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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. Source

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. Source

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. Source

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. Source

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. Source

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