High Degree Of Crystallization Research Articles

Decoding multiple zoning patterns in clinopyroxene phenocrysts at Vulcano Island: A record of dynamic crystallization through interconnected reservoirs

Here we document how the different growth features and intracrystalline distributions of both major and trace cations in clinopyroxene phenocrysts are important recorders of the intricate magma dynamics at Vulcano Island (Aeolian Arc, Italy). The compositions of clinopyroxene phenocrysts from products erupted over the last ~54 ka cluster at different degrees of evolution, paralleling the polybaric-polythermal differentiation of mantle-derived mafic magmas into more evolved silicic melts. The hotter lower crust is the most favorable location for the storage of mafic magmas and the early crystallization of diopsidic (Mg#91) clinopyroxene (Pmax ≈ 750 MPa and Tmax ≈ 1220 °C). Diopsidic phenocrysts are depleted in both rare earth elements (REE) and high field strength elements (HFSE) but are enriched in transition elements (TE). The transfer and accumulation of primitive magmas in the colder upper crustal regions lead to the formation of an interconnected series of more differentiated magmatic reservoirs (P ≈ 100–450 MPa and T ≈ 1100–1180 °C) hosting discrete populations of clinopyroxene (Mg#84–85) with a broad spectrum of zonations and dissolution features. Recharge bands in clinopyroxene are markers of multiple inputs of primitive REE-HFSE-poor, TE-rich magmas from depth. Augitic phenocrysts (Mg#82) with strong negative Eu anomaly and REE + HFSE enrichments crystallizes from highly differentiated trachytic and rhyolitic melts stored at very shallow crustal conditions (P ≤ 50 MPa and T ≤ 1100 °C). These silicic reservoirs represent residual melts trapped-extracted from crystal-dominated mush regions in the uppermost part of the plumbing system. The residence time of clinopyroxene increases from ∼0.1 to ∼44 years from basalt to rhyolite, together with an increasing number of recharge bands. The mineral assemblage in more silicic and viscous mush melts is sufficiently resilient to record numerous mafic injections and high degrees of magma mixing, hybridization, and crystallization before eruption. Overall, the compositional zoning pattern of clinopyroxene presents a picture of plumbing system that extends through the crust and is characterized by distributions of melts and crystals which are progressively more evolved and heterogeneous in both space and time.

Petrogenesis of Himalayan Leucogranites: Perspective From a Combined Elemental and Fe‐Sr‐Nd Isotope Study

AbstractThe petrogenesis of Himalayan leucogranites remains crucial for understanding the thermal and tectonic evolution of the Himalayan orogen. To understand whether they are largely pristine melts of crustal anatexis or have experienced a high degree of fractional crystallization (FC), we present Fe isotopic data of 30 representative Himalayan leucogranites and 9 local metasedimentary rocks. Excepting three garnet leucogranites with low δ56Fe (−0.04‰–0.06‰) that are likely affected by garnet accumulation, tourmaline, and two‐mica leucogranites have largely homogeneous δ56Fe from 0.13‰ to 0.24‰ irrespective of their highly variable SiO2, MgO, and FeOt contents. Combined with observed mineral assemblages and available fractionation factors, this does not support a high degree of FC (with or without assimilation) in their petrogenesis. The elevated δ56Fe relative to the supposed source rocks, represented by metasedimentary rocks and/or metabasite with a δ56Fe value of 0.10‰, by ∼0.07‰, may reflect Fe isotope fractionation during crustal anatexis. This study indicates most leucogranites can provide robust constraints on the conditions of crustal anatexis and thus the thermal and tectonic evolution of the Himalayan orogen.

Design of Novel POB/h-BN Co-Filled PTFE Composites with Enhanced Thermal–Mechanical Properties

Polytetrafluoroethylene (PTFE) is provided with excellent self-lubricating properties and corrosion resistance. However, the lower thermal resistance greatly limits its high-temperature applications. In the present work, two types of fillers with rigid organic polymers and submicron-sized inorganic hexagonal boron nitride (h-BN) were added to the PTFE matrix. The microstructure and thermal–mechanical properties of PTFE-based composites with different filler types or ratios were comparatively investigated. The results suggested that the polyphenyl ester (POB)/h-BN co-filled PTFE composites exhibited excellent thermal–mechanical properties compared with the polyimide (PI)/h-BN/PTFE materials at high temperature. The optimal ratios of POB and h-BN were 25 wt.% and 5 wt.%, respectively. The Vicat softening temperature of 25 wt.% POB/5 wt.% PI/PTFE composite increased by 41.3% compared to that of pure PTFE, which was due to the cross-linked reticulation structure with regularly distributed pores and higher crystallization degree. The storage modulus increased from 51.99 MPa to 685.76 MPa at 260 °C and reached 187.82 MPa at 320 °C. The uniform distribution of anisotropic orientation of the h-BN flakes showed an obvious pinning effect, and further improved the thermal–mechanical stability of POB/h-BN/PTFE composites.

Highly stable yellow-emitting fluorescent film based on graphene quantum dots for white laser-emitting devices

Green-emitting graphene quantum dots (GQDs) with a high crystallization degree were prepared by a two-step solvothermal method. Owing to the co-doping of nitrogen and oxygen, carbonyl and amide groups were introduced into GQDs. The quantum yield (QY) of GQD solution is up to 47.09%, which is higher than that of other GQDs synthesized by top-down methods. Since GQD solution exhibits concentration-dependent photoluminescence (PL) properties, green, yellow, and orange emissions were realized by adjusting GQD concentration. A high concentration (no less than 6.0 mg mL−1) GQD solution was mixed with KH-792 to form a yellow-emitting fluorescent film with an excellent fluorescence and thermal stability, which was used as color converters and combined with 405 nm laser diodes (LDs) to realize the devices with white laser-emitting. The Commission Internationale de L'Eclairage (CIE) coordinate of the laser device is (0.34, 0.39), the correlated color temperature (CCT) is 5288 K, and the color rendering index (CRI) is 70. This work provides an advanced way for the development of laser fluorescent materials.

Preparation of xLi2MnO3·(1-x)(LiMn1/3Co1/3Ni1/3)O2 cathode material and its electrochemical properties for Li-ion batteries

The layered xLi2MnO3·(1-x)(LiMn1/3Co1/3Ni1/3)O2 (x = 0.15, 0.3, 0.45) as cathode materials in Li-ion batteries were prepared by co-precipitation of hydroxides. The effects of sintering duration, chemical composition and temperature on the structure and electrochemical performance were studied. The results show that the 0.3Li2MnO3·0.7(LiMn1/3Co1/3Ni1/3)O2 material prepared at 800 °C for 20 h has higher crystallization degree and better electrochemical performance. The charge capacity in the first circle was 359.8 mAh·g-1, the discharge capacity was 240.3 mAh·g-1, the discharge efficiency was 66.8% and the capacity retention was also 97.6% after 20 cycles.

Bi-functional modular graphene network with high rate and cycling performance

Three-dimensional bi-functional modular graphene network (3D bmG) is developed by using metal powder assisted soluble salt templates method. The 3D bmG contains two kinds of modules with different functions: the 3D graphene catalyzed by Ni powder (3D bmG-n) and the 3D graphene grown on NaCl crystals (3D bmG-s). The 3D bmG-n with high crystallization degree ensures the high electrical conductivity and structural stability and protects the 3D bmG-s from etching in electrolyte. The 3D bmG-s with more defects and pores provides high capacity and rate properties. Thus, the synergistic effects of the two modules endow the 3D bmG excellent electrochemical performance as both cathode and anode of lithium-ion capacitors (LICs). The as-prepared “all-carbon” bmG//bmG full LIC with a high voltage window of 4.5 V presents high energy densities of 278 Wh kg−1 and 52.2 Wh kg−1 at power densities of 405 W kg−1 and 16200 W kg−1, respectively, and excellent cycling stability with a capacity retention ratio of 88.57% after 3000 cycles, which is superior compared with LICs reported previously. These properties indicate promising application of 3D bmG in high performance energy storage devices, and the modular design in this work will inspire more designs and types of 3D materials.

Structural and optical properties of GdAlO3:Tb3+ crystal obtained by optical floating zone method

Gadolinium aluminate single crystal (GdAlO3: Tb3+, GAP:Tb) was obtained by optical floating zone technique (OFZ). The crystal was grown at a fast pulling rate (7.0 mm/h) in atmosphere ambient. The structural characterization proves the crystal having a high degree of crystallization and perovskite nature by XRD, SAED and IR. SEM/EDS results show neither element segregation nor defects in the crystal. Residual stress in this crystal, without annealing treatment, is close to YAG crystal made by Bridgman method. Absorption and photoluminescence spectra suggest a strong absorption in 200–400 nm (related to Tb3+-O2- and Gd3+ 8S7/2→6G/D/I/PJ) and a bright green emission centered at 548 nm (related to Tb3+ 5D4→7F5). The energy spectrum also show GdAlO3:Tb3+ crystal could be a good scintillator.

Two episodic Nb-Ta mineralization events and genesis of the Zhaojinggou rare-metal deposit, north margin of the North China Craton

The Zhaojinggou rare-metal deposit is located in the Wulashan-Daqingshan region, central north margin of the North China Craton. Nb-Ta mineralizations are mainly hosted in the biotite alkali-feldspar granite (BAG) and albite granite (AG), with subordinate mineralization in the alkali-feldspar aplite dyke (AFA), the amazonite granitic pegmatite dyke (AGP), and the greisen (black + white colored greisen). In this paper, we present a systematic work of geochronology (CGM U-Pb combined with cassiterite U-Pb, monazite U-Th-Pb, and muscovite 40Ar-39Ar dating), whole-rock geochemistry, and Sr-Nd isotopes to understanding the timing of mineralization, petrogenesis, geodynamic setting, and ore-forming processes. Our geochronological data reveal two episodic Nb-Ta mineralization events in the Zhaojinggou deposit during the Early Cretaceous. The first and major ore-forming episode occurred at ~130 Ma, forming a sequence of ore-bearing rocks of the BAG-AG-greisen-AFA. The second but subordinate ore-forming episode occurred at ~114 Ma, forming the ore-bearing AGP. The whole-rock geochemistry indicates the granitic rocks (the BAG-AG-AFA and AGP) from the two episodes are highly evolved with analogous trace element and REE patterns, and have A-type affinity. The whole-rock εNd(t) values of these granitic rocks are relative similar, ranging from −9.6 to −7.6, with corresponding T2DM ages of 1490–1713 Ma. These features suggest that these A-type granites from the two discrete episodes are derived from the same magma reservoir by high-temperature partial melting of the Middle Proterozoic basement in an infracrustal extensional environment. These A-type granites experienced extremely fractional crystallization during emplacement. The whole-rock REE tetrad effects, element ratios (Nb/Ta, Zr/Hf and K/Rb), and Nb-Ta fractionation modeling indicate that both magmatic and hydrothermal processes are involved to form the two episodic Nb-Ta mineralizations. High degree of factional crystallization and magmatic-hydrothermal processes after high-temperature anataxis are crucial to form the Zhaojinggou rare-metal deposit. Moreover, these highly-evolved A-type granites (the BAG-AG-AFA and AGP) formed during the Early Cretaceous (at ~ 130 Ma and ~ 114 Ma respectively) are the important targets for rare-metals prospecting in the central north margin of the NCC.

Petrogenesis of the Xingluokeng W-bearing granitic stock, western Fujian Province, SE China and its genetic link to W mineralization

The Xingluokeng deposit is the largest tungsten deposit discovered in the Wuyi metallogenic belt, with 30.43 Mt WO3 reserves averaging at 0.23%. The main orebody mainly occurs in an altered granitic stock, comprising veinlet-disseminated and vein-type scheelite and wolframite mineralization. A comprehensive study of field investigations with whole-rock and in-situ geochemical and isotopic compositions was conducted on different intrusive phases of the Xingluokeng ore-bearing granitic stock, aiming to constrain the petrogenesis and its genetic link to W mineralization. The Xingluokeng stock is mainly composed of the porphyritic biotite granite (G1) as the upper part of the stock, intruded by the medium- to fine-grained biotite granite (G2) in the deep. Petrographic observations suggest that the stock experienced intense fractional crystallization as well as assimilation of country rocks close to stock margins. Zircon U − Pb geochronology and trace element analyses indicate that G1 and G2 were emplaced coevally at ~152 Ma at a relatively lower oxygen fugacity condition (Ce4+/Ce3+ = 44 ± 18 for G1, and 104 ± 41 for G2). Ti-in-zircon thermometer and AlT-in-biotite geobarometer reveal average crystallization temperature and depth at 762 ℃−740 ℃ and 7.3–7.0 km, respectively. Geochemically, obvious negative correlation between SiO2 and P2O5 and low A/CNK values (mostly < 1.1) indicate that they belong to the weakly peraluminous I-type granite, rather than S-type granite as proposed previously. Whole-rock geochemical compositions from G1 to G2 display systematic variations, with a general decrease in major oxides (such as Al2O3, TiO2, FeOT, MgO, CaO) and Zr/Hf ratio, but a gradual increase in DI value, Rb/Sr ratio and δEu with increasing SiO2, suggesting fractional crystallization is the major factor that controls the compositional variations between G1 and G2. They have consistent initial 87Sr/86Sr ratios of 0.71170 to 0.71477 and εNd(t) values of −12.5 to −10.8, as well as zircon εHf(t) values of −17.4 to −9.2 with Paleoproterozoic Nd − Hf model ages (1783–2081 Ma), suggesting a mixed crustal source of about 88% Paleoproterozoic meta-basaltic rocks and about 22% Paleoproterozoic gneissic granites, with minor assimilation of country rocks. These results favor that the Xingluokeng granites were formed by co-magmatic evolution via K-feldspar-dominated fractionation. High degrees of fractional crystallization have immensely enriched W in reduced magma, then intensive fluid-rock interaction liberated Ca from the G1 to form the scheelite and some Fe might come from the country rocks (biotite hornfels) to precipitate the wolframite.

Nature of the Features of Kimberlite Placement

The obtained evidence of hot heterogeneous accretion of the Earth leads to a fundamentally new solution to genetic problems. According to these data, the kimberlites were formed as a result of the rise of the last residual melts of the bottom peridotite layer of the magmatic ocean, which arose as a result of impact heat release during accretion. The diamond crystallized due to the accumulation of carbon in the residual melts during fractionation. The absence of kimberlites in oceanic and collision regions is due to the expansion of the fractionation products of the magmatic ocean by surfaced mantle plumes during the formation of these regions. The all-earth distribution of the magmatic ocean explains the presence of kimberlites on all the studied ancient platforms. A very high degree of crystallization of the peridotite layer is the reason for the small volume of kimberlite residual melts and the bodies formed by them. The low temperature of kimberlite magmas caused their decompression solidification after boiling at the shallow stage of ascent and explosion under the influence of the high pressure of the fluid phase preserved by solidification. This is the reason for the formation of kimberlite pipes and the absence of kimberlite lavas.

TEM characterization of turbostratic and rhombohedral BN interphases synthesized by chemical vapour infiltration in SiC/SiC-Si composites

BN interphases were synthesized by chemical vapour infiltration (CVI) from BCl3 and NH3 at 900 °C and 1200 °C within preforms made of a single 2D woven SiC fibre ply. Then CVI of a SiC matrix followed by molten silicon infiltration resulted in laboratory-made single-ply SiC/SiC-Si composites representative of similar industrial ceramic matrix composites. The interphases and interfaces were characterized by transmission electron microscopy. It has been found that, in the two cases, the interphases are mostly turbostratic BN. Those synthesized at 900 °C are very poorly crystallized and exhibit a quasi-isotropic microstructure. An equiaxed interlayer is obtained prior to the columnar CVI growth of SiC matrix. Interphases synthesized at 1200 °C exhibit high degrees of crystallization and structural anisotropy. The SiC matrix grows directly in columns on BN. For interphase thicknesses of 300 nm and more, triangular-shaped crystallites of rhombohedral BN appear in turbostratic BN and the columnar growth of SiC is disoriented.

Biotite composition as a tool for exploration: An example from Sn-W-Mo-bearing Mount Douglas Granite, New Brunswick, Canada

The Mount Douglas Granite (MDG) in southwestern New Brunswick (Canada) consists of three geochemically different intrusive phases, from earlier to late, changing from barren coarse-grained granite (Dmd1) to more fractionated medium- to fine-grained fertile granites (Dmd2 and Dmd3). This provides a unique geological setting to apply different techniques in order to constrain petrogenesis and metallogeny of the system. This study uses biotite chemistry to test its applicability as a mineral exploration tool to discriminate the least evolved non-mineralized Dmd1 from more highly evolved mineralized Dmd2 and Dmd3. Chemical composition of magmatic biotite was determined by EPMA and in situ laser ablation ICP-MS for different phases within the MDG. Applying the reconstruction of trace element contents accompanied with determined minerals-melt partition coefficients, we were able to further constrain the genetic relationship between the Dmd1, Dmd2, and Dmd3 from the composition of biotite. Biotite trace element contents follow a differentiation trend from the least to most evolved phases, indicative of a continuous magmatic evolutionary series. The fact that high degrees of fractional crystallization produced units Dmd2 and Dmd3 associated with endogranitic Sn, W (Mo), Bi, Zn and U mineralization is reflected in the composition of biotite from mineralized units. Remarkably, the biotite from the Dmd2 and Dmd3 is enriched in Zn (≤ 879 ppm), Pb (≤ 248 ppm), Sn (≤ 164 ppm), Ta (≤ 163 ppm), Ga (≤ 113 ppm), Cu (≤ 44 ppm), W (≤ 14 ppm), and U (≤ 6 ppm); it is also rich in incompatible elements, such as Li, Cs, Rb, Ta, and Nb, as well as substantial contents of F (≤ 2.87 wt%) and Cl (≤ 0.71 wt%). The geochemical compositions of biotite not only demonstrate a continuous fractional crystallization of magmas, but also can be used as a fertility indicator.

Synthesis of Modifiers in the System Cao-Sio&lt;sub&gt;2&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;O and their Influence on the Non-Autoclave Silicate Materials’ Properties Using Aluminosilicate Binder

Improving the hydration hardening building materials’ operational properties is possible due to the stable macro-, micro-and nanostructures’ creation by the cementing material crystalline aggregate directed modification, which can be achieved through the use of various additives acting as crystallization centers. In the course of the studies, the synthesized modifier effect nature represented by the system was revealed CaO-SiO2-H2O (CSH) on the properties of non-autoclave silicate materials using aluminosilicate binder of various compositions. It has been established that the use of an aluminosilicate binder together with the addition of a CSH modifier increases the presence of a crystalline phase at all stages of hardening, as well as intensifies the synthesis of low-basic calcium hydro silicates with a higher crystallization degree in the system CaO-SiO2(Al2O3)-H2O represented by lime and clay rocks. This contributes to the micro-reinforced crystalline framework formation of the neoplasms with increased strength. Due to this, the pore space decreases and the amount of synthesized crystalline substance increases, which helps to increase the water resistance of the samples in all compositions. The samples using an aluminosilicate binder and the addition of a CSH modifier achieve maximum strength with a CaO content of not more than 10 wt. % The optimal CSH modifier addition is up to 1.5 wt. %, with 7 wt. %, CaO content in a mixture increase in strength is up to 6%.

Influence of Myrrh Extracts on the Properties of PLA Films and Melt-Spun Multifilament Yarns.

A possible approach for providing new properties for textiles is the insertion of natural ingredients into the textile product during the process of its manufacture. Myrrh has long been used in medicine as an antibacterial and antifungal material. Polylactide (PLA) is a thermoplastic synthetic biopolymer obtained from renewable resources—and due its biodegradability, is also widely used in medicine. In this study, films and multifilament yarns from modified biodegradable PLA granules with ethanolic and aqueous myrrh extracts were developed and characterized. Optical microscopy was used to determine the surface morphology of PLA/myrrh multifilament yarns. Tensile tests, ultraviolet-visible (UV-vis), differential scanning calorimetry (DSC) were applied to determine, consequently, mechanical, optical properties and degree of crystallinity of PLA/myrrh films and multifilament yarns. The chemical composition of PLA/myrrh multifilament yarns was estimated by Fourier-transform infrared (FTIR) spectroscopy method. The results showed that it is possible to form PLA melt-spun multifilament yarns with myrrh extract. The type of myrrh extract (ethanolic or aqueous) has a significant influence on the mechanical and optical properties of the PLA films and melt-spun yarns. The mechanical properties of PLA films and melt-spun multifilament yarns formed from PLA granules with aqueous myrrh extract decreased 19% and 21% more than PLA with ethanolic extract, respectively. Analysis of UV-vis spectra showed that, due to the yellow hue, the reflectance of PLA films and melt-spun PLA multifilament yarns modified with myrrh extracts decreased exponentially. The DSC test showed that multifilament yarns from PLA modified with aqueous extract had the highest degree of crystallization.

Crystallization behavior of zinc oxide/poly(lactic acid) nanocomposites

In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with average diameter around 100 nm and ZnO concentrations of 0.1, 0.25, 0.3 and 0.5 mass% were prepared by flat die extrusion. The addition of nano-ZnO had an objective to promote the crystallization of PLA, but it decreased the thermal stability of the films. Both neat PLA and PLA/nano-ZnO composites films did not crystallize during the cooling, but crystallize during a first heating, showing a cold crystallization process, which was significantly influenced by the heating rate. A low chain mobility was evidenced by the values of relaxation time (T1H). This low chain mobility avoided the high degree of crystallization of the films which were predominantly amorphous. For all films, an enthalpic relaxation phenomenon was detected during the first heating. The glass transition temperature (Tg) was shifted to higher values as the heating rate and nanofiller content are increased. Addition of nano-ZnO in PLA films did not increase their crystallinity, indicating that it is not an effective nucleating agent for this low-crystallinity PLA grade.

Crystalline NiFe layered double hydroxide with large pore volume as oxygen evolution electrocatalysts

Cost-effective and earth-abundant electrocatalysts with high activity for oxygen evolution reaction (OER) is essential for achieving efficient and economical electrochemical water splitting. In this work, we developed a facile low-temperature coprecipitation approach to synthesize NiFe layered double hydroxide (NiFe LDH). By tuning Ni/Fe feed ratio and using Na2CO3 as precipitant, mesoporous NiFe LDH nanoparticles were obtained. The special physicochemical features of these NiFe LDH nanoparticles, including high degree of crystallization, large pore volume and abundant crystalline/amorphous interfaces, synergistically endowed the catalyst with enriched active sites. Consequently, the optimal Ni0.66Fe0.33 LDH electrocatalyst showed excellent activity toward OER in alkaline media, with a low overpotential of 248 mV to deliver a current density of 10 mA cm−2, a small Tafel slope of 46 mV dec−1, and strong durability. This work opens an innovative avenue toward the design of advanced NiFe-based catalysts.

Geochronology and geochemistry of the igneous rocks and ore-forming age in the Huangtan Au[sbnd]Cu deposit in the Kalatag district, Eastern Tianshan, NW China: Implications for petrogenesis, geodynamic setting, and mineralization

The Huangtan AuCu deposit is was recently discovered in the Kalatag district, Xinjiang, NW China. It is one of the few Early Paleozoic volcanic massive sulfide (VMS) deposits in the East Tianshan. The deposit is predominantly hosted by Early Paleozoic volcanic rocks and quartz diorite pluton. The dacitic tuff and quartz diorite have zircon ages of 438 ± 5 Ma and 439.2 ± 1.4 Ma, respectively, determined by LA-ICP-MS UPb dating. ReOs dating of pyrite from the vein ore yielded a weighted average age of 437.9 ± 6.6 Ma, which is classified as Early Silurian. These ages and geological observations demonstrate that CuAu mineralization is temporally and spatially related to the quartz diorite and volcanic rocks.The volcanic rocks, including basalt, andesite, and dacitic tuff, are calc-alkaline with low Mg# values (22.6–45.1), enriched in light rare earth elements (LREE) and depleted in high-field-strength elements (HFSE) (e.g., Nb, Ta, and Ti) and are characterized by high εNd(t) (+5.3 − +7.2), low (87Sr/86Sr)i (0.70367–0.70474) and high εHf(t) (+6.94 − +12.76). They are considered to be originated from mantle-derived mafic magmas that mixed with partial melting of a juvenile basaltic lower crust and underwent a high degree of fractional crystallization during emplacement. The quartz diorite is classified as metaluminous-to-peraluminous, calc-alkaline to high-K calc-alkaline. It is enriched in large ion lithophile elements (LILE) (e.g., K, Ba, Rb, and Sr), and depleted in HFSEs (e.g., Nb, Ta, and Ti) with lower Sr/Y ratios, indicating a subduction-related origin. It displays low (87Sr/86Sr)i (0.70381–0.70469), high εNd(t) (+6.2 − +7.1) and zircon εHf(t) (+8.82 − +14.90). The quartz diorite has a similar magma source with volcanic rocks and was likely derived from depleted mantle metasomatized by subduction-related fluids.A tectonic model is consequently proposed to explain the Early Paleozoic magmatism and VMS mineralization in the Kalatag area. Huangtan igneous rocks were generated by the northward subduction of the North Tianshan oceanic plate beneath the Dananhu-Harlik island arc during Early Paleozoic. The Huangtan AuCu deposit may be an important branch of the adjacent Huangtupo VMS deposit, providing a model for the exploration of Early Paleozoic VMS Cu-metallogenic systems in the Eastern Tianshan region, NW China.

Combined Zircon, Molybdenite, and Cassiterite Geochronology and Cassiterite Geochemistry of the Kuntabin Tin-Tungsten Deposit in Myanmar

AbstractThe Kuntabin Sn-W deposit, located in southern Myanmar, is characterized by abundant greisen-type and quartz vein-type cassiterite and wolframite mineralization. We have conducted multiple geochronological methods and isotope and trace element analyses to reveal the age and evolution of the Kuntabin magmatichydrothermal system.Zircon U-Pb dating of the two-mica granite yielded a weighted mean 206Pb/238U age of 90.1 ± 0.7 Ma. Cassiterite U-Pb dating provided a lower intercept age of 88.1 ± 1.9 Ma in the Tera-Wasserburg U-Pb concordia diagram. Molybdenite Re-Os dating returned a weighted mean model age of 87.7 ± 0.5 Ma and an isochron age of 88.7 ± 2.7 Ma. These ages indicate a genetic relationship between granite and Sn-W mineralization in the Kuntabin deposit and record the earliest magmatism and Sn-W mineralization in the Sibumasu and Tengchong terranes related to subduction of the Neo-Tethys oceanic slab. Three generations of cassiterite have been identified with distinctive cathodoluminescence textures and trace element patterns, indicating the episodic input of ore-forming fluids and distinctive changes in the physical-chemical conditions of the Kuntabin magmatichydrothermal system. Sudden changes of fluid pressure, temperature, pH, etc., may have facilitated the deposition of Sn and W. Rhenium contents of molybdenite from the Kuntabin deposit and many other Sn-W deposits in Myanmar are characteristically low compared to porphyry Cu-Mo-(Au) deposits worldwide. In combination with zircon Hf isotope signatures, we infer that granites associated with Sn-W deposits in Myanmar were predominantly derived by melting of ancient continental crust and contain minimal mantle contribution.Subduction of the Neo-Tethys oceanic slab from west of the West Burma terrane reached beneath the Sibumasu terrane and led to magmatism and Sn-W mineralization at ~90 Ma when the Kuntabin deposit was formed. The Paleoproterozoic Sibumasu crust was activated during the subduction-related magmatism to form predominantly crust derived melts. After a high degree of fractional crystallization and fluid exsolution, physical-chemical changes of the hydrothermal fluid resulted in Sn and W precipitation to form the Kuntabin Sn-W deposit.

Development of waste tire‐derived graphene reinforced polypropylene nanocomposites with controlled polymer grade, crystallization and mechanical characteristics via melt‐mixing

AbstractIn the present work, single layer graphene nanoplatelets (GNPs) derived from waste tires by recycling and upcycling approaches were integrated in homopolymer (Homo‐) and copolymer (Copo‐) polypropylene (PP) matrices by fast and efficient mixing in the melt phase. The effect of GNP content on crystallization and mechanical behaviors was investigated in detail at different loading levels. Regarding isothermal and non‐isothermal crystallization experiments, GNPs significantly accelerated the nucleation and growth of crystallites, and the crystallization degree in Homo‐PP nanocomposites was slightly higher than that of Copo‐PP based nanocomposites. Also, there was significant improvement in mechanical and thermal properties of GNP reinforced polymers compared to neat polymers. As the GNP concentration increased from 1 to 5 wt%, there was a gradual increase in flexural modulus and strength values. In tensile tests, an increase in GNP content in both polymer grades led to a slight increase in yield strength coming from the proper distribution of nano‐reinforcement by creating stress concentration sites. After the yield point, Homo‐PP based nanocomposites showed higher strain hardening than GNP reinforced Copo‐PP owing to a high crystallization degree and linear chains of Homo‐PP. This work showed that functionalized graphene can act as both nucleating and reinforcing agent in the compounding process and its exfoliation through polymer chains is much better in homopolymers at a faster and high shear rate. © 2020 Society of Chemical Industry

Metallogeny of the continental collision-related Jiagang W-Mo deposit, Tibet: Evidence from geochronology and petrogenesis

The Jiagang W-Mo deposit is the first greisen-type tungsten deposit recognized in the Lhasa terrane, and thus it has important genetic implications for understanding the regional tungsten mineralization potential. Greisen-type orebodies dominate in the deposit. Ores characterized by veinlets and dissemination are located in intensively altered monzogranite and contact zones between the monzogranites and sedimentary rocks. The minor quartz vein-type orebodies occuring as large quartz veins mainly precipitated in the sedimentary rocks. Intrusions associated with the Jiagang deposit are monzogranites, which can be subdivided into medium-grained monzogranite (MMG), porphyritic monzogranite (PMG), and fine-grained monzogranite (FMG). The zircon U-Pb ages of the PMG and MMG are 18.2 ± 0.2 Ma and 18.6 ± 0.1 Ma, respectively. These ages are consistent with the muscovite 40Ar-39Ar plateau ages (18.7 ± 0.2 Ma, 18.5 ± 0.2 Ma) and the molybdenite Re-Os isochron age (19.0 ± 0.3 Ma) within errors, indicating that the Jiagang W-Mo mineralization took place during the post-collisional stage of the Indo-Asian continental collision. The mineralization is temporally, spatially and genetically associated with the monzogranitic intrusions. The FMGs have the lowest SiO2 contents (70.8–71.5 wt%), lowest differentiation index (DI = 85.7–86.3) and least obviously negative Eu anomalies (Eu/Eu* = 0.22–0.42). The PMGs and MMGs have higher SiO2 contents (72.6–76.3 wt%), higher differentiation index (DI = 89.3–92.7) and more negative Eu anomalies (Eu/Eu* = 0.11–0.24). Almost all of the rocks are strongly peraluminous (A/CNK = 1.02–1.29), enriched in LILEs and depleted in HFSEs. Concentrations of K2O, CaO, FeOT and TiO2 of the three types of monzogranites show negative correlations with SiO2, while P2O5 exhibits the opposite trend. Values of Nb/Ta decrease with SiO2 contents, and those of (La/Yb)N increase with La contents. Whole rock εNd(t) of the FMGs range from −11.3 to −11.1 with two-stage Nd isotopic model ages (TDM2) of 1741–1797 Ma, which are similar to those of the PMGs and MMGs (εNd(t) = −10.9– −10.6; TDM2 = 1709–1816 Ma). Zircon εHf(t) values of the PMG and MMG range from −13.8 to −5.3 with two-stage Hf isotopic model ages of 1439–1979 Ma. These data suggest that the ore-forming monzogranites are strongly peraluminous S-type granites, which should be derived from anatexis of the Proterozoic metagreywackes underneath the central Lhasa subterrane. The PMG and MMG are highly fractionated through various degrees of fractional crystallization of plagioclase, K-feldspar, biotite, monazite and allanite from the parental melts represented by the FMG. Zircon trace elements suggest that oxygen fugacity of the ore-forming magmas is relatively low and decreased as the magmas evolved, which is favorable to remove substantial tungsten from melts into the tungsten-mineralizing hydrothermal fluids. A high degree of fractional crystallization of the crustally-derived magmas with relatively low magmatic oxidation state are the critical factors determining the generation of the tungsten mineralization in the Jiagang deposit. Combined with the existing breakthroughs in prospecting exploration, we propose that the central Lhasa subterrane has great metallogenic potential in W-(Mo) mineralization associated with the Indo-Asian continental collision.