Comparative Study on the Origin and Characteristics of Chinese (Manas) and Russian (East Sayan) Green Nephrites

Green nephrites are widely pursued for their mild texture and vivid color. In recent years, many Russian green nephrites appeared in China (the world’s largest nephrite market) and competed with the Chinese Manas green nephrites, which are traditionally highly valued. In this study, we compared the appearance, mineralogy and geochemical features (with EPMA and LA-ICP-MS) of Chinese (Manas) and Russian (East Sayan) green nephrites to objectively characterize and distinguish between these two nephrites. Chinese (Manas) and Russian (East Sayan) green nephrites are mined from serpentinized ultramafic units in the northern Tian Shan and East Sayan orogen, respectively. In terms of appearance, the Manas green nephrites are slightly bluish or grayish, whilst their East Sayan counterparts are brighter (duck-egg cyan). The Manas nephrites commonly have a caramel color, crumple structure, characteristic white globules and sinuous veins, green stains and yellow–green veins, together with a local fibrous structure. The East Sayan green nephrites are more transparent, with a gentler fine texture, uniform color, many black spots and a few green spots. Some green nephrites from the Arahushun mine of East Sayan have an ice-like appearance. Microscopic petrography and EPMA analysis indicate that both the Manas and East Sayan green nephrites comprise mainly tremolite with minor actinolite. Minor minerals in the Manas samples include chromite, chlorite-group minerals, and uvarovite; whilst those in the East Sayan samples include actinolite, chromite, chlorite-group minerals, and bornite. Bornite is not found in any other sources of green nephrite, and thus is characteristic of Russian (East Sayan) green nephrites. LA-ICP-MS trace element data in their amphiboles and Single-Factor Analysis of Variance (ANOVA) results suggest that the differences in Cr, Zn, Y, Ba, and Sr contents and values of δEu, Eu/Sm, (La/Yb)N, (La/Sm)N, (Gd/Yb)N, ∑HREE, ∑LREE/∑HREE between the two nephrites are present, and can be used as their origin trace.

Quantitative analysis of surfaces of cross-section in butt welding of aluminum alloy 5083 using laser–arc hybrid welding

The alloy aluminum of 5000 series will have relatively high strength through solid solution strengthening of Mg. However, when laser welding the 5000 series aluminum alloys, the Mg is selectively evaporated by welding heat due to its low melting and vaporization points, resulting in a reduction in the strength of welds. Therefore, laser welding application is difficult because of such a reduction in strength1[Formula: see text]2 [M. Peel, A. Steuwer, M. Preuss and P. J. Withers,Acta Mater. 51, 4791 (2003); A. Haboudou, P. Peyre, A. B. Vannes and G. Peix, Mater. Sci. Eng. A 363, 40 (2003)]. In this paper, welding experiments were carried out using laser and laser–arc hybrids on aluminum alloy 5083 with 8-mm thickness. Tensile testing, scanning electron microscopy (SEM) analysis and electron probe microanalyzer (EPMA) analysis were carried out on specimens on which the laser and laser–arc hybrid weldings were performed. According to the tensile test results, the tensile strength during laser–arc hybrid welding was greater than 85% of the parent metal. In addition, EPMA analysis showed that the strength of the laser–arc hybrid welds was maintained by supplementing the optional evaporating Mg element, since they use the filler wire.

Iron- and Nickel Enriched Olivine from Phlogopite Harzburgite of the Bug Granulite Complex (Ukrainian Shield)

An abundance of the trace elements has been determined in olivine of the Archean spinel-bearing phlogopite harzburgite enclave (sample UR17/2) from the Bug granulite complex of the Ukrainian Shield by SIMS analysis. Major elements were analyzed in the olivine by SEM-EDS and EPMA analysis. The olivine shows a homogeneous chemical composition: MgO — 45.20—45.64 wt.%, FeO — 13.66—14.23 wt.%, with Fo85—86 and Fe/Mn ratio of 68.3—68.6 which corresponds to the ratio of 60—70 in olivine of peridotites. Ni content in the UR17/2 olivine ranges from 4730 to 5612 ppm, which is higher than in olivine from mantle peridotites, high magnesium OIB and Hawaiian picrites. The olivine has average content of Ti — 20.6 ppm, Nb — 0.03 ppm, Zr — 0.32—0.60 ppm, the low total REE (0.1—0.5 ppm). The olivine crystallization temperature, calculated using an Al-in-olivine thermometer, corresponds to ~ 900°C. Enrichment in Fe and Ni is the main feature that distinguishes the UR17/2 olivine from other mantle-derived olivine. Сomposition of the UR17/2 olivine and host harzburgite indicates an influence of T, P, the oxygen fugacity and composition of parent magma on the partition coefficients of Fe and Ni. Сomposition and structure (degree of polymerization) of magma are the main factors responsible for the olivine enrichment by iron and nickel.

Wyroby ze szkła i fajansu egipskiego

During archaeological research in the cremation cemetery in Żelazna Nowa, 106 glass and four faience artefacts were uncovered. Most of them were found in eleven cremation burials (1, 2, 19A, 33, 34, vicinity of 36, 37, 39, 44, 47, 54) dated between the 1st and 3rd centuries AD. The glass pieces are highly fragmented, melted, or fused with other elements of the pyre, with only one glass bead completely preserved (type 218c acc. to Tempelmann-Mączyńska). The faience objects have survived in better shape: these are two complete beads and two fragments, all representing type 171 (acc. to Tempelmann-Mączyńska). Chemical compositions of 12 glass pieces and one fragment of a faience bead were determined using EPMA analysis. All the analysed artefacts turned out to be sodium glasses, made using both mineral sodium (natron) and sodium from the ash of halophytic plants (one sample). Natron glasses represent three groups distinguished by varying contents of MgO and K2O. The differences in concentrations of these components indicate that sands from different deposits were added in the glass-making process. This corroborates a hypothesis positing multiple centres of glass production during the Roman Period.

Brittle–ductile fabrics and P–T conditions of deformation in the East Pernambuco shear zone (Borborema Province, NE Brazil)

Fabrics of the East Pernambuco shear zone (EPSZ) were studied via microstructural analysis, mineral chemistry and isochemical phase diagram modelling to constrain the pressure and temperature conditions of deformation during shearing. Granitic mylonites show fractured feldspar porphyroclasts embedded in a fine-grained, recrystallized quartzo-feldspathic matrix. These mylonites grade laterally into banded ultramylonites characterized by stretched feldspar clasts alternated with recrystallized quartz bands. Fractures in these ultramylonites are filled by phyllosilicates. The mineral chemistry of the feldspars points to systematic changes between porphyroclasts, grains within fractures and fine-grained mixtures. Quartz crystallographic fabrics in the mylonites suggest activation of prism slip, while the ultramylonites show the activation of both rhomb and basal slip systems. Thermodynamic modelling suggests that the mylonites were formed at 4.75 ± 0.25 kbar and 526 ± 9°C, while the ultramylonites yield conditions of 5.9 ± 1 kbar and 437 ± 17°C. These observations suggest that the EPSZ records a heterogeneous path of strain accommodation, marked by decreasing temperature from its western sector to its eastern termination. The differences in metamorphic conditions are consistent with a transitional, brittle–ductile strain regime. Such characteristics indicate that the EPSZ is a Neoproterozoic shear belt nucleated and heterogeneously exhumed at the brittle–ductile transition, possibly in an intracontinental setting.Supplementary Material: EPMA analysis of feldspars in Caruaru and Gravatá domains and T-X(O2) pseudosections are available at https://doi.org/10.6084/m9.figshare.c.5125957

“Garnierite” in weathering crust of ultramafic blocks from Cao Bang area, north Viet Nam

"Garnierite" is an important group of ore minerals in the supergene nickel deposits. Garnierite group minerals are Ni-bearing hydrous magnesium silicate formed due to the lateritic weathering of ultramafic rocks under humid tropical conditions. In the weathering crust on ultra-mafic blocks Ha Tri and Phan Thanh (Cao Bang province), garnierite group minerals have been found in the saprolite zone or as a coating on the surface of the fissures. Analytical results show that garnierite consists of a mixture of three solid solutions: (i) serpentine-like - 7Ao (lizardite-nepouite), (ii) talc-like - 10 Ao (pimelite-willemseite) and (iii) chlorite-like - 14 Ao (clinochlore-minite). EPMA analysis shows that garnierite in Cao Bang area is characterized by high Ni content (25.50-40.06%), low Fe content (0.09-0.9%) and almost no Al (<0.02%), similar to garnierite in the famous nickel mines in New Caledonia, Dominican Republic, etc... Notable, Ni and Mg contents in garnierite show a clear negative correlation, indicating the replacement for each other in the phases. Under the scanning electron microscope (SEM), garnierite has a raspberry shape forming continuous zones covering the unfinished weathered rock surface. These zones represent different stages of garnierite formation. The results of the study allow proposing a model of garnierite formation in the lateritic weathering zone in ultramafic blocks in the Cao Bang area.

“Garnierite” in weathering crust of ultramafic blocks from Cao Bang area, north Viet Nam

"Garnierite" is an important group of ore minerals in the supergene nickel deposits. Garnierite group minerals are Ni-bearing hydrous magnesium silicate formed due to the lateritic weathering of ultramafic rocks under humid tropical conditions. In the weathering crust on ultra-mafic blocks Ha Tri and Phan Thanh (Cao Bang province), garnierite group minerals have been found in the saprolite zone or as a coating on the surface of the fissures. Analytical results show that garnierite consists of a mixture of three solid solutions: (i) serpentine-like - 7Ao (lizardite-nepouite), (ii) talc-like - 10 Ao (pimelite-willemseite) and (iii) chlorite-like - 14 Ao (clinochlore-minite). EPMA analysis shows that garnierite in Cao Bang area is characterized by high Ni content (25.50-40.06%), low Fe content (0.09-0.9%) and almost no Al (<0.02%), similar to garnierite in the famous nickel mines in New Caledonia, Dominican Republic, etc... Notable, Ni and Mg contents in garnierite show a clear negative correlation, indicating the replacement for each other in the phases. Under the scanning electron microscope (SEM), garnierite has a raspberry shape forming continuous zones covering the unfinished weathered rock surface. These zones represent different stages of garnierite formation. The results of the study allow proposing a model of garnierite formation in the lateritic weathering zone in ultramafic blocks in the Cao Bang area.

Natural Aging Behavior of Double-Sided MIG Welded A7N01-T5 Aluminum Alloy

A heat treatable A7N01 (Al-Zn-Mg) aluminum alloy mainly used to fabricate high-speed train body structures was double-sided welded by MIG welding. The natural aging behavior of the joint was systematically studied by local and global mechanical property testing method. Based on TEM observation and EPMA analysis, the key factors that lead to different natural aging behavior among various regions of the joint were discussed. The global tensile strength of the joints increased obviously after natural aging. All the joint samples fractured in the weld zone, which demonstrated the weld zone was the weakest zone of the joints. And the strength of the global welds were depended on the microstructure and natural aging ability of the weld zone. Moreover, the increase of the tensile property of the three local regions in the weld zone after post natural aging decreased as Middle>lower>upper. The above phenomenon was also further confirmed by microhardness measurement. The age hardening behavior is greatly influenced by the concentration of strengthening precipitates forming element Zn. The Zn content in the weld zone determined by EPMA showed that element Zn was dispersed unevenly, which is attributed to the double V-groove design used in this work and Zn vaporization in the molten pool during welding. The Zn content in the middle layer metals is higher than that of the upper and lower layers, resulting in the remarkable hardening response for the middle layer of the weld zone during natural aging process. Additionally, the solution zone containing the same Zn content as the base metal and undergoing sufficient solid solution during welding was found to possess the high hardening ability after natural aging process.

Electrodeposition and the Optimization of Molybdenum Layer on Nb-Ti-Si Based Ultra-High Alloys from Aqueous Solution

Depositing a molybdenum layer through electrodeposition is a possible and economical way to prepare Mo layer. It could be a new preparation of MoSi2coating on Nb-Ti-Si based alloys combined with halide pack cementation. In this paper, the effects of pre-coated Re layer on the substrate, pH of the electrolyte, water to acetate ratio and the applied current density on the deposition were investigated and optimized to obtain low oxygen content, adherent molybdenum coating on Nb-Ti-Si based alloys. The surface morphology and cross section were characterized by SEM. The thickness of the deposit is about 6 μm and nodules and cracks were observed on the surface. EDS and EPMA analysis suggested the presence of Mo and its oxides in the deposit; XPS results confirmed the presence of Mo, Mo2O3and MoO3in the as-deposited layer. The crystal structure of as-prepared coating was amorphous by the XRD investigation, and the metallic molybdenum was the main existence form of the molybdenum element in the deposit.