Search Results (9)

Ni-based catalysts have been widely used in catalytic reactions by researchers due to their advantages such as abundant resources, high catalytic activity and lower prices than precious metals. However, the problems of easy agglomeration and poor dispersion of Ni-based catalysts have hindered their large-scale application. Therefore, it is necessary to select a suitable preparation method to reduce the agglomeration of the catalyst and improve its dispersion. In this paper, the Ni-NiAl₂O₄/tourmaline composite material was prepared by using the microwave hydrothermal reduction method. The most favorable conditions for preparing NiAl₂O₄/tourmaline are as follows: using TEOA as the additive, the microwave hydrothermal temperature is 220 °C, the calcination temperature is 800 °C, and the addition amount of tourmaline is 7.4 wt.%. NiAl₂O₄ has a good dispersion over the surface of tourmaline support and the optimal NiAl₂O₄/tourmaline catalyst exhibits a specific surface area of 106.5 m²/g. Metallic nickel was reduced at 650 °C to further obtain Ni-NiAl₂O₄/tourmaline composites. Finally, the Ni-NiAl₂O₄/tourmaline composites showed significantly improved catalytic dry reforming of methane (DRM) activity compared to Ni-NiAl₂O₄ sample under low-temperature conditions (500–600 °C), meaning that the tourmaline carrier could effectively optimize the low-temperature catalytic performance of Ni-NiAl₂O₄. Full article

The origin of Oligocene sediments in the Bengal Basin and associated tectonic setting remain poorly understood. This study investigates the framework mineralogy and major element geochemistry of the Barail Group sandstones from the Sylhet Trough within the Bengal Basin to clarify the provenance and tectonic history of the Oligocene. Modal analysis (Q₈₃F₇L₁₀) and geochemical data support a classification of sublitharenite to subarkose, some with Fe enrichment. The heavy mineral assemblage is dominated by opaque minerals, followed by ultrastable minerals with zircon > tourmaline > rutile. The sub-angular to sub-rounded sand grains with a compositionally moderate mature nature suggest that the sediments were deposited close to the source area. The mineralogical and geochemical provenance discrimination diagram suggests contributions from felsic igneous, sedimentary/metasedimentary, and low-grade metamorphic sources, with detritus derived from the Indian craton and proto-Himalaya region. Data suggest moderate to intense chemical weathering, indicative of low relief and a sub-humid to humid climate in the source area. The tectonic analyses indicate that the Bengal Basin transitioned from a predominantly passive margin to an active tectonic margin setting during the Oligocene. Full article

The Bayan-Uul porphyry Au-Cu-(Mo) deposit occurs within the Mongol–Okhotsk Orogenic Belt, which is a part of the Central Asian Orogenic Belt. To understand geotectonic, petrogenesis, mineralization, and ore-forming fluid evolution of the Bayan-Uul deposit, we report petrographic and geochemical analyses of host rocks, mineralogy of ores, and fluid inclusion characteristics. Based on petrographic and mineralogical analyses, Cu, Mo, and Au mineralization occurs as disseminated and sulfide-bearing quartz–tourmaline veins hosted within granodiorites, monzodiorites, and diorite porphyry and tourmaline breccia. Four main alteration assemblages are identified: potassic, phyllic, argillic, and quartz–tourmaline alteration. The ore mineralogy of quartz–tourmaline veinlets are classified into A-type veinlets (quartz + tourmaline + chalcopyrite + magnetite + pyrite ± electrum), B-type veinlets (quartz + tourmaline + molybdenum + chalcopyrite + pyrite), and C-type veinlets (quartz + tourmaline + pyrite ± chalcopyrite). Fluid inclusions are found in quartz–tourmaline veinlets consisting mainly of liquid-rich two-phase (L-type), vapor-rich two-phase (V-type), and solid-bearing multi-phase (S-type) inclusions. The homogenization temperatures for the fluid inclusions in A-type, B-type, and C-type veinlets range from 215 to 490°C, 215 to 500 °C, and 160 to 350 °C and their salinity varies from 5.4 to 43.5 wt.%, 16 to 51.1 wt.%, and 3.4 to 24.1 wt.% NaCl equivalent, respectively. Coexistance of (L-type), (V-type), and (S-type) inclusions support fluid boiling. The δ¹⁸O values of ore fluids from different mineralizing A-, B-, and C-type veins are 8.7‰, 10.9‰, and 8.4‰, respectively, and the δ³⁴S values of sulfide minerals range from −1.4‰ to 5.3‰, which indicates magmatic origin. Full article

The Salt Range, in Pakistan, preserves an insightful sedimentary record of passive margin dynamics along the NW margin of the Indian Plate during the Mesozoic. This study develops provenance analyses of the Upper Triassic (Kingriali Formation) to Lower Jurassic (Datta Formation) siliciclastics from the Salt and Trans Indus ranges based on outcrop analysis, petrography, bulk sediment elemental geochemistry, and heavy-mineral data. The sandstones are texturally and compositionally mature quartz arenites and the conglomerates are quartz rich oligomictic conglomerates. Geochemical proxies support sediment derivation from acidic sources and deposition under a passive margin setting. The transparent heavy mineral suite consists of zircon, tourmaline, and rutile (ZTR) with minor staurolite in the Triassic strata that diminishes in the Jurassic strata. Together, these data indicate that the sediments were supplied by erosion of the older siliciclastics of the eastern Salt Range and adjoining areas of the Indian Plate. The proportion of recycled component exceeds the previous literature estimates for direct sediment derivation from the Indian Shield. A possible increase in detritus supply from the Salt Range itself indicates notably different conditions of sediment generation, during the Triassic–Jurassic transition. The present results suggest that, during the Triassic–Jurassic transition in the Salt Range, direct sediment supply from the Indian Shield was probably reduced and the Triassic and older siliciclastics were exhumed on an elevated passive margin and reworked by a locally established fluvio-deltaic system. The sediment transport had a north-northwestward trend parallel to the northwestern Tethyan margin of the Indian Plate and normal to its opening axis. During the Late Triassic, hot and arid hot-house palaeoclimate prevailed in the area that gave way to a hot and humid greenhouse palaeoclimate across the Triassic–Jurassic Boundary. Sedimentological similarity between the Salt Range succession and the Neo-Tethyan succession exposed to the east on the northern Indian passive Neo-Tethyan margin suggests a possible westward extension of this margin. Full article

Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the pegmatitic melts. To deal with these issues, the aplite-pegmatite dykes from the Tres Arroyos area, which constitute a zoned pegmatitic field related to the Nisa-Alburquerque granitic batholith, have been studied. This work comprises a complete study of Nb-Ta-Sn oxides’ mineralogy, whole-rock geochemistry, and U-Pb geochronology of the aplite-pegmatites that have been grouped as barren, intermediate, and Li-rich. The most abundant Nb-Ta-Sn oxides from Tres Arroyos correspond to columbite-(Fe), columbite-(Mn) and cassiterite. Niobium-Ta oxides show a marked increase in the Mn/(Mn+Fe) ratio from the barren aplite-pegmatites up to the Li-rich bodies, whereas variations in the Ta/(Ta+Nb) ratio are not continuous. The probable factors controlling fractionation of Mn/Fe and Ta/Nb reflected in Nb-Ta oxides may be attributed to the crystallization of tourmaline, phosphates and micas. The lack of a progressive Ta/Nb increase with the fractionation may be also influenced by the high F and P availability in the parental pegmatitic melts. Most of the primary Nb-Ta oxides would have crystallized by punctual chemical variations in the boundary layer, whereas cassiterite formation would be related to an undercooling of the system. Whole-rock composition of the distinguished lithotypes reflects similar tendencies to those observed in mineral chemistry, supporting a single path of fractional crystallization from the parental Nisa-Alburquerque monzogranite up to the most evolved Li-rich aplite-pegmatites. The age of 305 ± 9 Ma, determined by LA-ICP-MS U-Pb dating of columbite-tantalite oxides, reinforces the linkage of the studied aplite-pegmatites and the cited parental monzogranite. Full article

The precise timing, petrogenesis, and geodynamic significance of three granitoid bodies (Beidao granite, Caochuanpu granite, Yuanlongzhen granite, and the Roche type rock) of the Tianshui area in the Western Qinling Orogen, central China, are poorly constrained. We performed an integrated study of petrology, geochemistry, and zircon U-Pb dating to constrain their genesis and tectonic implication. Petrographic investigation of the granites shows that the rocks are mainly monzogranites. The Al saturation index (A/CNK versus SiO₂) of the granitoid samples indicates meta-aluminous to peraluminous I-type granites. Their magmas were likely generated by the partial melting of igneous protoliths during the syn-collisional tectonic regime. Rare-earth-elements data further support their origin from a magma that was formed by the partial melting of lower continental crust. The Beidao, Caochuanpu, and Yuanlongzhen granites yielded U-Pb zircon weighted mean ages of 417 ± 5 Ma, 216 ± 3 Ma, and 219 ± 3 Ma, respectively. This study shows that the Beidao granite possibly formed in syn- to post-collision tectonic settings due to the subduction of the Proto-Tethys under the North China Block, and can be linked to the generally reported Caledonian orogeny (440–400 Ma) in the western segment of the North Qinling belt, whereas Yuanlongzhen and Caochuanpu granites can be linked to the widely known Indosinian orogeny (255–210 Ma). These granitoids formed due to the subduction of the oceanic lithospheres of the Proto-Tethyan Qinling and Paleo-Tethyan Qinling. The Roche type rock, tourmaline-rich, was possibly formed from the hydrothermal fluids as indicated by the higher concentrations of boron leftover during the late-stages of magmatic crystallization of the granites. Full article

Various natural materials, namely ilmenite, diopside, tourmaline, olivine, garnet, and basalt, were plasma-sprayed and analyzed. This paper summarizes the various achievements of our earlier research and adds new results—mainly dielectric and optical characterizations. Plasma spraying of all of the materials was rather easy with a high feed-rate plasma system, which could process many kilograms of powder per hour. For easier characterizations, the coatings were detached from substrates in order to remain self-supporting. The plasma-sprayed layers that were coated from all studied materials acted as medium-permittivity and low-loss dielectrics, antireflective optical materials, and medium quality anti-abrasive barriers. Phase composition and microhardness were evaluated in addition to microstructure observations. Some coatings were amorphous and crystallized after further heating. As the melting points were well above 1000 °C, all of them could also serve as thermal barriers for aluminum alloys and similar metals. The only material that was not easily sprayed was tourmaline, which gave very porous coatings without environmental barrier or dielectric characteristics. Full article

The use of borehole imaging tools has become widespread in recent years with more specialized studies of reservoir properties, particularly in highly-porous and fractured carbonate systems. In this study, the Formation MicroScanner (FMS) borehole imaging tool and conventional well log data have been used to study the secondary porosity of the dolomitic Alamein Formation in the Alamein Field, north Western Desert, Egypt. Based on well log analyses of the formation from Tourmaline-1X and N.Alamein-6X wells, we show that secondary porosity occurs across the formation, and is filled mostly with hydrocarbon. We also show that the formation has good average effective porosity and hydrocarbon saturation. FMS images of the Tourmaline-1X well confirms that the formation is intermittently vuggy with solution-filled channels from the top to its base. The vug pores are observed to be well-connected, which supports good effective porosity values interpreted from petrophysical data. An additional set of core photographs of the Alamein Formation from N.Alamein-5X well confirms the presence of secondary pores, which are filled by hydrocarbon, and exhibit intense fluorescence under UV light. Our results show that the abundance of secondary porosity in Alamein Formation would play a key role in evaluating its reservoir quality and reservoir performance. Full article

This study investigated the photocatalytic activity of tourmaline by itself. Under irradiation of a 13 W, 254 nm UV lamp, 50% of methyl blue disappeared in the presence of 130 mg·L⁻¹ tourmaline. The reaction was inhibited by the addition of ethanol, Cl⁻, SO₄²⁻ and Cu²⁺, and promoted a little by addition of 50 mg/L Mg²⁺, which supports the inference of involvement of ^•OH radicals. This is the first proposal of tourmaline as a single photocatalyst without the need to add any artificial chemical products. Results from this study might contribute to the broadened usage of this mineral to approach the goals of saving energy and eliminate direct or indirect environmental pollution. Full article