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Zhou Z.,CAS Nanjing Institute of Geology and Palaeontology | Yuan W.,CAS Nanjing Institute of Geology and Palaeontology | Zhou Z.,Xian Institute of Geology and Mineral Resources
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

Ovalocephalus has a long stratigraphic range and wide geographical distribution in Ordovician peri-Gondwana. Based largely on the well-preserved specimens recently collected from China, all known forms are revised and listed. Phylogenetic analysis was conducted on the genus, involving 10 species. As suggested by the strict consensus tree, evolutional trends of the genus include mainly the isolation of the anterior glabellar portion anterior to S1, the forward shifting of eyes and the related lengthening (exsag.) of the posterior fixigena, the reduction of the number of pygidial axial segments and pleural abaxial rounded free tips, the shortening of the pygidial postaxial region, and the development of cranidial genal spines. Ovalocephalus may have originated in shallow-water sites of the South China Plate in the Early Floian, but migrated into the deep-water regions from the Darriwilian onwards. All the records of the genus from the Early Floian to Early Katian were confined to eastern peri-Gondwanan plates and terranes in low-latitude zones. It was only restricted to the South China, Tarim and North China plates until the Middle Darriwilian, but the Late Darriwilian eustatic sea-level rise and especially the Sandbian-Early Katian immense transgression may have brought about its dispersal to Alborz, Sibumasu and central Asian terranes. Following the closure of the Tornquist Sea, the genus was even able to spread to Baltica during the latest Katian, and the pre-Hirnantian warming (the Boda event) may have promoted a wider distribution of Ovalocephalus to western peri-Gondwana (the Taurides and Armorica terranes) in the thenhigh latitudes. © 2009 The Royal Society.


Huang R.,Northwest University, China | Yang B.,Xian Institute of Geology and Mineral Resources | Liu Q.,Northwest University, China
Journal of Applied Polymer Science | Year: 2013

This articles provided information on Cr(VI) adsorption onto protonated crosslinked chitosan particles (PCPs) as an adsorbent. Batch experiments were performed to investigate the effects of the adsorbent dosage, pH, contact time, initial Cr(VI) concentration, and coexisting ions on the adsorption capacity and the regeneration ability of the adsorbent. The equilibrium data fit well with the Freundlich and Redlich-Peterson isotherm models. The presence of other anions weakened Cr(VI) adsorption, especially high-valence anion such as sulfate. PCP could be regenerated well by a 0.1N sodium hydroxide solution. Electrostatic attraction was the main driving force for Cr(VI) adsorption. Copyright © 2013 Wiley Periodicals, Inc.


Huang R.,Northwest University, China | Yang B.,Xian Institute of Geology and Mineral Resources | Liu Q.,Northwest University, China | Ding K.,Northwest University, China
Journal of Fluorine Chemistry | Year: 2012

Protonated cross-linked chitosan particles (PCP) were used to remove fluoride from aqueous solution. PCP were characterized using FTIR, XRD and SEM. Adsorption isotherms, the effects of adsorbent dosage, pH, contact time and co-existing anions on adsorption process, and the regeneration ability of PCP were investigated. The optimum pH value was achieved at 7. The equilibrium was attained in 40 min. The presence of co-existing anions weakened fluoride adsorption on PCP, especially the high valence anions such as sulfate. The equilibrium data fitted well with Langmuir and Freundlich isotherm models, and the maximum monolayer adsorption capacity was 8.10 mg g -1 at room temperature. 0.1 M HCl was identified as the best eluent. Electrostatic attraction was the main driving force for fluoride adsorption. © 2012 Elsevier B.V. All rights reserved.


Diwu C.,Northwest University, China | Sun Y.,Northwest University, China | Guo A.,Northwest University, China | Wang H.,Xian Institute of Geology and Mineral Resources | Liu X.,Northwest University, China
Gondwana Research | Year: 2011

The Dengfeng complex is located on the southern margin of the North China Craton (NCC) and belongs to the southern portion of the Trans-North China Orogen. This terrane is important to understand the formation and evolution of NCC during late Neoarchean (~2.5Ga). The Dengfeng complex is well exposed in the Junzhao region and comprises two distinct lithologic units: supracrustal assemblage and plutonic rocks. LA-ICPMS magmatic zircon U-Pb age data shows that the rocks formed within the range of 2547-2504Ma. The available Hf isotope data indicate that the majority of ca. 2.5Ga zircons from the Dengfeng complex have high εHf(t) values close to the initial Hf isotope ratios of the contemporaneous depleted mantle. These data indicate that the rocks in the Dengfeng represent juvenile crust. The TTG gneisses in the Dengfeng complex display low Mg# (41-48), MgO (<2wt.%), Cr (6-14ppm), Ni (9-22ppm) contents and low Nb/Ta ratio (6-12), which are interpreted to have been produced by the partial melting of a flatly subducted slab. The metadiorites of the Dengfeng complex are typically characterized by high Mg# (59-69), MgO (3.5-6.6wt.%), Ni (82-130ppm) and Cr (148-237ppm) abundances, elevated Sr (1759-1927ppm) and Ba (1742-2289ppm) concentrations, and high LREE (LaN=38-487). Such geochemical features are similar to Archean sanukitoids. A two-stage model is applied here to explain the genesis of metadiorites of Dengfeng complex: (1) firstly, the mantle is metasomatized either by melts or by aqueous fluids from a subducted slab; (2) subsequently, sanukitoid magmas were produced by partial melting of the hybridized mantle. Furthermore, the amphibolites of supracrustal rocks have a mixture of MORB- and arc-like geochemical affinities, suggesting the development of a back-arc in the southern NCC at ca. 2.5Ga. The contemporary late Neoarchean TTGs, sanukitoids and MORB-back arc association may represent a late Neoarchean tectonic mélange, implying a Neoarchean subduction-accretion process which would suggest that modern-style plate tectonics processes was probably initiated in the southern NCC by 2.5Ga. © 2011 International Association for Gondwana Research.


Liu Q.,Northwest University, China | Yang B.,Xian Institute of Geology and Mineral Resources | Zhang L.,Northwest University, China | Huang R.,Northwest University, China
International Journal of Biological Macromolecules | Year: 2015

In this study, cross-linked chitosan (CCS)/bentonite (BT) composite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction between chitosan and glutaraldehyde. CCS/BT composite was characterized by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analyses (TGA). Their adsorption characteristics were assessed by using an azo dye (Amido Black 10B) as a model adsorbate. The adsorption of Amido Black 10B onto the CCS/BT composite was found to be optimal at pH 2. The adsorption isotherm was well described by the Langmuir model and the maximum adsorption capacity was 323.6. mg/g at 293. K and pH 2. Amido Black 10B adsorption kinetics followed a pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Amido Black 10B by CCS/BT composite was spontaneous and endothermic in nature. © 2014 Elsevier B.V.


Liu Q.,Northwest University, China | Zhang L.,Northwest University, China | Yang B.,Xian Institute of Geology and Mineral Resources | Huang R.,Northwest University, China
International Journal of Biological Macromolecules | Year: 2015

In the present paper, zirconium immobilized cross-linked chitosan (Zr-CCS) was reported for the adsorption of fluoride. Zr-CCS was synthesized by methods of membrane-forming and subsequent cross-linking reaction. Zr-CCS was characterized by FTIR, XRD, and SEM technologies. Batch adsorption experiments were performed to evaluate the adsorption capacity of Zr-CCS toward fluoride. The adsorption of fluoride onto the Zr-CCS favored at low pH values, and reduced in the presence of other co-anions. The adsorption equilibrium data had a good agreement with the Langmuir isotherm model, and the maximum adsorption capacity was calculated as 48.26. mg/g for fluoride at 303. K and natural pH (6.0). Thermodynamic parameters indicate that the nature of fluoride adsorption was spontaneous and endothermic. The adsorption mechanism of fluoride onto the Zr-CCS was controlled by chemical ion-exchange and electrostatic attraction between Zr-CCS and fluoride. © 2015 Elsevier B.V.


Huang R.,Northwest University, China | Yang B.,Xian Institute of Geology and Mineral Resources | Liu Q.,Northwest University, China | Liu Y.,Northwest University, China
Journal of Applied Polymer Science | Year: 2014

Activated carbon/chitosan composite has been used as an adsorbent to remove aniline and Cr(VI) ions from aqueous solutions simultaneously. The effects of preparation conditions such as the ratio of activated carbon to chitosan, crosslinking reagents, crosslinking time, and adsorption conditions including adsorbent dosage, pH value of solution, and contact time on simultaneous adsorption of aniline and Cr(VI) ion were investigated. Experimental results showed that epichlorohydrin was the proper crosslinking reagent, and the ratio of activated carbon to chitosan was kept at 1. When the adsorbent dosage was 4.0 g/L, and the concentrations of aniline and Cr(VI) were lower than 50 and 100 mg/L, respectively, both aniline and Cr(VI) were simultaneously removed at natural pH with high removals (>95%). The presence of Cr(VI) enhanced the adsorption of aniline, while the presence of aniline almost had no influence on the adsorption of Cr(VI). The adsorption processes of both aniline and Cr(VI) followed the pseudo-second-order kinetics model, but the sorption of Cr(VI) was preferential to that of aniline by this composite. © 2013 Wiley Periodicals, Inc.


Xia L.-Q.,Xian Institute of Geology and Mineral Resources
Earth-Science Reviews | Year: 2014

Contamination by continental crust or lithosphere can impart subduction-like signatures and lead to the misidentification of contaminated continental intraplate basaltic rocks as arc related ones. Uncontaminated plume-derived continental basaltic rocks are normally characterized by high Nb/La ratios of higher than or near one, low 87Sr/86Sr(t) ratios, high εNd(t) values and "hump-shaped" OIB-like mantle-normalized multi-element patterns without negative Nb, Ta and Ti anomalies. As the uncontaminated plume-derived basaltic rocks have been found in the studied volcanic successions, the possibility can be basically excluded that they belong to island-arc or active continental margin volcanic rocks. The contaminated continental basaltic lavas have higher 87Sr/86Sr, concentrations of incompatible trace elements and lower εNd relative to the arc related ones. For the basaltic lavas with subduction-like signatures, we can judge whether they are really island-arc or active continental margin basalts by utilizing the geochemical diagrams which do not use Nb, Ta or Ti as discriminating factors. The contaminated continental basalts can be distinguished from continental margin by two factors: 1) the overall level of the incompatible elements, including Nb is higher for the contaminated continental basalts, and 2) on trace element diagrams that do not involve Nb, Ta and Ti, even the contaminated basalts exhibit within plate character. © 2014 Elsevier B.V.


Xia L.,Xian Institute of Geology and Mineral Resources | Li X.,Xian Institute of Geology and Mineral Resources | Ma Z.,Xian Institute of Geology and Mineral Resources | Xu X.,Xian Institute of Geology and Mineral Resources | Xia Z.,Xian Institute of Geology and Mineral Resources
Gondwana Research | Year: 2011

Cenozoic volcanism on the Tibetan plateau, which shows systematic variations in space and time, is the volcanic response to the India-Asia continental collision. The volcanism gradually changed from Na-rich. +. K-rich to potassic-ultrapotassic. +. adakitic compositions along with the India-Asia collision shifting from contact-collision (i.e. "soft collision" or "syn-collision") to all-sided collision (i.e. "hard collision"). The sodium-rich and potasium-rich lavas with ages of 65-40. Ma distribute mainly in the Lhasa terrane of southern Tibet and subordinately in the Qiangtang terrane of central Tibet. The widespread potassic-ultrapotassic lavas and subordinate adakites were generated from ~. 45 to 26. Ma in the Qiangtang terrane of central Tibet. Subsequent post-collisional volcanism migrated southwards, producing ultrapotassic and adakitic lavas coevally between ~. 26 and 8. Ma in the Lhasa terrane. Then potassic and minor adakitic volcanism was renewed to the north and has become extensive and semicontinuous since ~. 20. Ma in the western Qiangtang and Songpan-Ganze terranes. Such spatial-temporal variations provide important constraints on the geodynamic processes that evolved at depth to form the Tibetan plateau. These processes involve roll-back and break-off of the subducted Neo-Tethyan slab followed by removal of the thickened Lhasa lithospheric root, and consequently northward underthrusting of the Indian lithosphere. The Tibetan plateau is suggested to have risen diachronously from south to north. Whereas the southern part of the plateau may have been created and maintained since the late-Oligocene, the northern plateau would have not attained its present-day elevation and size until the mid-Miocene when the lower part of the western Qiangtang and Songpan-Ganze lithospheres began to founder and detach owing to the persistently northward push of the underthrust Indian lithosphere. © 2010 International Association for Gondwana Research.


Xia L.,Xian Institute of Geology and Mineral Resources | Xia Z.,Xian Institute of Geology and Mineral Resources | Xu X.,Xian Institute of Geology and Mineral Resources | Li X.,Xian Institute of Geology and Mineral Resources | Ma Z.,Xian Institute of Geology and Mineral Resources
Earth-Science Reviews | Year: 2013

Late Paleoproterozoic (1.84-1.62Ga) magmatic rocks including dykes/sills/intrusions and volcanic rocks occur throughout the North China Craton (NCC), which is considered to be part of the Columbia supercontinent by ca. 1.9-1.85Ga. On the basis of petrogeochemical data, these magmatic rocks can be classified into three major magma types: HN (Nb/La>0.8, Ce/Nb=1.7-3, (Th/Nb)N=0.6-1.2), MN (Nb/La=0.8-0.5, Ce/Nb=3-5, (Th/Nb)N=0.9-3.5) and LN (Nb/La<0.5, Ce/Nb=5-80, (Th/Nb)N=1-60). The geochemical variation of the MN and LN rocks can be explained by lithospheric contamination of asthenosphere- (or plume-) derived magmas, whereas the parental magmas of the HN rocks did not undergo, during their ascent, pronounced lithospheric contamination. These magmatic rocks exhibit at least two characteristics: (1) most displaying a spectrum of compositions from mafic to silicic; (2) forming in an intracontinental rift setting. This Late Paleoproterozoic rift-related magmatism is the most distinguishing feature of the rifting of the Columbia supercontinent. © 2013 Elsevier B.V.

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