Genesis of Highly Fractionated I-Type Granites from Fengshun Complex:Implications to Tectonic Evolutions of South China

The South China Block is characterized by the large-scale emplacement of felsic magmas and giant ore deposits during the Yanshanian. We present zircon Hf isotopic compositions, whole-rock major and trace element compositions of the Fengshun complex, located in eastern Guangdong Province, South China. The Fengshun complex is a multi-stage magmatic intrusion. It is composed of two main units, i.e., the Mantoushan（MTS） syeno-monzogranites, alkali feldspar granites and the Hulutian（HLT） alkali feldspar granites. LA-ICPMS zircon dating shows that the complex emplaced in 166–161 and 139±2 Ma, respectively. Geochemically, the MTS granites show relatively various geochemical compositions with low REE contents（87.76×10-6–249.71×10-6）, Rb/Sr ratios（1.19–58.93）, pronounced Eu negative anomaly（0.01–0.37） and low Nb/Ta ratios（2.40–6.82）. In contrast, the HLT granites exhibit relatively stable geochemical characteristics with high REE contents（147.35×10-6– 282.17×10-6）, Rb/Sr ratios（2.05–10.30） and relatively high Nb/Ta ratios（4.45–13.00）. The isotopic data of the MTS granites display relatively enriched values, with ISr varying from 0.708 2 to 0.709 7, εNd（t） from-7.8 to-6.9 and εHf（t） from-7.4 to-3.2, in comparison with those of the HLT which are ISr=0.703 05–0.704 77, εNd（t）=-5–-3.4 and εHf（t）=-0.7–1.8）. The two-stage model ages of the MTS granites（T2DM（Nd）=1.51–1.59 Ga and T2DM（Hf）=1.26–1.48 Ga） are also higher than those of the HLT granites（T2DM（Nd）=1.21–1.34 Ga and T2DM（Hf）=0.96–1.10 Ga）. Thus the MTS and HLT granites might originate from different sources. The former is more likely derived from partial melting of Meso-Proterozoic basement triggered by upwelling of asthenosphere and/or underplate of the basaltic magma and then extensive fractional crystallisation, similar to the genesis of Early Yanshanian granitoids of the EW-trending tectono-magmatism belt in the Nanling range. In comparison, the latter might have involved with asthenosphere component, similar to the Early Cretaceous granitoids of NE-NNE-trending granitoid-volcanic belt in coastal region, southeastern China. We propose that the MTS granites were mainly formed in Paleo-Tethyan post-orogenic extensional tectonic setting whereas the HLT granites were formed in the back-arc extensional tectonic setting. The period at 139 Ma represents the initial time of roll-back of the paleo-Pacific Plate in SE-trending.

Magmatic Evolution of Garnet-Bearing highly Fractionated Granitic Rocks from Macao,Southeast China:Implications for Granite-Related Mineralization Processes

The widespread W-(Mo)-Sn-Nb-Ta polymetallic mineralization in Southeast(SE)China is genetically associated with Mesozoic highly fractionated granitic rocks.Such rocks have enigmatic mineralogical and geochemical features,making its petrogenesis an intensely debated topic.To better understand the underlying magma evolution processes,petrography,garnet chemistry and whole-rock major and trace element data are reported for Jurassic highly fractionated granitic rocks and associated microgranite and aplitepegmatite dikes from Macao and compared with coeval similar granitic rocks from nearby areas in SE China.Despite the fact that the most evolved rocks in Macao are garnet-bearing aplite-pegmatite dikes,the existence of coeval two-mica and garnet-bearing biotite and muscovite granites displaying more evolved compositions(e.g.,lower Zr/Hf ratios)indicates that the differentiation sequence reached higher degrees of fractionation at a regional scale.Although crystal fractionation played an important role,late-stage fluid/melt interactions,involving F-rich fluids,imparted specific geochemical characteristics to Macao and SE China highly fractionated granitic rocks such as the non-CHARAC(CHArge-and-RAdius-Controlled)behavior of trace elements,leading,for example,to non-chondritic Zr/Hf ratios,Rare Earth Elements(REE)tetrad effects and Nb-Ta enrichment and fractionation.Such process contributed to the late-stage crystallization of accessory phases only found in these highly evolved facies.Among the latter,two populations of garnet were identified in MGI(Macao GroupⅠ)highly fractionated granitic rocks:small grossular-poor euhedral grains and large grossular-rich skeletal garnet grains with quartz inclusions.The first group was mainly formed through precipitation from highly evolved Mn-rich slightly peraluminous melts under low-pressure and relatively low temperature(~700℃)conditions.Assimilation of upper crust metasedimentary materials may have contributed as a source of Mn and Al to the formation of garnet.The second group has a metasomatic origin related to the interaction of magmatic fluids with previously crystallized mineral phases and,possibly,with assimilated metasedimentary enclaves or surrounding metasedimentary strata.The highly fractionated granitic rocks in Macao represent the first stage in the development of granite-related W-(Mo)-Sn-Nb-Ta mineralization associated with coeval more evolved lithotypes in SE China.

Evaluation of Mechanical Properties of Highly Filled Jute Fiber Reinforced Composites

This study aims for development of highly filled jute fiber reinforced composites that contains jute fiber over fiber weight fraction 60%,and jute fiber reinforced composite was fabricated by the hot-pressing method.The molding temperature was changed from 175°C to 230°C,to investigate the effect of molding temperature on the mechanical properties of jute fiber reinforced composites.The effect of surface treatment of jute fiber on the mechanical properties of jute fiber reinforced composites was also investigated.As a result,the jute fiber reinforced composites using surface treated fiber has low porosity,and the jute fiber reinforced composite having low porosity has high flexural strength and modulus.The jute fiber reinforced composite using acetone treated fiber molded at 200°C has the maximum flexural strength and modulus.

Petrogenesis of Kejie Granite in the Northern Changning-Menglian Zone, Western Yunnan: Constraints from Zircon U-Pb Geochronology, Geochemistry and Hf Isotope

The Kejie pluton is located in the north of the Changning-Menglian suture zone. The rock types are mainly biotite-granite. Zircon LA-ICP-MS U-Pb dating indicates that the Kejie pluton emplaced at about 80-77 Ma, Late Cretaceous. The Kejie pluton samples are characterized by high SiO2 （71.68%-72.47%）, K2O （4.73%-5.54%）, total alkali （K2O ＋ Na2O = 8.21%-8.53%）, K2O/Na2O ratios （1.36-1.94） and low P2O5 （0.13%-0.17%）, with A/CNK of 1.025-1.055; enriched in U, Th, and K, depleted in Ba, Nb, St, Ti, P and Eu. They are highly fractionated, slightly peraluminous 1-type granite. The two samples of the Kejie pluton give a large variation of εHf（t） values （-5.04 to 1.96） and Hf isotope crustal model ages of 1.16-1.5 Ga. Zircon Hf isotopes and zircon saturation temperatures of whole-rock （801℃-823℃） show that the mantle-derived materials maybe have played a vital role in the generation of the Kejie pluton. The Kejie pluton was most likely generated in a setting associated with the eastward subduction of the neo-Tethys ocean, where intrusion of mantle wedge basaltic magmas in the crust caused the anatexis of the latter, forming hybrid melts, which subsequently experienced high-degree fractional crystallization.

Geochronology and geochemistry of Late Carboniferous dykes in the Aqishan-Yamansu belt,eastern Tianshan:Evidence for a post-collisional slab breakoff

With aim of providing constraints on the Late Paleozoic tectonic evolution of the southern Central Asian Orogenic Belt(CAOB),an integrated study was conducted on the geochronological and geochemical data for dioritic,granitic and diabase dykes from the Aqishan-Yamansu belt in the eastern Tianshan,NW China.Zircon U-Pb dating indicates that the dioritic and granitic dykes were both emplaced in the Late Carboniferous(~311 Ma and^315 Ma).The dioritic dykes show adakitic characteristics and have high Na2 O and positiveεHf(t)values(+12 to+17),which suggest an origin from partial melts of a subducted oceanic slab.The granitic dykes have high SiO2 and K2 O contents and are characterized by en riched light rare earth elements(LREE)and slightly flat heavy rare earth elements(HREE),with negative Eu and Nb-Ta-Ti anomalies.These dykes are alkali-calcic and show geochemical features of highly fractionated Itype granites.Their positiveεHf(t)values(+16 to+17)suggest that they were derived from a juvenile accreted oceanic crustal sou rce.The coeval diabase dykes have low SiO2 and K2 O contents but high TiO2,MgO and Mg#(54-59).They are enriched in LREE and show characteristics of enriched mid-ocean ridge basalts(E-MORB).The relatively high Ba/Th,slightly low Th/Ta ratios,and negative Nb-Ta anomalies imply a mantle source metasomatised by slab-derived fluids.Thus,these basic dykes were generated likely by partial melting of the upwelling asthenosphere mantle with a slight influence of slab-derived fluids.Therefore,we suggest that the formation of these Late Carboniferous dykes were triggered by a post-collisional slab breakoff and the Aqishan-Yamansu belt was a continental arc formed by southdipping subduction of the Kangguer oceanic plate.

Petrogenesis and Geodynamic Implications of Early Cretaceous(~130 Ma)Magmatism in the Baingoin Batholith,Central Tibet:Products of Subducting Slab Rollback

The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane.Its petrogenesis and tectonic setting have been studied for decades,but remain controversial.Here we report data on geochronology,geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith,which provide more evidence to uncover its petrogenesis and regional geodynamic processes.The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I-type,S-type and highly fractionated granites.The I-and S-type granites exhibit medium SiO2,high K_(2)O/Na_(2)O with negativeεNd(t)andεHf(t)values,whereas,the albite granites have very high SiO_(2)(79.04%–80.40%),very low K_(2)O/N_(2)O,negativeεNd(t)and a large variation inεHf(t).Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area.The granodiorites involved had a hybrid origin from partial melting of basalt-derived and Al-rich rocks in the crust,the porphyritic monzogranites being derived from partial melting of pelitic rocks.The albite granites crystallized from residual melt separated from K-rich magma within the‘mush’process and underwent fractionation of K-feldspar.We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward-subducting slab of the NTO.

Microstructure and Wear Performance of High Volume Fraction Carbide M_7C_3 Reinforced Fe-based Composite Coating Fabricated by Plasma Transferred Arc Welding

The fabrication of high volume fraction （HVF） M7C3 （M=Cr, Fe） reinforced Fe-based composite coating on ASTM A36 steel plate using plasma transferred arc （PTA） welding was studied. The results showed that the volume fraction of carbide M7C3 was more than sixty percent, and the relative wear resistance of the coating tested on a block-on-ring dry sliding tester at constant load （100 N） and variable loads （from 100 to 300 N） respectively was about 9 and 14 times higher than that of non-reinforced a-Fe coating. In addition, under constant load condition the friction coefficients （FCs） of two coatings increased first and then decreased with increasing sliding distance. However, under variable loads condition the FCs of non-reinforced a-Fe based coating increased gradually, while that of HVF MTC3 reinforced coating decreased as the load exceeded 220 N. The worn surface of non-reinforced a-Fe based coating was easily deformed and grooved, while that of the HVF M7C3 reinforced coating was difficult to be deformed and grooved.

Flow Characteristics of Crude Oil with High Water Fraction during Non-heating Gathering and Transportation

In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.

New CICC Design Versions with High Copper Fraction for HT-7U Tokamak

The peak fields of HT-7U TF/PF coils are designed at 5.8 T and 4.5 T, respectively. The superconducting (SC) NbTi/Cu strands for the coils have a quite low copper fraction (0.58). To increase the ratio of the limiting current Vs. critical current for the cable in conduit conductor (CICC), the first-stage subcable consists of several copper strands twisted around a SC composite one. The copper strand diameter is different from the SC one. Based on Bottura's CICC design approach we take the product of total copper cross-section and wetted perimeter as one of the key design parameters to meet with stability margin requirement. The product reaches 114 cm3 for 15.5 kA TF CICC at operating temperature of 4.2 K and 139 cm3 for 15 kA PF CICC at 3.8 K to obtain stability margins of 280 and 700 mJ/cm3, respectively.

Maximum Power Point Tracking With Fractional Order High Pass Filter for Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell(PEMFC) is widely recognized as a potentially renewable and green energy source based on hydrogen. Maximum power point tracking(MPPT) is one of the most important working conditions to be considered. In order to improve the performance such as convergence and robustness under disturbance and uncertainty,a fractional order high pass filter(FOHPF) is applied for the MPPT controller design based on the traditional extremum seeking control(ESC). The controller is designed with integerorder integrator(IO-I) and low pass filter(IO-LPF) together with fractional order high pass filter(FOHPF), by substituting the normal HPF in the original ESC system. With this FOHPF ESC,better convergence and smoother performance are achieved while maintaining the robust specifications. First, tracking stability is discussed under the commensurate-order condition. Then,simulation results are included to validate the proposed new FOHPF ESC scheme under disturbance. Finally, comparison results between FOHPF ESC and the traditional ESC method are also provided.

Petrogenesis, Tectonic Evolution and Geothermal Implications of Mesozoic Granites in the Huangshadong Geothermal Field, South China

Mesozoic multi-stage tectono-magmatic events produced widely distributed granitoids in the South China Block. Huangshadong(HSD) is located in south-eastern South China Block, where closely spaced hot springs accompany outcrops of Mesozoic granites. New data on whole-rock geochemistry, zircon U-Pb geochronology, and zircon Lu-Hf isotopes are presented, to study the petrogenesis and tectonic evolution of the granites, and to explore the relationship between granites and geothermal anomalies. Zircon U-Pb isotopes display three periods of granites in the HSD area: Indosinian(ca. 253 Ma, G4) muscovite-bearing monzonitic granite, early Yanshanian(ca. 175–155 Ma, G5 and G3) monzonitic granite and granodiorite, and late Yanshanian(ca. 140 Ma, G1 and G2) biotite monzonitic granite. In petrogenetic type, granites of the three periods are I-type granite. Among them, G1, G2, G3, and G4 are characterized by high fractionation, with high values of SiO2, alkalis, Ga/Al, and Rb/Sr, and depletion in Sr, Ba, Zr, Nb, Ti, REEs, with low(La/Yb)N, Nb/Ta, and Zr/Hf ratios and negative Eu anomalies. In terms of tectonic setting, 253 Ma G4 may be the product of partial melting of the ancient lower crust under post-orogenic extensional tectonics, as the closure of the Paleo-Tethys Ocean resulted in an intracontinental orogeny. At 175 Ma, the subduction of the Pacific Plate became the dominant tectonic system, and low-angle subduction of the Paleo-Pacific Plate facilitated partial melting of the subducted oceanic crust and basement to generate the hornblende-bearing I-type granodiorite. As the dip angle of the subducting plate increased, the continental arc tectonic setting was transformed to back-arc extension, inducing intense partial melting of the lower crust at ca. 158 Ma and resulting in the most frequent granitic magmatic activity in the South China hinterland. When slab foundering occurred at ca. 140 Ma, underplating of mantle-derived magmas caused melting of the continental crust, generating extensive highly fractionated granites in HSD. Combining the granitic evolution of HSD and adjacent areas and radioactive heat production rates, it is suggested that highly fractionated granites are connected to the enrichments in U and Th with magma evolution. The high radioactive heat derived from the Yanshanian granites is an important part of the crustal heat, which contributes significantly to the terrestrial heat flow. Drilling ZK8 reveals deep, ca. 140 Ma granite, which implies the heat source of the geothermal anomalies is mainly the concealed Yanshanian granites, combining the granite distribution on the surface.

Strengthening Mechanisms of 15 vol.% Al_(2)O_(3) Nanoparticles Reinforced Aluminum Matrix Nanocomposite Fabricated by High Energy Ball Milling and Vacuum Hot Pressing

Increasing nanoparticle volume fraction has been proved to be effective in improving the strength of nanoparticle reinforced Al matrix nanocomposite. However, the underlying mechanisms for the ultrahigh strength of those nanocomposites with high volume fraction(> 10 vol.%) nanoparticles are short of experimental research. In this study, the strengthening mechanisms of high strength Al matrix nanocomposite reinforced with 15 vol.% Al_(2)O_(3) nanoparticles were investigated experimentally and analyzed theoretically. The results show that the thermal mismatch induced geometrically necessary dislocations exhibit a negligible strengthening effect, because of their low density in the nanocomposite that is contradiction to the conventional dislocation punch model. Orowan mechanism makes a major strengthening contribution in view of the deformation process dominated by nanoparticle-dislocation interactions due to the extreme pinning effect of nanoparticles on dislocation motion. In addition, the several mechanisms including grain boundary strengthening, load transfer strengthening, and elastic modulus mismatch induced dislocation strengthening contribute to the strength increase.

On a Class of Non-local Operators in Conformal Geometry

In this expository article, the authors discuss the connection between the study of non-local operators on Euclidean space to the study of fractional GJMS operators in conformal geometry. The emphasis is on the study of a class of fourth order operators and their third order boundary operators. These third order operators are generalizations of the Dirichlet-to-Neumann operator.