High Ta Contents Research Articles

Microstructure and mechanical properties of LBW and EBW weld joints of CLF-1 steel: A comparative analysis

This study was focused on welding joints of reduced-activation ferritic/martensitic (RAFM) CLF-1 steel medium-to-thick plates produced via laser beam welding (LBW) and electron beam welding (EBW). Such joints were used in the ITER project, in particular, in the back plate mockup of Helium Cooled Ceramic Breeder Test Blanket System developed in China in 2015. The microstructural evolutions and the mechanical properties of fusion zones (FZs), weld zones (WZs), and heat-affected zones (HAZs) of LBW and EBW joints were analyzed and compared using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Moreover, the microstructural differences between the two types of joints and their effect on the impact properties were discussed. Results showed that the well-formed welds without defects, such as pores, incomplete fusion, and cracks, could be obtained via LBW and EBW. Different heat inputs led to the differences in the grain size gradients, the boundary angles, the content of carbides, and the distribution of dislocations. Despite obvious differences in morphology among FZ, WZ, and HAZ, both types of joints exhibited excellent tensile properties and impact toughness. The tensile strengths of the LBW and EBW joints were 633 and 634 MPa at room temperature, respectively, versus 370 and 366 MPa at 550 °C. The mean impact-absorbing energy values of LBW and EBW joints were 251 and 284 J. The further analysis revealed that the low δ-ferrite content, small effective grain size, large grain size gradient, high grain boundary angle, diminutive size of M23C6 carbides, high-Ta content in MX carbides and low dislocation density led to high impact toughness of the LBW joint, while the microstructure of EBW joint failed to show the improvement of impact toughness, and the extraordinary impact toughness could be attributed to the high scattering band.

Validity of Selection Breeding for High Ephedrine-Alkaloid Content in E. sinica under Different Environments in Japan.

Dried terrestrial stems of Ephedra sinica are called 'Ephedra herb,' whose pharmacological effects are due mainly to two major ingredients, (-)-ephedrine and (+)-pseudoephedrine (total alkaloids which are defined in Japanese Pharmacopoeia (TA)). Ephedra herb is an important crude drug in Japan. However, E. sinica is widely distributed in arid areas of northeastern China and Mongolia. Recently, E. sinica has started to be cultivated in Japan. This study aimed to assess the validity of selection breeding on TA content of E. sinica in several locations in Japan. In this experiment, we grew approximately 350 seedlings and divided them randomly into seven groups. Nearly fifty plants were cultivated at each of seven locations. In Ibaraki, Yamanashi, and Shizuoka, average TA content of whole samples satisfied the criteria for Ephedra herb defined in Japanese Pharmacopoeia (7.0 mg/g of dry weight (DW)). Plants with high and intermediate TA content at four locations were selected and transplanted to Ibaraki. There were significant differences in TA content between selected plants with high and intermediate TA content before and after transplanting (p < 0.05). TA content of high-TA plants was significantly higher than that of control plants cultivated continuously at Ibaraki (p < 0.05). These results suggest that the selection on content of ephedrine alkaloids in E. sinica under various locations in Japan is valid, and high- TA E. sinica plants can be selected at various locations.

In-situ boron isotopic and geochemical compositions of tourmaline from the Shangbao Nb–Ta bearing monzogranite, Nanling Range: Implication for magmatic-hydrothermal evolution of Nb and Ta

The enrichment mechanism of tantalum and niobium are still in dispute due to complex textural features of Nb–Ta minerals. Tourmaline is an accurate passive geochemical monitor related to the W-Sn-Nb-Ta-Li mineralization, which can record Nb and Ta variations in melt/fluid. The newly discovered Shangbao Nb–Ta bearing monzogranite is located in Nanling Range, South China, which is characterized by tourmaline wide occurrence. In this paper, we systematically investigate the different types of tourmaline using in-situ major, trace elemental and boron isotope for studying the origin of tourmaline, boron source, and Nb–Ta enrichment process. Three types of tourmaline have been identified, namely, disseminated tourmaline (TD type) in monzogranite, nodular tourmaline (TN type), consisting of the yellow core (TNy type) and blue rim (TNb type), and veined tourmaline (TV type). Almost all tourmalines from the Shangbao Nb–Ta deposit exhibit very low Ca content, X-site occupancy and high ratio of Fe / (Fe + Mg), pertaining to the group of schorl and alkali. Trace elements primarily present the low concentrations of <10 ppm, while the contents of Sc, Li and Zn are higher.Based on the petrography and Al occupations in the Y-site of tourmaline, TD type tourmaline was precipitated straightly from the melt at the late magmatic stage, while TN type tourmaline crystallized during the magmatic-hydrothermal transition process, and TV type tourmaline was the origin of hydrothermal fluid. In-situ boron isotope analyses of TD and TN type tourmaline by MC-ICP-MS show the narrow δ11B values from −17.16‰ to −14.81‰, demonstrating the same boron source. TV type tourmaline shows the weak higher δ11B values of −14.48‰ to −13.46‰ likely resulted by Rayleigh fractionation. The concentration of Nb in TD and TV type tourmaline can reach up to 20 ppm, which is higher than that in TN type tourmaline. However, TN type tourmaline contains higher Ta content than other types, revealing magmatic-hydrothermal transitional stage is critical to Ta enrichment. Compared with tourmaline in other type deposits, tourmaline in Shangbao monzogranite contains high Nb and Ta contents, indicating that it is a suitable tool for exploration, and the tourmaline is available to targeting Nb and Ta mineralization.

Petrogenesis of volcanic rocks of the Devonian – Carboniferous Dahalajunshan Formation, Western Tianshan: Implications for crustal growth in an accretionary orogen

Magmatism associated with plate subduction and collision plays an important role in crustal growth during the evolution of the Earth, but the detailed mechanisms regarding how magmatism contributes to the vertical growth of the crust remain unclear, in part due to controversies on the petrogenesis of intermediate-felsic rocks. In the Central Asian Orogenic Belt (CAOB), although it has been recognized that both pre-existing crustal component and juvenile mantle-derived melt played a role in the crustal evolution of the orogens, the mechanics of how they contributed to vertical crustal growth remain uncertain. This study presents new geochronological, major and trace element geochemical, and Nd–Hf isotopic data for the Late Paleozoic intermediate-felsic volcanic rocks of the northern Yili terrane, Western Tianshan Orogen, with the aims to constrain the petrogenesis of the andesitic magma and to offer new insights into the deep interaction processes between crustal- and mantle-derived magmas. According to zircon U–Pb dating, trace element and isotopic compositional data, these volcanic rocks can be divided into two groups. Group 1 rocks (365–375 Ma) have relatively low whole-rock εNd(t) values (−4.2 – −1.6) and display high contents of Th (11.8–20.4 ppm), U (2.7–5.1 ppm), Nb (14.1–36.7 ppm) and Ta (1.1–3.1 ppm) that suggest they were derived from the partial melting of pre-existing crust. Group 2 rocks (346–349 Ma) show REE and trace elemental patterns typical of subduction-related calc-alkaline volcanic rocks with relatively high whole-rock εNd(t) values (−1.89 – +2.4), and with variable zircon Hf isotopic values (εHf(t) = +1.9 – +13.5) that can be attributed a juvenile crust with variable input of mantle material. Hf–Nd isotopic decoupling of the group 2 rocks suggests a replenishment by more mafic magmas. Samples from the entire Yili terrane show an increasing trend in εNd(t) values with younger ages that suggest an increasing involvement of melted juvenile crustal rocks. Overall, these results suggest a crustal evolutionary scenario in which: 1) pre-existing crustal components were melted and ascended to the upper crust (group 1) during the southward subduction of the Junggar-North Tianshan ocean in the early stage; and, 2) a later stage in which newly input mantle material solidified to form new arc crust that was also melted by basaltic underplating and that was probably associated with the rollback of the Junggar oceanic slab. This two-stage crustal growth model seems to be an efficient process for vertical crustal growth during the formation of an accretionary orogen.

Petrogenesis of Neoproterozoic rare metal granite-pegmatite suite in Jiangnan Orogen and its implications for rare metal mineralization of peraluminous rock in South China

Recent studies have demonstrated the Mesozoic explosive metallogeny of rare metals in China; however, Precambrian rare metal mineralization event is rarely reported or studied. The Jiangnan Orogen (JO) is a well-preserved Neoproterozoic orogenic belt in South China, and although it abounds with a huge amount of Neoproterozoic granitoids, lacks the equivalent amount granitic pegmatite. In this study, the geology, mineralogy, whole-rock composition, zircon U-Pb age and Hf isotope compositions of the Fanjingshan granite and surrounding rare metal pegmatites, and bulk composition of sedimentary wall rocks of the Taojinhe Formation in Guizhou province, western Jiangnan Orogen (JO), were studied to reveal the petrogenesis of the granite and pegmatite and the source relationship of the pegmatite with the Paleozoic and Mesozoic rare metal ore deposits in South China. The Fanjingshan granite and pegmatite both show Sn-Ta-Nb mineralization and have consistent zircon U-Pb ages of ca. 830 Ma, indicating the existence of the Neoproterozoic rare metal granite-pegmatite suite in the JO. The geology, mineralogy, whole-rock composition and zircon U-Pb age and Hf isotope study results demonstrate that the Fanjingshan rare metal pegmatite belongs to the Li-P-B-Sn-Ta-Nb granitic pegmatite in the Chemical composition-Mineral assemblage-Structural geology (CMS) classification (Dill, 2016), and has close spatial–temporal and source-differentiation connections with the Fanjingshan granite. The petrography and whole-rock composition studies revealed that the Taojinhe formation was formed by the deposition of mature and immature source materials from acidic igneous rocks in a continental arc setting. Comparison of the Hf isotope compositions of the Fangjingshan granite-pegmatite suite with those of the Fangjinshan Group and the high Li, Sn, Rb, W, Ta and Nb background concentrations in the Taojinhe Formation support the conclusion that the Taojinhe Formation was a contributing source to the granite-pegmatite suite. A comparative study of the Fanjingshan granite with synchronous S-type granitoids revealed that the granitoids in the eastern and western JO have distinct sources and degrees of differentiation, indicating the limited ore-forming potential of the Neoproterozoic granitoids in the eastern JO. The Fanjingshan rare-metal granite-pegmatite suite has consistent Hf isotope model ages of 1.6–2.3 Ga with the Paleozoic and Mesozoic Nb-Ta ± Sn-W ± Be-Li ore deposits in South China, indicating a common origin from the Paleoproterozoic crust and the source inheritance of the western JO from the Cathaysia Block.

The Yichun Ta-Sn-Li Deposit, South China: Evidence for Extreme Chemical Fractionation in F-Li-P-Rich Magma

Abstract The Yichun Ta-Sn-Li deposit occurs within the 9.5-km2 Yashan Igneous Complex, which is made up of felsic, peraluminous intrusions including two-mica, Li-mica, and topaz-lepidolite granites. The topaz-lepidolite granite forms a thin sheet confined to the upper part of the Li-mica granite and is separated from the host metasediments by a marginal pegmatite. The topaz-lepidolite granite is characterized by the presence of snowball textures in which quartz, K-feldspar, and topaz phenocrysts contain albite laths and rare lepidolite and columbite arranged along growth zones. These textures indicate simultaneous crystallization of these phases and attest to the subsolvus character of the topaz-lepidolite granite. Minor and accessory phases in the topaz-lepidolite granite include amblygonite, cassiterite, columbite-tantalite, microlite, wodginite, zircon, monazite, and pollucite. The topaz-lepidolite granite is characterized by low SiO2 (68.6–69.7 wt %), TiO2 (0.01 wt %), Fe2O3(total) (0.15–0.33 wt %), MgO (0.01–0.05 wt %), and CaO (0.15–0.19 wt %), whereas Al2O3 (17.97–18.26 wt %), Li2O (0.90–2.09 wt %), P2O5 (0.43–0.54 wt %), and F (1.09–2.30 wt %) are all very high. Na2O ≫ K2O due to both high Na2O (5.18–6.30 wt %) and low K2O (2.63–3.05 wt %). The topaz-lepidolite granite contains extremely high concentrations of Rb (&amp;gt;3,300 ppm), Cs (&amp;gt;340 ppm), Sn (&amp;gt;140 ppm), and Ta (&amp;gt;120 ppm), with very low Zr/Hf and Nb/Ta. Gaps of &amp;gt;3.5 wt % SiO2 and &amp;gt;2.5 wt % Al2O3 together with large increases in F, Li2O, and P2O5 between the Li-mica and topaz-lepidolite granites are not compatible with an evolution by Rayleigh fractionation processes. It is proposed instead that early crystallization of the Li-mica granite led to the formation of an Si-poor, Al-, Na-, and flux-rich boundary layer whose low viscosity and density allowed effective separation from the remaining melt and crystals. This melt concentrated incompatible elements including tin and tantalum and accumulated in the upper part of the magma chamber where it crystallized the sheet-like bodies of marginal pegmatite and topaz-lepidolite granite. The uppermost part of the topaz-lepidolite granite consists of aplite and overlying quartz lepidolite rock, which is composed mainly of quartz, lepidolite, albite, K-feldspar, topaz, amblygonite, cassiterite, and columbite. Compared to the topaz-lepidolite granite the aplite and quartz-lepidolite rock shows a number of complementary element enrichments and depletions. The quartz-lepidolite rock is enriched in Fe, Mn, K, Rb, Cs, Li, F, Ba, Sr, Ti, Zr, Nb, W, Th, and Sm. The formation of the quartz-lepidolite rock is interpreted to result from separation of an F- and Li-rich alkaline phase, which accumulated beneath the already crystallized marginal pegmatite. Complementary to this was crystallization of the strongly peraluminous sodic aplite with the highest tantalum contents measured in this study.

Mineralogical-geochemical features of black shales from the frame of the Yayu igneous complex, Polar Urals

The results of study of mineralogical-geochemical features of black shales from the frame of the Yayu igneous complex (Polar Urals) are presented on the basis of modern analytical methods in order to identify possible mobilization, redeposition and concentration of ore material during intensive hydrothermal alteration. The high contents of Li, Be, Ba, Ti, Mn, Zr, Rb, Sc, Cs, P, Nb, Ta, Th, and REE are revealed. Rare metal and rare-earth minerals and a silver mineral (most likely, hessite) are found, the presence of alluvial gold in alluvium is established. The metallogenic features of carbonaceous sedimentary rocks afected by hydrothermal processes at the contact zone with igneous rocks are determined. The conclusion is made on a possible fnding of primary gold related to hydrothermal mineralisation in black shale of the region.

Oxidation behavior and interdiffusion of Ta[sbnd]Al multilayer films and Inconel 617 alloy

In this study, TaAl multilayer films were cosputtered on Inconel 617 through cyclical gradient concentration deposition. The oxidation behavior of the TaAl films and the interdiffusion between the TaAl films and Inconel 617 were evaluated through thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and Auger electron spectroscopy after the films were annealed in air at 400–800 °C. The results indicated that the Ta0.79Al0.21 multilayer films had a low O content even though O diffused inward through the entire film thickness after 8 h of annealing at 800 °C, which was attributed to the formation of an Al oxide scale due to the outward diffusion of Al in the initial oxidation stage. This under-stoichiometric Al2O3/Ta2O5 structure caused the produced films to exhibit a high hardness of 23.2 GPa and a high Young's modulus of 316 GPa. Moreover, the outward diffusion of Inconel 617 elements, namely Ni and Cr, was restricted by the oxidized films. However, the high Ta content in the TaAl films deteriorated the film adherence to the substrates due to a high volume ratio of Ta2O5/Ta. Furthermore, laminated Ta0.79Al0.21/Ta0.34Al0.66/Ti films were fabricated to improve the film–substrate adhesion. These films exhibited a high hardness of 17.1 GPa after annealing at 800 °C for 24 h.

Origin and evolution of ore-forming fluids in a tungsten mineralization system, Middle Jiangnan orogenic belt, South China: Constraints from in-situ LA-ICP-MS analyses of scheelite

The Middle Jiangnan orogenic belt is a very important tungsten (W) polymetallic belt in China. There are many types of W deposits in the belt, including veinlet-disseminated and stratabound deposits, which have different origins. The veinlet-disseminated Dahutang W deposit has undergone extensive alteration, such as biotitization (potassic alteration), and greisenization. Scheelite in veinlet-disseminated W mineralization displays a zoned texture indicating at least two generations. The early generation (D1) from the Dahutang W deposit exhibits magmatic hydrothermal characteristics with comparatively high Nb, Ta, and Mo concentrations, but a low Sr concentration (44 to 95 ppm). In contrast, the scheelite samples from the Xi’an W deposit has relatively low Nb, Ta, and Mo concentrations, but a high Sr concentration (582 to 861 ppm), mainly originating from a metamorphic fluid that mixed with meteoric water. The composition of the late generation of scheelite (D2) samples from the Dahutang deposit are intermediate between the composition of scheelite (D1) and scheelite of the Xi’an depsoit. The mineral chemistry of the scheelite samples indicate that the ore-forming fluids of the Dahutang deposit were dominated by magmatic hydrothermal fluids during the early stage, and that meteoric water was added during fluid evolution. The rare earth elements (REEs) in the scheelite samples, especially the variation of the δEu (EuN/((SmN × GdN)0.5)) values, record the change in oxygen fugacity. The ore-forming fluids in the early stage of the Dahutang deposit were reduced becoming oxidized during the precipitation of the D2 scheelite, whereas the ore-forming fluids of the Xi’an deposit were oxidized. An increased oxygen fugacity of the ore-forming fluids of the Dahutang deposit restricted the precipitation of wolframite and promoted the formation of scheelite. Extensive alteration resulted in the decomposition of plagioclase, thus releasing Ca and Sr for the crystallization of scheelite at the Dahutang tungsten deposit.

Effects of covalent interactions and gel characteristics on soy protein-tannic acid conjugates prepared under alkaline conditions

The effects of covalent cross-linking of soy protein isolate (SPI-12%) with tannic acid (TA-29,58,88,117,146 μmol/g SPI) in an alkaline environment on the structure, antioxidant activity and gelation characteristics of SPI-TA conjugates were found to improve all properties. After alkali treatment, the tryptophan content in the conjugate decreased and the covalent binding rate increased. The addition of TA initiated irreversible SPI modifications, as shown by sodium dodecyl sulfate−polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy and thermogravimetry. The texture analysis of the gel showed that hardness and elasticity were optimal at pH 11, and the rheological properties of the storage modulus (G′) and loss modulus (G″) increased with higher TA concentrations. Analysis of the microstructure indicates that an increase in TA concentration results in a more compact network structure. Our results indicate that pH-dependent interactions between SPI and TA modify the formation of the gel in a way that improves the rheology and textural properties of the gels.

Late Cretaceous granitic magmatism and Sn mineralization in the giant Yinyan porphyry tin deposit, South China: constraints from zircon and cassiterite U–Pb and molybdenite Re–Os geochronology

The Yinyan porphyry tin deposit in western Guangdong is spatially associated with quartz porphyry and granite porphyry. LA–ICP–MS zircon U–Pb dating defined an emplacement age of 78.5 ± 0.4 Ma for the quartz porphyry and 79.2 ± 0.9 Ma for the granite porphyry. LA–ICP–MS cassiterite U–Pb dating yielded Tera–Wasserburg lower intercept ages of 78.5 ± 0.6, 78.6 ± 1.2, and 78.2 ± 0.7 Ma, for cassiterite from a cassiterite–sulfide vein, cassiterite–sulfide ore, and a cassiterite–topaz–quartz stringer, respectively. Re–Os dating of molybdenite from seven different veins yielded an isochron age of 77.0 ± 0.5 Ma. All these new age data are indistinguishable within analytical uncertainty and, therefore, indicate a genetic relationship between the Sn mineralization and the porphyry magmatism in the Yinyan deposit. The REE tetrad effect and very low Nb/Ta and Zr/Hf ratios indicate that the quartz porphyry and the granite porphyry are highly evolved. The U–Pb dated cassiterite is enriched in Fe, W, and U and in high field strength elements (HFSEs) such as Zr, Hf, Nb, and Ta. The high Fe, Nb, and Ta contents may be responsible for the dark luminescence of cassiterite in CL images. The Zr/Hf ratio of cassiterite may potentially be used to distinguish the mineralization type. Cassiterite from pegmatites has lower Zr/Hf ratios (~ 5–6) in comparison with granite/greisen-related (~ 9–30) cassiterite. Cassiterite from the early hydrothermal stage typically contains higher amounts of Ti, Nb, Ta, Zr, and Hf than that from the late hydrothermal stage. In combination with published geochronological data of other Sn–W deposits in the western Guangdong Province, two Sn–W metallogenic events at ca. 85 and 77–80 Ma have been identified. These two metallogenic events are part of a larger-scale 75–100 Ma Sn–W mineralization event in South China, which we suggest was probably related to the subduction of the Neo-Tethyan oceanic plate.

Rare-metal pegmatites of the Soldat-Myl’k pegmatite field: geology, geochemistry of rare elements

Rare-metal pegmatites, in which spodumene is a major mineral of lithium, form vein series, or occur as individual veins in pegmatite fields. One such example is the Soldat-Myl’k pegmatite field located in the south-eastern Kola rare-metal pegmatite belt of the Baltic Shield (Kola Peninsula, Russia). Geologically the pegmatite field is situated on the Kolmozero-Voronya greenstone belt, and includes a vein of albite-spodumene pegmatites, veins of Ta-Nb feldspar pegmatites, and veins of ore-free pegmatites. The new data on a rare element content in rare-metal pegmatites determined using the ICP-MS method have been obtained. The study results have indicated that albite-spodumene pegmatites correspond to LCT rare-metal pegmatites by their mineralogical and geochemical features. Compared to a granite clarke, albite-spodumene pegmatites are enriched in Li, Nb, Ta, Be, Cs, Rb, Hf, U, depleted in Ba, Sr, Y, Th, REE, and have low values of indicators of ratios, i.e. Mg/Li (0.43), Nb/Ta (1.29), Zr/Hf (8.3), Ba/Rb (0.01), Sr/Rb (0.02). Ore minerals in pegmatites occur as spodumene, beryl, and minerals of the columbite group. Spodumene content in pegmatites is ∼20% of the total volume of veins. Albite-spodumene pegmatites of the Soldat-Myl’k pegmatite field differ from rare-metal pegmatites of the Kolmozero lithium deposit by higher contents of boron (29-fold enrichment), phosphorus, medium (Gd, Tb, Dy) and heavy lanthanoids, lower contents of lithium (17-fold depletion), and a weakly differentiated spectrum of lanthanoid dissemination. Feldspar pegmatites with the Ta-Nb mineralisation have high contents of Ta, Nb, Rb, Hf, U, B, and are depleted in Ba, Sr, Y, Th, REE. There is a lowering (ppm) of LREE (1.91 and 1.07, respectively), MREE (2.11 and 0.61, respectively), LREE (0.29 and 0.19, respectively) from Ta-Nb feldspar pegmatites to albite-spodumene pegmatites. Mean values of indicators of ratios, i.e. Mg/Li, Nb/Ta, Zr/Hf, Ba/Rb, Sr/Rb, also indicate a characteristic lowering from feldspar pegmatites with the Ta-Nb mineralisation (9.74, 1.70, 10.9, 0.05, 0.06, respectively) to albite-spodumene pegmatites with the Be-Nb-Ta mineralisation (0.43, 1.29, 8.3, 0.01, 0.02, respectively). Results of geochemical studies taking into account the mineralogical data indicate that rare-metal pegmatites of the Soldat-Myl’k pegmatite field can be of practical interest in relation to the rare-metal mineralisation.

Ga-(Nb+Ta)-(Nb/Ta)(Zr/Hf) Ternary Diagram: An Excellent Tool for Discriminating Barren and Ta-Hosting Granite-Pegmatite Systems

Discriminating barren and fertile intrusions is one of the main challenges in the search for rare-element pegmatites. Diagrams comprising more than one element can make discrimination of productive and barren samples more valid. These diagrams distinguish samples by simultaneous means of positive and/or negative correlations between variables. A ternary diagram for S-type peraluminous granites has been obtained in this study. Firstly, a database composed of Ta-bearing and barren granitic systems was created, then geochemical behavior of trace elements was studied, and statistical investigations were done using GCDkit software, which resulted in the Ga-(Nb+Ta)-(Nb/Ta)(Zr/Hf) ternary diagram which can distinguish the non-mineralized granites from productive ones. The Ta-bearing samples, which are situated in the fertile field in the diagram, are those which have high Nb and Ta contents, elevated Ga content and the lowest Nb/Ta and Zr/Hf values.

Tuning of mechanical properties of Ti1−xAlxN coatings through Ta alloying

The effect of alloying Ti1−x-yAlxTayN coatings with Ta on their structure and mechanical characteristics was studied by X-ray diffraction, nanoindentation and spherical indentation tests. The coatings with low Ta contents (y ≤ 0.2) were shown to demonstrate (111) texture in the growth direction, while a preferred orientation along (200) direction tended to form at high Ta contents (y > 0.35). It was revealed that the hardness and Young's modulus of the coatings exhibit overall decreasing trend with increasing the Ta content. However, the hardness breaks this trend at medium Ta contents and attains a peak value at y = 0.35. In contrast, the fracture toughness of the Ti1−x-yAlxTayN coatings extracted from the results of the spherical indentation exhibits an increasing trend with a local peak at the same Ta content (y = 0.35). This behavior of the hardness and fracture toughness is attributed to the changes in the character of interatomic bonding as well as to the evolution of the compressive residual stresses in the coatings, which are caused by Ta alloying.

Compositional Variations of Pyrochlore Group Minerals in Ongonite and Zwitter of the Verkhneurmiysky Pluton, Russian Far East

The pyrochlore-group minerals in ongonite and zwitter of the Verkhneurmiysky granite pluton in the Badzhal district, Russian Far East are reported. The composition, genesis, and crystallization sequence are characterized. Three rare species of pyrochlore, pyrochlore-I and pyrochlore-II in ongonite, and pyrochlore-III in zwitter are found for the first time in the Russian Far East. Pyrochlore-I is a possible new member of the pyrochlore group, bismuth-bearing “oxyferropyrochlore”; pyrochlore-II is an uranium-bearing and iron-bearing hydrokenopyrochlore; and pyrochlore-III is a lead-and iron-bearing hydrokenopyrochlore. All three pyrochlore species result from an alteration of early accessory minerals: niobium wolframite, samarskite, ishikawaite, wolframoixiolite, scheelite, and fergusonite. The Far East pyrochlore is characterized by extremely high Ta, W, and Fe contents. Compositional variations in pyrochlore are caused by substitution of Nb, Ta, W at the B site of the crystal structure and exchange of U, Pb, Bi, and Fe at the A site. The Ta, Bi, and Th concentrations decrease during transition from the late magmatic to greisen stage; the mineral forming significance of Nb, W, U, Y, Pb, and H2O increases as followed: Ta, Nb, Bi, Fe, Th, As, P, Ca, Ti → Nb, Ta, W, U, Fe, HREE, Sc, Mn, Na, H2O → Nb, Pb, W, Fe, Y, H2O.

Paleoproterozoic (~2.0 Ga) volcano‐plutonism in the southeastern region of the Amazon Craton: Petrological aspects and geotectonic implications

Detailed studies on the volcano‐plutonic associations of the Amazon Craton (AC) have been conducted since the 1980s. Since then, several issues concerning the definition of the lithostratigraphic units and their role in the AC evolution have been improved. Recently, a volcano‐plutonic association of around 2.0 Ga was described in the south‐central part of the AC, named as Jarinã Formation (volcanic rocks) and Vila Rica Intrusive Suite (granitoids). The present work deals with the unexpected occurrence of this volcano‐plutonic association in the southeastern region of the Amazon Craton. In the study area (Santaninha region), the rocks of the Jarinã Formation comprise two volcanic successions with distinct petrographic and compositional features. The amount and shape of the phenocrysts and crystal fragments allow the individualization of effusive and pyroclastic rocks. The geochemical character indicates that the volcanic rocks belong to two distinct successions as follows: intermediate to acid magnesian I‐type and acid ferroan A‐type. The I‐type succession shows high MgO, TiO2, P2O5, and Sr content and low K2O, Zr, Nb, Ta, Y, and heavy rare earth element and consists of undeformed andesitic to dacitic ignimbrites and subordinate effusive rhyodacites. The A‐type succession present high K2O, FeOt, Zr, Nb, Ta, Y, and heavy rare earth element content and low TiO2, P2O5, and Sr and comprises undeformed rhyolitic ignimbrites and subordinate effusive rhyolites. The granitoids of the Vila Rica Intrusive Suite crosscut the volcanic rocks of the Jarinã Formation and include two phaneritic facies as follows: coarse‐ to medium‐grained granite and medium‐grained granite. The MgO, TiO2, P2O5, Sr, K2O, Zr, Nb, Ta, Y, and rare earth element content demonstrate that the medium‐grained granite facies present geochemical characteristic of I‐type granites. Laser‐ablation inductively coupled plasma mass spectrometry U–Pb zircon data indicate crystallization ages of 2,009 ± 9 Ma for the I‐type dacitic ignimbrite, 1,994 ± 16 Ma for the A‐type rhyolitic ignimbrite, and 1,995 ± 14 Ma for the I‐type medium‐grained granite. These ages agree with the previous data of the Jarinã Formation in the south‐central region of the Amazon Craton and of the Vilca Rica Intrusive Suite in the southeastern of the Amazon Craton. The understanding of the geological context of these units carry on meaningful implications to the contextualization of the ~2.0 Ga volcano‐plutonic event in the AC and, consequently, to the compartimentalization of its geotectonic provinces.

Geological controls on enrichment of Mn, Nb (Ta), Zr (Hf), and REY within the Early Permian coals of the Jimunai Depression, Xinjiang Province, NW China

Previous investigations on major and trace elements within the Early Permian coals from Xinjiang Province are very scarce. This paper reports on the geochemistry of the Early Permian coals and associated non-coal rocks in the Jimunai depression, Xinjiang Province, northwestern China. Samples collected from coal exploration boreholes ZK2603, ZK3003, and ZKH1102 as well as the Haerjiao underground coal mine (Nos. HRJ-7 and HRJ-9 Coals) in the Jimunai Depression were analyzed using SEM-EDS, ICP-AES, and ICP-MS. These Early Permian coals reach the rank of semi-anthracite to anthracite and have low-sulfur contents (0.30% on average). In comparison with the average element concentrations of world coals, Zr, Hf, and rare earth elements and Y (REY) are slightly enriched (concentration coefficient (CC) = 2–5, as the ratio of element content in sample vs. that in world coals) and Mn is enriched (CC = 5–10) in the ZK2603, ZK3003, and ZKH1102 coals. Niobium and Ta are highly enriched in the ZK2603 and ZK3003 coals (CC = 10–100). The HRJ-7 and HRJ-9 coals are slightly enriched in Mn (CC = 2–5).The coals have a sediment source region mainly composed of intermediate-felsic compositions from the Saur Volcanic Arc to the south of the Jimunai Depression, which may have provided relatively high geochemical background concentrations of Zr, Hf, Nb, and Ta. Manganese is hosted mainly in ankerite that was derived from epigenetic precipitation from Mn-bearing hydrothermal fluids. Zirconium and Hf in the ZK2603, ZK3003, and ZKH1102 coals are controlled primarily by detrital matter or hydrothermal fluids, the latter of which results in the higher Zr/Hf ratio in the ZK2603 and ZK3003 coals due to the re-distribution of Zr and Hf. Niobium and Ta in the ZK2603 and ZK3003 coals are concentrated chiefly in zircon, and hydrothermal fluid activity caused the release of Nb and Ta from previously-existing inorganic constituents and subsequent incorporation into zircon, resulting in the lower Nb/Ta ratio due to Ta being more easily incorporated into zircon than Nb. REY are hosted primarily within multiple mineral phases (e.g., zircon, phosphates, anatase, clay minerals) and their enrichment results from a combination of detrital matter input and hydrothermal fluid influx, the former of which is evidenced by the occurrence of REY-bearing detrital zircon and anatase, and the latter of which is indicated by the existence of REY-bearing authigenic rhabdophane and anatase and corroded anatase particles, as well as by the positive Gd anomalies and MREY-type or HREY-type REY distribution patterns.

The Genetic Association between Quartz Vein- and Greisen-Type Mineralization at the Maoping W–Sn Deposit, Southern Jiangxi, China: Insights from Zircon and Cassiterite U–Pb Ages and Cassiterite Trace Element Composition

The large-scale Maoping W–Sn deposit in the Gannan metallogenic belt of the eastern Nanling Range, South China, spatially associated with the Maoping granite pluton, hosts total ore reserves of 103,000 t WO3 and 50,000 t Sn. Two different types of mineralization developed in this deposit: Upper quartz vein-type mineralization, mostly within the Cambrian metamorphosed sandstone and slate, and underneath greisen-type mineralization within the Maoping granite. Cassiterites from both types of mineralization coexist with wolframite. Here we report for the first time in situ U–Pb data on cassiterite and zircon of the Maoping deposit obtained by LA-ICP-MS. Cassiterite from quartz vein and greisen yielded weighted average 206Pb/238U ages of 156.8 ± 1.5 Ma and 156.9 ± 1.4 Ma, respectively, which indicates that the two types of mineralization formed roughly at the same time. In addition, the two mineralization ages are consistent with the emplacement age of the Maoping granite (159.0 ± 1.5 Ma) within error, suggesting a close temporal and genetic link between W–Sn mineralization and granitic magmatism. The two types of mineralization formed at the same magmatic-hydrothermal event. Cassiterite from both types of mineralization shows high Fe, Ta, and Zr contents with a low Zr/Hf ratio, suggesting that the ore-forming fluid should be derived from the highly differentiated Maoping granite pluton. Cassiterite in greisen has higher contents of Nb and Ta but a lower concentration of Ti compared with that in quartz vein, indicating that the formation temperature of greisen-type mineralization is little higher than that of quartz-vein-type mineralization.

Zircons reveal multi-stage genesis of the Xiangdong (Dengfuxian) tungsten deposit, South China

As a typical tungsten deposit of the Xitian ore field (Nanling Range, South China), the Xiangdong deposit is a quartz vein-type W deposit related to a Triassic-Jurassic granitic complex, with total ore reserves of ∼7 Mt (WO3 > 30 Kt). In this study, zircon CL and BSE imaging, LA-(MC)-ICP-MS U–Pb dating, trace element, and Hf isotopic analyses were carried out on the fluid-altered granites and related W ores in the Xiangdong deposits, aiming to reveal the genesis of the deposit. Zircon U–Pb dating yielded three age clusters: pre-Triassic (>250 Ma) (n = 19), Triassic (227–214 Ma, or “∼220 Ma”) (n = 111), and Jurassic (159–149 Ma, or “∼150 Ma”) (n = 27). Zircon morphology and geochemistry suggest that Triassic granites and Jurassic quartz veins experienced stronger influences from high-temperature hydrothermal fluids than other geological bodies in the deposit. High contents of P, Y, Pb and U are found in Triassic granite zircons, whereas high concentrations of Nb and Ta occur in Jurassic quartz-vein zircons, indicating different hydrothermal fluid systems during the Triassic and Jurassic. The Triassic and Jurassic zircons yield high Y/Ho ratios (up to 35), representing fractionated non-chondritic compositions, which are indicative of a late-stage residual melt that co-existed with F-rich fluids. Decreases in zircon Ce/Ce* and Eu/Eu* ratios from the Triassic to the Jurassic suggest a decline in fO2 that is likely to have facilitated large-scale Jurassic W mineralization. High 176Yb/177Hf and 176Lu/177Hf ratios in the hydrothermally altered Jurassic zircons indicate intense fluid exsolution from the source magma, whereas the more variable 176Hf/177Hf ratios and Hf model ages of the Triassic zircons suggest multiple fluid sources and more complex alteration processes. A new ore genesis model is proposed for the Xiangdong W deposit: initial enrichment of ore materials during the Late Triassic followed by large-scale tungsten precipitation during the Late Jurassic. The Triassic granite provided the initial W source, whereas granite-derived fluids successively formed magma-differentiated ore veins and infilling-metasomatic ore veins during the Jurassic.

Rejuvenation and plasticization of Zr-based bulk metallic glass with various Ta content upon deep cryogenic cycling

In this paper, the rejuvenation of Zr-Cu-Al-Ni-Ta bulk metallic glasses (BMGs) upon deep cryogenic cycling treatment (DCT) has been studied. The samples show rejuvenation upon DCT with an increased enthalpy of relaxation (ΔHrelax) and a decreased density. With more Ta addition, the BMGs can be rejuvenated to a higher energy state, that is, the increment in both ΔHrelax and reduced free volume is larger for the BMGs with a higher Ta content. The fracture strength and plastic strain under compression increase with Ta content due to the evolution of intrinsic heterogeneous microstructures. Furthermore, the DCT treated samples show even better plasticity than the as-cast counterparts for the more induced free volume, which contribute to the generation of multiple shear bands. This study proves the universality of DCT on rejuvenating Zr-based BMGs and explains the effect of composition on rejuvenation and plasticization behavior.