Search Results (16)

Acoustic energy penetrates into the Si substrate at cavity boundaries. Due to this, the air cavity-based bulk acoustic resonators experience higher harmonic mode, parasitic resonance, and spurious mode. To overcome these effects and enhance the performance parameters, a backside air cavity is fabricated using the deep reactive ion etching (DRIE) method. The DRIE method helps to achieve the optimized active area of the resonator. SiO₂ film on a silicon substrate as the support layer and ZnO as the piezoelectric (PZE) film are used for the resonator. The crystal growth and surface morphology of ZnO film were investigated with X-ray diffraction, scanning electron microscopy, and atomic force microscopy. FBAR is modeled in a 1-D modified Butterworth–Van Dyke (mBVD) equivalent circuit. As RF measurement results, we successfully demonstrated a FBAR with optimized active area of 320 × 320 μm², center frequency of 1.261 GHz, having a quality factor of 583.8. Overall, this suppression of higher harmonic mode shows the great potential for improving the selectivity of the sensor and also in RF filter design applications. This integration of DRIE-based cavity formation with ZnO-based FBAR architecture not only enables compact design but also effectively suppresses spurious and higher-order modes, which demonstrates a performance-enhancing fabrication strategy not fully explored in the current literature. Full article

Wuhan is dotted with lakes, is known as the “City with Hundreds of Lakes”, and the development of the city is inseparable from the river and lake waters, with the evolution of the lakes affecting the construction and layout of the city. Since the 20th century, the lake evolution in the main urban area of Wuhan has been the most intense and the urban development has also been the most rapid. Therefore, on the basis of the study of the origin of different types of lakes, based on the precious high-precision historical maps of Wuhan in the early- and mid-20th century, combined with the information about lakes in Wuhan obtained from satellite remote sensing images, the evolution characteristics of the lakes in Wuhan in the past 100 years (1920~2019) were investigated through the theory of landscape fractal, and the response mechanism of lake evolution to urban expansion was further explored by being combined with the trajectory of urban expansion. The results show that the area of lakes in Wuhan declined from 2133.5 km² in 1920 to 550.8 km² in 2019, with a total decrease of 1582.7 km², an area shrinkage rate of 74.18%, and a strong amplitude of area change. The changes in the fractal dimension and the shoreline development coefficient of lakes in Wuhan city show synchronization as a whole, with occasional fluctuations, but on the whole, the fractal dimension and shoreline development coefficient of lakes are becoming smaller over a century. Specifically, the evolution of lakes in the Hankou area is mainly affected by the construction of dykes and lake filling, and most of the lakes are resolved and fragmented under the influence of urban expansion, whereas the evolution of lakes in Wuchang and Hanyang is mainly caused by the urban construction around the lakes, and many lake branches have been cut for various urban constructions, and the shape of the lake tends to be simple and regular under the influence of urban expansion. This study is of great significance for filling in the history of lake evolution in Wuhan before the popularization of remote sensing, and for guiding the rational development of lakes in Wuhan and the sustainable and healthy development of Wuhan. Full article

The selection of an appropriate mining method, along with the corresponding machinery, is a crucial and highly strategic decision in the field of mining engineering. This decision directly influences the efficiency, safety, and economic viability of a mining operation. An optimal combination of mining techniques and equipment is essential to ensure the effective exploitation of the ore deposit while minimizing costs and maximizing productivity. This paper briefly overviews existing mechanized mining machines for narrow reef mining. The NRE fleet is presented in more detail, together with the results of trial tests conducted using the NRE Drill Rig in narrow reef platinum mines situated in the Great Dyke of Zimbabwe and the Bushveld Igneous Complex in South Africa. The trials were carried out using two distinct mining layouts: the bord and pillar layout and the breast mining layout. The test results clearly demonstrated that the Drill Rig is more effective in breast mining layout compared to the bord and pillar layout in narrow reef mining. The breast mining layout showed superior performance in terms of the number of drilled boreholes and overall efficiency despite the lower availability and utilization of the Drill Rig. Full article

The Messejana–Plasencia great dyke (MPGD) is a Late Triassic tholeiitic gabbro intrusion related to the Central Atlantic Magmatic Province. Its large outcrop extent (~530 km), combined with its prolongation below the Duero basin (additional 100 km), makes it one of the world’s largest dykes known. We have studied felsic granophyric bodies appearing in its northernmost segment at different scales, from mm-sized (interstitial micrographic pockets) to felsic dykes of up to 10 m thick and 1.5 km long, intruding within the gabbros. Significant differences exist in the mineral and whole-rock composition of gabbros and granophyres, including the Sr–Nd isotopic ratios. The chemical variation in the gabbros is coherent with fractionation of olivine, clinopyroxene and plagioclase at depth. However, the presence of a compositional gap between gabbros and granophyres (absence of intermediate compositions) and the formation of these late-stage intergranular felsic melts within the gabbro mesostasis suggest that they could be derived by liquid immiscibility. The Sr–Nd isotopic heterogeneity in the MPGD gabbros and the presence of zircons with Variscan ages (~286 Ma), inherited from granulitic rocks, indicate that the mafic magmas experienced some degree of lower crust assimilation during fractionation close to the Moho depth. On the contrary, the scarce xenocrystic Variscan zircon crystals found in a granophyric dyke within the MPGD gabbro display similar textures and ages (~299 Ma) to those of the country rock granites and point to contamination at a different crustal level. Full article

Lithium (Li) has grown to be a strategic key metal due to the enormous demand for the development of new energy industries over the world. As one of the most significant sources of Li resources, pegmatite-type Li deposits hold a large share of the mining market. In recent years, several large and super-large spodumene (Spd)-rich pegmatite deposits have been discovered successively in the Hoh-Xil–Songpan-Garzê (HXSG) orogenic belt of the northern Tibetan Plateau, indicative of the great Li prospecting potential of this belt. Hyperspectral remote sensing (HRS), as a rapidly developing exploration technology, is especially sensitive to the identification of alteration minerals, and has made important breakthroughs in porphyry copper deposit exploration. However, due to the small width of the pegmatite dykes and the lack of typical alteration zones, the ability of HRS in the exploration of Li-rich pegmatite deposits remains to be explored. In this study, Li-rich pegmatite anomalies were directly extracted from ZY1-02D hyperspectral imagery in the Zhawulong (ZWL) area of western Sichuan, China, using target detection techniques including Adaptive Cosine Estimator (ACE), Constrained Energy Minimization (CEM), Spectral Angle Mapper (SAM), and SAM with BandMax (SAMBM). Further, the Li-rich anomalies were superimposed with the distribution of pegmatite dykes delineated based on GF-2 high-resolution imagery. Our final results accurately identified the known range of Spd pegmatite dykes and further predicted two new exploration target areas. The approaches used in this study could be easily extended to other potential mineralization areas to discover new rare metal pegmatite deposits on the Tibetan Plateau. Full article

Agricultural Heritage Systems exhibit multiple functions of agricultural production, ecological protection, and invaluable cultures and landscapes. The mulberry-dyke and fish-pond system is an important agricultural heritage. The Nanxun District of Huzhou, China is currently the area with the most complete and largest mulberry dykes and fish ponds in the world. In the past thirty years, with changes in labor force distribution and consumer demand, the production function of mulberry dyke and fish ponds has been challenged, and the production landscape as the carrier of farming culture has been threatened. Studying the spatial characteristics and optimization of mulberry dykes and fish ponds is of great significance to the sustainable development of the regional economy, culture, and environment. This study analyzes the spatial and temporal pattern evolution of mulberry dyke and fish ponds in Nanxun District since 1975. Based on the evaluation of the environmental carrying capacity of fish ponds, and according to the development goals of agricultural heritage inheritance and “planting and breeding balance”, the Future Land Use Simulation model is adopted to optimize the study area. The results show the following findings: (1) From 1975 to 2019, fish ponds and construction land increased significantly, mulberry fields and paddy fields decreased significantly, the scale of mulberry dykes and fish ponds decreased significantly, and the proportion of mulberry dykes and fish ponds was seriously unbalanced; (2) The overall scale of fish-pond breeding in Nanxun District is too large, and the proportion of farming and breeding needs to be adjusted; (3) In view of economic growth, cultural inheritance, and environmental protection, this paper simulates the spatial layout of mulberry dykes and fish ponds in 2035, and divides mulberry dykes and fish ponds in Nanxun District into a display area and an industrial development area. The display area restores the traditional mulberry dykes and fish ponds to the greatest extent. The industrial development zone maximizes the economic benefits of agriculture on the basis of “balancing planting and breeding”. Overall, this study provides a reference for protecting Huzhou mulberry-dyke and fish-pond agricultural heritage, optimizing agricultural production space, balancing human–environment relationship, and promoting regional sustainable development. Full article

The Chakabeishan (CKBS) deposit is the first pegmatite-type Li-Be deposit discovered in the eastern North Qaidam Tectonic Belt (NQTB) of Tibetan Plateau. The correct understanding of its petrogenesis and the precise determination of its formation age are of great significance for further regional prospecting and the discovery of new economically valuable rare-metal deposits. Therefore, a systematic study of texture, major-element composition, and U-Pb dating of columbite-tantalite group minerals (CGMs) in the spodumene pegmatite dyke from the CKBS deposit was undertaken. Three types of CGMs were identified, including concentric oscillatory ferrocolumbite (CGMs-1), homogeneous ferrocolumbite (CGMs-2), and irregular ferrotantalite (minor manganocolumbite) with abundant early ferrocolumbite replacement remnants (CGMs-3). The zoning patterns and chemical compositions in the CGMs record the complex evolutionary history of their host pegmatite from the magmatic stage (CGMs-1, disequilibrium crystallization) to the magmatic-hydrothermal transition stage (CGMs-2, equilibrium crystallization) and then to the late metasomatic stage (CGMs-3, replacement/re-equilibrium). CGMs U-Pb dating results suggest that the spodumene pegmatite dyke (No.15) emplaced at 230.1 ± 2.6 Ma. Subsequently, it experienced fluid metasomatism at 221 ± 5.3 Ma. Based on the new age data and published geochronological data, it can be concluded that the spodumene pegmatite dykes in the CKBS deposit formed in an oceanic subduction-related setting, representing a new metallogenic event in western China. Except for the CKBS deposit, a large number of rare-metal pegmatite dykes have also been discovered in the eastern NQTB, indicating that the eastern NQTB may be an important potential rare-metal metallogenic belt that should be explored in detail and arouse painstaking attention. Full article

The Middle Atlas Volcanic Field (MAVF) covers an area of 1500 km², with a total erupted volume of solid products (e.g., Dense Rock Equivalent or DRE) estimated to be more than 80 km³. The MAVF comprises 87 monogenetic basaltic volcanoes of Tertiary-Quaternary age as scoria cones (71%) and maars (29%). These monogenetic basaltic volcanoes have various morphologies (e.g., circular, semi-elliptic, elliptic in map views). They can be isolated or form clustered monogenetic complexes. They are largely grouped in the Middle Atlas, in an intraplate geotectonic context forming two distinct major alignments (N160–170° and N40–50°), each closely associated with regional structural elements. By the best estimates, the preserved bulk pyroclastic products do not exceed 0.7 km³, and they show large textural and componentry diversity (e.g., bedded/unbedded, coarse/fine, dense/scoriaceous fallout and pyroclastic density current deposit, etc.). Lava flows also demonstrate great variety of preserved surface textures, including pāhoehoe, ‘a’ā, and clastogenic types. Morphostructural features of lava flows linked to lava flow dynamics have also been recognized, and the presence of hornitos, columnar jointed basaltic flow units, lava tubes, tumuli, and clastogenic lava flows have been recognized and mapped. Some half-sectioned dykes expose interior parts of magmatic shallow feeding pipes. The current morphology of the volcanoes of the MAVF reflects various syn- and post-eruptive processes, including (1) erosional features due to weathering, (2) gravitational instability during and after volcanic activity, (3) vegetation impact, and (4) successive burial of lava flows. The documented volcanic features of this typical monogenetic volcanic field form the core of the region’s geoheritage elements and are considered to be unique in the new African geoheritage context. Hence, they will likely form the basis of future geotourism, geoeducation, and geoconservation ventures. Full article

The U–Pb measurements of youngest, coherent group of zircons from the Mielnik IG1 dolerite at the Teisseyre-Tornquist margin (TTZ) of East European Craton (EEC) in Poland yielded age of 300 ± 4 Ma. Zircon dated an evolved portion of magma at the late stage crystallization. It is shown that this isolated dyke from the northern margin of the Lublin Podlasie basin (Podlasie Depression) and regional dyke swarms of close ages from the Swedish Scania, Bornholm and Rügen islands, Oslo rift, Norway, and the Great Whine Sill in northeastern England, were coeval. They have been controlled by the same prominent tectonic event. The Mielnik IG1 dolerite is mafic rock with Mg-number between 52 and 50 composed of the clinopyroxene, olivine-pseudomorph, plagioclase, titanite, magnetite mineral assemblage, indicating relatively evolved melt. This hypabyssal rock has been affected by postmagmatic alteration. The subalkaline basalt composition, enrichment in incompatible trace elements, progressive crustal contamination, including abundance of zircon xenocrysts determines individual characteristics of the Mielnik IG1 dolerite. The revised age of dolerite, emplaced in vicinity of TTZ provides more evidences documenting the reach of the Permo-Carboniferous extension and rifting accompanied by magmatic pulses, that were widespread across Europe including the margin of the EEC incorporated that time into the broad foreland of the Variscan orogen. Full article

Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study of two high-viscosity dykes (10⁶ Pa·s) in the Chachahuén volcano, Argentina, the Great Dyke and the Sosa Dyke. To quantify dyke geometries, magma flow indicators, and magma viscosity, we combine photogrammetry, microstructural analysis, igneous petrology, Fourier-Transform-Infrared-Spectroscopy, and Anisotropy of Magnetic Susceptibility (AMS). Our results show that the dykes consist of 3 to 8 mappable segments up to 2 km long. Segments often end in a bifurcation, and segment tips are predominantly oval, but elliptical tips occur in the outermost segments of the Great Dyke. Furthermore, variations in host rocks have no observable impact on dyke geometry. AMS fabrics and other flow indicators in the Sosa Dyke show lateral magma flow in contrast to the vertical flow suggested by the segment geometries. A comparison with segment geometries of low-viscosity dykes shows that our high-viscosity dykes follow the same geometrical trend. In fact, the data compilation supports that dyke segment and tip geometries reflect different stages in dyke emplacement, questioning the current usage for final sheet geometries as proxies for emplacement mechanism. Full article

In China, freshwater is an increasingly scarce resource and wetlands are under great pressure. This study focuses on China’s second largest freshwater lake in the middle reaches of the Yangtze River—the Dongting Lake—and its surrounding wetlands, which are declared a protected Ramsar site. The Dongting Lake area is also a research region of focus within the Sino-European Dragon Programme, aiming for the international collaboration of Earth Observation researchers. ESA’s Copernicus Programme enables comprehensive monitoring with area-wide coverage, which is especially advantageous for large wetlands that are difficult to access during floods. The first year completely covered by Sentinel-1 SAR satellite data was 2016, which is used here to focus on Dongting Lake’s wetland dynamics. The well-established, threshold-based approach and the high spatio-temporal resolution of Sentinel-1 imagery enabled the generation of monthly surface water maps and the analysis of the inundation frequency at a 10 m resolution. The maximum extent of the Dongting Lake derived from Sentinel-1 occurred in July 2016, at 2465 km², indicating an extreme flood year. The minimum size of the lake was detected in October, at 1331 km². Time series analysis reveals detailed inundation patterns and small-scale structures within the lake that were not known from previous studies. Sentinel-1 also proves to be capable of mapping the wetland management practices for Dongting Lake polders and dykes. For validation, the lake extent and inundation duration derived from the Sentinel-1 data were compared with excerpts from the Global WaterPack (frequently derived by the German Aerospace Center, DLR), high-resolution optical data, and in situ water level data, which showed very good agreement for the period studied. The mean monthly extent of the lake in 2016 from Sentinel-1 was 1798 km², which is consistent with the Global WaterPack, deviating by only 4%. In summary, the presented analysis of the complete annual time series of the Sentinel-1 data provides information on the monthly behavior of water expansion, which is of interest and relevance to local authorities involved in water resource management tasks in the region, as well as to wetland conservationists concerned with the Ramsar site wetlands of Dongting Lake and to local researchers. Full article

Zircon is a main mineral used for dating rhyolitic magmas as well as reconstructing their differentiation. It is common that different populations of zircon grains occur in a single rhyolitic sample. The presence of both autocrystic and antecrystic zircon grains is reflected in their strongly varied chemical compositions and slight spread of ages. However, postmagmatic processes may induce lead loss, which is also recorded as a spread of zircon ages. Therefore, new approaches to identify different zircon populations in rhyolitic rocks are needed. In this study, we suggest that detailed examination of zircon positions in the thin sections of rhyolitic rocks provides valuable information on zircon sources that can be used to identify autocrystic and antecrystic zircon populations. Automated Scanning Electron Microscope (SEM) analyses are of great applicability in determining this, as they return both qualitative and quantitative information and allow for quick comparisons between different rhyolite localities. Five localities of Permo-Carboniferous rhyolites related to post-Variscan extension in Central Europe (Organy, Bieberstein, Halle, Chemnitz, Krucze) were analyzed by automated SEM (MLA-SEM). The samples covered a range of Zr whole rock contents and displayed both crystalline and glassy groundmass. Surprisingly, each locality seemed to have its own special zircon fingerprint. Based on comparisons of whole rocks, modal composition and SEM images Chemnitz ignimbrite was interpreted as containing mostly (or fully) antecrystic zircon, whereas the Bieberstein dyke was shown to possibly contain both types, with the antecrystic zircon being associated with disturbed cumulates. On the other hand, Organy was probably dominated by autocrystic zircon, and Krucze contained dismembered, subhedral zircon in its matrix, whereas Halle zircon was located partly in late veins, filling cracks in laccolith. Both localities may, therefore, contain zircon populations that represent later stages than the crystallization of the main rhyolitic body. Full article

Diverse studies were performed in order to investigate the behavior of the platinum-group minerals (PGM) in the weathering cycle in the Bushveld Complex of South Africa and the Great Dyke of Zimbabwe. Samples were obtained underground, from core, in surface outcrops, and from alluvial sediments in rivers draining the intrusions. The investigations applied conventional mineralogical methods (reflected light microscopy) complemented by modern techniques (scanning electron microscopy (SEM), mineral liberation analysis (MLA), electron-probe microanalysis (EPMA), and LA-ICPMS analysis). This review aims at combining the findings to a coherent model also with respect to the debate regarding allogenic versus authigenic origin of placer PGM. In the pristine sulfide ores, the PGE are present as discrete PGM, dominantly PGE-bismuthotellurides, -sulfides, -arsenides, -sulfarsenides, and -alloys, and substantial though variable proportions of Pd and Rh are hosted in pentlandite. Pt–Fe alloys, sperrylite, and most PGE-sulfides survive the weathering of the ores, whereas the base metal sulfides and the (Pt,Pd)-bismuthotellurides are destroyed, and ill-defined (Pt,Pd)-oxides or -hydroxides develop. In addition, elevated contents of Pt and Pd are located in Fe/Mn/Co-oxides/hydroxides and smectites. In the placers, the PGE-sulfides experience further modification, whereas sperrylite largely remains a stable phase, and grains of Pt–Fe alloys and native Pt increase in relative proportion. In the Bushveld/Great Dyke case, the main impact of weathering on the PGM assemblages is destruction of the unstable PGM and PGE-carriers of the pristine ores and of the intermediate products of the oxidized ores. Dissolution and redistribution of PGE is taking place, however, the newly-formed products are thin films, nano-sized particles, small crystallites, or rarely µm-sized grains primarily on substrates of precursor detrital/allogenic PGM grains, and they are of subordinate significance. In the Bushveld/Great Dyke scenario, and in all probability universally, authigenic growth and formation of discrete, larger PGM crystals or nuggets in the supergene environment plays no substantial role, and any proof of PGM “neoformation” in a grand style is missing. The final PGM suite which survived the weathering process en route from sulfide ores via oxidized ores into placers results from the continuous elimination of unstable PGM and the dispersion of soluble PGE. Therefore, the alluvial PGM assemblage represents a PGM rest spectrum of residual, detrital grains. Full article

The emplacement age of the Great Udzha Dyke (northern Siberian Craton) was determined by the U-Pb dating of apatite using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). This produced an age of 1386 ± 30 Ma. This dyke along with two other adjacent intrusions, which cross-cut the sedimentary units of the Udzha paleo-rift, were subjected to paleomagnetic investigation. The paleomagnetic poles for the Udzha paleo-rift intrusions are consistent with previous results published for the Chieress dyke in the Anabar shield of the Siberian Craton (1384 ± 2 Ma). Our results suggest that there was a period of intense volcanism in the northern Siberian Craton, as well as allow us to reconstruct the apparent migration of the Siberian Craton during the Mesoproterozoic. Full article

Platinum group elements (PGEs) are an important resource for many applications, such as automotive catalytic converters for vehicles, jewelry, electrical devices and as catalysts in the chemical and petroleum industries. At present, the greatest share of global PGE supply is extracted from the South African Bushveld Complex and from the Zimbabwean Great Dyke. In this context, this article provides a comprehensive summary of detailed mining data between 2010 and 2015 and discusses these in regard to the global PGE market. On the supply side, the data reveal that the production volumes as well as the ore grades fluctuated in recent years, while the mining and processing of economically less favorable Upper Group 2 (UG2) ore increased. The average head grade from 2010 to 2015 was 3.58 g 6E/t. In the long term, the ore grades decreased. On the market side, PGE prices and increasing (primary) production costs can be observed. On the market side, the demand for vehicles is expected to grow globally resulting in an increase in PGE demand. At the same time, secondary production is expected to increase and will eventually compete with primary production. These findings indicate challenging conditions for the Southern African PGE industry. Full article