Potassium‐ion hybrid capacitors have attracted increasing attention due to good energy density, high power density, and low cost. Ti3C2Tx‐MXene is considered as a promising anode material for K ion ...storage. However, undesirable stacking issues decrease its exposed area and breeds sluggish K ion transport. Herein, a facile spray‐lyophilization strategy is proposed to construct stacking‐resistant Ti3C2Tx with 3D structures. As‐prepared Ti3C2Tx hollow spheres/tubes present stack resistance, a large specific surface area, and a short ion diffusion pathway. When serving as an anode material, it shows enhanced capacity and thickness‐independent rate performance compared to 2D Ti3C2Tx. After 10 000 cycles, a specific capacity of 122 mAh g−1 is obtained at 1 A g−1. Systematic kinetics analyses demonstrate the significance of concentration polarization on the electrode's rate ability. Furthermore, a 3D Ti3C2Tx‖hierarchical porous activated carbon (HPAC) K‐ion hybrid capacitor is assembled and displays remarkable energy and power densities with energy retention of 100% after 10 000 cycles at 1 A g−1 . Following this strategy, other 3D structures from nanosheets can also be obtained, such as 3D Ti3C2Tx microtubes and graphene oxide nanoscrolls. This study provides a viable approach to solve the stacking issues of 2D nanosheets to promote the application of 2D materials.
A spray‐lyophilization strategy is proposed to transform 2D nanosheets such as Ti3C2Tx, Ti2CTx, and graphene oxide into 3D architectures. The obtained 3D Ti3C2Tx presents an aggregation‐resistant, large specific surface, and a short ion transport path, leading to enhanced K ion storage ability. A 3D Ti3C2Tx‖hierarchical porous activated carbon (HPAC) K‐ion hybrid capacitor is assembled and displays remarkable energy and power densities with ultrastable cycling performance.
Subduction zone geochemistry Zheng, Yong-Fei
Di xue qian yuan.,
07/2019, Letnik:
10, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Crustal recycling at convergent plate boundaries is essential to mantle heterogeneity. However, crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily ...incorporated in the form of liquid rather than solid phases. The physicochemical property of liquid phases is determined by the dehydration behavior of crustal rocks at the slab-mantle interface in subduction channels. Because of the significant fractionation in incompatible trace elements but the full inheritance in radiogenic isotopes relative to their crustal sources, the production of liquid phases is crucial to the geochemical transfer from the subducting crust into the mantle. In this process, the stability of specific minerals in subducting crustal rocks exerts a primary control on the enrichment of given trace elements in the liquid phases. For this reason, geochemically enriched oceanic basalts can be categorized into two types in terms of their trace element distribution patterns in the primitive mantle-normalized diagram. One is island arc basalts (IAB), showing enrichment in LILE, Pb and LREE but depletion in HFSE such as Nb and Ta relative to HREE. The other is ocean island basalts (OIB), exhibiting enrichment in LILE and LREE, enrichment or non-depletion in HFSE but depletion in Pb relative to HREE. In either types, these basalts show the enhanced enrichment of LILE and LREE with increasing their incompatibility relative to normal mid-ocean ridge basalts (MORB).
The thermal regime of subduction zones can be categorized into two stages in both time and space. The first stage is characterized by compressional tectonism at low thermal gradients. As a consequence, metamorphic dehydration of the subducting crust prevails at forearc to subarc depths due to the breakdown of hydrous minerals such as mica and amphibole in the stability field of garnet and rutile, resulting in the liberation of aqueous solutions with the trace element composition that is considerably enriched in LILE, Pb and LREE but depleted in HFSE and HREE relative to normal MORB. This provides the crustal signature for the mantle sources of IAB. The second stage is indicated by extensional tectonism at high thermal gradients, leading to the partial melting of metamorphically dehydrated crustal rocks at subarc to postarc depths. This involves not only the breakdown of hydrous minerals such as amphibole, phengite and allanite in the stability field of garnet but also the dissolution of rutile into hydrous melts. As such, the hydrous melts can acquire the trace element composition that is significantly enriched in LILE, HFSE and LREE but depleted in Pb and HREE relative to normal MORB, providing the crustal signature for the mantle sources of OIB. In either case, these liquid phases would metasomatize the overlying mantle wedge peridotite at different depths, generating ultramafic metasomatites such as serpentinized and chloritized peridotites, and olivine-poor pyroxenites and hornblendites. As a consequence, the crustal signatures are transferred by the liquid phases from the subducting slab into the mantle.
Display omitted
•The thermal structure of subduction zones changes in both time and space at different depths.•The fractionation of incompatible trace elements is significant during dehydration and melting of crustal rocks.•Crustal signatures are transferred by liquid phases into the mantle source of basaltic rocks.•The geochemical composition of liquid phases is central to that of metasomatites in the mantle wedge.•Crustal metasomatism is the physicochemical mechanism for the geochemical transfer at subduction zones.
•The U→∞ 1D Hubbard model in electric field has been exactly solved.•The charge current strangely shows a dissipationless behavior despite the strong correlation interactions.•The physics behind such ...dissipationless behavior of charge current has been discussed.
The U→+∞ one-dimensional Hubbard model in electric field has been exactly solved. The exact time-evolution states have been obtained, with which we have calculated the charge current exactly. We find that the charge current, despite the strong correlation interactions of electrons, can show undamped Bloch oscillations strangely, which has been further revealed to be mainly due to the temporal periodicity of the Hamiltonian in electric field.
Chemical geodynamics is an integrated discipline that studies the geochemical structure and tectonic evolution of geospheres with the aim of linking tectonic processes to geochemical products in the ...Earth system. It was primarily focused on mantle geochemistry, with an emphasis on geochemical recycling in oceanic subduction zones. It has been extended to geochemical reworking and recycling under high-pressure (HP) to ultrahigh-pressure (UHP) conditions in all convergent plate margins. In particular, UHP terranes, along with UHP metamorphic minerals and rocks in continental subduction zones, represent natural laboratories for investigating geochemical transport and fluid action during subduction and exhumation of continental crust. As a result of this extension, the study of UHP terranes has significantly advanced our understanding of tectonic processes in collisional orogens. This understanding has principally benefited from the deciphering of petrological and geochemical records in deeply subducted crustal rocks that occur in different petrotectonic settings. This review focuses on the following issues in continental subduction zones: the time and duration of UHP metamorphism, the origin and action of metamorphic fluid/melt inside UHP slices, the element and isotope mobilities under HP to UHP conditions during continental collision, the origin of premetamorphic protoliths and its bearing on continental collision types, and the crustal detachment and crust–mantle interaction in subduction channels. The synthesis presented herein suggests that the nature of premetamorphic protoliths is a key to the type of collisional orogens and the size of UHP terranes. The source mixing in subduction channels is a basic mechanism responsible for the geochemical diversity of continental and oceanic basaltic rocks. Therefore, the geochemical study of HP to UHP metamorphic rocks and their derivatives has greatly facilitated our understanding of the geodynamic processes that drive the tectonic evolution of convergent plate margins from oceanic subduction to continental collision. Consequently, the study of chemical geodynamics has been developed from oceanic subduction zones to continental collision zones, and it has enabled important contributions to development of plate tectonic theory.
► Geochronological constraints on the time and duration of UHP metamorphism at mantle depths during continental collision. ► Geochemical transport and fluid action during UHP metamorphism due to subduction and exhumation of continental crust. ► Geochemical competition between thermodynamics and kinetics during continental subduction-zone metamorphism. ► Temporal and spatial relationships between protolith origin and collision type in continental subduction zones. ► Crustal detachment and crust–mantle interaction in subduction channels during continental collision.
An overview is presented for the formation and evolution of Precambrian continental lithosphere in South China. This is primarily based on an integrated study of zircon U–Pb ages and Lu–Hf isotopes ...in crustal rocks, with additional constraints from Re–Os isotopes in mantle-derived rocks. Available Re–Os isotope data on xenolith peridotites suggest that the oldest subcontinental lithospheric mantle beneath South China is primarily of Paleoproterozoic age. The zircon U–Pb ages and Lu–Hf isotope studies reveal growth and reworking of the juvenile crust at different ages. Both the Yangtze and Cathaysia terranes contain crustal materials of Archean U–Pb ages. Nevertheless, zircon U–Pb ages exhibit two peaks at 2.9–3.0Ga and ~2.5Ga in Yangtze but only one peak at ~2.5Ga in Cathaysia. Both massive rocks and crustal remnants (i.e., zircon) of Archean U–Pb ages occur in Yangtze, but only crustal remnants of Archean U–Pb ages occur in Cathaysia. Zircon U–Pb and Lu–Hf isotopes in the Kongling complex of Yangtze suggest the earliest episode of crustal growth in the Paleoarchean and two episodes of crustal reworking at 3.1–3.3Ga and 2.8–3.0Ga. Both negative and positive εHf(t) values are associated with Archean U–Pb ages of zircon in South China, indicating both the growth of juvenile crust and the reworking of ancient crust in the Archean. Paleoproterozoic rocks in Yangtze exhibit four groups of U–Pb ages at 2.1Ga, 1.9–2.0Ga, ~1.85Ga and ~1.7Ga, respectively. They are associated not only with reworking of the ancient Archean crust in the interior of Yangtze, but also with the growth of the contemporaneous juvenile crust in the periphery of Yangtze. In contrast, Paleoproterozoic rocks in Cathaysia were primarily derived from reworking of Archean crust at 1.8–1.9Ga. The exposure of Mesoproterozoic rocks are very limited in South China, but zircon Hf model ages suggest the growth of juvenile crust in this period due to island arc magmatism of the Grenvillian oceanic subduction. Magmatic rocks of middle Neoproterozoic U–Pb ages are widespread in South China, exhibiting two peaks at about 830–800Ma and 780–740Ma, respectively. Both negative and positive εHf(t) values are associated with the middle Neoproterozoic U–Pb ages of zircon, suggesting not only growth and reworking of the juvenile Mesoproterozoic crust but also reworking of the ancient Archean and Paleoproterozoic crust in the middle Neoproterozoic. The tectonic setting for this period of magmatism would be transformed from arc–continent collision to continental rifting with reference to the plate tectonic regime in South China.
Display omitted
► Crustal growth and reworking are episodic from Eoarchean to Neoproterozoic in South China. ► The growth of juvenile crust is significant in the Archean, but no Archean SCLM is measured. ► Both growth and reworking of mantle and crustal lithospheres are prominent in the middle Paleoproterozoic. ► Both juvenile and ancient crusts underwent intensive reworking in the middle Neoproterozoic. ► The arc–continent collision is a tectonic mechanism for continental accretion in South China.
Many studies of experimental petrology have devoted to partial melting of crustal rocks. In order to provide lithochemical constraints on granite petrogenesis, this paper presents a compilation and ...synthesis of available experimental data for the major element compositions of felsic melts derived from partial melting of natural or synthetic materials in the compositional range of crustal rocks. The experimental melts are categorized into four types according to the species of hydrous minerals in starting materials: (I) amphibole-bearing; (II) amphibole- and biotite-bearing; (III) biotite-bearing; and (IV) biotite- and muscovite-bearing. If dehydration melting takes place at normal crustal conditions (P=5–10kbar, T≤1000°C), experimental melts are rich in SiO2 but poor in MgO+FeOT except those from amphibole-bearing sources. A comprehensive comparison of compositions between experimental melts and starting materials indicates that geochemical fractionation is variable for different major elements and their ratios. Source composition and melting temperature exert stronger controls on the compositional variations of experimental melts than pressure and fluid. By comparing the experimental melts with natural granites, the following insights into granite petrogenesis can be got: (1) while peritectic assemblage entrainment may be the dominant mechanism for the compositional variations of garnet/cordierite-rich S-type granites, fractional crystallization of diverse melts from heterogeneous metasedimentary precursors probably governs the compositional variations of garnet/cordierite-poor S-type granites; (2) relatively K2O-rich mafic to intermediate rocks are appropriate sources for calc-alkaline I-type granites. The compositional variations of calc-alkaline granites are jointly controlled by peritectic assemblage entrainment and subsequent fractional crystallization; (3) while dehydration melting at T>950°C is appropriate for the production of ferroan and alkali-rich granitic melts from intermediate magnesian tonalite or granodiorite, it is also possible for ferroan, alkali–rich and fluorine-rich granitic melts to be produced by dehydration melting of moderately magnesian mica–bearing materials at T≤900°C. Nevertheless, the low-T melts are more peraluminous than the high-T ones. Therefore, the composition of source rocks exerts the first-order control on the composition of granitic melts in closed systems. In addition, the dehydration melting of crustal rocks under different conditions is also responsible for variations in the composition of granites.
•Lithochemical data of experimental melts are grouped based on the species of hydrous minerals in starting materials.•Lithochemical fractionation is significant between experimental melts and starting materials.•Source composition and melting temperature are controlling factors on the lithochemistry of granitic melts.•The experimental results provide lithochemical constraints on granite petrogenesis in closed systems.
Plate tectonics was originally established as a kinematic theory of global tectonics, in which the Earth’s rigid outer layer, the lithosphere, consists of different size plates that move relative to ...each other along divergent, convergent or transform boundaries overlying the ductile asthenosphere. It comprises three elements: rigid lithosphere plates, ductile asthenosphere, and coupled movement systems. It operates through the interlinked processes of continental drift, seafloor spreading and lithospheric subduction, resulting in the generation, modification and demise of lithospheres throughout geological time. The system of lithospheric plates in horizontal and vertical movements forms the spatiotemporal linkages of matter and energy between the surface and interior of Earth, advancing the kinematic theory with a dynamic explanation. While top-down tectonics through lithospheric subduction plays a key role in the operation of plate tectonics, it is balanced for the conservation of both mass and momentum on the spherical Earth by bottom-up tectonics through asthenospheric upwelling to yield seafloor spreading after continental breakup. The gravity-driven subduction of cool lithosphere proceeds through convergence between two plates on one side, and rollback of the subducting slab makes the vacancy for upwelling of the hotter asthenosphere to form active rifting in backarc sites. Plate convergence is coupled with plate divergence between two plates along mid-ocean ridges on the other side, inducing passive rifting for seafloor spreading as a remote effect. Thus, plate tectonics is recognizable in rock records produced by tectonic processes along divergent and convergent plate margins. Although the asthenospheric upwelling along fossil suture zones may result in continental breakup, seafloor spreading is only induced by gravitational pull of the subducting oceanic slab on the remote side. Therefore, the onset and operation of plate tectonics are associated with a series of plate divergent-convergent coupling systems, and they are critically dependent on whether both construction and destruction of plates would have achieved and maintained the conservation of both mass and momentum on the spherical Earth. Plate margins experience different types of deformation, metamorphism and magmatism during their divergence, convergence or strike-slip, leaving various geological records in the interior of continental plates. After plate convergence, the thickened lithosphere along fossil suture zones in intracontinental regions may be thinned by foundering. This causes the asthenospheric upwelling to reactivate the thinned lithosphere, resulting in superimposition and modification of the geological record at previous plate margins. The operation of plate tectonics, likely since the Eoarchean, has led to heat loss at plate margins and secular cooling of the mantle, resulting in the decrease of geothermal gradients and the increase of rheological strength at convergent plate margins. Modern plate tectonics is characterized by the predominance of rigid plate margins for cold subduction, and it has prevailed through the Phanerozoic. In contrast, ancient plate tectonics, that prevailed in the Archean and Proterozoic, is dominated by relatively ductile plate margins for collisional thickening at forearc depths and then warm subduction to subarc depths. In either period, the plate divergence after lithospheric breakup must be coupled with the plate convergence in both time and space, otherwise it is impossible for the operation of plate tectonics. In this context, the creation and maintenance of plate divergent-convergent coupling systems are responsible for the onset and operation of plate tectonics, respectively. Although a global network of mobile belts is common between major plates on modern Earth, it is difficult to find its geological record on early Earth if microplates would prevail at that time. In either case, it is important to identify different types of the geological record on Earth in order to discriminate between the different styles of plate tectonics in different periods of geological history.
The SARS-CoV-2-infected disease (COVID-19) outbreak is a major threat to human beings. Previous studies mainly focused on Wuhan and typical symptoms. We analysed 74 confirmed COVID-19 cases with GI ...symptoms in the Zhejiang province to determine epidemiological, clinical and virological characteristics.
COVID-19 hospital patients were admitted in the Zhejiang province from 17 January 2020 to 8 February 2020. Epidemiological, demographic, clinical, laboratory, management and outcome data of patients with GI symptoms were analysed using multivariate analysis for risk of severe/critical type. Bioinformatics were used to analyse features of SARS-CoV-2 from Zhejiang province.
Among enrolled 651 patients, 74 (11.4%) presented with at least one GI symptom (nausea, vomiting or diarrhoea), average age of 46.14 years, 4-day incubation period and 10.8% had pre-existing liver disease. Of patients with COVID-19 with GI symptoms, 17 (22.97%) and 23 (31.08%) had severe/critical types and family clustering, respectively, significantly higher than those without GI symptoms, 47 (8.14%) and 118 (20.45%). Of patients with COVID-19 with GI symptoms, 29 (39.19%), 23 (31.08%), 8 (10.81%) and 16 (21.62%) had significantly higher rates of fever >38.5°C, fatigue, shortness of breath and headache, respectively. Low-dose glucocorticoids and antibiotics were administered to 14.86% and 41.89% of patients, respectively. Sputum production and increased lactate dehydrogenase/glucose levels were risk factors for severe/critical type. Bioinformatics showed sequence mutation of SARS-CoV-2 with m
A methylation and changed binding capacity with ACE2.
We report COVID-19 cases with GI symptoms with novel features outside Wuhan. Attention to patients with COVID-19 with non-classic symptoms should increase to protect health providers.
PDF
