Adakitic rocks associated with the Shilu copper–molybdenum deposit in the Yangchun Basin,South China,and their tectonic implications

South China is famous for the extensive magmatism and polymetallic mineralization that took place there in the Mesozoic. Shilu is a large porphyry–skarn Cu–Mo deposit in the Yangchun Basin, South China. The lithology of the Shilu intrusion is granodiorite and quartz diorite, both of which are high-K calc-alkaline series, with high Sr([400 ppm) content along with low Y and Yb contents. Most of the samples have characteristics of adakite except for a few samples that have slightly higher Y and Yb contents, which may be plausibly explained by crustal contamination. Laser Ablation Inductively Coupled Plasma Mass Spectrometry zircon U–Pb dating revealed ages between 106.6 ± 1.3 and 103.9 ± 0.5 Ma, with multiple magmatic pulses. Molybdenite Re–Os isochron age of 102.2 ± 2.9 Ma(MSWD = 9.4) was determined, which is identical to the youngest zircon U–Pb age(103.9 ± 0.5 Ma) within error.The Shilu intrusion has high oxygen fugacity as indicated by high zircon Ce^(4+)/Ce^(3+) and Eu_N/Eu_N* ratios. Considering the geochemical characteristics(high Sr, and low Y and Yb contents), high oxygen fugacity, and copper mineralization of the Shilu intrusion, it was most likely formed by partial melting of a subducted young oceanic slab. Whole-rock Sr–Nd isotope-, zircon Hf isotope-, and whole-rock trace element analyses show that Shilu adakitic magmas may have interacted with type II enriched mantle and/or crustal materials during ascent. South China was affected by the Pacific tectonic regime to the east and the Neo-Tethys tectonic regime to the south in the Cretaceous. Based on the Pacific Plate drifting and rotation history, it is hard to explain how the Pacific Plate would have subducted and melted, forming adakitic rocks in the Shilu region. Considering the tectonic history of Southeast Asia and the South China Sea, the Neo-Tethys trench should have been much closer to the South China Block in the Cretaceous, and thus have had a greater impact on the South China Block. Based on the subduction direction, time of subduction,and distance between the Neo-Tethys subduction zone and the Shilu deposit, subduction of the Neo-Tethys ridge is the best mechanism for explaining the Shilu adakitic rocks and Cu–Mo mineralization.

Interference-Free Pilot Design and Channel Estimation Using ZCZ Sequences for MIMO-OFDM-Based C-V2X Communications

Cellular vehicle-to-everything(C-V2X) communications is regarded as a promising and feasible solution for 5G-enabled vehicular communications and networking. In this paper, we investigate the pilot design and channel estimation problem in MIMO-OFDM-based C-V2X systems with severe co-channel interference due to spectrum reusing among different V2X communication links. By using zero-correlation zone(ZCZ) sequences, we provide an interference-free pilot design scheme and a corresponding time-domain(TD) correlation-based channel estimation(TD-CCE) method. We employ the ZCZ sequences from the same family set to be designed as the TD pilot symbols and guarantee the pilot sequeneces for neighboring V2X communication links are code-division multiplexing(CDM). The co-channel pilot interference of the deisgned pilot symbols can be effectively eliminated by exploiting the provided TD-CCE method. Simulation results indicate that the accuracy of channel estimation can be effectively improved by the proposed scheme, whose performance is close to that of the non-interference situation.

5G ENABLED VEHICULAR COMMUNICATIONS AND NETWORKING

Vehicular communications and networking(VCN)is considered a billion-dollar industry.Its development not only possesses economic value,but also has enormous social potential.The earliest vehicular network started from the dedicated short range networks,such as the IEEE 802.11p standard established at the beginning of this century.In recent years,the public access network based VCN has been rapidly advanced.For example,LTE-V based on 4G LTE is under standardization。

Substitution of Ni for Zn on microstructure and mechanical properties of Mg-Gd-Y-Zn-Mn alloy

This study analyzes the effect of substitution of Ni for Zn on microstructure and mechanical properties of Mg-Gd-Y-Zn-Mn alloy.Our results show that the volume fraction of Mg5(Gd,Y)and(Mg,Zn)3RE phase decreased and LPSO phase increased with more substitution of Ni.After homogenization,onlyα-Mg and LPSO phase existed.In Mg-Gd-Y-Zn-Mn alloys,the LPSO phases mainly consisted of the 14H type.While in Mg-Gd-Y-Ni-Mn alloy,the LPSO phases consisted of the 18R type.In addition,compared with Mg-Gd-Y-Zn-Mn alloy,the mechanical properties of as-extruded Ni-substitution alloys were improved due to the better refinement of the size of grains and LPSO phases.The tensile strength in as-extruded Mg-Gd-Y-Ni-Mn alloy could reach up to 400 MPa with 18%of the elongation to failure.

In situ LA-ICP-MS analyses of mica and wolframite from the Maoping tungsten deposit,southern Jiangxi,China

The Maoping tungsten deposit is located in the Nanling W-Sn metallogenic belt in South China.Greisen and quartz vein types of mineralization developed in this deposit.Protolithionite occurs in the granite.Zinnwaldite is occurs mainly in greisen and wolframite-quartz veins whereas phengite is found in the underground quartz veinlets.In granite and greisen,protolithionite,and zinnwaldite are partly replaced by Li-phengite.LA-ICP-MS trace element analyses of micas and wolframite are employed to characterize the ore-forming source and evolution of ore forming fluids.Micas show compositional variation trend in vertical directions with a decrease of W,Sn,Nb,and Ta and an increase of MgO,V,Ni,and Co.Wolframite in greisen has higher Mo,Sn,Nb,Ta,and REEs than those in quartz veins.All wolframites show similar REE patterns with enrichment of HREE.Wolframites in greisen and quartz veins have negative Eu anomalies,while wolframites in quartz veinlet display positive Eu anomalies.Compositions of mica and wolframite from different mining levels of the Maoping deposit suggest that the ore-forming fluids are dominated by magmatic hydrothermal fluids in the deep with a slight addition of meteoric water in the shallow.Brittle fractureinduced depressurization and fluid mixing controlled the evolution of ore-forming fluids and possibly lead to the wolframite deposition.

In situ observations of tungsten speciation and partitioning behavior during fluid exsolution from granitic melt

Most economically important tungsten(W)deposits are of magmatic-hydrothermal origin.The species and partitioning of W during fluid exsolution,considered to be the controlling factors for the formation of ore deposits,are thus of great significance to investigate.However,this issue has not been well addressed mainly due to the significant difference in reported partition coefficients(e.g.,from strongly incompatible to strongly compatible)between fluid and melt(D_(W)^(fluid/melt)).Here,we used an in situ Raman spectroscopic approach to describe the W speciation,and to quantitatively determine the Dfluid/melt of individual and total W species in granite melts and coexisting Na2WO4 solutions at elevated temperatures(T;700–800C)and pressures(P;0.35–1.08 GPa).Results show that WO_(4)^(2-)and HWO4are predominant W species,and the fractions of these two species are similar in melt and coexisting fluid.The partitioning behaviors of WO_(4)^(2-)and HWO4are comparable,exhibiting strong enrichment in the fluid.The total DW fluid/melt ranges from 8.6 to 37.1.Specifically,DW fluid/melt decreases with rising T–P,indicating that shallow exsolution favors enrichment of W in evolved fluids.Furthermore,Rayleigh fractionation modeling based on the obtained D_(W)^(fluid/melt)data was used to describe the fluid exsolution processes.Our results strongly support that fluid exsolution can serve as an important mechanism to generate W-rich oreforming fluids.This study also indicates that in situ approach can be used to further investigate the geochemical behavior of ore-forming elements during the magmatic-hydrothermal transition,especially for rare metals associated with granite and pegmatite.

Full-Duplex Energy-Harvesting Relay Networks:Capacity-Maximizing Relay Selection

In this study,we investigate the relay selection(RS)problem in full-duplex energy-harvesting(FDEH)relay networks,where the relays are wirelessly powered by harvesting a portion of the received signal power from the source.We extend the investigation of the relay selection problem in FDEH relay networks to enable multiple relays to be selected simultaneously for improved performance.This is in contrast with existing studies on RS in similar setups,where only one relay can be selected in a transmission cycle.Our simulations show that selecting only a single relay is not always optimal,especially at low signal-to-noise ratios(SNRs).Furthermore,in this paper,we present the design of a greedy RS method with quadratic complexity for FDEH relay networks.Compared with the exhaustive-search-based RS,the proposed greedy RS achieves near-optimum performance in terms of the end-to-end capacity with significantly reduced complexity.

Distributed Beamforming for Energy-Harvesting Relaying in Vehicular Networks

Recently,battery capacity and charging speed have been the bottlenecks of mobile communication networks.Energy harvesting(EH)relaying has become a promising solution for green 5th generation mobile communication with the advancement of wireless power transfer technology.In this paper,we investigate EH relaying in vehicular networks and adopt distributed beamforming(DB)to enhance the reliability and capacity of EH relaying.To be more specific,we propose a DB solution based on the joint optimization of power-splitting(PS)factors.For amplify-and-forward relaying,to transform the optimization problem into a quasi-convex one,we apply the semidefinite relaxation(SDR)method so that we can effectively attain the global optimal solution,while the suboptimal DB solution with distributed optimal PS factor which only requires local channel state information is also proposed.For decode-and-forward relaying,to get the optimal PS factors,we set a signal-to-noise ratio threshold at the relays,which can reduce the system error rate caused by the poor transmission link.Simulation results demonstrate the efficiency of our proposed DB-based EH relaying scheme in vehicular networks.