Hasil untuk "Mineralogy"

P. Sandberg

R. Mitchell

Xuejuan Song, Meng Wu, Nong Zhang et al.

Traditional coal quality assessment methods rely exclusively on the laboratory testing of physical samples, which impedes detailed stratigraphic evaluation and limits the integration of intelligent precision mining technologies. To resolve this challenge, this study investigates geophysical logging as an innovative method for coal quality prediction. By integrating scanning electron microscopy (SEM), X-ray analysis, and optical microscopy with interdisciplinary methodologies spanning mathematics, mineralogy, and applied geophysics, this research analyzes the coal quality and mineral composition of the Shanxi Formation coal seams in northern Jiangsu, China. A predictive model linking geophysical logging responses to coal quality parameters was established to delineate relationships between subsurface geophysical data and material properties. The results demonstrate that the Shanxi Formation coals are gas coal (a medium-metamorphic bituminous subclass) characterized by low sulfur content, low ash yield, low fixed carbon, high volatile matter, and high calorific value. Mineralogical analysis identifies calcite, pyrite, and clay minerals as the dominant constituents. Pyrite occurs in diverse microscopic forms, including euhedral and semi-euhedral fine grains, fissure-filling aggregates, irregular blocky structures, framboidal clusters, and disseminated particles. Systematic relationships were observed between logging parameters and coal quality: moisture, ash content, and volatile matter exhibit an initial decrease, followed by an increase with rising apparent resistivity (LLD) and bulk density (DEN). Conversely, fixed carbon and calorific value display an inverse trend, peaking at intermediate LLD/DEN values before declining. Total sulfur increases with density up to a threshold before decreasing, while showing a concave upward relationship with resistivity. Negative correlations exist between moisture, fixed carbon, calorific value lateral resistivity (LLS), natural gamma (GR), short-spaced gamma-gamma (SSGG), and acoustic transit time (AC). In contrast, ash yield, volatile matter, and total sulfur correlate positively with these logging parameters. These trends are governed by coalification processes, lithotype composition, reservoir physical properties, and the types and mass fractions of minerals. Validation through independent two-sample <i>t</i>-tests confirms the feasibility of the neural network model for predicting coal quality parameters from geophysical logging data. The predictive model provides technical and theoretical support for advancing intelligent coal mining practices and optimizing efficiency in coal chemical industries, enabling real-time subsurface characterization to facilitate precision resource extraction.

M. Zolensky, T. Zega, H. Yano et al.

Magdalena Balonis, B. Lothenbach, G. Saoût et al.

Stephan V. Kozhukharov, Christian Girginov, Stefania Portolesi et al.

Although their exceptional re-passivation ability, Al-alloys are susceptible to corrosion due to the amphoteric nature of the alumina passivation films. This issue is exacerbated by the disruption of these films by intermetallics on the surfaces of highly doped ones, like AA2024-T3 aircraft alloy. The combination of anodized aluminium oxide (AAO) and cerium conversion coatings (CeCC) shows promise as a coating primer. However, the defective structures of CeO2 and Al2O3 require additional sealing. This research proposes sealing the CeCC/AAO layer by boiling it for 10 minutes in two relatively neutral Lourier buffers, adjusted to pH 7.75, and in a mixture of them. The samples underwent a series of analyses to compare the impact of the sealing procedure on surface topology, properties (e.g., colour and wettability on two samples from each set), and corrosion protective ability. It was assessed after 24 hours of exposure to 3.5 % NaCl model corrosive medium on six samples from each set. The assessments included electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS) techniques. The results indicate that the borate buffer improves the corrosion protection of the coating primers more effectively than the phosphate and mixed ones.

Tri Candra Setiawati, Mohammad Nurcholis, Basuki Basuki et al.

The eruption of Mount Semeru at the end of 2021 was responsible for emitting volcanic ash with specific characteristics. These unique mineralogy and chemical properties have both positive and negative effects on soil fertility, as excessive heavy metals adversely affect soil, plants, and the environment. Therefore, this study aimed to determine the distribution of volcanic ash cover from the eruption of Mount Semeru and investigate elemental composition as well as mineral characteristics of volcanic ash and soil covered by volcanic ash. The investigation was carried out in Supiturang village, Pronojiwo District, Lumajang, East Java, Indonesia. Sampling was carried out following the toposequence method, covering agricultural land within approximately ± 15 km from Mount Semeru. Pure volcanic ash was collected at sites not contaminated with soil. At the site location, it was found that the depth of volcanic ash cover ranged from “thin” (<2 cm) to “very thick” (>10 cm). The results of SEM and XRD analyses showed that of the pure volcanic ash contained quartz (50%), rock fragments (15%), plagioclase (12%), hornblende (10%), opaque (8%), and pyroxene (5%) minerals. The results of XRF analysis showed that the dominant elements in volcanic ash and soil were silica (Si), aluminum (Al), calcium (Ca), iron (Fe), and potassium (K). Several non-essential heavy metal elements found were Pb, Sn, and As, while rare minerals discovered were Y, Nb, Eu, and Yb at relatively low concentrations. The SEM analysis showed the structure of volcanic ash dominated by prismatic and blocky.

M. S. Hollinetz, B. Huet, D. A. Schneider et al.

<p>We investigated rare earth element (REE) minerals in low- to medium-grade metapelites sampled in two nappes of the Austroalpine Unit (Eastern Alps, Austria). Combining microstructural and chemical characterization of the main and REE minerals with thermodynamic forward modeling, Raman spectroscopy on carbonaceous material (RSCM) thermometry and in situ U–Th–Pb dating reveal a polymetamorphic evolution of all samples. In the hanging wall nappe, allanite and REE epidote formed during Permian metamorphism (275–261 Ma, 475–520 °C, 0.3–0.4 GPa). In one sample, Cretaceous (ca. 109 Ma) REE epidote formed at <span class="inline-formula">∼440</span> °C and 0.4–0.8 GPa at the expense of Permian monazite clusters. In the footwall nappe, large, chemically zoned monazite porphyroblasts record both Permian (283–256 Ma, 560 °C, 0.4 GPa) and Cretaceous (ca. 87 Ma, 550 °C, 1.0–1.1 GPa) metamorphism. Polymetamorphism produced a wide range of complex REE-mineral-phase relationships and microstructures. Despite the complexity, we found that bulk rock Ca, Al and Na contents are the main factor controlling REE mineral stability; variations thereof explain differences in the REE mineral assemblages of samples with identical pressure and temperature (<span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span>) paths. Therefore, REE minerals are also excellent geochronometers to resolve the metamorphic evolution of low- to medium-grade rocks in complex tectonic settings. The recognition that the main metamorphic signature in the hanging wall is Permian implies a marked <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> difference of <span class="inline-formula">∼250</span> °C and at least 0.5 GPa, requiring a major normal fault between the two nappes which accommodated the exhumation of the footwall in the Cretaceous. Due to striking similarities in setting and timing, we put this low-angle detachment in context with other Late Cretaceous low-angle detachments from the Austroalpine domain. Together, they form an extensive crustal structure that we tentatively term the “Austroalpine Detachment System”.</p>

Philipp Leerhoff, Johannes C. Brouwer, Amir Mohseni Armaki et al.

In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB and OreC) for HIsarna ironmaking were analysed as an isolated process with a symmetrical thermogravimetric analyser (TGA) under an inert atmosphere. Using various methods, the chemical and mineralogical composition, particle size distribution, morphology and phase distribution of the ores were analysed. The ores differ in their mineralogy and morphology, where OreA only contains hematite as iron-bearing phase and OreB and OreC include goethite and hematite. To obtain the kinetic parameters in non-isothermal conditions, the Coats–Redfern Integral Method was applied for heating rates of 1, 2 and 5 K/min and a maximum temperature of 1773 K. The TGA results indicate that goethite and hematite decomposition occur as a two-stage process in an inert atmosphere of Ar. The proposed reaction mechanism for the first stage of goethite decomposition is chemical reaction with an activation energy ranging from 46.55 to 60.38 kJ/mol for OreB and from 69.90 to 134.47 kJ/mol for OreC. The proposed reaction mechanism for the second stage of goethite decomposition is diffusion, showing an activation energy ranging between 24.43 and 44.76 kJ/mol for OreB and between 3.32 and 23.29 kJ/mol for OreC. In terms of hematite decomposition, only the first stage was analysed. The proposed reaction mechanism is chemical reaction control. OreA shows an activation energy of 545.47 to 670.50 kJ/mol, OreB one of 587.68 to 831.54 kJ/mol and OreC one of 424.31 to 592.32 kJ/mol.

E. H. Christiansen, D. Burt, M. Sheridan et al.

J. Six, E. T. Elliott, K. Paustian

Fatemeh Kazemi, Ataallah Bahrami, Yousef Ghorbani et al.

The interaction and synergic effect of particle size on flotation efficiency were investigated by a comparison study between laboratories (size-by-size flotation modes) and industrial scale operational data (whole mixed size fraction). For this purpose, sampling was done from the feed, concentrate, and tailing of the flotation rougher cells of the Sungun copper processing complex (located in the northwest of Iran). In the size-by-size flotation mode (lab scale), the sample was first subjected to different size fractions, and then flotation tests were performed for each fraction. On an industrial scale, the particle size distribution of feed, concentrate, and tailing of flotation of the rougher stage have been analyzed. According to the results, in the case of industrial flotation mode (whole mixed size fraction), the particles with d80=84 μm were more likely to reach the tailing of flotation, and the particles within the size range of +63-180 μm constituted the highest amount of concentrate particles. In lab flotation mode (size-by-size), the maximum recovery was in the size fraction of +40-60 μm. By comparing the two flotation modes of industrial (whole mixed size fraction) and lab (size-by-size), for fractions 125 μm, the recovery trend was reversed and the lab flotation recovery was greater than the industrial flotation recovery. Coarse particle flotation has significant economic and technological benefits. By improving the recovery of coarse particles during the flotation process, the amount of grinding requirements will be reduced and consequently, it will considerably decrease the amount of energy consumption.

Marek Stadtműller, Jadwiga A. Jarzyna

The purpose of this review paper is to show the possibilities of carbonate reservoir characterization using well logging and laboratory measurements. Attention was focused on standard and new methods of well logging acquisition and interpretation including laboratory experiments to show a part of the history of carbonate rock investigations as hydrocarbon or water reservoirs. Brief information on the geology, mineralogy and petrography of carbonate rocks was delivered. Reservoir properties, i.e., porosity (including fracturing), permeability, and saturation, were defined to emphasize the specific features of carbonates, such as fractures, and vugs. Examples of methodologies were selected from the commonly used laboratory techniques (thin sections examination, mercury and helium porosimetry, X-ray diffraction—XRD) combined with the standard well logs (bulk density—RHOB, neutron porosity—NPHI, sonic slowness—DT, and deep resistivity—Rd) to show the methods that have been used since the very beginning of the scientific and engineering studies of carbonates. Novelty in well logging, i.e., resistivity and acoustic imaging, nuclear magnetic resonance–NMR, dipole shear sonic imaging–DSI, and a spectral neutron-gamma log-geochemical device–GLT combined with modern laboratory investigations (NMR laboratory experiments, scanning <i>electron</i> microscopy SEM), showed how continuous information on mineral composition, porosity and saturation could be obtained and juxtaposed with very detailed laboratory data. Computed X-ray tomography (CT) enabling the 2D and 3D analyses of pores and fractures was presented as a quantitative methodology, effective in pore space characterization, revealing rock filtration abilities. Deep learning and artificial intelligence were used for joining various types of data. It was shown that thanks to new computational technologies original data from very small samples (micro scale), extensively describing the flow ability of the reservoir, could be extended to mezzo scale (core samples) and macro scale (well log images). Selected examples from the published papers illustrated the review. References cited in the text, together with the issues included in them, were the rich source of the practical knowledge processed These were checked by the authors and could be used in other projects.

Gen Ito, Jessica Flahaut, Osvaldo González-Maurel et al.

The Altiplano-Puna Volcanic Complex (APVC) of the Central Andes is an arid region with extensive volcanism, possessing various geological features comparable to those of other solar system objects. The unique features of the APVC, e.g., hydrothermal fields and evaporite salars, have been used as planetary analogs before, but the complexity of the APVC presents a wealth of opportunities for more analog studies that have not been exploited previously. Motivated by the potential of using the APVC as an analog of the volcanic terrains of solar system objects, we mapped the mineralogy and silica content of the APVC up to ~100,000 km² in northern Chile based on a combination of remote sensing data resembling those of the Moon and Mars. The band ratio indices of Landsat 8 Operational Land Imager multispectral images and mineral classifications based on spectral hourglass approach using Earth Observing-1 Hyperion hyperspectral images (both in the visible to shortwave infrared wavelengths) were used to map iron-bearing and alteration minerals. We also used Hyperion imagery to detect feldspar spectral signatures and demonstrated that feldspar minerals can be detected on non-anorthosites, which may influence interpretations of feldspar spectral signatures on Mars. From the Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Emissivity Dataset, we derived the silica percentage of non-evaporite rocks within errors of approximately 2–3 wt.% SiO₂ for those in the 60–70 wt.% range (about 8 wt.% errors for the 50–60 wt.% range). Based on an integrated assessment of the three datasets, we highlighted three regions of particular interest worthy of further field investigation. We also evaluated the benefits and limitations of all three remote sensing methods for mapping key minerals and capturing rock diversity, based on available samples and existing geological maps.

M. Al-Mukhtar, Abdelmadjid Lasledj, J. Alcover

R. Green, C. Pieters, P. Mouroulis et al.

H. Dill

F. Kaminsky

C. Peters, M. Dekkers

وهاب سرفرازی, محمدرضا عجم زاده

ابعاد حفریات زیرزمینی یکی از پارمترهای کلیدی در پایداری آن است. در توده‌سنگ‌های ضعیف، حفریات بزرگ زمان پایداری کمی دارند بطوری که این زمان از زمان نصب نگهداری کمتر است. راک‌بولت‌ها به عنوان یکی از سیستم‌های نگهداری در پایدارسازی پروژه‌های مهندسی سنگ کاربرد دارند. نقش اصلی راک‌بولت‌ها، افزایش مقاومت زمین است. عملکرد راک‌بولت‌ها به کیفیت نصب آن‌ها بستگی دارد. با استفاده از روش‌های کشش راک‌بولت و تست گشتاور می‌توان از کیفیت نصب راک‌بولت مطلع شد. شبیه‌سازی‌های عددی از دیگر از روش‌هایی است که برای مطالعه رفتار راک‌بولت کاربرد دارند. در این روش‌ها می‌توان رفتار پیچیده راک‌بولت را که با مطالعه آزمایشگاهی امکان‌پذیر نیست، مطالعه کرد. در این مقاله سعی شده است که با استفاده از نرم‌افزار franc 2d تاثیر نیروی وارده از طرف راک‌بولت بر روی درزه Yشکل مدلسازی شود. زاویه درزه بزرگ نسبت به افق (β) صفر، 45 و 90 درجه است. زاویه درزه کوچک نسبت به درزه بزرگ (α)، 20، 40، 60، 80، 100، 120، 140 و 160 درجه است.  فاصله درزه از مرکز محل اعمال نیرو 2a، 3a و 4a است که a طول درزه بزرگ است. در این پژوهش 52 مدل مورد بررسی قرار گرفت. در حالتی که درزه افقی باشد بیشترین و در حالت قائم کمترین رشد درزه دیده می‌شود. بیشترین تعداد رشد درزه نیز در حالتی است که زاویه درزه بزرگ نسبت به افق 45 درجه باشد. بیشترین گسترش رشد شاخه کوچک در حالت افقی و بیشترین تعداد رشد شاخه کوچک درزه نیز در زاویه 45 درجه نسبت به افق اتفاق افتاده است.