Knowledge of the characteristics of the extensive late Palaeozoic volcanic rocks across the northern China-Mongolia tract is essential for understanding the tectonic evolution and continental crustal ...growth in the Central Asian Orogenic Belt. This geochronological and geochemical study documents the Early Permian mafic and felsic volcanic rocks from northwestern Inner Mongolia. The mafic rocks form two magma series with distinctive geochemical characteristics; one showing large ion lithophile element (LILE) enrichment relative to high field strength elements (HFSE) and an asthenosphere-like Sr-Nd-Pb isotopic signature, and the other featuring an elevated Nb and lithospheric isotopic signature. This result indicates that two mantle source components are involved in the magma generation: the subduction-related metasomatized asthenosphere and lithospheric mantle. The felsic rocks show strong enrichment of LILE and light REE, depletion in HFSE, and indistinguishable isotopic compositions from mafic ones. Such features are consistent with partial melts of mixed sources composed of predominant juvenile basaltic underplates and minor ancient crustal materials. These mafic and felsic rocks constitute a post-subduction high-potassium calc-alkaline magmatic suite possibly under a geodynamic regime of Palaeo-Asian Ocean slab breakoff. This regime not only provides a feasible trigger for the flipping of subduction polarity in the Solonker suture zone, but also presents a favourable venue for vertical continental crustal growth.
•Qinling Orogen was built through three-episode collision between the NCB and SCB.•Neoproterozoic southward subduction and accretion took place along the LLF and KPS.•Paleozoic northward subduction ...and accretion occurred along the Shangdan suture.•Late Triassic accretion occurred along the Mianlue suture between the SQB and SCB.
The Qinling Orogen was built through collision between the North China and South China Blocks. Previous detailed geological, geochemical and geochronological investigations revealed that the mountain range can be divided into four tectonic units with distinct tectono-lithostratigraphy, which are, from north to south, the southern sector of the North China Block, North Qinling Belt, South Qinling Belt and northern sector of the South China Block, separated by the Kuanping, Shangdan and Mianlue sutures. According to the petrology, geochemistry and geochronology of ophiolitic mélanges and related magmatic rocks, as well as the features of sedimentary units, we think that the North China Block, the North Qinling Belt and the South China Block were originally independent continental units while the South Qinling Belt had been the northern part of the South China Block. These units experienced three episodes of accretionary tectonic processes and amalgamation from south to north.
The Neoproterozoic accretion took place along the Luonan-Luanchuan Fault and Kuanping ophiolitic mélange belt as a result of southward subduction and subsequent collision between the North Qinling and North China Blocks during ca. 1.0–0.8Ga related to the formation of the supercontinent of Rodinia. The Paleozoic accretion occurred along the Shangdan suture resulted from northward subduction of oceanic lithosphere in the Early Paleozoic and subsequent continental subduction in the Late Paleozoic. Late Triassic accretion took place along the Mianlue suture between the South Qinling and South China Blocks due to northward subduction of the Mianlue oceanic lithosphere during the Permian–Early Triassic and subsequent collision in the Late Triassic. After the Late Triassic collision along the Mianlue suture the whole Qinling Mountain range entered the phase of intense intracontinental deformation.
Laser ablation inductively coupled plasma mass spectrometry zircon U-Pb dating and geochemical data document the Early Devonian Sandaogou alkaline complex (409 Ma) from the northern margin of the ...North China craton. The rock suite includes pyroxene syenite, quartz syenite and monzonite. These rocks exhibit high contents of K2O (5-13 wt%), strong enrichments in large ion lithophile elements and light REE, slightly negative Eu anomalies, and pronounced depletions in high field strength elements. They are characterized by moderate 87Sr/86Sri ratios of 0.7052-0.7071, low εNd(t) values of -12.7 to -17.9 and zircon εHf(t) values from -27.8 to -32.3. These geochemical features and quantitative isotopic modelling suggest that they might have been formed through simultaneous fractional crystallization and lower crustal assimilation of a metasomatized mantle-derived alkali basaltic magma. These trachytic rocks, together with the Middle Devonian alkaline rocks and mafic-ultramafic complex from neighbouring regions, constitute a linear post-collisional magmatic belt along the northern North China craton, possibly formed under a tectonic regime of slab breakoff. They serve not only as a magmatic milestone for marking the termination of Early Palaeozoic orogenic cycle around the northern North China craton, but also as a spatial tracer for locating the position of the potential ancient slab breakoff at the surface.
•Kuanping ophiolite indicates an ocean between North Qinling and North China Blocks.•Zircon U–Pb age of 1445±60Ma for N-MORB constrains the age of Kuanping ophiolite.•Southward subduction of Kuanping ...Ocean beneath North Qinling island-arc terrain.•North Qinling amalgamated to North China Block in Neoproterozoic due to subduction.
The Proterozoic tectonic evolution of the Qinling Orogenic Belt is a key to understanding the convergent processes between the North China and South China Blocks. The widely exposed Kuanping ophiolite melange between the North Qinling Terrain and the North China Block provides important constraints on the Meso-Neoproterozoic tectonic evolutionary processes between the North Qinling Terrain and North China Block. Detailed geological mapping reveal that the Kuanping ophiolite melange consists of an ophiolite and a meta-sedimentary unit. According to our new geochemical investigations, the ophiolite unit can be briefly divided into two groups: (1) N-MORB and (2) E-MORB. The former is characterized by depletion in light rare earth elements, large-ion lithophile elements, and non-differentiation in high field strength elements. The latter shows slight enrichment in light rare earth elements, large-ion lithophile elements, and minor differentiation in high field strength elements. Accordingly, it is inferred that the Kuanping ophiolite likely represents remnants of an oceanic crust (named as Kuanping Ocean) between the North Qinling Terrain and the North China Block. One metamorphosed N-MORB sample from the Kuanping ophiolite was selected for LA-ICPMS zircon U–Pb dating, which displays an age of 1445±60Ma, probably represents the formation time of the Kuanping Ocean. Integrated with the regional geological, geochemical and geochronological data, we propose that the North Qinling Terrain amalgamated to the North China Block after a southward subduction of a Mesoproterozoic ocean represented by the Kuanping ophiolite.
Lower crustal processes played a key role during the destruction of the North China Craton. Petrological and geochemical analyses were performed on the granulite and pyroxenite xenoliths in the late ...Cretaceous basalt from Western Liaoning of the North China Craton to investigate the nature and evolution of the lower crust during the Mesozoic. The granulite xenoliths are predominantly intermediate–silicic granulite with subordinate basic granulite. The intermediate–silicic granulites exhibit relatively low Mg# values (0.46–0.63), positive Eu, Pb and Sr anomalies, a large range of Sr–Nd–Pb isotopic compositions and negative correlations between
87
Sr/
86
Sr and
143
Nd/
144
Nd ratios. The sample HS20-19 shows the lowest SiO
2
and MgO contents than that of other intermediate–silicic granulites. Generally, the intermediate–silicic granulites have mineralogical and whole-rock geochemical affinities to the Archean granulite terrains of the North China Craton. In contrast, the basic granulite has a higher Mg# value (0.73), and depletions of La and Sr, but similar Sr–Nd–Pb isotopic compositions to the intermediate–silicic granulite xenoliths and terrains. These observations indicate that most intermediate–silicic granulites represent modified Archean lower crust by underplated magma, whereas HS20-19 and the basic granulite can be explained as restites left after partial melting of the ancient lower crust. The pyroxenite xenoliths exhibit a cumulate texture, variable Mg# values (85.9–88.6), and convex-upward rare-earth element patterns with high-field-strength elements depletions in the clinopyroxene.
87
Sr/
86
Sr ratios (0.7036–0.7063) are negatively correlated with Mg# values and positively correlated with Ba and Pb contents in the clinopyroxene. These observations imply that the pyroxenite xenoliths originated as cumulates from an asthenospheric magma and were contaminated by the lower crust at the crust–mantle transition. All xenoliths experienced decompression event induced by the lithosphere extension in the early Cretaceous. Combined with the previous studies on the Mesozoic volcanic rocks from the Western Liaoning, we conclude that the continuous magmatic underplating not only formed the pyroxenite cumulates but also provided heat for remelting of the ancient lower crust, resulting in the formation of voluminous intermediate–silicic volcanic rocks during the Mesozoic. These processes led to the transformations of the Archean lower crust beneath the Western Liaoning and the entire North China Craton.
As environmental protection policies become more stringent, lower and lower NOx emission targets are required. Accurate NOx concentration prediction model plays an important role in low NOx emission ...control in power stations. This study aims to accurately predict the future sequence of NOx emission in the next horizon. Through the analysis on formation mechanism of NOx and the reaction mechanism of SCR reactor, a sequence to sequence dynamic prediction model is proposed, which can fit multivariable coupling, nonlinear and large delay systems. In particular, considering the different effects of multivariate on NOx, a new attention mechanism is necessary to be put forward. A large amount of historical data is used to fully train this dynamic prediction model. The results show that, the prediction accuracy of the NOx concentration and fluctuation trend based on this model is superior to comparison algorithms. Furthermore, some interesting features of this prediction model, such as error accumulation and bidirectional encoder, are also discussed in depth.
•The prediction of NOx is a sequence in the next horizon, that can reflect the trend of fluctuation.•Variable selection attention mechanism is designed, considering the different effects of multivariate on NOx emission.•Maximal Information Coefficient-based feature selection is used for selecting optimal inputs.•A modeling method for multivariable nonlinear large delay systems with attention mechanism is proposed.
Destruction of the North China Craton Zhu, RiXiang; Xu, YiGang; Zhu, Guang ...
Science China. Earth sciences,
10/2012, Letnik:
55, Številka:
10
Journal Article
Recenzirano
A National Science Foundation of China （NSFC） major research project, Destruction of the North China Craton （NCC）, has been carried out in the past few years by Chinese scientists through an in-depth ...and systematic observations, experiments and theoretical analyses, with an emphasis on the spatio-temporal distribution of the NCC destruction, the structure of deep earth and shallow geological records of the craton evolution, the mechanism and dynamics of the craton destruction. From this work the foUowing conclusions can be drawn： （1） Significant spatial heterogeneity exists in the NCC lithospheric thickness and crustal structure, which constrains the scope of the NCC destruction. （2） The nature of the Paleozoic, Mesozoic and Cenozoic sub-continental lithospheric mantle （CLM） underneath the NCC is characterized in detail. In terms of water content, the late Mesozoic CLM was rich in water, but Cenozoic CLM was highly water deficient. （3） The correlation between magmatism and surface geological response confirms that the geological and tectonic evolution is governed by cratonic destruction processes. （4） Pacific subduction is the main dynamic factor that triggered the destruction of the NCC, which highlights the role of cratonic destruction in plate tectonics.
The lower crust beneath the North China Craton (NCC) was transformed during the craton destruction in the Mesozoic, however, the transformation processes are yet to be fully understood. Compositional ...and geochronological variations of granulite and pyroxenite xenoliths provided insights into the nature of the lower crust before and after the craton destruction. In this study, we summarized the latest results of geochemistry and zircon geochronology coupled with Hf-O isotopes from granulite and pyroxenite xenoliths hosted by Phanerozoic igneous rocks in NCC. Comparing previous studies on the granulite terranes and adakitic rocks of NCC, we aim to discuss the destruction processes of lower crust beneath the NCC. The granulite and pyroxenite xenoliths of NCC were divided into two and three groups, respectively, based on the differences of geochemical features. Group I granulite xenoliths from the NCC have silicic-basic compositions, with metamorphic ferrosilite. The Group I granulite xenoliths show relatively lower Mg# values of pyroxenes and whole-rock than that of the Group II granulite xenoliths, and enrichments of light rare earth elements and Sr-Nd isotopic compositions. Their zircons display Archean-Phanerozoic ages with three peaks of Neoarchean, Paleoproterozoic, and Mesozoic. Generally, Group I granulite xenoliths show close affinities to the granulite terranes of the NCC in terms of the major and trace elements and Sr-Nd isotopic compositions, with a consistent Archean-Proterozoic evolutionary history. However, Group I granulite xenoliths have abundant Phanerozoic zircons with variable Hf isotopic compositions from depleted to enriched, which could be formed by modifications of magma underplating. Therefore, Group I granulite xenoliths represent the modified ancient lower crust beneath the NCC. The Group II granulite and Group III pyroxenite xenoliths from the NCC have similar geochemical features and are basic in compositions, with metamorphic to magmatic orthopyroxenes. The Group II granulite and Group III pyroxenite xenoliths usually show higher MgO and lower incompatible elements compositions in minerals and bulk rocks than that in the granulite terranes and Group I granulite xenoliths, but their Sr-Nd isotopic compositions fall into the fields of granulite terranes and group I granulite xenoliths. Zircons from the Group II granulite and Group III pyroxenite xenoliths are predominantly Phanerozoic with subordinate Archean-Proterozoic ages, and the Hf-O isotopic compositions of zircons are similar to those in the Group I granulite xenoliths. Additionally, the trace element compositions of Group II granulite and Group III pyroxenite xenoliths are complementary to those of the adakitic rocks from the NCC. Furthermore, the similar Sr-Nd and zircon Hf isotopic compositions among Group II granulite and Group III pyroxenite xenoliths and adakitic rocks indicate that they are cognate. Therefore, we suggest that the Group II granulite and Group III pyroxenite xenoliths could be restites left after partial melting of the ancient basic lower crust that produced voluminous adakitic rocks. In contrast, Group I and II pyroxenite xenoliths from the NCC have cumulate and reaction origins, respectively. The Group I and II pyroxenite xenoliths commonly have magmatic enstatite and show higher Mg# values and depleted Sr-Nd isotopic compositions of minerals and bulk rocks relative to that in the granulite and Group III pyroxenite xenoliths. Formation of voluminous Group I pyroxenite cumulates in the crust-mantle transition zones implies extensive magma underplating beneath the NCC during the Mesozoic-Cenozoic, which also provided exotic materials and heat for the reworking of the ancient lower crust. Therefore, the destruction of the lower crust beneath the NCC could result from continuous modifications and remelting of the ancient lower crust triggered by magma underplating. These processes led to not only the transformations of some ancient basic lower crust into granulite and pyroxenite restites but also the compositional modifications of the ancient lower crust. Consequently, the lower crust beneath the NCC showed downward rejuvenation, similar to the lithospheric mantle.
Archaean–Proterozoic crust, atop a thick (180 km), cold (40 mW/m
2), melt-depleted mantle keel, characterised the North China Craton (NCC) at the end of the Precambrian. Differing ages for ...Pre-Cambrian crust and underlying mantle reveal decoupling brought about by repeated orogenic events over the history of the NCC. The most recent thermo-tectonic episode in the Mesozoic–Cenozoic virtually replaced/transformed all of the Precambrian lithosphere. Whether this was caused by “top-down” rapid delamination (<
5 Ma) or “bottom-up” more protracted thermal/chemical erosion (ca. 100 Ma) depends on the interpretation of Jurassic to Cretaceous geological events. The eastern part of the craton east of the North–South Gravity Lineament lithospheric boundary has experienced the most re-activation. In the Palaeozoic–Mesozoic this region was intruded by kimberlitic magmas and cross-cut by the Tan-Lu fault zone and in the Mesozoic–Cenozoic, the eastern craton was the site of major mafic igneous activity. By the end of the Cenozoic the eastern craton was characterised by thermal highs >
64 mW/m
2, thin continental lithosphere (<
50 km) and thin crust (<
32 km) adjacent to the intra-cratonic Bohai Sea.
Pigs are one of the most important economic livestock. Gut microbiota is not only critical to the health but also the production efficiency of pigs. Manipulating gut microbiota relies on the full ...view of gut microbiome and the understanding of drive forces shaping microbial communities. 16s rDNA sequencing was used to profile microbiota along the longitudinal and radical axes to obtain the topographical map of microbiome in different intestinal compartments in young pigs. Alpha and beta-diversities revealed distinct differences in microbial compositions between the distal ileum and cecum and colon, as well as between the lumen and mucosa.
and
dominated in the ileum, constituting 95 and 80% of the luminal and mucosa-attached microbiome. Transitioning from the small intestine to the large intestine, luminal
increased from 1.69 to 45.98% in the cecum and 40.09% in the colon, while mucosal
raised from 9 to 35.36% and 27.96%. Concurrently, luminal
and
and mucosal-attached
remarkably decreased. By co-occurrence network analyses,
and
were recognized as the central nodes of luminal microbial network, and
and
were identified as mucosal central nodes. Co-abundance was uncovered among
, and
in the luminal and mucosal microbiome, while opportunistic pathogens from γ-
in the mucosa. Strong co-exclusion was shown between
with
-centered microbial groups in the lumen. Redundancy analysis found bile acids and short chain fatty acids explained 37.1 and 41% of variations in the luminal microbial composition, respectively. Primary bile acid, taurine- and glycine- conjugated bile acids were positively correlated with
, whereas secondary bile acids, acetate, propionate, butyrate, and valerate were positively correlated with
. Functional analyses demonstrated that
, and
were positively correlated with gene functions related to amino acids, energy, cofactors and vitamins metabolism, which are indispensable for the hosts. These results suggested site specific colonization and co-occurrence of swine gut microbiome closely relate to the microenvironment in each niche. Interactions of core gut microbiome greatly contributed to metabolism and/or immunity in the swine intestine.
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