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1.
The intraplate uplift of the Qinghai-Tibet Plateau took place on the basis of breakup and assembly of the Precambrian supercontinent, and southward ocean-continent transition of the Proto-, Paleo-, Meso-and Neo-Tethys during the Caledonian, Indosinian, Yanshanian and Early Himalayan movements. The intraplate tectonic evolution of the Qinghai-Tibet Plateau underwent the early stage of intraplate orogeny characterized by migrational tectonic uplift, horizontal movement and geological processes during 180-7 Ma, and the late stage of isostatic mountain building characterized by pulsative rapid uplift, vertical movement and geographical processes since 3.6 Ma. The spatial-temporal evolution of the intraplate orogeny within the Qinghai-Tibet Plateau shows a regular transition from the northern part through the central part to the southern part during 180-120 Ma, 65-35 Ma, and 25-7 Ma respectively, with extensive intraplate faulting, folding, block movement, magmatism and metallogenesis. Simultaneous intraplate orogeny and basin formation resulted from crustal rheological stratification and basin-orogen coupling that was induced by lateral viscous flow in the lower crust. This continental dynamic process was controlled by lateral flow of hot and soft materials within the lower crust because of slab dehydration and melted mantle upwelling above the subducted plates during the southward Tethyan ocean-continent transition processes or asthenosphere diapirism. Intraplate orogeny and basin formation were irrelevant to plate collision. The Qinghai-Tibet Plateau as a whole was actually formed by the isostatic mountain building processes since 3.6 Ma that were characterized by crust-scale vertical movement, and integral rapid uplift of the plateau, accompanied by isostatic subsidence of peripheral basins and depressions, and great changes in topography and environment. A series of pulsative mountain building events, associated with gravity equilibrium and isostatic adjustment of crustal materials, at 3.6 Ma, 2.5 Ma, 1.8-1.2 Ma, 0.9-0.8 Ma and 0.15-0.12 Ma led to the formation of a composite orogenic belt by unifying the originally relatively independent Himalayas, Gangdisê, Tanghla, Longmenshan, Kunlun, Altyn Tagh, and Qilian mountains, and the formation of the complete Qinghai-Tibet Plateau with a unified mountain root after Miocene uplift of the plateau as a whole.  相似文献   

2.
This is a review of the formation and tectonic evolution of the continental Asia in Phanerozoic.The continental Asia has formed on the bases of some pre-Cambrian cratons,such as the Siberia,India,Arabia,North China,Tarim,South China,and Indochina,through multi-stage plate convergence and collisional collages in Phanerozoic.The north-central Asia had experienced the expansion and subduction of the Paleo-Asian Ocean(PAO)in the early Paleozoic and the closure of the PAO in the late Paleozoic and early Mesozoic,forming the PAO regime and Central Asian orogenic belt(CAOB).In the core of the CAOB,the Mongol-Okhotsk Ocean(MOO)opened with limited expansion in the Early Permian and finally closed in the Late Jurassic–Early Cretaceous.The south-central Asia had experienced mainly multi-stage oceanic opening,subduction and collision evolution in the Tethys Ocean,forming the Tethys regime and Himalaya-Tibetan orogenic belt.In eastern Asia,the plate subduction and continental margin orogeny on western margin of the Pacific Ocean,forms the West Pacific regime and West Pacific orogenic belt.The PAO,Tethys,and West Pacific regimes,together with Precambrian cratons among or surrounding them,made up the major tectonic and dynamic systems of the continental Asia in Phanerozoic.Major tectonic events,such as the Early Paleozoic Qilian,Uralian,and Dunhuang orogeneses,the late Paleozoic East Junggar,Tianshan and West Junggar orogeneses,the Middle to Late Permian Ailaoshan orogeny and NorthSouth Lhasa collision,the early Mesozoic Indochina-South China and North-South China collisions,the late Mesozoic Mongolia-Okhotsk orogeny,Lhasa-Qiangtang collision,and intra-continental Yanshanian orogeny,and the Cenozoic IndoAsian,Arab-Asian,and West Pacific margin collisions,constrained the formation and evolution of the continental Asia.The complex dynamic systems have left large number of deformation features,such as large-scale strike-slip faults,thrustfold systems and extensional detachments on the continental Asia.Based on past tectonics,a future supercontinent,the Ameurasia,is prospected for the development of the Asia in ca.250 Myr.  相似文献   

3.
<正>Ophiolites are fragments of ancient ocean lithosphere emplaced on continental margins,in island arcs or in accretionary prisms,and have long been studied to better understand the evolution of ocean basins and collision of tectonic plates,the processes of mountain building and the occurrence of valuable ore bodies,such as podiform  相似文献   

4.
New isotopic,geochemical and geochronological data justify the widespread occurrence of middle Paleocene to early Eocene(60–53 Ma) post-subduction felsic magmatism across the entire Sikhote-Alin territory(southeastern Russia),conform with previous observations in Northeast China,the southern Korean Peninsula,and the Inner Zone of Japan.This igneous activity in East Asia coincided with the reactivation(after tectonic quiescence between ～93–60 Ma) of left-lateral strike-slip displacements along the Tan-Lu and Central Sikhote-Alin faults and with the post-60 Ma cessation of subduction/accretion recorded in the Shimanto belt of SW Japan.The SikhoteAlin post-subduction igneous A-type rocks present diverse mineralogical and geochemical features that suggest interactions of the subducting plate with anhydrous mantle upwelling through slab tears in the continental margin.The middle Paleocene–early Eocene magmatism is not related to subduction but is synchronous with strikeslip tectonics and the termination of accretionary prism development,suggesting a shift in tectonic regime from oceanic plate subduction at a convergent margin to parallel sliding and initiation of a transform continental margin.These new observations are inconsistent with the current tectonic model of 60–50 Ma Izanagi-Pacific ridge subduction beneath East Asian continental margin.  相似文献   

5.
The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements, rare-earth dements and trace elements of the Mesozoic-Cenozoic sandstones in the Lanping Basin are studied in this paper, revealing that the tectonic settings of the provenance for Mesozoic-Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography, it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic, whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust, and are composed mainly of felsic rocks, mixed with some andesitic rocks and old sediment components. Therefore, the Lanping Mesozoic-Cenozoic Basin is a typical continental-type basin. This provides strong geochemical evidence for the evolution of the paleo-Tethys and theb asin-range transition.  相似文献   

6.
With acquisition and accumulation of new data of structural geological investigations and high-resolution isotopic dating data, we have greatly improved our understanding of the tectonic events occurring in eastern China during the period from the Late Jurassic to Early Cretaceous and may give a new interpretation of the nature, timing and geodynamic settings of the “Yanshan Movement”. During the Mid-Late Jurassic （165±5 Ma）, great readjustment of plate amalgamation kinematics took place in East Asia and the tectonic regime underwent great transformation, thus initiating a new tectonic regime in which the North China Block was the center and different plates converged toward it from the north, east and southwest and forming the “East Asia convergent” tectonic system characterized by intracontinental subduction and orogeny. As a consequence, the crustal lithosphere of the East Asian continent thickened considerably during the Late Jurassic, followed immediately by Early Cretaceous substantial lithospheric thinning and craton destruction featured by drastic lithospheric extension and widespread volcano-magmatic activities, resulting in a major biotic turnover from the Yanliao biota to Jehol Biota. Such a tremendous tectonic event that took place in the continent of China and East Asia is the basic connotation of the “Yanshan Movement”. In the paper, according to the deformation patterns, geodynamic settings and deep processes, the “Yanshan Movement” is redefined as the Late Jurassic East Asian multi-directional plate convergent tectonic regime and its associated extensive intracontinental orogeny and great tectonic change that started at -165±5 Ma. The substantial lithospheric attenuation in East China is considered the post-effect of the Yanshanian intracontinental orogeny and deformation.  相似文献   

7.
The fundamental theoretical framework of the Multisphere Tectonics of the Earth System is as follows: (1) It intends to extend the geotectonic studies from the crustal and lithospheric tectonics to the multisphere tectonics of the Earth system as a whole. (2) The global dynamics driven by both the Earth system and the cosmic celestial system: solar energy, multispheric interactions of the Earth system and the combined effects of the motions of celestial bodies in the cosmos system are the driving forces of various geological processes. (3) The Continent-Ocean transformation theory: the continent and ocean are two opposite yet unified geological units, which can be transformed into each other; neither continent nor ocean will survive forever; there is no one-way development of continental accretion or ocean extinction; the simple theory of one-way continental accretion is regarded as invalid. (4) The continental crust and mantle are characterized by multiple layers, with different layers liable to slide along the interfaces between them, but corroboration is needed that continents move as a whole or even drift freely. (5) The cyclic evolution theory: the development of Earth’s tectonics is not a uniform change, but a spiral forward evolution, characterized by a combination of non-uniform, non-linear, gradual and catastrophic changes; different evolutionary stages (tectonic cycles) of Earth have distinctive global tectonic patterns and characteristics, one tectonic model should not be applied to different tectonic cycles or evolutionary stages. (6) The structure and evolution of Earth are asymmetric and heterogeneous, thus one tectonic model cannot be applied to different areas of the world. (7) The polycyclic evolution of the continental crust: the continental crust is formed by polycyclic tectonics and magmatism, rather than simply lateral or vertical accretion. (8) The role of deep faults: the deep fault zones cutting through different layers of the crust and mantle usually play important roles in tectonic evolution. For example, the present-day mid-ocean ridge fault zones, transform fault zones and Benioff zones outline the global tectonic framework. Different tectonic cycles and stages of Earth’s evolution must have their own distinctive deep fault systems which control the global tectonic framework and evolutionary processes during different tectonic cycles and stages. Starting from the two mantle superplumes Jason (Pacific) and Tuzo (Africa), the study of the evolutionary process of the composition and structure of the crust and mantle during the great transformation and reorganization of the Meso-Cenozoic tectonic framework in China and the other regions of Asia is a good demonstration of theory of Multisphere Tectonics of the Earth System.  相似文献   

8.
The Earth is the only body in the solar system for which significant observational constraints are accessible to such a degree that they can be used to discriminate between competing models of Earth's tectonic evolution.It is a natural tendency to use observations of the Earth to inform more general models of planetary evolution.However,our understating of Earth's evolution is far from complete.In recent years,there has been growing geodynamic and geochemical evidence that suggests that plate tectonics may not have operated on the early Earth,with both the timing of its onset and the length of its activity far from certain.Recently,the potential of tectonic bi-stability(multiple stable,energetically allowed solutions)has been shown to be dynamically viable,both from analytical analysis and through numeric experiments in two and three dimensions.This indicates that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution.It also allows for the potential that feedback mechanisms between the internal dynamics and surface processes(e.g.,surface temperature changes driven by long term climate evolution),acting at different thermal evolution times,can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales.The implication within this framework is that terrestrial planets have the potential to migrate through tectonic regimes at similar‘thermal evolution times'(e.g.,points were they have a similar bulk mantle temperature and energies),but at very different'temporal times'(time since planetary formation).It can be further shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random variations.Here,we will discuss constraints on the tectonic evolution of the Earth and present a novel framework of planetary evolution that moves toward probabilistic arguments based on general physical principals,as opposed to particular rheologies,and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable at equivalent physical and chemical conditions.  相似文献   

9.
Continent-continent collision is the most important driving mechanism for the occurrence of various geological processes in the continental lithosphere. How to recognize and determine continent-continent collision,especially its four-dimensional temporal-spatial evolution, is a subject that geological communities have long been concerned about and studied. Continent-continent collision is mainly manifested by strong underthrnsting (subduction) of the underlying block along an intracontinental subduction zone and continuous obduction (thrusting propagation) of the overlying block along the intracontinental subduction zone, the occurrence of a basin-range tectonic framework in a direction perpendicular to the subduction zone and the flexure and disruption of the Moho. On the basis of numerical modeling, the authors discuss in detail the couplings between various amounts and rates of displacement caused by basin subsidence, mountain uplift and Moho updoming and downflexure during obduction (thrusting propagation) and subduction and the migration pattern of basin centers. They are probably indications or criteria for judgment or determination of continent-continent collision.  相似文献   

10.
The evolution of Earth＇s biosphere,atmosphere and hydrosphere is tied to the formation of continental crust and its subsequent movements on tectonic plates.The supercontinent cycle posits that the continental crust is periodically amalgamated into a single landmass,subsequently breaking up and dispersing into various continental fragments.Columbia is possibly the first true supercontinent,it amalgamated during the 2.0-1.7 Ga period,and collisional orogenesis resulting from its formation peaked at 1.95-1.85 Ga.Geological and palaeomagnetic evidence indicate that Columbia remained as a quasi-integral continental lid until at least 1.3 Ga.Numerous break-up attempts are evidenced by dyke swarms with a large temporal and spatial range; however,palaeomagnetic and geologic evidence suggest these attempts remained unsuccessful.Rather than dispersing into continental fragments,the Columbia supercontinent underwent only minor modifications to form the next supercontinent （Rodinia） at 1.1 -0.9 Ga; these included the transformation of external accretionary belts into the internal Grenville and equivalent collisional belts.Although Columbia provides evidence for a form of ‘lid tectonics’,modern style plate tectonics occurred on its periphery in the form of accretionary orogens.The detrital zircon and preserved geological record are compatible with an increase in the volume of continental crust during Columbia＇s lifespan; this is a consequence of the continuous accretionary processes along its margins.The quiescence in plate tectonic movements during Columbia＇s lifespan is correlative with a long period of stability in Earth＇s atmospheric and oceanic chemistry.Increased variability starting at 1.3 Ga in the environmental record coincides with the transformation of Columbia to Rodinia; thus,the link between plate tectonics and environmental change is strengthened with this interpretation of supercontinent history.  相似文献   

11.
Progress of machine learning in geosciences: Preface   总被引：1，自引：1，他引：0  
正In the past two decades,artificial intelligence(AI)algorithms have proved to be promising tools for solving several tough scientific problems.As a broad subfield of AI,machine learning is concerned with algorithms and techniques that allow computers to"learn".The machine learning approach covers main domains such as data mining,difficult-to-program applications,and software applications.It is a collection of a variety of algorithms that  相似文献   

12.
Tarim Precambrian bedrocks are well exposed in the Kuluketage and Aksu areas,where twenty four samples were taken to reveal the denudation history of the northern Tarim Craton.Apatite fission track dating and thermal history modeling suggest that the northern Tarim experienced multi-stage cooling events which were assumed to be associated with the distant effects of the Cimmerian orogeny and India-Eurasia collision in the past.But the first episode of exhumation in the northern Tarim,occurring in the mid-Permian to Triassic,is here suggested to be induced by docking of the Tarim Craton and final amalgamation of the Central Asian Orogenic Belt.The cooling event at ca.170 Ma may be triggered by the Qiangtang-Eurasia collision.Widespread Cretaceous exhumation could be linked with docking of the Lhasa terrane in the late Jurassic.Cenozoic reheating and recooling likely occurred because of the northpropagating stress,however,this has not affected the northern Tarim much because the Tarim is characterized by rigid block-like motion.  相似文献   

13.
The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over the United States in establishing outbreak-favorable environments. The predictability of Rossby wavetrain phasing is strongly related to numerous climate-scale interannual variability indices, which are predictable many months in advance. To formalize the relationship between interannual variability indices and seasonal tornado outbreak frequency, indices derived from monthly mean Northern Hemisphere 500-hPa and 1000-hPa geopotential height fields and Ni?o 3.4 indices for ENSO phase were compared to annual tornado outbreak seasonal frequencies. Statistical models predicting seasonal outbreak frequency were established using linear(stepwise multivariate linear regressione SMLR) and nonlinear(support vector regressione SVR) statistical modeling techniques.The stepwise methodology revealed predictors that are important in establishing outbreak-favorable environments at long lead times. Additionally, the results of the statistical modeling revealed that the nonlinear SVR technique reduced root mean square errors produced by the control SMLR technique by 28% and provided more consistent forecasts. A preliminary physical analysis revealed that years with high outbreak frequencies were associated with the presence of 500-mb troughs over the central and western US during the peak of outbreak season, while lower frequencies were consistent with ridging over the US or northwest flow over the Plains. These patterns support the results of the statistical modeling, which demonstrate the utility of geopotential height variability as a predictability measure of outbreak frequency.  相似文献   

14.
Seafloor polymetallic sulfide resources exhibit significant development potential.In 2011,China received the exploration rights for 10,000 km~2 of a polymetallic sulfides area in the Southwest Indian Ocean;China will be permitted to retain only 25%of the area in 2021.However,an exploration of seafloor hydrothermal sulfide deposits in China remains in the initial stage.According to the quantitative prediction theory and the exploration status of seafloor sulfides,this paper systematically proposes a quantitative prediction evaluation process of oceanic polymetallic sulfide resources and divides it into three stages:prediction in a large area,prediction in the prospecting region,and the verification and evaluation of targets.The first two stages of the prediction process have been employed in seafloor sulfides prospecting of the Chinese contract area.The results of stage one suggest that the Chinese contract area is located in the high posterior probability area,which indicates good prospecting potential area in the Indian Ocean.In stage two,the Chinese contract area of 48°-52° E has the highest posterior probability value,which can be selected as the reserved region for additional exploration.In stage three,the method of numerical simulation is employed to reproduce the ore-forming process of sulfides to verify the accuracy of the reserved targets obtained from the three-stage prediction.By narrowing the exploration area and gradually improving the exploration accuracy,the prediction will provide a basis for the exploration and exploitation of seafloor polymetallic sulfide resources.  相似文献   

15.
The intense study of coleopteran inclusions from Spanish(Albian in age) and French(Albian-Santonian in age) Cretaceous ambers,both of Laurasian origin,has revealed that the majority of samples belong to the Polyphaga suborder and,in contrast to the case of the compression fossils,only one family of Archostemata,one of Adephaga,and no Myxophaga suborders are represented.A total of 30 families from Spain and 16 families from France have been identified(with almost twice bioinclusions identified in Spain than in France);13 of these families have their most ancient representatives within these ambers.A similar study had previously only been performed on Lebanese ambers(Barremian in age and Gondwanan in origin),recording 36 coleopteran families.Few lists of taxa were available for Myanmar(Burmese) amber(early Cenomanian in age and Laurasian in origin).Coleopteran families found in Cretaceous ambers share with their modern relatives mainly saproxylic and detritivorous habits in the larval or adult stages,rather than wood-boring behavior.Fifteen of the coleopteran families occur in both the Lebanese and Spanish ambers;while only five are present in both Spanish and French.Considering the paleogeographic proximity and similarity of age of the Spanish and French ambers,the small number of taxa found in common at both areas is surprising.The ancient origin for the Lebanese and Spanish ambers,the paleogeography(including some barriers for terrestrial biota) and the local paleohabitats are factors that may explain the dissimilarity with the French specimens.Wildfires are believed to be a more likely cause of resin production during the Cretaceous than infestation by beetles.Current knowledge of the beetle species found in the Cretaceous ambers is introduced.  相似文献   

16.
The Lajeado Group in the Ribeira Belt,southeastern Brazil,corresponds to an open-sea carbonate platform,comprised of seven overlapping siliciclastic and carbonatic formations,intruded in its upper portion by the Apiai Gabbro.These rocks have a Neoproterozoic tectonometamorphic overprint related to arc magmatism and the Brasiliano collisional orogeny.Geochronological constraints are given by new UPb SHRIMP and LA-ICP-MS data for Lajeado Group detrital zircons and for magmatic zircons from the Apiai Gabbro.The youngest detrital zircons in the Lajeado Group are 1400-1200 Ma,and constrain its maximum age of deposition to be 1200 Ma,whereas the 877 ± 8 Ma age for magmatic zircons in the Apiai Gabbro give the minimum age.Detritus source areas are mainly Paleoproterozoic(2200-1800 Ma)with some Archean and Mesoproterozoic contribution(1500-1200 Ma),with distal or tectonic stable cratonic character.The Lajeado Group should be a Stenian-Tonian carbonate platform passive margin of a continent at this time,namely the Columbia/Nuna or the Rodinia.The Apiai Gabbro displays similar age to other intrusive basic rocks in the Lajeado and Itaiacoca groups and represents tholeiitic MORB-like magmatism that we relate to the initial break-up of a Mesoproterozoic continent and the formation of the Brasiliano oceans.  相似文献   

17.
http://www.sciencedirect.com/science/article/pii/S1674987115000882   总被引：1，自引：0，他引：1  
A detailed vibrational Raman-IR spectroscopic and diffractional analyses have been performed on basalts from two locations from Tenerife Island:(1) the Arenas Negras volcano which belongs to the historical eruption not showing visible alteration and(2) Pillow Lavas zone from Anaga Massif which shows a clearly fluid-rock interaction caused by submarine alteration.These places have been extensively studied due to its similarity with the surface of Mars.The analysis is based on the mineral detection of selected samples by a Micro-Raman study of the materials.The complementary techniques have confirmed the mineralogy detected by the Raman measurement.The results show a volcanic environment behavior with primary phases like olivine,pyroxene,and feldspar/plagioclase.Moreover,the presence of accessory minerals or secondary mineralization like phosphate,iron oxides,zeolite or carbonates shows the alteration processes on each outcrop.The variation in the crystallinity and amorphous phases is related to fluid-rock interaction caused by hydrothermal episodes and external weathering processes,which shows several analogies with the ancient volcanic activity from Mars.  相似文献   

18.
In the present paper lignites from the Cambay basin have been studied for their hydrocarbon potential.The samples were collected from three lignite fieldse Vastan, Rajpardi and Tadkeshwar, and were investigated by petrography, chemical analyses and Rock-Eval pyrolysis. The results are well comparable with the empirically derived values. The study reveals that these ‘low rank C' lignites are exceedingly rich in reactive macerals(huminite t liptinite) while inertinite occurs in low concentration. These high volatile lignites generally have low ash yield except in few sections. The Rock-Eval data indicates the dominance of kerogen type-III with a little bit of type-II. The study reveals that the lignites of Vastan(lower and upper seams) and Tadkeshwar upper seam are more gas-prone while Rajpardi and Tadkeshwar lower seams are oil-prone. Further, the fixed hydrocarbons are several times higher than the free hydrocarbons. The relation between TOC and fixed hydrocarbon indicates that these lignites are excellent source rock for hydrocarbon which could be obtained mainly through thermal cracking. The empirically derived values reveal a high conversion(94e96%) and high oil yield(64e66%) for these lignites.  相似文献   

19.
U-Pb analyses were carried out on detrital zircon grains from major river-mouth sediments draining South Korea to infer provenance characteristics and the crustal growth history of the southern Korean Peninsula, using a laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS). The Korean Peninsula is located in the East Asian continental margin and mainly comprises three Precambrian massifs and two metamorphic belts in between them. We obtained 515 concordant to slightly discordant zircon ages ranging from ca. 3566 to ca. 48 Ma. Regardless of river-mouth location, predominance of Mesozoic(249e79 Ma) and Paleoproterozoic(2491e1691 Ma) ages with subordinate Archean ages indicates that the zircon ages reflect present exposures of plutonic/metamorphic rocks in the drainage basins of the South Korean rivers and the crustal growth of the southern Korean Peninsula was focused in these two periods. Comparison of detrital zircon-age data between the North and South Korean river sediments reveals that the Paleoproterozoic zircon age distributions of both regions are nearly identical,while the Neoproterozoice Paleozoic ages exist and the Mesozoic ages are dominant in southern Korean Peninsula. This result suggests that Precambrian terrains in Korea record the similar pre-Mesozoic magmatic history and that the influence of Mesozoic magmatism was mainly focused in South Korea.  相似文献   

20.
The Semail ophiolite of Oman and the United Arab Emirates(UAE) provides the best preserved large slice of oceanic lithosphere exposed on the continental crust,and offers unique opportunities to study processes of ocean crust formation,subduction initiation and obduction.Metamorphic rocks exposed in the eastern UAE have traditionally been interpreted as a metamorphic sole to the Semail ophiolite.However,there has been some debate over the possibility that the exposures contain components of older Arabian continental crust.To help answer this question,presented here are new zircon and rutile U-Pb geochronological data from various units of the metamorphic rocks.Zircon was absent in most samples.Those that yielded zircon and rutile provide dominant single age populations that are 95-93 Ma,partially overlapping with the known age of oceanic crust formation(96.5-94.5 Ma),and partially overlapping with cooling ages of the metamorphic rocks(95-90 Ma).The data are interpreted as dating high-grade metamorphism during subduction burial of the sediments into hot mantle lithosphere,and rapid cooling during their subsequent exhumation.A few discordant zircon ages,interpreted as late Neoproterozoic and younger,represent minor detrital input from the continent.No evidence is found in favour of the existence of older Arabian continental crust within the metamorphic rocks of the UAE.  相似文献   

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