SHRIMP U-Pb zircon ages and geochemical and Nd isotopic data are reported for mid-Neoproterozoic igneous rocks in northern Zhejiang Province, South China. The Shenwu dolerite dykes, the Daolinshan ...granite-diabase complex, and the Shangshu bimodal (basalt-rhyolite) volcanic rocks were dated at 849
±
7 Ma, 794
±
9 Ma and 792
±
5 Ma, respectively. All the studied mafic rocks are tholeiitic in compositions and exhibit overall moderate enrichments in most incompatible trace elements, resembling intraplate basaltic rocks in continental rifts. The ∼850 Ma Shenwu dolerites are the earliest anorogenic basaltic rocks identified so far after the ca. 1.1–0.9 Ga Sibao Orogeny, but seem to predate the Neoproterozoic rifting. Our results are clearly at variance with the alternative tectonic model that an active continental margin existed along the southern margin of the Yangtze Block until ca. 800 Ma. The intensive ∼790 Ma bimodal volcanic and plutonic rocks, part of a major phase of mid-Neoproterozoic rifting, are concurrent with the widespread mid-Neoproterozoic intraplate magmatism throughout South China. They are most likely related to the proposed mantle superplume that led to the breakup of the supercontinent Rodinia.
The Moon has a magmatic and thermal history that is distinct from that of the terrestrial planets
. Radioisotope dating of lunar samples suggests that most lunar basaltic magmatism ceased by around ...2.9-2.8 billion years ago (Ga)
, although younger basalts between 3 Ga and 1 Ga have been suggested by crater-counting chronology, which has large uncertainties owing to the lack of returned samples for calibration
. Here we report a precise lead-lead age of 2,030 ± 4 million years ago for basalt clasts returned by the Chang'e-5 mission, and a
U/
Pb ratio (µ value)
of about 680 for a source that evolved through two stages of differentiation. This is the youngest crystallization age reported so far for lunar basalts by radiometric dating, extending the duration of lunar volcanism by approximately 800-900 million years. The µ value of the Chang'e-5 basalt mantle source is within the range of low-titanium and high-titanium basalts from Apollo sites (µ value of about 300-1,000), but notably lower than those of potassium, rare-earth elements and phosphorus (KREEP) and high-aluminium basalts
(µ value of about 2,600-3,700), indicating that the Chang'e-5 basalts were produced by melting of a KREEP-poor source. This age provides a pivotal calibration point for crater-counting chronology in the inner Solar System and provides insight on the volcanic and thermal history of the Moon.
The Gangbian alkaline complex in the southeastern Yangtze Block (South China) is composed of Si-undersaturated pyroxene syenites and Si-saturated to -oversaturated syenites and quartz monzonites. ...SIMS zircon U–Pb analyses indicate that the complex was emplaced at 848
±
4 Ma, during a previously-recognized interval of magmatic quiescence between the ca 1.0–0.89 Ga Sibaoan orogenic magmatism and the ca 0.83–0.78 Ga magmatic flare-up. The Gangbian rocks are characterized by wide, coherent variations in major and trace elements (SiO
2
=
47.6–68.4%, K
2O
+
Na
2O
=
4.5–10.5%, K
2O/Na
2O
=
0.4–1.2, MgO
=
1.2–8.5%, Cr
=
4.5–239 ppm, and Ni
=
4.5–143 ppm) and by enrichment in LIL and LREE and depletion in Nb, Ta and P in trace element spidergrams. Their whole-rock εNd(
T) (−
6.5 to −
0.4) and εHf(
T) (−
10.7 to 0.4) are positively correlated, suggesting involvement of both metasomatized mantle and continental crust materials in their genesis.
In situ zircon Hf–O isotopic measurements for the most evolved quartz monzonite sample yield a binary mixing trend between the mantle- and supracrustal-derived melts. It is suggested that the pyroxene syenites were derived by partial melting of metasomatized, phlogopite-bearing lithospheric mantle, and the parental magma experienced extensive fractionation of pyroxene and olivine associated with varying degrees of crustal contamination. Subsequent fractional crystallization of hornblende and minor amounts of plagioclase from the alkali basaltic magmas, accompanied by crustal contamination, produced the Si-saturated to -oversaturated syenites and quartz monzonites. These ca. 0.85 Ga alkaline rocks and neighboring contemporaneous dolerite dykes are the products of the anorogenic magmatism after the Sibao Orogeny. They post-date the final amalgamation between the Yangtze and Cathaysia Blocks, most likely manifesting the initial rifting of South China within the Rodinia supercontinent.
The middle-lower reaches of the Yangtze River is one of the most important metallogenic belts in China, hosting numerous Cu–Fe–Au–Mo deposits. Previous chronological and geochemical investigations ...mostly focused on the magmatic rocks and associated deposits in the lower reaches of the river, but the timing and genesis of the Cu–Au–(Mo) mineralized porphyries in the middle reaches are yet to be well constrained. In this study we carried out precise SIMS U–Pb zircon age determinations for a number of Cu–Au–(Mo) mineralized porphyries and barren granitoid intrusions in the Jiurui and Edong mining districts in the middle reaches of the Yangtze River valley. Our new age results reveal two discrete magmatic and mineralization events at ca. 145–146
Ma and ca. 140
Ma in the study area. The ca. 145–146
Ma granitoids signify the start of the Cretaceous magmatism in the Yangtze River Metallogenic Belt, coinciding temporally with a regional tectonic switching from a Late Jurassic transpressive tectonic regime to an earliest Cretaceous extensional regime in eastern China.
►The Cu–Au–(Mo) mineralized porphyries and barren granitoids in the Jiurui and Edong mining districts in Yangtze River Metallogenic Belt were precisely dated at ca. 145–146
Ma and ca. 140
Ma. ►The ca. 145–146
Ma mineralized porphyries and barren granitoids signify the initiation of the Cretaceous magmatism in the Yangtze River Metallogenic Belt. ►These igneous rocks are most likely generated in response to the regional tectonic switch from the Late Jurassic transpressive to earliest Cretaceous extensional regimes.
Zircon has long been recognized as the best geochronometer and the most important timekeeper in geosciences. Modern microbeam techniques such as SIMS and LA‐ICPMS have been successfully applied to in ...situ U‐Pb zircon age determinations, at spatial resolutions of 20–30 μm or less. Matrix‐matched calibration by external standardization of well‐characterized natural zircon references is a principal requirement for precise microbeam U‐Pb zircon age determination due to fractionation effects between Pb and U, which usually result in an external age error exceeding 1%. Alternatively, zircons with a closed U‐Pb system can be directly dated by measurement of 207Pb/206Pb isotopic ratio without external standardization, which has been a common practice for zircons older than 1.0 Ga, but not for relatively young (<1.0 Ga and particularly Phanerozoic) ones because of limitations of analytical precision. We describe in this paper a method of 207Pb/206Pb measurement on Phanerozoic zircons using a new generation of large radius magnetic sector multicollector Cameca IMS‐1280 SIMS. In combination with multicollector mode, a Nuclear Magnetic Resonance (NMR) magnet controller and oxygen flooding techniques, we achieve precisions of 207Pb/206Pb ratio of <0.1% and 0.1 ∼ 0.2%, propagating to Pb/Pb age errors <0.4% and 1–3% (excluding U decay constant uncertainties), for zircons of latest Neoproterozoic and late Paleozoic to Mesozoic age, respectively. Therefore, the multicollector SIMS is capable of direct determination of zircon Pb/Pb ages as young as Mesozoic age with uncertainties of geological significance. This technique is useful for direct dating of zircons in thin sections. Moreover, it has significance for dating of some other U‐rich minerals (i.e., baddeleyite and zirconolite) that are not suitable for SIMS U‐Pb dating by external standardization.
Dirac electronic materials beyond graphene and topological insulators have recently attracted considerable attention. Cd3As2 is a Dirac semimetal with linear dispersion along all three momentum ...directions and can be viewed as a three-dimensional analogue of graphene. By breaking of either time-reversal symmetry or spatial inversion symmetry, the Dirac semimetal is believed to transform into a Weyl semimetal with an exotic chiral anomaly effect, however the experimental evidence of the chiral anomaly is still missing in Cd3As2. Here we show a large negative magnetoresistance with magnitude of -63% at 60 K and -11% at 300 K in individual Cd3As2 nanowires. The negative magnetoresistance can be modulated by gate voltage and temperature through tuning the density of chiral states at the Fermi level and the inter-valley scatterings between Weyl nodes. The results give evidence of the chiral anomaly effect and are valuable for understanding the Weyl fermions in Dirac semimetals.
The strong interaction between graphene oxides (GO) and water molecules has trigged enormous research interest in developing GO‐based separation films, sensors, and actuators. However, sophisticated ...control over the ultrafast water transmission among the GO sheets and the consequent deformation of the entire GO film is still challenging. Inspired from the natural “quantum‐tunneling‐fluidics‐effect,” here quantum‐confined‐superfluidics‐enabled moisture actuation of GO paper by introducing periodic gratings unilaterally is reported. The folded GO nanosheets that act as quantum‐confined‐superfluidics channels can significantly promote water adsorption, enabling controllable and sensitive moisture actuation. Water‐adsorption‐induced expansion along and against the normal direction of a GO paper is investigated both theoretically and experimentally. Featuring state‐of‐the‐art of ultrafast response (1.24 cm−1 s−1), large deformation degree, and complex and predictable deformation, the smart GO papers are used for biomimetic mini‐robots including a creeping centipede and a smart leaf that can catch a living ladybug. The reported method is simple and universal for 2D materials, revealing great potential for developing graphene‐based smart robots.
Inspired by the natural “quantum‐tunneling‐fluidics‐effect,” moisture actuation of a solo graphene oxide (GO) paper enabled by quantum‐confined superfluidics is achieved by introducing unilateral nanofolding. Featuring a state‐of‐the‐art ultrafast response, large deformation degree, and complex and predictable deformation, the smart GO films are used for a creeping centipede and a smart leaf that can catch a living ladybug.
Phase change memory (PCM) is an emerging non‐volatile data storage technology concerned by the semiconductor industry. To improve the performances, previous efforts have mainly focused on partially ...replacing or doping elements in the flagship Ge‐Sb‐Te (GST) alloy based on experimental “trial‐and‐error” methods. Here, the current largest scale PCM materials searching is reported, starting with 124 515 candidate materials, using a rational high‐throughput screening strategy consisting of criteria related to PCM characteristics. In the results, there are 158 candidates screened for PCM materials, of which ≈68% are not employed. By further analyses, including cohesive energy, bond angle analyses, and Born effective charge, there are 52 materials with properties similar to the GST system, including Ge2Bi2Te5, GeAs4Te7, GeAs2Te4, so on and other candidates that have not been reported, such as TlBiTe2, TlSbTe2, CdPb3Se4, etc. Compared with GST, materials with close cohesive energy include AgBiTe2, TlSbTe2, As2Te3, TlBiTe2, etc., indicating possible low power consumption. Through further melt‐quenching molecular dynamic calculation and structural/electronic analyses, Ge2Bi2Te5, CdPb3Se4, MnBi2Te4, and TlBiTe2 are found suitable for optical/electrical PCM applications, which further verifies the effectiveness of this strategy. The present study will accelerate the exploration and development of advanced PCM materials for current and future big‐data applications.
Phase‐change memory (PCM) is a state‐of‐the‐art nonvolatile data memory technology depending on transitions between amorphous and crystalline phases of PCM materials. To explore advanced material candidates, the current largest scale material searching is carried out using a rational high‐throughput screening strategy consisting of criteria related to PCM characteristics. A series of unreported materials are found potentially suitable for PCM applications.
It has been generally accepted that the South China Block was formed through amalgamation of the Yangtze and Cathaysia Blocks during the Proterozoic Sibaoan orogenesis, but the timing and kinematics ...of the Sibao orogeny are still not well constrained. We report here SHRIMP U–Pb zircon geochronological and geochemical data for the Taohong and Xiqiu tonalite–granodiorite stocks from northeastern Zhejiang, southeastern margin of the Yangtze Block. Our data demonstrate that these rocks, dated at 913
±
15 Ma and 905
±
14 Ma, are typical amphibole-rich calc-alkaline granitoids formed in an active continental margin. Combined with previously reported isotopic dates for the ∼
1.0 Ga ophiolites and ∼
0.97 Ga adakitic rocks from northeastern Jiangxi, the timing of the Sibao orogenesis is thus believed to be between ∼
1.0 and ∼
0.9 Ga in its eastern segment. It is noted that the Sibao orogeny in South China is in general contemporaneous with some other early Neoproterozoic (1.0–0.9 Ga) orogenic belts such as the Eastern Ghats Belt of India and the Rayner Province in East Antarctica, indicating that the assembly of Rodinia was not finally completed until ∼
0.9 Ga.
A bottom‐up synthetic strategy is developed to fabricate a highly porous wave‐superposed perchlorate‐doped polypyrrole nanocoating on nickel nanotube arrays. The delicate nanostructure and the unique ...surface chemistry synergistically endow the obtained electrode with revealable pseudocapacitance, large operating potential window, and excellent cycling stability, which are highly promising for both asymmetric and symmetric supercapacitors.
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