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Search Results (1,736)

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Keywords = mineralizing fluids

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24 pages, 6356 KiB  
Article
Tectonic Rift-Related Manganese Mineralization System and Its Geophysical Signature in the Nanpanjiang Basin
by Daman Cui, Zhifang Zhao, Wenlong Liu, Haiying Yang, Yun Liu, Jianliang Liu and Baowen Shi
Remote Sens. 2025, 17(15), 2702; https://doi.org/10.3390/rs17152702 (registering DOI) - 4 Aug 2025
Abstract
The southeastern Yunnan region in the southwestern Nanpanjiang Basin is one of the most important manganese enrichment zones in China. Manganese mineralization is mainly confined to marine mud–sand–carbonate interbeds of the Middle Triassic Ladinian Falang Formation (T2f), which contains several [...] Read more.
The southeastern Yunnan region in the southwestern Nanpanjiang Basin is one of the most important manganese enrichment zones in China. Manganese mineralization is mainly confined to marine mud–sand–carbonate interbeds of the Middle Triassic Ladinian Falang Formation (T2f), which contains several medium to large deposits such as Dounan, Baixian, and Yanzijiao. However, the geological processes that control manganese mineralization in this region remain insufficiently understood. Understanding the tectonic evolution of the basin is therefore essential to unravel the mechanisms of Middle Triassic metallogenesis. This study investigates how rift-related tectonic activity influences manganese ore formation. This study integrates global gravity and magnetic field models (WGM2012, EMAG2v3), audio-frequency magnetotelluric (AMT) profiles, and regional geological data to investigate ore-controlling structures. A distinct gravity low–magnetic high belt is delineated along the basin axis, indicating lithospheric thinning and enhanced mantle-derived heat flow. Structural interpretation reveals a rift system with a checkerboard pattern formed by intersecting NE-trending major faults and NW-trending secondary faults. Four hydrothermal plume centers are identified at these fault intersections. AMT profiles show that manganese ore bodies correspond to stable low-resistivity zones, suggesting fluid-rich, hydrothermally altered horizons. These findings demonstrate a strong spatial coupling between hydrothermal activity and mineralization. This study provides the first identification of the internal rift architecture within the Nanpanjiang Basin. The basin-scale rift–graben system exerts first-order control on sedimentation and manganese metallogenesis, supporting a trinity model of tectonic control, hydrothermal fluid transport, and sedimentary enrichment. These insights not only improve our understanding of rift-related manganese formation in southeastern Yunnan but also offer a methodological framework applicable to similar rift basins worldwide. Full article
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20 pages, 4663 KiB  
Article
Investigation on Imbibition Recovery Characteristics in Jimusar Shale Oil and White Mineral Oil by NMR
by Dunqing Liu, Chengzhi Jia and Keji Chen
Energies 2025, 18(15), 4111; https://doi.org/10.3390/en18154111 (registering DOI) - 2 Aug 2025
Viewed by 51
Abstract
Recovering oil by fracturing fluid imbibition has demonstrated significant potential for enhanced oil recovery (EOR) in tight oil reservoirs. White mineral oil (WMO), kerosene, or saturated alkanes with matched apparent viscosity have been widely used as “crude oil” to investigate imbibition mechanisms in [...] Read more.
Recovering oil by fracturing fluid imbibition has demonstrated significant potential for enhanced oil recovery (EOR) in tight oil reservoirs. White mineral oil (WMO), kerosene, or saturated alkanes with matched apparent viscosity have been widely used as “crude oil” to investigate imbibition mechanisms in light shale oil or tight oil. However, the representativeness of these simulated oils for low-maturity crude oils with higher viscosity and greater content of resins and asphaltenes requires further research. In this study, imbibition experiments were conducted and T2 and T1T2 nuclear magnetic resonance (NMR) spectra were adopted to investigate the oil recovery characteristics among resin–asphaltene-rich Jimusar shale oil and two WMOs. The overall imbibition recovery rates, pore scale recovery characteristics, mobility variations among oils with different occurrence states, as well as key factors influencing imbibition efficiency were analyzed. The results show the following: (1) WMO, kerosene, or alkanes with matched apparent viscosity may not comprehensively replicate the imbibition behavior of resin–asphaltene-rich crude oils. These simplified systems fail to capture the pore-scale occurrence characteristics of resins/asphaltenes, their influence on pore wettability alteration, and may consequently overestimate the intrinsic imbibition displacement efficiency in reservoir formations. (2) Surfactant optimization must holistically address the intrinsic coupling between interfacial tension reduction, wettability modification, and pore-scale crude oil mobilization mechanisms. The alteration of overall wettability exhibits higher priority over interfacial tension in governing displacement dynamics. (3) Imbibition displacement exhibits selective mobilization characteristics for oil phases in pores. Specifically, when the oil phase contains complex hydrocarbon components, lighter fractions in larger pores are preferentially mobilized; when the oil composition is homogeneous, oil in smaller pores is mobilized first. Full article
(This article belongs to the Special Issue New Progress in Unconventional Oil and Gas Development: 2nd Edition)
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16 pages, 744 KiB  
Article
Investigation of Effects of Low Ruminal pH Values on Serum Concentrations of Macrominerals, Trace Elements, and Vitamins and Oxidative Status of Dairy Cows
by Panagiotis D. Katsoulos, Bengü Bilgiç, Duygu Tarhan, Fatma Ateş, Suat Ekin, Süleyman Kozat, Banu Dokuzeylül, Mehmet Erman Or, Emmanouil Kalaitzakis, Georgios E. Valergakis and Nikolaos Panousis
Ruminants 2025, 5(3), 35; https://doi.org/10.3390/ruminants5030035 (registering DOI) - 2 Aug 2025
Viewed by 44
Abstract
Due to the feeding system (high-concentrate diet) during the early lactation stage, ruminal pH in dairy cows follows a diurnal pattern and can remain below the critical level of 5.5 for extended periods of the day. This study aimed to evaluate the effect [...] Read more.
Due to the feeding system (high-concentrate diet) during the early lactation stage, ruminal pH in dairy cows follows a diurnal pattern and can remain below the critical level of 5.5 for extended periods of the day. This study aimed to evaluate the effect of low ruminal pH on blood concentrations of certain macrominerals, trace minerals, and fat-soluble vitamins and on the oxidative status of dairy cows during the first half of lactation. Fifty-three randomly selected lactating Holstein cows were used; blood and ruminal fluid samples were collected from all cows on days 30, 90 and 150 of lactation. Blood samples were obtained via coccygeal venipuncture, while the ruminal fluid was obtained by rumenocentesis and the pH was measured immediately after collection. Using a threshold pH of 5.5, samples were classified as normal (pH > 5.5) or low pH (pH ≤ 5.5). Serum concentrations of Ca, Mg, K, Cr, Mn, Zn, Se, and vitamins A, D3, E, and K were not significantly affected by ruminal pH, either by days in milk or by their interaction (p > 0.05). Plasma malondialdehyde and reduced glutathione followed the same trend (p > 0.05). Copper concentration was significantly higher (p < 0.05), and Fe concentration tended to be higher in cows with low pH compared to those with normal pH (p = 0.052). On day 150 of lactation, Cu, Fe, and Co concentrations were significantly higher in low-pH cows compared to normal-pH cows (p < 0.05). Low ruminal pH is associated with significant changes in serum concentrations of copper, iron, and cobalt but has no significant effect on the oxidative status of the animals or on the serum concentrations of the macro elements and fat-soluble vitamins studied. Full article
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29 pages, 4812 KiB  
Article
Geochemical Assessment of Long-Term CO2 Storage from Core- to Field-Scale Models
by Paa Kwesi Ntaako Boison, William Ampomah, Jason D. Simmons, Dung Bui, Najmudeen Sibaweihi, Adewale Amosu and Kwamena Opoku Duartey
Energies 2025, 18(15), 4089; https://doi.org/10.3390/en18154089 (registering DOI) - 1 Aug 2025
Viewed by 129
Abstract
Numerical simulations enable us to couple multiphase flow and geochemical processes to evaluate how sequestration impacts brine chemistry and reservoir properties. This study investigates these impacts during CO2 storage at the San Juan Basin CarbonSAFE (SJB) site. The hydrodynamic model was calibrated [...] Read more.
Numerical simulations enable us to couple multiphase flow and geochemical processes to evaluate how sequestration impacts brine chemistry and reservoir properties. This study investigates these impacts during CO2 storage at the San Juan Basin CarbonSAFE (SJB) site. The hydrodynamic model was calibrated through history-matching, utilizing data from saltwater disposal wells to improve predictive accuracy. Core-scale simulations incorporating mineral interactions and equilibrium reactions validated the model against laboratory flow-through experiments. The calibrated geochemical model was subsequently upscaled into a field-scale 3D model of the SJB site to predict how mineral precipitation and dissolution affect reservoir properties. The results indicate that the majority of the injected CO2 is trapped structurally, followed by residual trapping and dissolution trapping; mineral trapping was found to be negligible in this study. Although quartz and calcite precipitation occurred, the dissolution of feldspars, phyllosilicates, and clay minerals counteracted these effects, resulting in a minimal reduction in porosity—less than 0.1%. The concentration of the various ions in the brine is directly influenced by dissolution/precipitation trends. This study provides valuable insights into CO2 sequestration’s effects on reservoir fluid dynamics, mineralogy, and rock properties in the San Juan Basin. It highlights the importance of reservoir simulation in assessing long-term CO2 storage effectiveness, particularly focusing on geochemical interactions. Full article
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31 pages, 10410 KiB  
Article
Integrated Prospectivity Mapping for Copper Mineralization in the Koldar Massif, Kazakhstan
by Dinara Talgarbayeva, Andrey Vilayev, Elmira Serikbayeva, Elmira Orynbassarova, Hemayatullah Ahmadi, Zhanibek Saurykov, Nurmakhambet Sydyk, Aigerim Bermukhanova and Berik Iskakov
Minerals 2025, 15(8), 805; https://doi.org/10.3390/min15080805 - 30 Jul 2025
Viewed by 340
Abstract
This study developed a copper mineral prospectivity map for the Koldar massif, Kazakhstan, using an integrated approach combining geophysical and satellite methods. A strong spatialgenetic link was identified between faults and hydrothermal mineralization, with faults acting as key conduits for ore-bearing fluids. Lineament [...] Read more.
This study developed a copper mineral prospectivity map for the Koldar massif, Kazakhstan, using an integrated approach combining geophysical and satellite methods. A strong spatialgenetic link was identified between faults and hydrothermal mineralization, with faults acting as key conduits for ore-bearing fluids. Lineament analysis and density mapping confirmed the high permeability of the Koldar massif, indicating its structural prospectivity. Hyperspectral and multispectral data (ASTER, PRISMA, WorldView-3) were applied for detailed mapping of hydrothermal alteration (phyllic, propylitic, argillic zones), which are critical for discovering porphyry copper deposits. In particular, WorldView-3 imagery facilitated the identification of new prospective zones. The transformation of magnetic and gravity data successfully delineated geological features and structural boundaries, confirming the fractured nature of the massif, a key structural factor for mineralization. The resulting map of prospective zones, created by normalizing and integrating four evidential layers (lineament density, PRISMA-derived hydrothermal alteration, magnetic, and gravity anomalies), is thoroughly validated, successfully outlining the known Aktogay, Aidarly, and Kyzylkiya deposits. Furthermore, new, previously underestimated prospective areas were identified. This work fills a significant knowledge gap concerning the Koldar massif, which had not been extensively studied using satellite methods previously. The key advantage of this research lies in its comprehensive approach and the successful application of high-quality hyperspectral imagery for mapping new prospective zones, offering a cost-effective and efficient alternative to traditional ground-based investigations. Full article
(This article belongs to the Section Mineral Exploration Methods and Applications)
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17 pages, 2495 KiB  
Article
Production Capacity and Temperature–Pressure Variation Laws in Depressurization Exploitation of Unconsolidated Hydrate Reservoir in Shenhu Sea Area
by Yuanwei Sun, Yuanfang Cheng, Yanli Wang, Jian Zhao, Xian Shi, Xiaodong Dai and Fengxia Shi
Processes 2025, 13(8), 2418; https://doi.org/10.3390/pr13082418 - 30 Jul 2025
Viewed by 227
Abstract
The Shenhu sea area is rich in unconsolidated hydrate reserves, but the formation mineral particles are small, the rock cementation is weak, and the coupling mechanism of hydrate phase change, fluid seepage, and formation deformation is complex, resulting in unclear productivity change law [...] Read more.
The Shenhu sea area is rich in unconsolidated hydrate reserves, but the formation mineral particles are small, the rock cementation is weak, and the coupling mechanism of hydrate phase change, fluid seepage, and formation deformation is complex, resulting in unclear productivity change law under depressurization exploitation. Therefore, a thermal–fluid–solid–chemical coupling model for natural gas hydrate depressurization exploitation in the Shenhu sea area was constructed to analyze the variation law of reservoir parameters and productivity. The results show that within 0–30 days, rapid near-well pressure drop (13.83→9.8 MPa, 36.37%) drives peak gas production (25,000 m3/d) via hydrate dissociation, with porosity (0.41→0.52) and permeability (75→100 mD) increasing. Within 30–60 days, slower pressure decline (9.8→8.6 MPa, 12.24%) and fines migration cause permeability fluctuations (120→90 mD), reducing gas production to 20,000 m3/d. Within 60–120 days, pressure stabilizes (~7.6 MPa) with residual hydrate saturation < 0.1, leading to stable low permeability (60 mD) and gas production (15,000 m3/d), with cumulative production reaching 2.2 × 106 m3. This study clarifies that productivity is governed by coupled “pressure-driven dissociation–heat limitation–fines migration” mechanisms, providing key insights for optimizing depressurization strategies (e.g., timed heat supplementation, anti-clogging measures) to enhance commercial viability of unconsolidated hydrate reservoirs. Full article
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24 pages, 6356 KiB  
Article
The Significance of Metasomatism in the Formation of the Tanbreez REE Deposit in South Greenland
by Hans Kristian Schønwandt, Thomas Ulrich, Greg Barnes and Ole Christiansen
Minerals 2025, 15(8), 797; https://doi.org/10.3390/min15080797 - 29 Jul 2025
Viewed by 92
Abstract
The layering of the lower layered kakortokite in the per-alkaline Ilímaussaq complex has been interpreted as an orthocumulus rock. Petrographic observation and mineral chemical data from the topmost and the lowest part of the layered kakortokite show signs that indicate massive metasomatic overprint. [...] Read more.
The layering of the lower layered kakortokite in the per-alkaline Ilímaussaq complex has been interpreted as an orthocumulus rock. Petrographic observation and mineral chemical data from the topmost and the lowest part of the layered kakortokite show signs that indicate massive metasomatic overprint. The occurrence of globular structures in the top part of kakortokite and fine-grained inclusions in the lower layered kakortokite are interpreted as the precursor of kakortokite and the result of a subsolidus reaction between a fluid phase and the underlying rock, respectively. Two different processes led to the formation of kakortokite, a precursor where a clear repetitive layering occurs and a chemical reaction between a fluid phase and the underlying rock where different kakortokite types are randomly interstratified. Both metasomatic events led to a higher rare earth element (REE) grade of the original REE mineralization. Full article
(This article belongs to the Special Issue Ore Deposits Related to Metamorphism)
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15 pages, 2361 KiB  
Article
Geochemical Characteristics of the Hida Granitoids in the Unazuki and Katakaigawa Areas, Central Japan
by Kazuki Oishi, Rui Kuwahara, Kazuya Shimooka and Motohiro Tsuboi
Geosciences 2025, 15(8), 285; https://doi.org/10.3390/geosciences15080285 - 29 Jul 2025
Viewed by 222
Abstract
The Hida Belt in central Japan is a key geological unit for understanding the crustal growth of the Eurasian continent in the Mesozoic. However, while previous studies have focused primarily on geochronology, the geochemical characteristics of its rocks and minerals remain largely unexplored. [...] Read more.
The Hida Belt in central Japan is a key geological unit for understanding the crustal growth of the Eurasian continent in the Mesozoic. However, while previous studies have focused primarily on geochronology, the geochemical characteristics of its rocks and minerals remain largely unexplored. This study investigates the geochemical characteristics and magmatic processes of the Hida granitoids, including adakitic rocks, distributed in the Unazuki and Katakaigawa areas. Whole-rock major oxides and trace elements, as well as Rb-Sr isotopes, were analyzed. Based on Rb–Sr isotopic compositions, the Hida granitoids are classified into two types. The younger and older granitoids in the Unazuki area, categorized as Type I, exhibit a narrow range of isotopic ratios, whereas the older granitoids in the Katakaigawa area, classified as Type II, display significantly higher values than those of Type I. The geochemical data suggest that the adakitic rocks in the older granitoids originated from interaction with alkali-rich melts or fluids, while those in the younger granitoids were derived from hydrous felsic magmas sourced from subducted oceanic crust. These findings provide new insights into the formation and evolution of granitic magmatism in the Hida Belt. Full article
(This article belongs to the Section Geochemistry)
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39 pages, 8119 KiB  
Article
Magmatic Redox Evolution and Porphyry–Skarn Transition in Multiphase Cu-Mo-W-Au Systems of the Eocene Tavşanlı Belt, NW Türkiye
by Hüseyin Kocatürk, Mustafa Kumral, Hüseyin Sendir, Mustafa Kaya, Robert A. Creaser and Amr Abdelnasser
Minerals 2025, 15(8), 792; https://doi.org/10.3390/min15080792 - 28 Jul 2025
Viewed by 286
Abstract
This study explores the magmatic and hydrothermal evolution of porphyry–skarn–transitional Cu-Mo-W-Au systems within the Nilüfer Mineralization Complex (NMC), located in the westernmost segment of the Eocene Tavşanlı Metallogenic Belt, NW Türkiye. Through integration of field data, whole-rock geochemistry, Re–Os molybdenite dating, and amphibole–biotite [...] Read more.
This study explores the magmatic and hydrothermal evolution of porphyry–skarn–transitional Cu-Mo-W-Au systems within the Nilüfer Mineralization Complex (NMC), located in the westernmost segment of the Eocene Tavşanlı Metallogenic Belt, NW Türkiye. Through integration of field data, whole-rock geochemistry, Re–Os molybdenite dating, and amphibole–biotite mineral chemistry, the petrogenetic controls on mineralization across four spatially associated mineralized regions (Kirazgedik, Güneybudaklar, Kozbudaklar, and Delice) were examined. The earliest and thermally most distinct phase is represented by the Kirazgedik porphyry system, characterized by high temperature (~930 °C), oxidized quartz monzodioritic intrusions emplaced at ~2.7 kbar. Rising fO2 and volatile enrichment during magma ascent facilitated structurally focused Cu-Mo mineralization. At Güneybudaklar, Re–Os geochronology yields an age of ~49.9 Ma, linking Mo- and W-rich mineralization to a transitional porphyry–skarn environment developed under moderately oxidized (ΔFMQ + 1.8 to +0.5) and hydrous (up to 7 wt.% H2O) magmatic conditions. Kozbudaklar represents a more reduced, volatile-poor skarn system, leading to Mo-enriched scheelite mineralization typical of late-stage W-skarns. The Delice system, developed at the contact of felsic cupolas and carbonates, records the broadest range of redox and fluid compositions. Mixed oxidized–reduced fluid signatures and intense fluid–rock interaction reflect complex, multistage fluid evolution involving both magmatic and external inputs. Geochemical and mineralogical trends—from increasing silica and Rb to decreasing Sr and V—trace a systematic evolution from mantle-derived to felsic, volatile-rich magmas. Structurally, mineralization is controlled by oblique fault zones that localize magma emplacement and hydrothermal flow. These findings support a unified genetic model in which porphyry and skarn mineralization styles evolved continuously from multiphase magmatic systems during syn-to-post-subduction processes, offering implications for exploration models in the Western Tethyan domain. Full article
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13 pages, 3716 KiB  
Article
Mineralogy and Preparation of High-Purity Quartz: A Case Study from Pegmatite in the Eastern Sector of the North Qinling Orogenic Belt
by Deshui Yu, Yameng Ma, Shoujing Wang, Chi Ma and Fushuai Wei
Minerals 2025, 15(8), 788; https://doi.org/10.3390/min15080788 - 27 Jul 2025
Viewed by 251
Abstract
High-purity quartz (HPQ), an indispensable industrial mineral, serves as a critical raw material for advanced technology sectors. Derived from natural quartz precursors through processing, HPQ preparation efficiency fundamentally depends on raw material selection. Two pegmatite samples (muscovite pegmatite and two-mica pegmatite) sampled from [...] Read more.
High-purity quartz (HPQ), an indispensable industrial mineral, serves as a critical raw material for advanced technology sectors. Derived from natural quartz precursors through processing, HPQ preparation efficiency fundamentally depends on raw material selection. Two pegmatite samples (muscovite pegmatite and two-mica pegmatite) sampled from the eastern sector of the North Qinling Orogenic Belt were investigated through a suite of analytical techniques, as well as processing and purification, to evaluate their potential as raw materials for high-purity quartz. Muscovite pegmatite is predominantly composed of quartz, plagioclase, K-feldspar, muscovite, and garnet, with accessory phases including limonite and kaolinite. However, in addition to quartz, plagioclase, K-feldspar, muscovite, garnet, and limonite, two-mica pegmatite contains minerals such as biotite and calcite. The fluid inclusions in both muscovite and two-mica pegmatite quartz are small, but the former has fewer fluid inclusions. Compared with muscovite pegmatite, surface discontinuity (i.e., cracks, pits, cavities) development is more pronounced in two-mica pegmatite purified quartz, which may be related to its high content of fluid inclusions. Following purification, the total concentration of trace elements decreased significantly. However, the concentrations of Al and Ti appeared to remain the same. Titanium enrichment in purified two-mica pegmatite quartz likely derives from biotite, while Na and Ca concentrations may be related to fluid inclusions or microscopic mineral inclusions. The trace element content (27.69 ppm) in muscovite pegmatite is lower than that (45.28 ppm) of two-mica pegmatite, we thus suggest that muscovite pegmatite quartz is more likely to have the potential to produce high-purity quartz. Full article
(This article belongs to the Special Issue Physicochemical Properties and Purification of Quartz Minerals)
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14 pages, 4268 KiB  
Article
Experimental Investigation into the Mechanisms of Liquid-Phase Damage in Shale Oil Reservoirs: A Case Study from the Leijia Area
by Tuan Gu, Chenglong Ma, Yugang Li, Feng Zhao, Xiaoxiang Wang and Jinze Xu
Energies 2025, 18(15), 3990; https://doi.org/10.3390/en18153990 - 25 Jul 2025
Viewed by 209
Abstract
The fourth member of the Shahejie Formation in the Leijia area of the western depression of the Liaohe Oilfield represents a typical shale oil reservoir. However, post-hydraulic fracturing operations in this region are often hindered by significant discrepancies in well productivity, low fracturing [...] Read more.
The fourth member of the Shahejie Formation in the Leijia area of the western depression of the Liaohe Oilfield represents a typical shale oil reservoir. However, post-hydraulic fracturing operations in this region are often hindered by significant discrepancies in well productivity, low fracturing fluid flowback efficiency, and an unclear understanding of reservoir damage mechanisms during fracturing. These challenges have become major bottlenecks restricting the efficient exploration and development of shale oil in this block. In this study, a series of laboratory-simulated experiments were conducted to investigate the primary mechanisms of formation damage induced by fracturing fluids in shale oil reservoirs. An experimental methodology for evaluating reservoir damage caused by fracturing fluids was developed accordingly. Results indicate that guar gum-based fracturing fluids exhibit good compatibility with formation-sensitive minerals, resulting in relatively minor damage. In contrast, capillary trapping of the aqueous phase leads to moderate damage, while polymer adsorption and retention cause low to moderate impairment. The damage associated with fracturing fluid invasion into fractures is found to be moderately high. Overall, the dominant damage mechanisms of guar gum fracturing fluids in the Shahejie Member 4 shale oil reservoir are identified as aqueous phase trapping and polymer adsorption. Based on the identified damage mechanisms, corresponding optimization strategies for fracturing fluid formulations are proposed. The findings of this research provide critical insights for improving shale oil development strategies in the Leijia area. Full article
(This article belongs to the Special Issue Enhanced Oil Recovery: Numerical Simulation and Deep Machine Learning)
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24 pages, 5866 KiB  
Article
Multiscale Characterization of Thermo-Hydro-Chemical Interactions Between Proppants and Fluids in Low-Temperature EGS Conditions
by Bruce Mutume, Ali Ettehadi, B. Dulani Dhanapala, Terry Palisch and Mileva Radonjic
Energies 2025, 18(15), 3974; https://doi.org/10.3390/en18153974 - 25 Jul 2025
Viewed by 254
Abstract
Enhanced Geothermal Systems (EGS) require thermochemically stable proppant materials capable of sustaining fracture conductivity under harsh subsurface conditions. This study systematically investigates the response of commercial proppants to coupled thermo-hydro-chemical (THC) effects, focusing on chemical stability and microstructural evolution. Four proppant types were [...] Read more.
Enhanced Geothermal Systems (EGS) require thermochemically stable proppant materials capable of sustaining fracture conductivity under harsh subsurface conditions. This study systematically investigates the response of commercial proppants to coupled thermo-hydro-chemical (THC) effects, focusing on chemical stability and microstructural evolution. Four proppant types were evaluated: an ultra-low-density ceramic (ULD), a resin-coated sand (RCS), and two quartz-based silica sands. Experiments were conducted under simulated EGS conditions at 130 °C with daily thermal cycling over a 25-day period, using diluted site-specific Utah FORGE geothermal fluids. Static batch reactions were followed by comprehensive multi-modal characterization, including scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and micro-computed tomography (micro-CT). Proppants were tested in both granular and powdered forms to evaluate surface area effects and potential long-term reactivity. Results indicate that ULD proppants experienced notable resin degradation and secondary mineral precipitation within internal pore networks, evidenced by a 30.4% reduction in intragranular porosity (from CT analysis) and diminished amorphous peaks in the XRD spectra. RCS proppants exhibited a significant loss of surface carbon content from 72.98% to 53.05%, consistent with resin breakdown observed via SEM imaging. While the quartz-based sand proppants remained morphologically intact at the macro-scale, SEM-EDS revealed localized surface alteration and mineral precipitation. The brown sand proppant, in particular, showed the most extensive surface precipitation, with a 15.2% increase in newly detected mineral phases. These findings advance understanding of proppant–fluid interactions under low-temperature EGS conditions and underscore the importance of selecting proppants based on thermo-chemical compatibility. The results also highlight the need for continued development of chemically resilient proppant formulations tailored for long-term geothermal applications. Full article
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24 pages, 7393 KiB  
Article
Thermodynamic Modeling Constrains the Alteration and Mineralization Patterns of the Pulang Porphyry Cu-Au Deposits in Eastern Tibet
by Shaoying Zhang, Wenyan He, Huaqing Wang and Yiwu Xiao
Minerals 2025, 15(8), 780; https://doi.org/10.3390/min15080780 - 25 Jul 2025
Viewed by 312
Abstract
Thermodynamic simulations of fluid–rock interactions provide valuable insights into mineral deposit formation mechanisms. This study investigates the Pulang porphyry Cu-Au deposit in the Sanjiang Tethys Orogen, employing both Gibbs energy minimization (GEM) and the Law of mass action (LMA) method to understand alteration [...] Read more.
Thermodynamic simulations of fluid–rock interactions provide valuable insights into mineral deposit formation mechanisms. This study investigates the Pulang porphyry Cu-Au deposit in the Sanjiang Tethys Orogen, employing both Gibbs energy minimization (GEM) and the Law of mass action (LMA) method to understand alteration overprinting and metal precipitation. The modeling results suggest that the ore-forming fluid related to potassic alteration was initially oxidized (ΔFMQ = +3.54~+3.26) with a near-neutral pH (pH = 5.0~7.0). Continued fluid–rock interactions, combined with the input of reduced groundwater, resulted in a decrease in both pH (4.8~6.1) and redox potential (ΔFMQ~+1), leading to the precipitation of propylitic alteration minerals and pyrrhotite. As temperature further decreased, fluids associated with phyllic alteration showed a slight increase in pH (5.8~6.0) and redox potential (ΔFMQ = +2). The intense superposition of propylitic and phyllic alteration on the potassic alteration zone is attributed to the rapid temperature decline in the magmatic–hydrothermal system, triggering fluid collapse and reflux. Mo, mainly transported as HMoO4 and MoO4−2, precipitated in the high-temperature range; Cu, carried primarily by CuCl complexes (CuCl4−3, CuCl2, CuCl), precipitated over intermediate to high temperatures; and Au, transported as Au-S complexes (Au(HS)2, AuHS), precipitated from intermediate to low temperatures. This study demonstrates that fluid–rock interactions alone can account for the observed sequence of alteration and mineralization in porphyry systems. Full article
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21 pages, 3652 KiB  
Article
Mechanical Loading of Barite Rocks: A Nanoscale Perspective
by Hassan Abubakar Adamu, Seun Isaiah Olajuyi, Abdulhakeem Bello, Peter Azikiwe Onwualu, Olumide Samuel Oluwaseun Ogunmodimu and David Oluwasegun Afolayan
Minerals 2025, 15(8), 779; https://doi.org/10.3390/min15080779 (registering DOI) - 24 Jul 2025
Viewed by 404
Abstract
Barite, a mineral composed of barium sulphate, holds global significance due to its wide range of industrial applications. It plays a crucial role as a weighting agent in drilling fluids for the oil and gas industry, in radiation shielding, and as a filler [...] Read more.
Barite, a mineral composed of barium sulphate, holds global significance due to its wide range of industrial applications. It plays a crucial role as a weighting agent in drilling fluids for the oil and gas industry, in radiation shielding, and as a filler in paints and plastics. Although there are significant deposits of the mineral in commercial quantities in Nigeria, the use of barite of Nigerian origin has been low in the industry due to challenges that require further research and development. This research employed nanoindentation experiments using a model Ti950 Tribo indenter instrument equipped with a diamond Berkovich tip. Using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), we gained information about the structure and elements in the samples. The load–displacement curves were examined to determine the hardness and reduced elastic modulus of the barite samples. The SEM images showed that barite grains have a typical grainy shape, with clear splitting lines and sizes. XRD and EDX analysis confirmed that the main components are chlorite, albite, barium, and oxygen, along with small impurities like silicon and calcium from quartz and calcite. The average hardness of the IB3 and IB4 samples was 1.88 GPa and 1.18 GPa, respectively, meaning that the IB3 sample will need more energy to crush because its hardness is within the usual barite hardness range of 1.7 GPa to 2.0 GPa. The findings suggest further beneficiation processes to enhance the material’s suitability for drilling and other applications. Full article
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21 pages, 12225 KiB  
Article
Mineral Characterization of Gold Ore Occurrences in the Khaptasynnakh Ore Zone, Anabar Shield, Far East Region, Russia
by Boris Gerasimov and Larisa Kondratieva
Minerals 2025, 15(8), 774; https://doi.org/10.3390/min15080774 - 24 Jul 2025
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Abstract
Mineral characterization of gold-bearing metasomatites in the Khaptasynnakh ore zone of the Anabar Shield is provided in detail. The following ore formation sequence of mineral associations in the Khaptasynnakh zone was found: pyrite and pyrrhotite → gersdorffite and molybdenite → chalcopyrite, sphalerite, and [...] Read more.
Mineral characterization of gold-bearing metasomatites in the Khaptasynnakh ore zone of the Anabar Shield is provided in detail. The following ore formation sequence of mineral associations in the Khaptasynnakh zone was found: pyrite and pyrrhotite → gersdorffite and molybdenite → chalcopyrite, sphalerite, and galena → bornite and chalcocite → tellurides, native gold, stibnite, cinnabar, and native bismuth. Native gold is characterized by varying fineness (550 to 926‰) and Cu impurity (up to 7.87%) values. Most often, it forms symplectite intergrowths with Au telluride–calaverite. Native gold and Au tellurides showed inclusions of chalcocite, bornite, altaite, tellurobismuthite, rickardite, petzite, and clausthalite. A two-stage formation process of the examined gold is suggested: Low-fineness gold was introduced into the system during early potassium metasomatism, while higher-fineness gold related to silica metasomatism resulted from its additional mobilization by fluid during late-stage formation. The low-temperature gold–telluride association observed in the mineral paragenesis of ore-bearing rocks, as well as its inclusions in native gold, suggests epithermal gold–telluride mineralization. Mineral inclusions examined in placer gold validate a genetic relation between the examined ores and gold placers in the Khaptasynnakh ore zone. Full article
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