SE trending ductile dextral wrench shear zone. Intrusive rocks emplaced within the shear zone yielded radiometric ages of 305-300 Ma. Shear deformation leads to low temperature C-S mylonites and retrograde phyllonitic rocks with subhorizontal NW-SE trending stretching lineations. Kinematic analysis of the shear zone points to a dextral sense of shear with an amount of ductile displacement of about 7 km. Later low angle N-S and E-W trending normal faults are associated with cataclastic zones separating the Lower Unit from the Upper one. These faults originated during a later evolutionary stage of the shear zone. This shows a progressive change of deformation regime from duetile wrenching to brittle normal faulting. The Monte Grighini Complex is a good example of ductile wrench tectonics. followed by uplift and extension in the Paleozoic basement of Sardinia.  相似文献   

3.
Abstract

The Zentralgneise in the Hohe Tauern (Penninic Zone, Eastern Alps, Austria) can be interpreted essentially as metamorphosed Late Paleozoic orogenic plutonites with original compositions mainly of granites, granodiorites and tonalites, rarely also of diorites, quartzdiorites, quartzmonzodiorites, quartzmonzonites and quartzsyenites. Most of the granitoids show attributes of “Cordilleran I-type granites” respectively “volcanic arc granites”.

Due to their similarity to subduction derived granitoids from present day active continental margins in the Circum-Pacific area, it is assumed, that the I-type granitoids of the Hohe Tauern reflect the influence of a Variscan destructive plate boundary.

Among the Zentralgneise also minor amounts of granites with features towards the S-type occur, which are more likely related to collision than to subduction.

Seen as a whole, the Late Paleozoic plutonism played probably part in a compressional continental margin and originated during a Variscan subduction-collision scenario, that occurred along the southern flank of Central European Hercynian fold belt.  相似文献   

4.
Despite the important role played by the Sardinia‐Corsica block in the reconstruction of the Western Mediterranean geodynamics, the extent of involvement of the “Autochthonous” European margin exposed in Corsica (France) (i.e., Hercynian Corsica) in the Alpine orogeny remains uncertain. Stratigraphic and sedimentological studies in the post‐Variscan deposits on the Hercynian Corsica are scarce and even scarcer are the structural and metamorphic constraints. To face these uncertainties, we present new stratigraphic, structural and metamorphic data from the area of Razzo Bianco, Central Corsica, where a complete sequence belonging to the European continental margin is exposed. Field and structural investigations demonstrate that the sequence represents the easternmost edge of the downgoing European plate. Metamorphic studies on the Eocene deposits indicate that the margin was buried at depth up to blueschist facies conditions and, subsequently, it was progressively exhumed mainly through the activation of oblique top‐to‐the NW shear zones.  相似文献   

5.
《Gondwana Research》2010,18(4):704-714
The Iran continental crust was metamorphosed, intruded by granitoid magmas, folded and faulted during the Late Precambrian by the Pan-African Orogeny. The basement complex in the Takab Complex (northwest Iran) consists of gneisses, amphibolites, pelitic schists, meta-ultramafic and calc-silicate rocks. Geochemically, the protoliths of the Takab gneisses are slightly peraluminous and medium to high-potassic with calc-alkaline affinity. These gneisses may have been emplaced in volcanic arc tectonic setting. Furthermore, the metapelitic protolith is shale deposited in an active continental margin setting. All these characteristics, and presence of paleo-suture zone and ophiolitic rocks (i.e. serpentines, meta-mafic and meta-ultramafic rocks) around the high grade metamorphic rocks suggest that a continental-margin magmatic arc (Andean-type) formed the Takab Precambrian basement. The basement complexes are extensively overprinted by the Pan-African Orogeny and younger igneous events; this supports the inference that Early Cambrian orogenesis in the Takab Complex region of northwest Iran marks one of the fundamental lithospheric boundaries within Gondwana which belonged to a greater Late Neoproterozoic–Early Paleozoic orogenic system that was active along the Proto-Tethyan margin of the Gondwana supercontinent, extending at least from its Arabian margin to the Himalayan margin of the Indian subcontinent.  相似文献   

6.
Provenance studies have been performed utilising major and trace elements, Nd systematics, whole rock Pb–Pb isotopes and zircon U/Pb SHRIMP data on metasedimentary rocks of the Sierra de San Luis (Nogolí Metamorphic Complex, Pringles Metamorphic Complex, Conlara Metamorphic Complex and San Luis Formation) and the Puncoviscana Formation of the Cordillera Oriental. The goal was the characterisation of the different domains in the study area and to give insights to the location of the source rocks. An active continental margin setting with typical composition of the upper continental crust is depicted for all the complexes using major and trace elements. The Pringles Metamorphic Complex shows indications for crustal recycling, pointing to a bimodal provenance. Major volcanic input has to be rejected due to Th/Sc, Y/Ni and Cr/V ratios for all units. The εNd(540 Ma) data is lower for the San Luis Formation and higher for the Conlara Metamorphic Complex, as compared to the other units, in which a good consistency is given. This is similar to the TDM ages, where the metapsammitic samples of the San Luis Formation are slightly older. The spread of data is largest for the Pringles Metamorphic Complex, again implying two different sources. The whole rock 207Pb/206Pb isotopic data lies in between the South American and African sources, excluding Laurentian provenances. The whole rock Pb–Pb data is almost indistinguishable in the different investigated domains. Only the PMC shows slightly elevated 208Pb/204Pb values. Possible source rocks for the different domains could be the Quebrada Choja in the Central Arequipa–Antofalla domain, the Southern domain of the Arequipa–Antofalla basement, the Brazilian shield or southern Africa. Zircon SHRIMP data point to a connection between the Puncoviscana Formation and the Conlara Metamorphic Complex. Two maxima around 600 Ma and around 1000 Ma have been determined. The Nogolí Metamorphic Complex and the Pringles Metamorphic Complex show one peak of detrital zircons around 550 Ma, and only a few grains are older than 700 Ma. The detrital zircon ages for the San Luis Formation show age ranges between 590 and 550 Ma. A common basin can be assumed for the Conlara Metamorphic Complex and the Puncoviscana Formation, but the available data support different sources for the rest of the Complexes of the Sierra de San Luis. These share the diminished importance or the lack of the Grenvillian detrital peak, a common feature for the late Cambrian–early Ordovician basins of the Eastern Sierras Pampeanas, in contrast to the Sierras de Córdoba, the PVF and the Conlara Metamorphic Complex.  相似文献   

7.
《Geodinamica Acta》2013,26(3-4):155-164
New structural data pointed out the presence of an older scattered migmatization event (Devonian?, M1) overcome by the well known Variscan migmatization event (Lower-Middle Carboniferous, M2) related to the Late extensional tectonic that affected the High Grade Metamorphic Complex (HGMC) in the Variscan Belt of Sardinia (Italy). The M1 event is only recognizable in the kyanite – amphibole bearing migmatitic gneiss. Both migmatization events (M1 and M2) are characterized by a syn-tectonic non coaxial deformations (D1 and D2 deformational events). D1 shows a top to NW sense of shear while the D2 event a top to NE/SE sense of shear (the shear senses are considered at the present Sardinia – Corsica block position in the Mediterranean sea). The M2+D2 is characterized by a complicate, composite normal shear network; the M1+D1 by inverse shear zones. The M2+D2 is transposed by the late D3 strike slip shear event: the D3 is characterized by strike slip shear zones syn-kinematic to the emplacement of Late Carboniferous granitoids (320 Ma – 300 Ma). Despite the absence of geochronological data about the M1+D1 event, the field relationships suggest, for first time, an older migmatization process (Devonian?) syn-tectonic with the late stage of thickness of the Sardinia Variscan Belt. Similar evolutions are recognized in different segments of the Variscan Belt such as the Massif Central (France) or in the eastern mid-European Variscides.  相似文献   

8.
The northern part of the western Kunlun (southern margin of the Tarim basin) represents a Sinian rifted margin. To the south of this margin, the Sinian to Paleozoic Proto-Tethys Ocean formed. South-directed subduction of this ocean, beneath the continental southern Kunlun block during the Paleozoic, resulted in the collision between the northern and southern Kunlun blocks during the Devonian. The northern part of the Paleo-Tethys Ocean, located to the south of the southern Kunlun, was subducted to the north beneath the southern Kunlun during the Late Paleozoic to Early Mesozoic. This caused the formation of a subduction-accretion complex, including a sizeable accretionary wedge to the south of the southern Kunlun. A microcontinent (or oceanic plateau?), which we refer to as “Uygur terrane,” collided with the subduction complex during the Late Triassic. Both elements together represent the Kara-Kunlun. Final closure of the Paleo-Tethys Ocean took place during the Early Jurassic when the next southerly located continental block collided with the Kara-Kunlun area. From at least the Late Paleozoic to the Early Jurassic, the Tarim basin must be considered a back-arc region. The Kengxiwar lineament, which “connects” the Karakorum fault in the west and the Ruogiang-Xingxingxia/Altyn-Tagh fault zone in the east, shows signs of a polyphase strike-slip fault along which dextral and sinistral shearing occurred.  相似文献   

9.
Savchuk  Yu. S.  Volkov  A. V. 《Geotectonics》2020,54(6):771-784

The Central Ural uplift occupies the near-Vodorazdelnaya part of the Urals. It is composed of metaterrigenous and metavolcanogenic Riphean–Vendian formations. Distributed folds, which formed in several stages, and various tectonic faults are widespread. The study of these structures in the areas located in the Northern and Subpolar Urals showed their lateral and temporal variability, which was reflected in the difference in morphology and nature of faulting. In the Vodorazdelnaya area of the Northern Urals, as a result of thrust–fold deformations, a complex fold structure of the sequence was formed, subsequently broken by two submeridional subparallel faults into blocks. In the Khalmerya area of the Subpolar Urals, there are several tectonic blocks bounded by gently eastward dipping and overlapping tectonic blocks that form a duplex structure. This series of thrust structures created a complex cover structure contrasting in composition and degree of deformation. Later, a northeastern strike-slip fault zone arose. The orientation of early isoclinal folds in the rocks indicates pressure from the northeast, during the formation of tectonic scales and sheets in the Precambrian basement. Then this pressure occurred from the southeast and the Lower Paleozoic sediments were involved in the thrust process. Differences in the features of the formation of structures apparently depend on the morphology of the eastern margin of the East European platform and the change in the vector of displacement of the thrust sheet. The movement of the thrust sheets within the continental margin occurred along the main surface of the fault, with which the thrust structures are articulated at depth. At the final stages, extended strike-slip-upthrust zones were established, which affected the distribution of he gold mineralization.

  相似文献   

10.
Abstract

A new geodynamic model for the Sardinian segment of the Hercynian chain is presented. The improvement of knowledge regarding several geological, metamorphic, magmatic and geochronological aspects of the Sardinian Palaeozoic basement, mainly achieved in the last few years, allows us to propose a more complete picture of its evolution.

The occurrence of remnants of an oceanic suture along a major tectonic lineament in northern Sardinia, as well as the products of Ordovician calc-alkaline magmatism, testifies to the presence, during the Lower Paleozoic, of an ancient (Precambrian- Cambrian) oceanic domain and its consumption along an Andean- type subduction zone. The following Carboniferous continental collision caused crustal stacking with Barrovian metamorphism and southward-migrating deformation from the suture zone toward the foreland.

Early Carboniferous Culm-type facies sediments, deposited in the outermost zone of the chain, imply that continental collision took place earlier in the internal zone, from Late Devonian or Early Carboniferous.

The collisional orogenic wedge experienced ductile extension during the Late Carhoniferous as a result of gravitational collapse of the thickened continental crust.

Extensional tectonism enhanced the uplift of the chain and some regions underwent tectonic denudation or LP/HT metamorphism and somewhere anatexis. The emplacement of calc-alkaline batholiths and the development of Late Carboniferous - Early Permian molasse basins occurred during extension that prolonged throughout the Permian.  相似文献   

11.
The southernmost outcrops of the Río de la Plata cratonic region are exposed in the Tandilia System in eastern Argentina. The geological evolution comprises mainly an igneous-metamorphic Paleoproterozoic basement named Buenos Aires Complex, which is covered by Neoproterozoic to Early Paleozoic sedimentary units which display subhorizontal bedding. The basement of calc-alkaline signature consists mainly of granitic-tonalitic gneisses, migmatites, amphibolites, some ultramafic rocks, and granitoid plutons. Subordinate rock-types include schists, marbles, and dykes of acid and mafic composition. Tandilia was recognized as an important shear belt district with mylonite rocks derived mainly from granitoids. The tectonic scenario seems related to juvenile accretion event (2.25?C2.12?Ga) along an active continental margin, followed by continental collision (2.1?C2.08?Ga) after U?CPb zircon data. The collisional tectonic setting caused thrusting and transcurrent faulting favouring the anatexis of the crustal rocks. The tholeiitic dykes constrain the time of crustal extension associated with the last stages of the belt evolution. The basement was preserved from younger orogenies such as those of the Brasiliano cycle. After a long paleoweathering process, the Sierras Bayas Group (c. 185?m thick) represents a record of the first Neoproterozoic sedimentary unit (siliciclastic, dolostones, shales, limestones), superposed by Cerro Negro Formation (c. 150?C400?m thick, siliciclastics) assigned to Upper Neoproterozoic age. The final sedimentary transgression during Early Paleozoic was the Balcarce Formation (c. 90?C450?m thick) deposited over all the mentioned Precambrian units. Based on all the geological background, a tectonic evolution is offered.  相似文献   

12.
The Guarguardz Complex, basement of the Cordillera Frontal, included in the proposed Chilenia Terrane, consists of metasedimentary rocks deposited in clastic and carbonatic platforms. Turbiditic sequences point out to slope or external platform environments. According to geochemical data, the sedimentary protoliths derived through erosion of a mature cratonic continental basement. Volcanic and subvolcanic rocks with N and E-MORB signature were interbeded in the metasedimentary rocks during basin development. A compressional stage, starting with progressive deformation and metamorphism, followed this extensional stage. Continuing deformation led to the emplacement of slices of oceanic crust, conforming an accretionary prism during Late Devonian. The Guarguardz Complex and equivalent units in western Precordillera and also in the Chilean Coastal Cordillera share common evolutional stages, widely represented along the western Gondwana margin. These evidences imply that Chilenia is not an allochthonous terrane to Gondwana, but a portion of its Early Paleozoic margin. Regional configuration indicates that the Guarguardz Complex and equivalent units represent the accretionary prism of the Famatinian arc (Middle Ordovician-Late Devonian).  相似文献   

13.
苏北盆地为一新生代形成的拉张盆地,震旦纪至白垩纪地层构成了盆地的基底,本文对中、古生界碳酸盐岩盆地基底演化和盆地形成进行了四个阶段的古地热史恢复和生烃史模拟并依次叠加,得到了部分钻井的有机质的成熟度（Ｒ０值）。其结果基本上与地层实测（Ｒ０）值相吻合,为构造演化复杂的苏北地区中、古生界烃源岩成熟度提供了一些新的消息,并可作为该区进一步油气远景评价的参考。  相似文献   

14.
The Mesozoic rocks of Cuba are a key element in reconstructing the geological history of the Mesoamerican (Gulf of Mexico and the Caribbean) area. Four different Jurassic-Cretaceous sections are recorded in Cuba, including three from tectonostratigraphic terranes. From north to south they include the following: (1) a portion of the Mesozoic passive margin of North America, with outstanding zonality, especially in the Middle Cretaceous of central Cuba; (2) the Northern Ophiolitic Belt, also with Upper Jurassic-Lower Cretaceous rocks, which is a huge melange; all members of the ophiolitic suite are tectonically mingled along the northern part of Cuba; (3) the Volcanic Arc Terrane, mainly composed of Cretaceous volcanics, with older, primarily tholeiitic lavas (Aptian-Albian) and younger (Cenomanian-Campanian) calc-alkaline pyroclastics and lavas, with many sedimentary interbeds; Albian-Cenomanian deposits with a few volcanics separate both sequences, and an Upper Jurassic-Neocomian amphibolitic basement of the volcanic arc is present in some places; and (4) the Southern Metamorphic Terranes that contain rocks of a Mesozoic passive margin that experienced several metamorphic episodes during the Cretaceous.

The welding of these terranes occurred during the Cretaceous, and ended in the late Campanian and Maastrichtian. In the south, the volcanic terrane was emplaced upon the Southern Metamorphic Terranes, while in the north the volcanics and ophiolites were thrust over the Mesozoic margin of North America. In western Cuba, the beds are strongly deformed and thrust to the north or northwest. Nappes also are present in north-central Cuba, but an essentially Bahamian platform stratigraphy is present. Although the passive paleomargin of North America was deformed in the latest Cretaceous, this event is masked by the early Tertiary Cuban orogeny.

It is suggested that the Jurassic stratigraphy of the Southern Metamorphic Terranes shares features with the southern North American passive margin in western Cuba. The position of the Southern Metamorphic Terranes south of the ophiolite and arc terrane therefore does not support the idea of a Pacific origin for the Cretaceous island arcs of the Greater Antilles, but instead suggests that a proto-Caribbean genesis is more plausible.  相似文献   

15.
拉萨地块西段缺失晚古生代岩浆岩,造成不能从岩浆岩角度探索其晚古生代地质演化,因此沉积岩的对比研究对理解拉萨地块晚古生代的差异演化过程至关重要。本文通过对尼雄地区上石炭统—下二叠统拉嘎组碎屑岩地球化学特征分析,试图揭示其物源特征及源区构造背景,提供拉萨地块晚古生代沉积岩对比分析的基础信息。尼雄地区拉嘎组一段和二段主量和微量元素特征略有差异,二段较一段CaO、Na_2O含量更高,V、Cr、Ni、Co及轻稀土含量也更高,反映二者沉积源区有一定差异。拉嘎组物源区的构造背景兼具被动大陆边缘与活动大陆边缘特征,并且二段较一段显示更强的活动大陆边缘亲缘性。结合区域地质资料,认为拉嘎组碎屑岩主要来自成熟的大陆源区,为冈瓦纳大陆北缘基底岩石及早古生代沉积岩的再旋回沉积,二段源区的少量酸性及基性物质组分对应于冈瓦纳大陆北缘泛非期及寒武纪岩浆活动。  相似文献   

16.
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   

17.
The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt （CAOB）, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite （graywacke）-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are： （1） Altai-Mongolian terrane （AMT）; （2） subduction-accretionary （Rudny Altai, Gorny Altai） and collisional （Kalba-Narym） terranes; （3） Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones （SSZ）. The evolution of this orogen proceeded in five major stages： （i） late Neoproterozoic-early Paleozoic subduction-accretion in the Paleo-Asian Ocean; （ii） Ordovician-Silurian passive margin; （iii） Devonian-Carboniferous active margin and collision of AMT with the Siberian conti- nent; （iv） late Paleozoic closure of the PAO and coeval collisional magmatism; （v） Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian- Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane （continental versus active margin）, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes.  相似文献   

18.
《Gondwana Research》2008,13(4):489-508
U–Pb SHRIMP zircon geochronology, bulk-rock geochemistry, and Sr–Nd isotopic data are herein presented in order to better constrain the tectonic evolution of the Nico Pérez Terrane (NPT), Uruguay. The studies are focused on two key geological units located in the southern part of the NPT, namely Carapé Complex (CC) and Lavalleja Metamorphic Complex (LMC). The Carapé Complex, previously interpreted as part of a remnant magmatic arc, formed at 1.75 Ga mainly by partial melting of Archean crust (TDM model ages between 2.8 and 3.0 Ga with strong negative ɛNd (t) values). The Lavalleja Metamorphic Complex, previously interpreted as a back-arc basin, has volcanic units formed at 0.59 Ga during the Brasiliano Cycle, but may also contain older (Paleoproterozoic) units. The geochemistry of the LMC meta-igneous rocks indicates a complex scenario. Two distinct signatures have been recognized, one similar to MORBs and the other similar OIBs. Sm–Nd TDM model ages of basic rocks present a bimodal (Paleoproterozoic and Archean) distribution, which is also recognized in several other units of the NPT. In the light of new results, we conclude that the NPT represents a cratonic margin setting, characterized by the stacking of lithotectonic assemblages with Archean, Paleoproterozoic, and Neoproterozoic age at the margin of the Rio de la Plata Craton.  相似文献   

19.
秦岭造山带主要大地构造单元的新划分   总被引：48，自引：6，他引：42  
根据近年来的地层、沉积、岩浆-火山和构造变形及岩石地球化学等方面研究新进展,结合前人的成果,按照大地构造相单元划分原则,将秦岭造山带分为13个主要构造单元: ①华北南缘陆坡带,包括第一层序的青白口系大庄组、震旦系罗圈组和寒武系,与之对应的豫西栾川群;第二层序的奥陶纪陶湾群;②北秦岭弧后杂岩带,以宽坪群和部分二郎坪群中的基性火山岩与碳酸盐岩的构造块体与变质的古生代深海碎屑岩混杂为特征;③秦岭岛弧杂岩带,由丹凤群不同的古洋隆块体、富水幔源岛弧基性岩浆杂岩、云架山群、斜峪关群和草滩沟群的岛弧钙碱性岩浆岩和火山岩及深海沉积物及秦岭群弧基底杂岩等构成,时间跨度为奥陶纪-石炭纪;④秦岭弧前盆地系,泥盆系及其它晚古生代地层是其主要充填物,同沉积断裂控制了一系列的次级盆地;⑤秦岭增生混杂带,由泥、砂岩组成的基质和基性、超基性岩、火山岩、灰岩、硅质岩等岩块构成,最终形成于二叠纪末-三叠纪初;⑥南秦岭岛弧杂岩带,碧口群的基性-中酸性火山岩和岩浆岩组成,称碧口弧;由三花石群的中基性火山岩以及西乡群的中酸性火山岩共同构成,称西乡弧;由耀岭河群和郧西群中基性熔岩和中酸性火山岩组成,称安康弧;⑦南秦岭弧前盆地系,碧口弧前盆地充填物是以碎屑岩为主的横丹群和关家沟群;西乡弧前沉积主要由三花岩群包括王家坝组砂岩以及由泥岩、砂岩和中酸性火山岩变质而成的片岩、片麻岩和石英岩组成.安康弧前盆地具有明显的深海扇沉积特征梅子垭群和大贵坪组;⑧南秦岭弧后盆地系,包括后龙门山的茂县群和上古生界及三叠系,大巴山的洞河群和部分耀岭河群的火山岩;⑨南秦岭弧后陆坡带,只保留大巴山弧后陆缘,是高川-毛坝以南的下古生界;⑩南秦岭前陆褶冲带,包括龙门山北段、米仓山和大巴山前陆褶冲带.三带形成于印支-燕山期,但构造线不同,且在出现的时间上,由西到东由早到晚;(11)三叠纪残余海盆;(12)中-新生代走滑拉分和断陷盆地;(13)基底断块.  相似文献   

20.
合肥盆地基底构造属性   总被引：33，自引：4，他引：29       下载免费PDF全文
根据合肥盆地及周边地表地质、地震剖面、同位素测年及MT等新资料的综合研究,提出中-新生代合肥盆地的基底是一个不同构造类型基底的叠合与复合.上古生界以前的基底以六安断裂为界,其北为华北板块陆壳型-过渡壳型结晶基底及其上的华北克拉通-被动大陆边缘盆地沉积的上元古-下古生界基底;其南为大别型结晶基底及其上的北淮阳弧后盆地沉积的上元古-下古生界变质基底,而上古生界基底属于弧后前陆盆地型沉积.六安断裂是合肥盆地部位北大别弧、北淮阳晚元古-早古生代弧后盆地在早古生代晚期-晚古生代早期与华北板块的弧-陆碰撞缝合线.  相似文献   

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