Variation In Mineral Composition Research Articles

Mineralization process of the Changjiang uranium orefield in South China: Constraints from pitchblende geochemistry

The Changjiang uranium (U) orefield in northern Guangdong (South China) contains several important granite-related uranium deposits, including the Mianhuakeng deposit. The hydrothermal evolution and mineralization mechanism of the deposit remain unclear, and hence in this study we analyzed the mineral compositional variations of pitchblende from different elevation (−300 to −50 m) in the orebody at Mianhuakeng deposit. The results indicate that with decreasing depth, the hydrothermal mineral assemblage changes from a reducing one (pitchblende, pyrite, and chlorite) to a moderately oxidizing one (pitchblende, coffinite, hematite, and goethite). The contents of U, Sr, ∑REE, U/Th, and LREE/HREE ratios in the pitchblende decrease (whereas the Cu-Pb-Zn-Ni-Co-Sc-Rb contents increase) progressively with decreasing depth. Also, Ce anomaly (Ce/Ce*) changes from positive to negative, and Eu anomaly (Eu/Eu*) becomes more negative with decreasing depth. We interpreted such vertical variations to be caused by the ascent of deep, mid-to-high temperature, highly-oxidizing ore-forming fluid, which was reduced by early-stage reducing minerals in the wallrock, a process that also formed the mineralization at Changjiang. In addition, the pitchblende REE distribution patterns and Eu/Eu* at depth (−300 m) resemble those of the Zhuguang pluton, indicating that the ore-forming materials were originated from the U-bearing granite wallrocks. Therefore, the Ce/Ce* and Eu/Eu* variations of pitchblende can be used to guide deep uranium ore exploration.

Quality of Propolis Commercially Available on Podkarpacki Beekeeping Market

Abstract Eight samples of propolis commercially available on south-eastern Poland’s beekeeping market were compared in terms of quality, chemical composition and biological activity, including antioxidant and antimicrobial properties. The organoleptic characteristics and physicochemical requirements indicated that only 50% of tested propolis samples was classified to class II regarding obligatory limits, while the others were out-class. A big variation in mineral composition was determined by the ICP-OES method but all samples were free of heavy metals (Pb, Cd and Ni). Although mesophilic bacteria, yeasts and moulds occurred in tested propolis (in general lower than 102 CFU/g), E. coli and spore-forming sulphite-reducing bacteria as well as Salmonella and Shigella bacteria were not detected. High antioxidant activity and total phenolic content for all samples was confirmed, which was correlated with antibacterial activity tested against E. coli ATCC 11775 strain. Additionally, the propolis sample with the strongest antibacterial activity (MIC 0.33 mg/mL) inhibited biofilm formation of S. aureus and S. epidermidis ATCC 35984 (MBIC 0.66 and 5.25 mg/mL, respectively). However, great variation in terms of antioxidant activity and HPLC polyphenolic profile were observed, and sakuranetin and pinobanksin were identified as the most effective antioxidant components. Moreover, the usefulness of ATR-FTIR spectra analysis was confirmed as a quick method for initial testing of propolis quality.

Quantification of hydrogen depletion and mineral reactivity in underground hydrogen storage reservoirs

The utilisation of renewable energy has surged over the past decades due to shifts in climate patterns and the diminishing reserves of fossil fuels. Among the renewables, hydrogen energy has emerged as a promising clean energy carrier in recent years. In the hydrogen industry, storage faces a notable hurdle due to the relatively low density of hydrogen gas (0.0813 kg/m³ at 25 °C and 1 atm) and its lower storage density (7–27 kg/m³ at 25 °C and 100–400 atm). As a potential remedy, underground hydrogen storage emerges as a viable option, even though it is not without its challenges. Among these challenges, a prominent one involves the diversity in the composition and physical properties of the reservoir due to the influence of both biological and geo-chemical reactions. In this study, an extensive modelling effort was undertaken to gain insights into the impact of both bio and geo-chemical reactions, variations in porosity, hydrogen depletion, and the effects of diffusion across various levels of salinity, pressure, and temperature. Diverse Water/Rock ratios, distinct minerals, and residual gases were also considered. The modelled conditions encompassing mineral properties and parameters led to a cumulative hydrogen loss of 8.38% over a century. From this, 2.31% was identified due to the reactivity in reservoir rock and 6.07% due to the aqueous diffusion to cap rock and its reactivity. Among these reactions, carbonate dissolution emerged as the most noteworthy, resulting in considerable hydrogen loss contingent upon the presence of methanogenesis bacteria. As per the modelled scenario, porosity was reduced in reservoir rock by 0.41%, and in carbonate cap rock, it was increased by 56%, which could increase the hydrogen leakage. Also, methane (CH4) exhibited the most favourable characteristics as a cushion gas due to its lower reactivity. However, it's crucial to acknowledge that these figures could significantly fluctuate based on variations in mineral composition, bacterial populations and their growth, and the prevailing subsurface conditions. These modelled findings can serve as a valuable tool for comprehending the mechanisms of hydrogen loss and mineral reactivity within a given underground system.

Mechanistic study on the promotion of Ca2+ leaching in steel slag through high-temperature solid waste modification.

Indirect carbonation of steel slag is an effective method for CO2 storage, reducing emissions, and promoting cleaner production in the steel industry. However, challenges remain, such as low Ca2+ leaching rates and slag management complexities arising from variations in mineral compositions. To address this, a high-temperature modification process is proposed to alter the mineral composition and facilitate the synergistic utilization of calcium and iron. This study delves into the effects of various solid waste modifications on the leaching of Ca2+ and the total iron content within steel slag. Results show that high-basicity modified slag forms Ca2(Al, Fe)2O5, reducing calcium leaching. Low-alkalinity modified slag produces calcium-rich aluminum minerals and also reduces the leaching of Ca2+ ions. At a basicity of 2.5, coal gangue, fly ash, and blast slag achieve maximum Ca2+ leaching rates of 88.93%, 89.46%, and 90.17%, respectively, with corresponding total iron contents of 41.46%, 37.72%, and 35.29%. Upgraded coal gangue exhibits a 50.02% increase in calcium leaching and a 15.58% increase in total iron content compared to the original slag. This enhances CO2 fixation and iron resource utilization. Overall, the proposed indirect carbonation and iron enrichment modification offer a novel approach for the resource utilization and environmental stability of steel slag.

Enhanced thermoelectric properties of Mg2Si0.3Sn0.7 via Bi-doping under high pressure

A series of n-type Mg2(Si0.3Sn0.7)1-xBix compounds with 0≤x≤0.02 were successfully synthesized through a combined approach involving solid-state reaction, high-pressure synthesis, and spark plasma sintering techniques. The method yielded homogeneously distributed single-phase materials at the micron scale, although minor compositional variations were detected within nanoscale precipitates embedded in the grains. The sample with Bi content of 0.01 exhibited enhanced thermoelectric properties, reaching a peak thermoelectric figure of merit (ZT) of 1.45 at 700 K while maintaining an average ZT of about 1.1 over the temperature range of 300−773 K. The enhancement in thermoelectric performance is ascribed to the optimized carrier concentration, band convergence, and refined microstructure. The findings suggest a simplified approach to doping that could be beneficial in creating high-performance thermoelectric materials for energy conversion.

Pore Structure Evolution and Failure Mechanism of Limestone in the Taiyuan Formation of the Ordos Basin under High Temperature.

The study on the destruction of the limestone microstructure after high-temperature treatment has a significant value in the airtightness and safety of underground high-temperature geotechnical engineering. In order to truly simulate the influence of the underground high-temperature environment on limestone, taking seven groups of limestones of the Taiyuan Formation in the Ordos Basin as examples, we carried out a high-temperature (25-1200 °C) heating experiment of limestone in an argon atmosphere. The pore structure of limestone after the high temperature is studied based on scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), porosity, and permeability, and the change in the fractal dimension of the limestone pore structure was discussed based on the thermodynamic fractal theory, combined with X-ray diffraction (XRD) and thermogravimetry differential scanning calorimetry (TG-DSC), the variation of mineral composition with temperature is characterized, and the evolution mechanism of the limestone microstructure under high temperature is discussed. The results show that the evaporation of pore water does not destroy the lattice structure of limestone minerals; however, with the increase of temperature, the complete decomposition of dolomite and calcite occurs, along with the tensile fracture of calcite crystals under the effect of swelling stress. Moreover, the new minerals generated by the decomposition products under the effect of temperature severely damage the crystal structure, leading to the rapid increase of porosity and permeability. The comprehensive results show that the decomposition, expansion, and recrystallization of calcite and dolomite minerals after 800 °C led to the development of limestone macropores and fissures, increased the pore throat radius, enhanced the pore connectivity, simplified the pore structure, and sharply increased the permeability; thus, 800 °C can be used as the critical temperature to change the limestone pores and fractures. The research results can provide data support for subsurface high-temperature geotechnical engineering.

The implementation of dust mineralogy in COSMO5.05-MUSCAT

Abstract. Mineral dust aerosols are composed of a complex assemblage of various minerals depending on the region in which they originated. Given the different mineral composition of desert dust aerosols, different physicochemical properties and therefore varying climate effects are expected. Despite the known regional variations in mineral composition, chemical transport models typically assume that mineral dust aerosols have uniform composition. This study adds, for the first time, mineralogical information to the mineral dust emission scheme used in the chemical transport model COSMO–MUSCAT. We provide a detailed description of the implementation of the mineralogical database, GMINER (Nickovic et al., 2012), together with a specific set of physical parameterizations in the model's mineral dust emission module, which led to a general improvement of the model performance when comparing the simulated mineral dust aerosols with measurements over the Sahara region for January–February 2022. The simulated mineral dust aerosol vertical distribution is tested by a comparison with aerosol lidar measurements from the lidar system PollyXT, located at Cape Verde. For a lofted mineral dust aerosol layer on 2 February at 05:00 UTC the lidar retrievals yield a dust mass concentration peak of 156 µg m−3, while the model calculates the mineral dust peak at 136 µg m−3. The results highlight the possibility of using the model with resolved mineral dust composition for interpretation of the lidar measurements since a higher absorption in the UV–Vis wavelengths is correlated with particles having a higher hematite content. Additionally, the comparison with in situ mineralogical measurements of dust aerosol particles shows that more of them are needed for model evaluation.

Mineralogical properties of pyroclastic materials from Mount Merapi, Indonesia

Mount Merapi, located in Indonesia, is known as one of the most active volcanoes globally, often resulting in volcanic eruptions that produce pyroclastic materials. These materials from Mount Merapi’s eruptions have the potential to influence soil fertility in areas affected by the volcanic activities. This study aims to analyze the mineralogical properties of pyroclastic materials from Mount Merapi. The methodology involves collecting pyroclastic material samples from the 2010 eruption of Mount Merapi, followed by analysis using various mineralogical techniques such as polarized microscopy, X-ray diffraction, petrographic analysis, and wet chemical analysis. The findings offer detailed insights into the mineral composition, types of clay minerals, overall elemental presence, and the rock types forming these minerals in the pyroclastic materials. Variations in mineral composition are observed in the pyroclastic materials from Mount Merapi. Predominant minerals, including the plagioclase, pyroxene, and hornblende groups, are distinctly identified. These minerals’ presence suggests their susceptibility to weathering, categorized as easily weatherable minerals. This tendency for weathering is shown by the presence of elements like Na, Ca, and Mg in these minerals, which are crucial macro-nutrients for plant growth.

PERIDYNAMIC SIMULATION OF FRACTURING IN HETEROGENEOUS ROCK BASED ON X-RAY DIFFRACTION AND SCANNING ELECTRON MICROSCOPE TESTS

The mechanical properties and fracture behavior of rocks are significantly influenced by their microscopic characteristics. At present, there is a prevalent treatment of rocks as homogeneous materials or an oversimplified assumption of mesoscopic material properties following the Weibull distribution, often overlooking the impact of mineral composition and porosity. This study addresses these limitations by utilizing X-ray diffraction (XRD) and scanning electron microscope (SEM) tests to capture and characterize the microscopic features of rocks, including mineral composition and porosity. Subsequently, a mesoscopic peridynamic (PD) model is developed employing the Knuth-Durstenfeld shuffling algorithm to accurately reflect the real rock microstructure. The efficacy of this method is validated through experiments conducted on sandy mudstone and fine-grained sandstone. Moreover, a parametric analysis is performed, considering variations in porosities and mineral compositions. As porosity increases, numerous small cracks emerge laterally in the model, causing a notable decline in the rock's strength. Rock comprising a single mineral composition typically displays linear failure behavior. Conversely, a rock with a diverse array of minerals tends to exhibit non-linear failure behavior, indicating an increased level of heterogeneity within the material.

Accretionary and collisional processes of the Brasiliano Orogeny recorded by the Tonian La Tuna ophiolite, Dom Feliciano Belt, Uruguay

Accretionary to collisional orogenies such as the Brasiliano Orogeny of eastern South America present the opportunity to distinguish between oceanic-continental (accretionary) and continental (collisional) processes. However, the multitude of geotectonic processes involved and the reduced degree of preservation of the accretionary stage restrain the interpretation of evidence. This study focuses on a metasomatite associated with the La Tuna Ophiolite in the southern Dom Feliciano Belt of the Uruguayan Shield, as these can provide crucial insights into the accretionary stage of the Brasiliano Orogeny. The metasomatite occurs as a meter-sized massive tourmalinite body surrounded by a meter-wide chloritite lens, both enclosed by the La Tuna serpentinite. Our SEM-EDS and EPMA data revealed that the serpentines from the La Tuna ophiolite are antigorite and lizardite, while chlorite was identified as clinochlore. Abundant inclusions of sheridanite chlorite in dravite tourmaline suggests that tourmaline overgrew chlorite. Dravite crystals revealed the presence of three diffuse zones with minor compositional variations, mainly enrichments in Ca and Fe towards the rims. The U-Pb LA-ICP-MS dating of metasomatic zircon yielded ages of 743.2 ± 3.4 Ma (n = 22) for the chloritite and 743.1 ± 2.4 Ma (n = 31) for the tourmalinite. High δ11B values (+12.1‰ to + 18.1‰) of tourmaline (LA-ICP-MS) suggest that the metasomatic event was caused by seawater-derived fluids in a fluid-dominated environment. The single metasomatic U-Pb age combined with the high δ11B values suggest that the metasomatites underwent more intense metasomatic events than those associated with the Bossoroca (−8.5‰ to +1.8‰) and the Ibaré ophiolites (+3.2‰ to +5.2‰) further north in the São Gabriel Terrane of the Dom Feliciano Belt. Nonetheless, a few spots in tourmaline located within fracture zones and in contact with chlorite displayed negative (c. −5‰) and low positive δ11B values (c. 2‰). These are interpreted as overprinting by crustal fluids, either during the tectonic emplacement of the La Tuna Ophiolite or during exhumation. The calculated TDM Hf model ages for zircon in tourmalinite and chloritite range from 0.74 to 1.09 Ga and their ɛHf(T) values range from +4.9 to +11.2, indicating derivation from depleted mantle sources. The data corroborate earlier results indicating that the associated La Tuna amphibolites have composition similar to N-MORB. Furthermore, the trace element composition of zircon in the metasomatites is consistent with an oceanic environment (U/Yb < 0.1). Geotectonically, the La Tuna metasomatites formed at 743 ± 2 Ma in an oceanic setting, most likely in a juvenile Adamastor Ocean basin. During the collisional stage of the Brasiliano Orogeny, the La Tuna Ophiolite was tectonically emplaced within the <666 Ma La Micaela Schist of the Paso del Drágon Complex. As such, this study on the La Tuna Ophiolite contributes direct evidence on the oceanic evolution leading up to the accretionary stage of the Brasiliano Orogeny and provides new constraints on the transition towards the collisional stage.

Travel of faience beads and metal Pins: Evidence of long-distance trade in early Bronze Age I (3100–2900 BCE) Başur Höyük, Türkiye

This paper presents the compositional results of one stone and six faience beads together with five metal pin fragments from Başur Höyük, southeast Türkiye in order to preliminarily evaluate possible source and production regions. Dating to the Early Bronze Age I (ca. 3100–2900 BCE), the samples are part of burial contexts with more than 100,000 beads, hundreds of metal objects, and evidence of human sacrifice. The microstructures of blue and greenish-blue faience beads indicate the application of cementation and efflorescence techniques. The variations in mineral compositions and differences in production techniques of the faience beads indicate Başur Höyük’s access to at least two production centers for faience beads. Pins were made of copper and arsenical copper. Lead isotope analysis on metals indicates possible ties to Iran. Evaluated with further archaeological data from the site, consumption of copper from the Kerman and Sistan regions demonstrate the earliest evidence of the long-distance trade of southeast Anatolia with southeast Iran feasibly via southern Mesopotamian or Diyala region networks. This indicates considerable connectivity and organization in the aftermath of the Uruk collapse and shows both sophisticated technical knowledge and shared aesthetic values between regions.

Red edge excitation shift spectroscopy is highly sensitive to tryptophan composition.

Red edge excitation shift (REES) spectroscopy relies on the unique emission profiles of fluorophore-solvent interactions to profile protein molecular dynamics. Recently, we reported the use of REES to compare the stability of 32 polymorphic IgG antibodies natively containing tryptophan reporter fluorophores. Here, we expand on this work to investigate the sensitivity of REES to variations in tryptophan content using a subset of IgG3 antibodies containing arginine to tryptophan polymorphisms. Structural analysis revealed that the additional tryptophan residues were situated in highly solvated environments. Subsequently, REES showed clear differences in fluorescence emission profiles when compared with the unmutated variants, thereby limiting direct comparison of their structural dynamics. These findings highlight the exquisite sensitivity of REES to minor variations in protein structure and tryptophan composition.

Leaf surface features of maize cultivars and response to foliar phosphorus application: effect of leaf stage and plant phosphorus status.

Soil phosphorus (P) application is the most common fertilisation technique but may involve constraints due to chemical fixation and microbial immobilisation. Furthermore, excessive P fertilisation leads to P runoff into water bodies, threatening ecosystems, so targeted foliar P fertilisation is an interesting alternative. This study aimed to determine the importance of leaf surface characteristics for foliar P uptake in P-deficient maize (Zea mays L.). The leaf surface of four maize cultivars was characterised by electron microscopy, Fourier transform infrared spectroscopy and contact angle measurements. Uptake of foliar-applied P by maize cultivars was estimated, measuring also leaf photosynthetic rates after foliar P spraying. Plants of cultivar P7948 were found to be wettable from the 4th leaf in acropetal direction, whereas other cultivars were unwettable until the 6th leaf had developed. Minor variations in stomatal number and cuticle composition were recorded, but no differences in foliar P absorption were observed between cultivars. Nevertheless, cultivars showed variation in the improvement of photosynthetic capacity following foliar P application. Phosphorus deficiency resulted in ultrastructural disorganisation of mesophyll cells and chloroplasts, which impaired photosynthetic performance, yet there was no effect on stomatal frequency and leaf wettability. This study provides new insights into the influence of P deficiency and cultivar on leaf surface characteristics, foliar P uptake and its effect on physiological processes. Understanding the relationships between leaf characteristics and P uptake allows a more targeted evaluation of foliar P fertilisation as an application technique and contributes to the understanding of foliar uptake mechanisms.

Origin of the compositionally zoned Paso Puyehue Tephra, Antillanca Volcanic Complex, Chile

The origin of gaps or zoning in the composition of erupted products is critical to understanding how sub-volcanic reservoirs operate. We characterize the compositionally zoned magma that produced the 2053 ± 50 cal. yr BP Paso Puyehue Tephra from the Antillanca Volcanic Complex in the Andean Southern Volcanic Zone (SVZ). The 3.7 km3 Paso Puyehue Tephra is zoned from dacite (69 wt% SiO2) lapilli and ash comprising the lowermost 80% of the deposit that abruptly transitions upward into basaltic andesite scoria (54 wt% SiO2) making up the remaining ∼20%. Variations in whole-rock, matrix glass, and mineral compositions through the deposit allow us to estimate pre-eruptive magma storage conditions and to develop a model of how this magma body was generated.Our findings suggest that amphibole-bearing basaltic andesitic magma stored at ∼8.0 ± 1.3 km depth fractionally crystallized and cooled from 1048 ± 1.1 to 811 ± 28.6 °C under highly oxidizing conditions to produce silicic a melt that upon extraction and rise, pooled at ∼6.4 ± 1.2 km depth at temperatures as low as 810 °C before eruption. MELTS models suggest that crystallization of a basaltic andesite parent magma with 4 wt% dissolved H2O can produce the dacite under conditions predicted by mineral thermobarometers with phase compositions comparable to those measured in minerals. Pervasive normal zoning at the rims of plagioclase crystals—most pronounced at the transition between dacite and basaltic andesite, and compatible vs. incompatible trace element concentrations, suggest that magma mixing was limited and likely occurred at the interface between the dacitic and basaltic andesitic magmas during ascent within the conduit upon eruption. Compositionally bimodal tephras are increasingly recognized throughout the SVZ with several interpreted to reflect basaltic recharge and mixing into extant rhyolitic reservoirs. In further contrast to other SVZ rhyolitic products, e.g., from the nearby Cordón Callue and Mocho Choshuenco volcanoes, the Paso Puyehue magma was highly oxidized. This may reflect enhanced delivery of H2O from the subducting plate into the mantle wedge, which in turn may facilitate efficient extraction and separation of buoyant, low-viscosity rhyolitic melt from crystal-rich basaltic andesitic parent magmas and the co-eruption of both end members.

Variation in antioxidant capacity, antioxidant activity and mineral composition during flower development of oil-bearing rose (Rosa damascena Mill.)

Oil-bearing rose is an economically important rose species with a wide range of uses such as cosmetics, perfumery, food and health, but the changes in antioxidant capacity and antioxidant activity during flower development are not well understood. The antioxidant content and free radical scavenging properties of oil-bearing rose flowers are used in the cosmetic industry to modulate skin damage, and in the food industry as a source of antioxidants and sweeteners. The present investigation was carried out to explore the antioxidant capacity, antioxidant enzyme activity, and the composition and distribution of minerals in petals of oil-bearing rose at five flower development stages. The total antioxidant capacity of petals was determined using CUPRAC, DPPH, FRAP, FIC and ABTS methods. The antioxidant capacity of petals decreased during the flower development, suggesting that flowers in stage I and II are valuable sources of antioxidants. CUPRAC, DPPH, FRAP, FIC and ABTS scavenging activity of the petals at various developmental stages are strongly and positively correlated with each other. The activity of the antioxidant enzymes; superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase was highest at the bud stage (stage I), whereas the fully opened flowers (stage V) exhibited the lowest activity in oil-bearing rose petals. During the development of flower, malondialdehyde (MDA) content increased significantly from stage I to stage III and decreased at stage IV. Here we detected the contents of 15 elements in petals, some of them, especially calcium, magnesium, potassium and phosphorus showed significant changes during rose flowering. Generally, the highest mineral content was observed in stage I while the lowest content observed in stage V of flower development. These results showed a close link between flower development, antioxidant capacity, enzymatic antioxidant activity and mineral content, with stage I exhibiting the best antioxidant activity, mineral content and free radical scavenging potential. This work will serve as a baseline for understanding the possible roles of antioxidant capacity, antioxidant enzymes, mineral content and their interactions in the regulation of flower development.

Polygons with halite-crusted floors and gypsum-raised rims in western Qaidam Basin and implications for polygonal landforms on Mars

Polygons ranging in size from a few meters to kilometers have been observed in playa fields on Earth and Mars. The historically hyperarid climate of the Qaidam Basin has allowed the development of extensive polygonal landforms with diverse geometric and genetic types. Here we report a terrain of polygons with a pan-like structure, raised rims, and a size of about 60 to 120 m, and spatial variation in mineral composition and geometry from the Dalangtan area of the western Qaidam Basin on the Tibetan Plateau. Spatially, the polygons in the northeastern part of the study area have complete rims, while the polygons in the southwest have incomplete rims. These polygons consist of a halite crust in the subsurface and raised rims formed mainly of gypsum. In some areas, the polygonal rims are broadened and form boundary belts that are up to ~30 m wide and about 1.2 m high. We suggest that the formation of the halite crust in the subsurface redirects upward migration of evaporitic pore fluids that accumulate gypsum deposits to form the wide polygonal boundary belts. We argue that the similarly sized polygons with raised rims on Mars have similar lateral and vertical structures caused successively by the strong evaporation of lacustrine brines and subsurface pore fluids.

Fatty Acid Profile and Mineral Composition of Red-Toothed Triggerfish (Odonus niger) Landed in Karnataka, Southeastern Arabian Sea.

The seasonal and sex-wise variations in fatty acid and mineral composition in the tissue of Odonus niger collected from the Karnataka coast, southeastern Arabian Sea, were evaluated for the first time. The fatty acid profile was assessed using gas chromatography, nutritional indices were employed to evaluate lipid quality, and standard methods were utilized to estimate mineral composition and heavy metals. Palmitic acid (20.2-45.9%), oleic acid (10.0-19.2%), and docosahexaenoic acid (10.9-36.7%) were found in the highest proportions. The amount of ω3 fatty acids was significantly higher than ω6 fatty acids indicating the healthiest food fish and a promising source for nutrient supplementation. The P/S (PUFA/SFA) and ω3/ω6 ratios of the species were greater than those recommended by the UK Dept. of Health. Index of atherogenicity (IA) and thrombogenicity (IT) was low, and hypocholesterolemic to the hypercholesterolemic ratio (HH), unsaturation index (UI), health-promoting index (HPI), fish lipid quality (FLQ), and polyene index (PI) were high. The relationship between the quantities of macronutrients and trace elements was calculated as K > P > Na > Mg > Ca and B > Fe > Zn > Ga > Al respectively. Heavy metals like Be, Bi, Co, and Hg were found below the detection level. Benefit-risk ratio value indicates that the species is safe for consumption.

Favorable lithofacies and pore characteristics of the Permian Longtan Formation shale in the southern Sichuan Basin

The marine–continental transitional shale (MCTS) reservoirs of the Longtan Formation (LTF) are widely distributed in the Sichuan Basin. However, the LTF shale exhibits considerable variations in mineral composition and pore characteristics, which makes identifying the 'sweet spot'a challenging task. To address this issue, 10 samples from four typical shale gas wells in the LTF in the southern Sichuan Basin were selected and analyzed for total organic carbon (TOC) content, whole-rock composition using X-ray diffraction (XRD), low-pressure gas adsorption, and high-pressure mercury intrusion. The lithofacies distribution and pore structure of the MCTS were studied to determine the pore structural characteristics and the primary factors influencing pore formation in different types of shale lithofacies in the LTF. The lithofacies of the LTF shale in the study area can be classified into three categories: siliceous clay shale, clay shale and mixed shale. Mineral content has a significant impact on the pore characteristics, while TOC content has a minor effect on the pore volume and specific surface area of micropores and mesopores. It can be inferred that the mesopores in the MCTS are mainly related to clay mineral pores, and mineral dissolution and TOC content are not the primary factors contributing to pore formation.

Chemical Elements Concentration, Variations in Mineral Composition, and Current Rate of Sedimentation in Sapropel Deposits of Small Lakes in the Taiga Zone of Southern Siberia

Abstract —We studied the bottom sediments of lake systems located in the taiga landscape of Siberia. In the south of Western Siberia, there are 11 lakes in the subzone of the south taiga and 9 lakes in the subtaiga subzone. On the territory of the south of Eastern Siberia in the taiga zone there are 10 lakes on the southern coast of Lake Baikal, 5 lakes on its east coast and 6 lakes are located on the territory of the national park “Alkhanai” in Transbaikalia. Studies of the chemical composition of water, soil, and sediment samples were conducted at the Analytical Center for Multi-Elemental and Isotope Research SB RAS, Novosibirsk. The use of a complex of modern analytical methods in the study of the same lake samples made it possible to obtain more reliable information (1861 samples of bottom sediment were studied). Quartz and feldspars of pelitic dimension dominate in the mineral composition of the terrigenous fraction, organic matter and authigenic minerals (opal, pyrite, illite and sometimes calcite) are added to them during the bottom sediments formation. The absolute contents of the studied elements in the bottom sediments of all lakes are lower than their concentrations in the upper continental crust and sedimentary rocks of the Russian Plate, with the exception of Si, Hg, Cd. In the lakes of the subtaiga of the south of Western Siberia, an exception was established for Ca in the bottom sediments of which carbonates predominate. Contents variations of a number of elements in the bottom sediments of taiga lakes in different regions do not significantly differ. The dispersion of their concentrations between lakes with a total catchment area and lakes from different regions are comparable (Ca, Sr, Al, Mn, Fe, Cd, Hg, etc.). The current sedimentation rate in natural occurrence in the lakes of the taiga zone (southern Siberia) vary from 1.1 to 2.9 mm/year. Moreover, it is comparable to the current sedimentation rate in the lakes of the forest-steppe and steppe zones of south of Western Siberia.

Estimating the thermal conductivity of plutonic rocks from major oxide composition using machine learning

SUMMARY The accurate estimation of temperature distribution in the earth's crust and modelling of heat-related processes in geodynamics requires knowledge of the thermal conductivity of plutonic rocks. This study compiled an extensive data set of 530 representative plutonic rock samples, including thermal conductivity, major oxide composition and (for two subsets of data) modal mineralogy. For the first time, three machine learning algorithms (ML; i.e. support vector regression, random forest and extreme gradient boosting) were employed to estimate the thermal conductivity of plutonic rocks using the major oxide composition feature as input variables. The performance of these ML-based models was evaluated against a geochemically compositional model and eight mineral-driven physically based empirical mixing models. Results show that the means of predicted thermal conductivity by the ML-based models and the geochemically compositional model are not significantly different from the measured thermal conductivity at a significance level of 5 per cent. However, the ML-based models outperformed the best-performing non-ML model, the geochemically compositional model. The highest prediction accuracy was achieved by extreme gradient boosting, which reduced the mean absolute percentage error and root mean square error by more than 50 per cent. Furthermore, SiO2 is confirmed as the most important independent variable, followed by Al2O3, TiO2, CaO and K2O. The turning point observed in the thermal conductivity trend with SiO2 wt per cent may be primarily attributed to variations in mineral composition within the subgroup of igneous rock types classified based on SiO2 wt per cent. This study explores, for the first time, the use of ML algorithms to estimate the thermal conductivity of plutonic rocks from their major oxide composition.