Constraining timing and tectonic implications of Neoproterozoic metamorphic event in the Cathaysia Block, South China

We acknowledge the financial support by the Major State Research Development Program of China (Grant No. 2016YFC0600202), National Natural Science Foundation of China (Nos. 41330208 and 41572200) and State Key Laboratory for Mineral Deposits Research (Nanjing University) (ZZKT-201603).The Cathaysia Block of the South China Craton includes a Proterozoic basement that experienced a prolonged Precambrian crustal evolution but to date lacks evidence of Proterozoic metamorphic ages. At Lichuan and Jianning, in the Wuyi Domain of the eastern Cathaysia Block, Proterozoic rock units include migmatized paragneiss of the Wanyuan Group and minor amphibolite of the Tianjingping Formation, which are enveloped by schist of Mayuan Group, and all are intruded by Paleozoic and Mesozoic igneous rocks. Detrital zircon grains from the Wanyuan paragneiss display metamorphic rims that yield concordant weighted average 206Pb/238U ages of 860 ± 6 Ma and 435 ± 5 Ma, along with variably disconcordant ages with lower intercept ages of 442 ± 41 Ma. The zircon core ages range from 3015 Ma to 851 Ma, with three major age populations at 930–865 Ma, 1850–1200 Ma and 2650–2400 Ma. Detrital zircon grains from Mayuan schist samples at Jianning generally lack core-rim structures and yield three main age populations at 860–736 Ma, 1835–1775 Ma and 2720–2500 Ma. Metamorphic ages of ca. 860 Ma and ca. 435 Ma for the Wanyuan paragneiss along with the youngest detrital zircon constrain the depositional age of the protolith to ca. 865–860 Ma, whereas the Mayuan Group is younger and probably deposited after ca. 736 Ma. Characteristics of detrital zircon age populations along with regional geological data suggest accumulation of the Wanyuan Group in a convergent and/or collisional setting. Metamorphism and a possible subduction -collision process within the Cathaysia Block at around 860 Ma suggest it was not a unified block in early Neoproterozoic. The growth of ca. 440 Ma metamorphic rims is likely related to granitic magmatism, such as that exposed in the Lichuan region. The sparse evidence for early Neoproterozoic metamorphism likely reflects widespread overprinting by the Paleozoic tectonothermal event at around 440 Ma.PostprintPeer reviewe

Jiangnan Orogen, South China : a ~970–820 Ma Rodinia margin accretionary belt

Authors thank the Major State Research Development Program of China (Grant No. 2016YFC0600202) for financial support, as well as financial support from National Natural Science Foundation of China (Nos. 41330208, 41572200 and 41190070) and State Key Laboratory for Mineral Deposits Research (Nanjing University) (ZZKT–201603). Peter A. Cawood acknowledges support from Australian Research Council grant FL160100168.The Neoproterozoic Jiangnan Orogen in South China records a succession of arc-trench-basin assemblages culminating in accretion of the bounding Yangtze and Cathaysia blocks to form the stabilized South China Craton. The orogen can be traced over some 1500 km and extends up to 100 km across strike. It is divisible into three domains: the northeast domain (also referred to as the Huaiyu or Shuangxiwu Terrane), the central domain (Jiuling Terrane), and an undifferentiated southwest domain. The northeast domain contains arc type volcanic suites and I-type granitoids dated at ca. 970–850 Ma. It is interpreted as an intra–oceanic terrane based on the juvenile radiogenic isotopic signature of the igneous rocks, the absence of older detritus and inherited xenocrysts, and the presence of ophiolites along its southwestern and western margins. The central and southwest domains contain trench-arc-basin assemblages of clastic sedimentary units, mappable magmatic arc suites and ophiolitic mélanges (Sibao and equivalent groups) that range in age from ca. 880 to 820–815 Ma. The presence of old zircon grains within these two domains, both as detritus within sedimentary units and as inherited zircon in arc basalt, suggest they formed at convergent continental margins. S-type granites dated at 845–815 Ma are a distinctive element of the central and southwest domains. The ages of these granites overlap with convergent plate magmatism in the two domains, arguing against previous models for plume-rift and post-collisional geodynamic settings. Instead, these bodies likely formed in an accretionary orogenic margin setting in which granitic magmatism occurred in an extensional regime triggered by slab rollback. The slab-rollback process triggered mantle-sourced thermal input and partial melting of the older and buried arc-bounding basin sediments. Early Paleozoic S-type granites in the Lachlan and New England belts in eastern Australia and Jurassic ones in the Cordillera belt of the western US provide analogous geodynamic environments. Isotopic data indicate that the central Jiangnan domain experienced significant crustal growth, whereas in the southwest domain there was a greater degree of crustal reworking. The character and distribution of the early Neoproterozoic sedimentary and igneous succession in the orogen suggests it represents a ca. 970–820 Ma accretionary orogen. Upper age limits on the Jiangnan Orogen are provided by a regional angular unconformity in the central and southwest domains at ca. 810–805 Ma, and in the northeast domain at ca. 825 Ma, along with the overlying bimodal volcanic and clastic sedimentary successions mostly dated at ca. 810–730 Ma. Thus, timing of final assembly of South China displays variations across the Jiangnan Orogen, from ca. 825 Ma in the northeast to ca. 820–805 Ma in the central and southwest of the orogen. Post-assembly successions are parts of the Nanhua Basin and are interpreted to have formed during regional lithospheric extension across the eastern and central South China Craton. The age patterns across the South China Craton are indicative of northwest directed accretion of fragments and suggest an external rather than an internal position of the craton within the assembled Rodinia supercontinent. Paleomagnetic data, regional correlations and sedimentary records are consistent with a position along the northern margin of Rodinia, adjacent to India and Australia. The Jiangnan Orogen recorded the accretion of trench-arc assemblages and ultimately the Yangtze Block to the Cathaysia Block that was already located on the margin of Rodinia. The Panxi-Hanan belt, which lies along the western and northwestern margin of the Yangtze Block, formed on the upper plate to a subduction system that both overlaps with, and is younger than, the Jiangnan Orogen. The belt provides a record of ongoing accretion on the Rodinia margin until the mid-Neoproterozoic.PostprintPeer reviewe

An early Neoproterozoic accretionary prism ophiolitic mélange from the western Jiangnan orogenic belt, South China

The authors acknowledge the financial support provided by the National Basic Research Program of China (973 Program, 2012CB416701) and the National Natural Science Foundation of China (41330208 and 41572200).The Neoproterozoic Jiangnan orogenic belt delineates the suture zone between the Cathaysia and Yangtze blocks of the South China Craton. The western part of the belt, in the Longsheng region, consists of a disrupted mafic-ultramafic assemblage of pillow basalt, gabbro, diabase, and peridotite along with siliceous marble, ophicalcite, and jasper mixed with basalt. Significant talc deposits occur on the margins of the ultramafic bodies as well as in the transition zone between marble and basalt. Primary rock relations are largely overprinted by pervasive shearing, resulting in disruption of the assemblage into series of discontinuous blocks within a phyllite matrix. West-dipping thrust faults mark the eastern contact of blocks, and the overall succession has the appearance of a tectonic mélange. U-Pb zircon age data from the gabbros and diabases yield crystallization ages of 867 ± 10, 863 ± 8, and 869 ± 9 Ma, with positive εHf(t) values. The gabbro, basalt, serpentinite, and some talc samples display minor light rare earth element?enriched patterns with obvious depletion of Nb and Ta, indicating a subduction-related setting. The tuffaceous phyllite shows similar geochemical features. A few mafic rocks and the altered ultramafic rocks display mid-ocean ridge basalt (MORB) affinity. Overall lithostratigraphic relationships, age data, and geochemical signatures suggest a forearc setting that was imbricated and disrupted within an accretionary prism environment to form an ophiolitic mélange. The pillow basalt, red jasper, and MORB-type mafic-ultramafic rocks within the mélange occur as exotic blocks derived from the subducting oceanic plate, whereas the arc-type mafic rocks occur as autochthonous blocks, which are all exposed in a matrix of sandy and tuffaceous phyllite.Publisher PDFPeer reviewe

A Practical Guide for X-Ray Diffraction Characterization of Ga(Al, In)N Alloys

Ga(In, Al)N alloys are used as an active layer or cladding layer in light emitting diodes and laser diodes. x-ray diffraction is extensively used to evaluate the crystalline quality, the chemical composition and the residual strain in Ga(Al,In)N thin films, which directly determine the emission wavelength and the device performance. Due to the minor mismatch in lattice parameters between Ga(Al, In)N alloy and a GaN virtual substrate, x-ray diffraction comes to a problem to separate the signal from Ga(Al,In)N alloy and GaN. We give a detailed comparison on different diffraction planes. In order to balance the intensity and peak separation between Ga(Al,In)N alloy and GaN, (0004) and (1015) planes make the best choice for symmetric scan and asymmetric scan, respectively.Comment: 9 pages, 5 figure

UPS 2.0: unique probe selector for probe design and oligonucleotide microarrays at the pangenomic/ genomic level

<p>Abstract</p> <p>Background</p> <p>Nucleic acid hybridization is an extensively adopted principle in biomedical research, in which the performance of any hybridization-based method depends on the specificity of probes to their targets. To determine the optimal probe(s) for detecting target(s) from a sample cocktail, we developed a novel algorithm, which has been implemented into a web platform for probe designing. This probe design workflow is now upgraded to satisfy experiments that require a probe designing tool to take the increasing volume of sequence datasets.</p> <p>Results</p> <p>Algorithms and probe parameters applied in UPS 2.0 include GC content, the secondary structure, melting temperature (Tm), the stability of the probe-target duplex estimated by the thermodynamic model, sequence complexity, similarity of probes to non-target sequences, and other empirical parameters used in the laboratory. Several probe background options,<b><it>Unique probe within a group</it></b><it>,</it><b><it>Unique probe in a specific Unigene set</it></b><it>,</it><b><it>Unique probe based onthe pangenomic level</it></b><it>,</it> and <b><it>Unique Probe in the user-defined genome/transcriptome</it></b><it>,</it> are available to meet the scenarios that the experiments will be conducted. Parameters, such as salt concentration and the lower-bound Tm of probes, are available for users to optimize their probe design query. Output files are available for download on the result page. Probes designed by the UPS algorithm are suitable for generating microarrays, and the performance of UPS-designed probes has been validated by experiments.</p> <p>Conclusions</p> <p>The UPS 2.0 evaluates probe-to-target hybridization under a user-defined condition to ensure high-performance hybridization with minimal chance of non-specific binding at the pangenomic and genomic levels. The UPS algorithm mimics the target/non-target mixture in an experiment and is very useful in developing diagnostic kits and microarrays. The UPS 2.0 website has had more than 1,300 visits and 360,000 sequences performed the probe designing task in the last 30 months. It is freely accessible at <url>http://array.iis.sinica.edu.tw/ups/.</url></p> <p>Screen cast: <url>http://array.iis.sinica.edu.tw/ups/demo/demo.htm</url></p

Optical, electrical, and solar energy-conversion properties of gallium arsenide nanowire-array photoanodes

Periodic arrays of n-GaAs nanowires have been grown by selective-area metal–organic chemical-vapor deposition on Si and GaAs substrates. The optical absorption characteristics of the nanowire-arrays were investigated experimentally and theoretically, and the photoelectrochemical energy-conversion properties of GaAs nanowire arrays were evaluated in contact with one-electron, reversible, redox species in non-aqueous solvents. The radial semiconductor/liquid junction in the nanowires produced near-unity external carrier-collection efficiencies for nanowire-array photoanodes in contact with non-aqueous electrolytes. These anodes exhibited overall inherent photoelectrode energy-conversion efficiencies of [similar]8.1% under 100 mW cm^−2 simulated Air Mass 1.5 illumination, with open-circuit photovoltages of 590 ± 15 mV and short-circuit current densities of 24.6 ± 2.0 mA cm^−2. The high optical absorption, and minimal reflection, at both normal and off-normal incidence of the GaAs nanowire arrays that occupy <5% of the fractional area of the electrode can be attributed to efficient incoupling into radial nanowire guided and leaky waveguide modes

Confront Holographic QCD with Regge Trajectories of vectors and axial-vectors

We derive the general 5-dimension metric structure of the $Dp-Dq$ system in type II superstring theory, and demonstrate the physical meaning of the parameters characterizing the 5-dimension metric structure of the \textit{holographic} QCD model by relating them to the parameters describing Regge trajectories. By matching the spectra of vector mesons $\rho_1$ with deformed $Dp-Dq$ soft-wall model, we find that the spectra of vector mesons $\rho_1$ can be described very well in the soft-wall $D3-Dq$ model, i.e, $AdS_5$ soft-wall model. We then investigate how well the $AdS_5$ soft-wall model can describe the Regge trajectory of axial-vector mesons $a_1$. We find that the constant component of the 5-dimension mass square of axial-vector mesons plays an efficient role to realize the chiral symmetry breaking in the vacuum, and a small negative $z^4$ correction in the 5-dimension mass square is helpful to realize the chiral symmetry restoration in high excitation states.Comment: 9 pages, 3 figure and 3 tables, one section adde