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Shao J.A.,Peking University | Tang K.D.,Shenyang Institute of Geology and Mineral Resources | He G.Q.,Peking University
Acta Petrologica Sinica | Year: 2014

In contrast of the recently promoted view of point that there was a Paleo-Asian Ocean plate subducting towards the continents on its north and south sides in the Early Permian, the present authors prefer a different understanding. Through compilation of a tectono-palaeogeographic map of the concerned area based on all the facts about the sedimentary petrography, palaeogeography, biologic association, detrital materials of terrigenous origin, and hydrocarbon source rock in the Early Permian, it seems to the authors that what existed between the Central Asian massif and the North China Craton was a Late Paleozoic epicontinental sea and rift instead of a large-scale ocean experiencing spreading and closure. Our studies reveal the actual evolution of the concerned area in the Early Permian. In the early stage, the sedimentary process accompanying strong eruption of basic-acidic volcanic rocks is controlled by three syn-sedimentary rifts with near EW strike, with the thicknesses of sedimentary rocks of the littoral-shallow marine facies and volcanic rocks being > 8000m, > 5000m, and 2900m separately from north to south. The view point of sedimentation being controlled by deep faults is supported by the deep geophysical data. The sedimental rocks of the early stage are mainly consisted of coarse clastic rocks in which the greywackes and arkoses with lower maturity are distributed widely. Besides, the denudation areas are composed of neogenic continental crusts and the proximal sediments are characterized by quick-accumulation, as seen from compositions and origins of the terrigenous detrital materials. In the later stage, the sedimentary rocks appear as grey blocks of carbonaceous siltstone and slates interlaced with limestone lenses, in which the dark marine mudstones with increased organic abundance form hydrocarbon source rocks (R0 =1.01% ∼ 3. 67%) in prodeltas, shallow seas, and bathyal regions. The resulted sedimentary association reflect processes in which maturity of the continental crust become increased, the tectonic activities declined, and the epicontinental sea shrined. The Early Permian palaeocoenosis is mainly consisted of Brachiopods, corals, fusulinidss and bryozoan formed in a littoral-shallow sea environment, among which the corals can only live in clear and warm littoral-shallow seas just outside the low-water lines and not deeper than 50 meters. Occurrence of phytoclasts also reflects the settings being paralic facies. By the end of the Early Permian, the palaeocoenos has become mixotrophic, with its main part consisted of the kind of the Arctic region such as Spiriferella everywhere and mixed with such elements of polytherm as Richtofenia, Enteletes, etc. Such a phenomenon indicates that collision of the two plates has already occurred before and no ocean basin exists in the Early Permian. Radiolarians could not be as the definite evidence of existence of an ocean crust because radiolarians may exist in waters of different depths, as shown by coexistence of fossils of the radiolarians, ammonoites, gastropods, bivalves, and even plants in the Zhesi Formation in Maodeng area. The magmatism of the area is featured as that the bimodal volcanic rocks of the Early Permian Dashizhai Formation (281 ∼ 270Ma) have their basaltic magma coming from a depleted mantle and mixed with crustal matters when uplifting (ISr = 0. 7024 ∼ 0. 7069, εNd (t) =-3. 6 ∼ +7. 9), and that the synchronous alkaline granites and large basic dykes (299 ∼263Ma) are distributed in large grabens as belts, and have Sr-Nd isotopic features of mantle source rocks: εNd(t) =3.0∼5.4, ISr = 0. 7053 ∼ 0. 7088, ε Hf(t) =-2.7∼2.4. The regional tectonic evolution of the area is characterized by that its magmatism is consistent with that of the synmagmatic rifting type (bimodal volcanic rocks and peralkalic plutonic rocks) in Mongolia, belonging to magmatism controlled by rifts in extending settings rather than one related with subduction in a compressive regime. The Late Palaeozoic Baolige rift in the concerned area is connected with Gebi-Tianshan rift in southern Mongolia to consistent so large-thousands of kilometers-a continental rift, clearly showing that the Central-Asia orogenic zone has already entered a new continental-crust evolution stage since Carboniferous-Permian under the extended tectonic setting.


Shao J.,Peking University | Tang K.,Shenyang Institute of Geology and Mineral Resources
Acta Petrologica Sinica | Year: 2015

A continental margin has been composed and transformed on the Asian continent as a unitary continental lithosphère plate since the Mesozoic. The Northeast Asia ocean-continent transitional zone is identified by the authors, according to the viewpoint of tectonostratigraphie terrane, as consisted of seven belts with different characters of biostratigraphy and collision orogenes: (1) the east margin of the North China Craton reconstructed by Tanlu fault system; (2) accretion zone I dominated by nearly terrigenous materials; (3) accretion zone II dominated by heterologous mélanges; (4) accretion zone III of the New Siberian-Chukotka-Alaska continental margin; (5) the volcano-plutonic zone of the continental margin; (6) accretion zone IV (the Koryak accretion zone); and (7) accretion zone V (Kamchatka-Sakhalin-Northeastern Japan accretion zone). Among those the Chukotka sea-East Sikhote-Alin volcano-plutonic zone, which is mainly of the Late Cretaceous, especially marks beginning of normal subduction of the Pacific plate and subsequent arc-magmatic activities. Early in the Late Triassic-Early Cretaceous, a large number of terranes migrated northward and joined together obliquely to the continental margin in a sinistral transcurrent faulting of the active transform margin. The evolution of the relative movements between the ocean and the continent in the Northeast Asia continental margin is clearly demonstrated by such a spatiotemporal pattern with its special zonation and periodicity. This study is used, jointly with recent results in related disciplines, to discussions of the relation between the Mesozoic magmatism in the eastern China with subduction of the Pacific plate. It is concluded that the peak period of the large-scale magmatism in the Late Jurassic-Early Cretaceous is in coincidence with period in which the ocean-continent transition zone is active and terranes accretion occurs in the Northeast Asia continental margin. As mentioned in this work, however, the normal subduction of Pacific Plate occurs in the end of the Early Cretaceous to the Late Cretaceous, when the large-scale magmatism has ended. It is, therefore, difficult to link the magmatic activities in eastern China with the subduction of the Pacific plate. Taking the Da Hinggan Mts.composed of young continental crust as an example, the authors suggest that the source characteristics of eastern China magmatism and its intrusive space are controlled by two geological processes in different depths in the Late Jurassic-Early Cretaceous simultaneously, i. e. the upwelling of deep diapers of asthenosphere and the deformation of the middle-upper crust subjected to shear strike-slip between the ocean and the continent.


Yang X.-J.,CAS Nanjing Institute of Geology and Palaeontology | Wang Y.-D.,CAS Nanjing Institute of Geology and Palaeontology | Zhang W.,Shenyang Institute of Geology and Mineral Resources
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

The Chinese Early Cretaceous flora was divided phytogeographically into the Northern Floristic Province and the Southern Floristic Province. The "temperate-wet vegetations" and "tropic-subtropic xeric vegetations" were proposed to represent the two different vegetation types. About 52 species of fossil woods belonging to Cycadophytes (2 species), Ginkgoales (1 species) and coniferales (49 species) have been discovered in the two floristic provinces, mainly from the Northeast China. The biodiversity and anatomical characteristics, especially the growth ring feature analysis of fossil woods indicated climatic conditions with seasonal variation in both the Northern and Southern Floristic Provinces during the Early Cretaceous. It suggests that a tropic to sub-tropic semi-arid climate might dominate over southern China, while warm or temperate, and wet climate prevailed in northern China during the Early Cretaceous. The wood evidence is in accordance with that of the leaf fossils collected from the corresponding formations of the Early Cretaceous in China. © 2013 Elsevier B.V.


Qin J.-F.,Northwest University, China | Lai S.-C.,Northwest University, China | Grapes R.,Korea University | Diwu C.-R.,Northwest University, China | And 2 more authors.
Lithos | Year: 2010

The origin of high-Mg adakitic granitoids in collisional orogens can provide important information about the nature of the lower crust and upper mantle during the orogenic process. Late-Triassic high-Mg adakitic granite and its mafic enclaves from the Dongjiangkou area, the Qinling orogenic belt, central China, were derived by partial melting of subducted continental crust and underwent interaction with the overlying mantle wedge peridotite. Adakitic affinity of the different facies of the Dongjiangkou granite body are: high Sr, Ba, high La/Yb and Sr/Y, low Y,Yb, Yb/Lu and Dy/Yb, and no significant Eu anomalies, suggesting amphibole+garnet and plagioclase-free restite in their source region. Evolved Sr-Nd-Pb isotopic compositions [(87Sr/86Sr)i=0.7050 to 0.7055,εNd(t)=-6.6 to -3.3; (206Pb/204Pb)i=17.599 to 17.799, (207Pb/204Pb)i=15.507 to 15.526, (208Pb/204Pb)i=37.775 to 37.795] and high K2O, Rb, together with a large variation in zircon Hf isotopic composition (εHf(t)=-9.8 to +5.0), suggest that the granite was derived from reworking of the ancient lower continental crust. CaO, P2O5, K2O/Na2O, Cr, Ni, Nb/Ta, Rb/Sr and Y increase, and SiO2, Sr/Y and Eu/Eu* decrease with increasing MgO, consistent with interaction of primitive adakitic melt and overlying mantle peridotite. Zircons separated from the host granites have U-Pb concordia ages of 214±2Ma to 222±2Ma, compatible with exhumation ages of Triassic UHP metamorphic rocks in the Dabie orogenic belt. Mafic microgranular enclaves and mafic dykes associated with the granite have identical zircon U-Pb ages of 220Ma, and are characterized by lower SiO2, high TiO2, Mg# and similar evolved Sr-Nd-Pb isotopic composition. Zircons from mafic microgranular enclaves (MMEs) and mafic dykes also show a large variation in Hf isotopic composition with εHf(t) between -11.3 and +11.3. It is inferred that they were formed by partial melting of enriched mantle lithosphere and contaminated by the host adakitic granite magma.In combination with the regional geology, high-Mg# adakitic granitoid rocks in the Dongjiangkou area are considered to have resulted from interaction between subducted Yangtze continental crust and the overlying mantle wedge. Triassic continental collision caused detachment of the Yangtze continental lithosphere subducted beneath the North China Craton, at ca. 220. Ma causing asthenosphere upwelling and exhumation of the continental crust. Triassic clockwise rotation of the Yangtze Craton caused extension in the Dabie area which led to rapid exhumation of the subducted continental lithosphere, while compression in the Qinling area and high-P partial melting (amphibole ± garnet stability field) of the subducted continental crust produced adakitic granitic magma that reacted with peridotite to form Mg-rich hybrid magma. © 2010.


Qin J.-F.,Northwest University, China | Lai S.-C.,Northwest University, China | Li Y.-F.,Shenyang Institute of Geology and Mineral Resources
Gondwana Research | Year: 2013

Detailed petrology and zircon U-Pb dating data indicate that the Wulong pluton is a zoned granitic intrusive, formed from successive increments of magmas. An age range of at least 30Ma is recorded from the 225-235Ma quartz diorite on the pluton margin, the ca. 218Ma granodiorite in the intermediate zone, and the ca. 207Ma monzogranite at the pluton center. All the granitoids display evolved Sr-Nd-Pb isotopic compositions, with 87Sr/86Sr(i) of 0.7044-0.7062, unradiogenic Nd (εNd(t) values of -6.1 to -3.0, Nd model ages of 1.1-1.3Ga, and moderately radiogenic Pb compositions (206Pb/204Pb(i)=17.500-17.872, 207Pb/204Pb(i)=15.513-15.549, 208Pb/204Pb(i)=37.743-38.001), in combination with variations in zircon Hf isotopic compositions (with εHf(t) values in each stage span 12 units) and the Hf isotopic model ages of 800-1600Ma. These features suggest that the granitoids might have been derived from the reworking of an old lower crust, mixed with Paleozoic and Proterozoic materials. The rocks also display an adakitic affinity with Sr (479-973ppm), high Sr/Y ratios (mostly >60) and negligible Eu anomalies (Eu/Eu*=0.78-0.97) but low Rb/Sr ratios, low Y (4.6-17ppm), HREE (Yb=0.95-1.7ppm), Yb/Lu (6-7) and Dy/Yb (1.9-2.4) ratios, suggesting the absence of plagioclase and presence of garnet+amphibole in their residue. Considering a large gap among their crystallization ages, we propose that the geochemical evolution from pluton margin to center was controlled mainly by melting conditions and source compositions rather than fractional crystallization. Mafic enclaves that were hosted in the quartz diorite and granodiorite are mainly syenogabbroic to syenodioritic in composition, and are metaluminous and enriched in LREE and LILEs, but are depleted in HFSE, and display an evolved Sr-Nd-Pb isotopic composition, suggesting that they may have been derived from the partial melting of an enriched mantle lithosphere, which was metasomatized by adakitic melts and fluids from a subducted continental crust.In combination with the results of the Triassic ultra-high pressure metamorphic rocks in the Dabie orogenic belt, we apply a model involving the exhumation of subducted continental crust to explain the formation of the Wulong pluton. At the first stage, a dense and refractory mafic lower crust that was trapped at mantle depth by continental subduction witnessed melting under high temperature conditions to produce the quartz diorite magma, characterized by low SiO2 (60.65-63.98wt.%) and high TiO2 (0.39-0.86wt.%). The magma subsequently interacted with mantle peridotite, leading to high Mg# (57-67) and the metasomatism of the overriding mantle wedge. At the second stage, an asthenosphere upwelling that was probably caused by slab break-off at ca. 220Ma melted the enriched sub-continental lithospheric mantle (SCLM) to produce mafic magmas, represented by the mafic enclaves that are hosted in the quartz and granodiorite, resulting in the partial melting of the shallower subducted crust, and generating the granodiorite that is distinguished by high SiO2 (69.16-70.82wt.%), high Al2O3 (15.33-16.22wt.%) and A/CNK values (mostly >1.05). At the third stage, the final collapse of the Triassic Qinling-Dabie Orogenic Belt at ca. 215-205Ma caused extensive partial melting of the thickened orogenic lower crust to produce the monzogranite, which is characterized by high SiO2 (67.68-70.29wt.%), low TiO2 (mostly <0.35wt.%) and high Sr/Y ratios of 86-151. © 2013.


Qin J.-F.,Northwest University, China | Lai S.-C.,Northwest University, China | Diwu C.-R.,Northwest University, China | Ju Y.-J.,Northwest University, China | Li Y.-F.,Shenyang Institute of Geology and Mineral Resources
Contributions to Mineralogy and Petrology | Year: 2010

Petrogenesis of high Mg# adakitic rocks in intracontinental settings is still a matter of debate. This paper reports major and trace element, whole-rock Sr-Nd isotope, zircon U-Pb and Hf isotope data for a suite of adakitic monzogranite and its mafic microgranular enclaves (MMEs) at Yangba in the northwestern margin of the South China Block. These geochemical data suggest that magma mixing between felsic adakitic magma derived from thickened lower continental crust and mafic magma derived from subcontinental lithospheric mantle (SCLM) may account for the origin of high Mg# adakitic rocks in the intracontinental setting. The host monzogranite and MMEs from the Yangba pluton have zircon U-Pb ages of 207 ± 2 and 208 ± 2 Ma, respectively. The MMEs show igneous textures and contain abundant acicular apatite that suggests quenching process. Their trace element and evolved Sr-Nd isotopic compositions [( 87Sr/ 86Sr) i = 0.707069-0.707138, and ε Nd(t) = -6.5] indicate an origin from SCLM. Some zircon grains from the MMEs have positive ε Hf(t) values of 2.3-8.2 with single-stage Hf model ages of 531-764 Ma. Thus, the MMEs would be derived from partial melts of the Neoproterozoic SCLM that formed during rift magmatism in response to breakup of supercontinent Rodinia, and experience subsequent fractional crystallization and magma mixing process. The host monzogranite exhibits typical geochemical characteristics of adakite, i.e., high La/Yb and Sr/Y ratios, low contents of Y (9.5-14.5 ppm) and Yb, no significant Eu anomalies (Eu/Eu* = 0.81-0.90), suggesting that garnet was stable in their source during partial melting. Its evolved Sr-Nd isotopic compositions [( 87Sr/ 86Sr) i = 0.7041-0.7061, and ε Nd(t) = -3.1 to -4.3] and high contents of K 2O (3.22-3.84%) and Th (13.7-19.0 ppm) clearly indicate an origin from the continental crust. In addition, its high Mg# (51-55), Cr and Ni contents may result from mixing with the SCLM-derived mafic magma. Most of the zircon grains from the adakitic monzogranite show negative ε Hf(t) values of -9.4 to -0.1 with two-stage Hf model ages of 1,043-1,517 Ma; some zircon grains display positive ε Hf(t) of 0.1-3.9 with single-stage Hf ages of 704-856 Ma. These indicate that the source region of adakitic monzogranite contains the Neoproterozoic juvenile crust that has the positive ε Hf(t) values in the Triassic. Thus, the high-Mg adakitic granites in the intracontinental setting would form by mixing between the crustal-derived adakitic magma and the SCLM-derived mafic magma. The mafic and adakitic magmas were generated coevally at Late Triassic, temporally consistent with the exhumation of deeply subducted continental crust in the northern margin of the South China Block. This bimodal magmatism postdates slab breakoff at mantle depths and therefore is suggested as a geodynamic response to lithospheric extension subsequent to the continental collision between the South China and North China Blocks. © Springer-Verlag 2009.


Hu Z.G.,Shenyang Institute of Geology and Mineral Resources
Advanced Materials Research | Year: 2013

The experimental sample consists of talc, magnesite and a little quartz, the grade of talc is 80%. By the floatation flowsheet of rougher and two times cleaner, and middling after regrinding return to rougher, the high grade talc concentrate can be obtained. The concentrate contains talc 95.67% (SiO2 61.68%). Talc recovery rate is 89.43%. By this way, the output of high class talc product is increased and talc resources are exploited very well. © (2013) Trans Tech Publications, Switzerland.


Zhuang F.,Shenyang Ligong University | Shu L.,Shenyang Institute of Geology and Mineral Resources
Proceedings - 3rd International Conference on Intelligent Networks and Intelligent Systems, ICINIS 2010 | Year: 2010

According to the deficiency of traditional soft-starter control accuracy caused by unsuitable initial value of PID or value shifting for disturbance of environment, a strategy of applying fuzzy PID instead of traditional PID into control process of the soft-starter is put forward in this paper. The fuzzy PID theory, soft-start theory are introduced. At last, electric motors' soft-start, smooth running and soft-stop is realized by computer simulation, and the result shows the truth and validity of this strategy. © 2010 IEEE.


Zhang Y.-P.,Shenyang Institute of Geology and Mineral Resources
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2011

Placing the main structural features of the Northeast China into Northeast Asia area, to analyze the tectonic setting, the Northeast Asia Late Mesozoic-Paleogene tectonic evolution can be divided into three periods: 1) the Middle-Late Jurassic, extension of the Tethys Ocean and the collision between North America and ancient Eurasia continental plate, resulting in Mongolia-Okhotsk Gulf closure and the formation of large-scale deep-level thrust in Mongolia and the North China block, and a long-range stacking effect in southern Mongolia and the northern margin of the North China block. 2) Late Jurassic-Early Cretaceous, the combined effects of Tethys Ocean, the Eurasian continental plate and the Paleo-Pacific tectonic domain (including the old Pacific or Izanaqi plate), resulted in continental crust creeping eastward, stretching and block breaking activities, which were, accompanied by development of a small rift basin group and metamorphic core complexes. 3) Early Cretaceous (Late Albian)-Neogene (Miocene), the combined effects of the tectonic domain between Tethys (later including the Indian plate), the Pacific tectonic domain (including Izanaqi plate) and Eurasia continental plate resulted in Izanaqi ocean disappeared, the collision between the Okhotsk Oceanic micro-plate and the Eurasian continent, and the formations of the Eurasian continental margin volcanic belt and the depression basin on the continental margin. During 100-60 Ma, the interaction between the Pacific tectonic domain (including Izanaqi plate) and the Eurasian continent, had a major influence on the eastern edge of the Eurasian continent and caused continental lithospheric-crust thinning, the change of mantle type and a strong deep magmatic activity. Meanwhile, producing a series of the surface block effects related to the continental margin faulted block activities.


Zhang Y.-P.,Shenyang Institute of Geology and Mineral Resources | Li J.-C.,Shenyang Institute of Geology and Mineral Resources
Geology in China | Year: 2010

A comparative study of geotectonic cycles and evolution characteristics of the tectonic domain from the Adantic Ocean to Paleo -Asia Ocean on the global scale is beneficial to understanding the regional tectonic evolution of the giant tectonic domain. The establishment of the concept of "dynamic behaviors" of the attributes of paleocontinents tectonic units and the correlation analysis of the composite orogenic area and its neighboring tectonic units have revealed that the formation and development of the North China foreland basin were closely related to the tectonic evolutionary process of the neighboring composite orogenic area. In North China and its northward areas, Late Paleozoic -Early Mesozoic tectonic framework has the following features:1)In the Mongolian-Da Hinggan composite orogenic area, Paleozoic fold belts were interwoven with intermediate massifs, leading to the development of the epicontinental sea basin and the aulacogen and superposed basins during the Carboniferous-Permian period and the inter-mountainous basin during the Triassic period, based on the fold belt of the earlier stage. 2)The foreland basin in North China was developed synchronically with the tectonic evolution process of the northern composite orogenic area and formed the marine facies, marine - continental interaction sediments on the old land during the Carboniferous period and the continental facies sediments during the Permian-Middle Triassic period, characterized by red bed and gypsum salt in local areas. 3)The "tectonomagmatic activation belt" on the North China continental margin in the Late Paleozoic?Early Mesozoic period was the southernmost tectonic unit of the Mongolian-Da Hinggan composite orogenic area.

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