Hasil untuk "Mineralogy"

Álvaro Sánchez Barrueco, Álvaro Sánchez Barrueco, Álvaro Sánchez Barrueco et al.

IntroductionSalivary stones, or sialoliths, are calcified concretions forming within salivary glands and their ducts through a two-stage process: an initial formation of a central core via precipitation of inorganic material mediated by organic substances, followed by layering of additional organic and inorganic material. Substrates for sialolith formation include mucoid agglomerates, organic vesicles, foreign bodies, and bacterial biofilms. Understanding the detailed structure of sialoliths may aid in developing specific preventive or therapeutic strategies.Materials and methodsThis study analyzed 137 sialoliths from 102 patients treated across three university hospitals. Stones were extracted via sialendoscopy, direct extraction, or spontaneous extrusion. Structural and compositional analyses were conducted using scanning electron microscopy (SEM-EDX) and x-ray diffraction (XRD).ResultsMost sialoliths were from the submandibular gland (82%), with the remainder from the parotid gland (18%). Parotid stones predominantly exhibited irregular shapes, while submandibular stones were generally ellipsoidal. All stones demonstrated an oolitic structure characterized by a central core surrounded by concentric layers and frequently associated with bacteria. Mineral composition predominantly included octacalcium phosphate (OCP), hydroxyapatite, and whitlockite. Larger sialoliths exhibited a higher proportion of hydroxyapatite, indicating increased crystallinity compared to OCP.DiscussionDespite diverse origins and locations, sialoliths share common morphological and compositional traits. Their formation begins with heterogeneous nucleation of calcium phosphates around organic spherules, likely induced by bacterial biofilms. These initial nuclei aggregate into a central core upon which additional layers of organic and inorganic materials deposit progressively. This layering increases the size and crystallinity of the sialoliths over time. The coexistence of amorphous phases and structural heterogeneity within layers explains the variability among stones. Detailed SEM-EDX analysis supports a unified conformational model for sialoliths that integrates the interplay of organic substrates, inorganic minerals, bacterial biofilms, and temporal factors.ConclusionsSialoliths are oolitic aggregates featuring a central core surrounded by concentric layers composed of organic and inorganic materials. Their formation process involves initial heterogeneous nucleation, bacterial influence, and progressive crystallization. This universal conformational model effectively describes sialolith formation irrespective of patient-specific or anatomical variations.

Sean Robert Schaefer, Fernando Montaño-López, Hannah Holland-Moritz et al.

The rhizosphere contains diverse groups of bacteria and fungi living near plant roots and mycorrhizal hyphae whose composition and function are key drivers of ecosystem and biogeochemical processes. Despite rich literature on rhizosphere communities, no studies have examined the drivers of rhizosphere communities across plants or soil types in the tundra. We collected 513 root samples from 141 individual plants representing six plant species and three mycorrhizal association types across four glacial histories in Northern Alaska. Glacial drifts ranged from 11 000 to 4.5 million years since deglaciation representing a gradient in glacial history and mineralogical weathering. We found that glacial history, a strong proxy for soil mineralogy, explained the most variation in rhizosphere bacterial communities (13.3%) while interactions between glacial history and host plants explained the most variation in fungal rhizosphere communities (11.6%). We found strong correlations between ectomycorrhizal and rhizosphere communities across spatial scales and sites for the shrub Betula nana (30.7%–54.7% correlated), and that ectomycorrhizal composition was most similar among root fragments of the same plant, followed by plants at the same site, and plants at different sites. This work serves to advance the ecological understanding of rhizosphere and ectomycorrhizal communities in response to shrubification.

Dhanalakshmi Padmaraj, Chinchu Cherian, Dali Naidu Arnepalli

Mineral carbonation is emerging as a reliable CO2 capture technology that can mitigate climate change. In lime-treated clayey soils, mineral carbonation occurs through the carbonation of free lime and cementitious products derived from pozzolanic reactions. The kinetics of the reactions in lime-treated clayey soils are variable and depend primarily on soil mineralogy. The present study demonstrates the role of soil mineralogy in CO2 capture and the subsequent changes caused by carbon mineralization in terms of the unconfined compressive strength (UCS) of lime-treated soils during their service life. Three clayey soils (kaolin, bentonite, and silty clay) with different mineralogical characteristics were treated with 4% lime content, and the samples were cured in a controlled environment for 7 d, 90 d, 180 d, and 365 d. After the specified curing periods, the samples were exposed to CO2 in a carbonation cell for 7 d. The non-carbonated samples purged with N2 gas were used as a benchmark to compare the mechanical, chemical-mineralogical, and microstructure changes caused by carbonation reactions. Experimental investigations indicated that exposure to CO2 resulted in an average increase of 10% in the UCS of lime-treated bentonite, whereas the strength of lime-treated kaolin and silty clay was reduced by an average of 35%. The chemical and microstructural analyses revealed that the precipitated carbonates effectively filled the macropores of the treated bentonite, compared to the inadequate cementation caused by pozzolanic reactions, resulting in strength enhancement. In contrast, strength loss in lime-treated kaolin and silty clay was attributed to the carbonation of cementitious phases and partly to the tensile stress induced by carbonate precipitation. In terms of carbon mineralization prospects, lime-treated kaolin exhibited maximum carbonation due to the higher availability of unreacted lime. The results suggest that, in addition to the increase in compressive strength, adequate calcium-bearing phases and macropores determine the efficiency of carbon mineralization in lime-treated clayey soils.

Marli de Jongh, David Benavente, Maureen Young et al.

The application of hydrophobic treatments as a means of protecting vulnerable stone heritage has been a topic of research for decades. The findings of previous research have shown that there are a number of factors that influence the efficiency of a treatment and that sometimes, if used incorrectly, such treatments can even accelerate stone weathering and decay. In this study, we revisit a hydrophobic treatment test area at Arbroath Abbey where the product was applied over 40 years ago, thus providing a rare opportunity to investigate the long-term efficiency of hydrophobic treatments. As well as assessing the condition of the treated area in situ by means of moisture analyses, lab-based accelerated salt weathering experiments are conducted to better understand the impact of silane-based treatments on sandstone durability. Moreover, the petrography and petrophysical properties of weathered sandstone (open porosity, capillary absorption, and vapour diffusion) before and after treatment are also characterised to provide a better understanding of how stone properties may influence the compatibility of the treatment. The field-based results show that the treated area has maintained a degree of hydrophobicity since its application over 40 years ago. Both field-based and lab-based analyses suggest that silane-based treatments can be used successfully in protecting sandstone when applied correctly, both in reducing the rate of decay and functioning over long periods of time. However, sandstone heterogeneity may mean that some individual stones are less compatible with the hydrophobic treatment tested than others. Further field-based analyses (including methods such as XRF and in situ vp) of the treated area is required in order to determine the state of conservation more accurately. These results highlight the complexity in selecting a suitable hydrophobic treatment, especially at built sites where the mineralogy and petrophysical properties of the stone may vary between blocks. However, such treatments may still be important to consider as many climates, including Scotland’s, are becoming progressively wetter, increasing the vulnerability of stone heritage to moisture ingress, accelerated decay, and eventual ruin.

Osman Parlak, Luca Menegon, Antony Morris et al.

The Mersin ophiolite of southern Turkey is a well-exposed, Late Cretaceous, Neo-Tethyan suprasubduction zone ophiolite. It is underlain by metamorphic sole rocks inferred to have formed at the top of a down-going plate during subduction. These have a well-developed foliation and lineation observable in the field (defined by the preferred orientations of hornblende and plagioclase crystals). Here we present the first magnetic fabric data reported from the Mersin ophiolite with such settings. Anisotropy of low field magnetic susceptibility ellipsoids in sampled amphibolites have clustered, NW-plunging minimum principal axes representing poles to a SE-dipping magnetic foliation that aligns with the macroscopic metamorphic foliation plane seen in the field. Maximum AMS principal axes define a SE-plunging magnetic lineation that is parallel to the macroscopic metamorphic lineation. Oblate magnetic fabrics at specimen-level and an overall triaxial fabric at localitylevel in these rocks are consistent with the development of the dominant metamorphic fabric by a combination of pure shear flattening and simple shearing during the formation and exhumation of the Mersin sole rocks. These observations are compatible with a recent tectonic model for the evolution of the ophiolite based on paleomagnetic data that invokes flattening and exhumation of the down-going slab in an incipient subduction zone during supra-subduction zone spreading.

S. S. Tsypukova, A. B. Perepelov, E. I. Demonterova et al.

The isotopic data showed that there are two stages distinguished in the Cenozoic history of the Darkhad depression volcanic activity, the Late Oligocene initial stage (~28.0–26.6 Ma) and the final Late Miocene – Early Pliocene stage (~5.8–4.2 Ma). It has been stated that the rocks of the initial stage are only represented by trachybasalts; however, among the final-stage basaltoids there are series of shield-volcano hawaite-basanite-phonotephrite rocks and compex trachybasaltic "valley" lava flows, the formation of which is the last stage in the territorial volcanic evolution. It has been shown that the initial-stage trachybasaltic andesites are characterized by their enrichment of TiO2, P2O5, Sr, Zn, Ga and low concentrations of Al2O3, MnO, CaO, Sc and HREE (La/Yb=27.2–30.2). Basaltoids of the final stage have a similar rare-element distribution and show an increase in the contents of TiO2, Al2O3, P2O5, LILE, HFSE, Th, U and in the degree of fractionation of REE (La/Yb from 12.2 to 20.9) towards the rocks alkalinity enhancement. Modeling of eclogite, pyroxenite and peridotite melting processes in the La/Yb – Sm/Yb system shows that trachybasaltic andesite melts could be formed at ~7–8 % melting of eclogitic matter or at ~10–11 % melting of Grt-containing pyroxenites, with trachybasalt formed at ~3 % melting of Grt-containing peridotites. The composition distribution of rocks in coordinates (Mg# – Fe/Mn) indicates that the parental magmas are the initial-stage trachybasaltic andesite magmas as well as the Early Pliocene trachybasaltic "valley" lava flows. Sr, Nd, Pb isotope characteristics of the Darkhad depression basaltoids show significant shift of isotopic ratios in time towards the relatively enriched mantle as compared with the depleted MORB mantle. The initial formation of trachybasaltic andesite melts occurred in the Late Oligicene at the pre-rift stage of the territory development involving metasomatized mantle matter, with the pyroxenite or eclogite component contained in the magma formation source. The origin of trachybasalt magmas of the final stage is associated with the processes of decompression melting of peridotites in a weakly metasomatized lithospheric mantle at the rift stage of the Darkhad structure development.

Pengfei Liu, Yongsheng Sun, Shuai Yuan et al.

The useful mineral in a high-iron manganese ore in Zambia is hematite and various manganese minerals, and the iron grade is 44.71%, the manganese grade is 17.86%. In order to make an appropriate sorting process, the chemical composition, mineral composition and embedded characteristics of the ore were studied by optical microscope, chemical analysis and X-ray diffraction. The research results show that the main iron mineral is hematite, the content is 61.53%; the main manganese minerals are anthracite, limonite and soft manganese, the content are 18.62%, 4.82% and 4.66%. Finally, pre-concentration-magnetization roasting-magnetic separation test was carried out on the ore, and the average TFe grade was 67.97%, the average recovery rate was 94.67%; the average Mn grade was 49.85%; the average recovery rate was 88.24%. The research results have certain guiding significance for the formulation of the ore sorting process, and also can provide a reference for similar ore.

Wei Yuan, Guangdi Liu, Xiaoxing Zhou et al.

The Chang 7 black shale in the Upper Triassic Yanchang Formation is the principal source rock of Mesozoic oil-bearing system in the southwest Ordos Basin, containing high abundances of organic matter and hydrocarbon potential. Our study discusses the role of lake-bottom hydrothermal activities in the enrichment of organic matter during the deposition of the Chang 7 black shale. A large number of basement faults developed in the interior and margin of the Ordos Basin, which provided channels for the upwelling of deep hydrothermal fluids. Moreover, the strong tectonic activities during the Chang 7 sedimentary period provided dynamic conditions for the activation of the faults and the upwelling of hydrothermal fluids. The occurrence of hydrothermal activities in the Chang 7 sedimentary period is proved by the evidences of mineralogy petrology, stable isotopes, major, and trace elements in the black shale. Abundant nutrients that were transported from the lake-bottom hydrothermal fluids into lake water promoted the lacustrine surface primary productivity, and then increased the supply of sedimentary organic matter. At the same time, the degradation of a large number of organic matters increased consumption of oxygen in the water column, resulting in the formation of bottom-water anoxic environments. The accumulation of organic matter in sediments was controlled by the lake-bottom hydrothermal activities by the means of increasing the lacustrine surface paleoproductivity and promoting the formation of anoxic environments.

Kristaly F., Sveda M., Sycheva A. et al.

Ti50Cu25Ni20Sn5 (at.%) powder was subjected to high-energy ball milling at room temperature and -78 °C. As a function of the milling time, evaluation of phases, morphology, and the refinement of grain size were investigated by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and laser-diffraction particle size analysis (PSA). The transformation of the crystalline structure into an amorphous structure and then the transformation into a nanocrystalline structure during further milling was detected. The stress-induced martensitic transformation occurred after 30 min milling time at both temperatures, the cubic Cu(Ni,Cu)Ti2 phase transformed into the orthogonal structure. The hardness value of powders after 150 min milling time increased from 506 to 780 HV0.01. The milling temperature did not significantly influence the amount of amorphous fraction (33-36 wt.%), however, the composition of amorphous content was more influenced by temperature. The interval of crystallite size was between 1.2 and 11.7 nm after 180 min of milling. The amount and the cell parameters of the Sncontaining phases were different for the two milling experiments because the diffusion coefficients of the Sn atom differed to a large extent.

Blanca Figuerola, Alyce M. Hancock, Narissa Bax et al.

Understanding the vulnerability of marine calcifiers to ocean acidification is a critical issue, especially in the Southern Ocean (SO), which is likely to be the one of the first, and most severely affected regions. Since the industrial revolution, ~30% of anthropogenic CO2 has been absorbed by the global oceans. Average surface seawater pH levels have already decreased by 0.1 and are projected to decline by ~0.3 by the year 2100. This process, known as ocean acidification (OA), is shallowing the saturation horizon, which is the depth below which calcium carbonate (CaCO3) dissolves, likely increasing the vulnerability of many resident marine calcifiers to dissolution. The negative impact of OA may be seen first in species depositing more soluble CaCO3 mineral phases such as aragonite and high-Mg calcite (HMC). Ocean warming could further exacerbate the effects of OA in these particular species. Here we combine a review and a quantitative meta-analysis to provide an overview of the current state of knowledge about skeletal mineralogy of major taxonomic groups of SO marine calcifiers and to make projections about how OA might affect a broad range of SO taxa. We consider a species' geographic range, skeletal mineralogy, biological traits, and potential strategies to overcome OA. The meta-analysis of studies investigating the effects of the OA on a range of biological responses such as shell state, development and growth rate illustrates that the response variation is largely dependent on mineralogical composition. Species-specific responses due to mineralogical composition indicate that taxa with calcitic, aragonitic, and HMC skeletons, could be at greater risk to expected future carbonate chemistry alterations, and low-Mg calcite (LMC) species could be mostly resilient to these changes. Environmental and biological control on the calcification process and/or Mg content in calcite, biological traits, and physiological processes are also expected to influence species-specific responses.

Jaime Antonio de Almeida, Pablo Grahl dos Santos

ABSTRACT Soils in the Depressão Central and Campanha Gaúcha in Rio Grande do Sul State, Brazil, developed from sedimentary rocks are mainly Alfisols (Luvissolos, Planossolos and Plintossolos) and Ultisols (Argissolos) with high textural contrast between A and/or E horizons and clayey B horizons. Red Ultisols dominate in well-drained areas in the summit. But many soils present redoximorphic features on the backslope and footslope, with mottled and/or nodules similar to plinthite due to the oscillating of the water table above the rock or poorly permeable saprolite. Identifying morphological features, mineralogical and chemical properties, and parent material differences are essential to identify the main processes responsible for their genesis. Knowledge of the relative distribution of different forms of iron in the soil is also of particular interest when interpreting pedogenesis. This study aimed to evaluated the main process responsible for the high textural contrast in soils developed from different sedimentary lithologies, and how the redoximorphic features observed in some soils may be related to genesis of plinthites and ferrolysis processes. The study area is located in the hydrographic basin of Rio Santa Maria, in the city of Rosário do Sul – RS, Brazil (30° 15’ 28” S and 54° 54’ 50” W), average altitude of 132 m and Cfa-type climate. Topolithosequences were defined based on soils developed from lithogies of Piramboia and Sanga-do-Cabral geological formations, by choosing soil profiles according to the source material, variations in relief, altitude and hydrological conditions. Morphological descriptions, particle size determinations, chemical analysis, mineralogy of the clay fraction by XRD analysis, determination of the main forms of iron, tests to identify plinthite were performed. Argiluviation, ferrolysis and plinthization were the most active processes identified in the genesis of most studied soils. The high textural contrast on these soils was not solely due to clay illuviation processes but also ferrolysis and lithological discontinuities in some soils, indicating polygenetic origin. Redoximorphic features in most soil revealed that iron segregation in most soils occurs like mottles and not plinthite, since they did not remain aggregated after the various wetting and drying cycles.

Olga Alexandrovna Doynikova

Xin Cai, Zilong Zhou, Kewei Liu et al.

The presence of water strongly affects rock properties and would be related to a series of geological disasters. To understand water saturation effects on the mechanical behavior of different rock types and interpret the underlying mechanisms of differences in water sensitivity, three kinds of rocks, namely sandstone, granite and marble, were selected for tests. Uniaxial compression experiments were conducted on specimens under oven-dried and water-saturated conditions. Acoustic emission (AE) techniques were also applied to monitor and record AE signals during tests. Experimental results reveal that water weakens the mechanical parameters of the three tested rocks, such as uniaxial compressive strength (UCS), elastic modulus and critical strain. The sandstone undergoes the greatest weakening with the addition of pore water, the mechanical properties of the granite exhibit relatively minor reductions, while the marble is the least affected by water saturation. The water-weakening degree of rock properties depends on the porosity as well as the mineralogy, especially the proportion of quartz and swelling clays. Moreover, after water saturation, the failure pattern of the sandstone and the granite tends to transform into the shear-dominant mode from the tensile one in dry state, probably due to frictional reduction. However, the water presence does not change the failure mode of the marble.

Bonnie Lewis, Janice M Lough, Merinda C Nash et al.

The presence of banding in the skeleton of coralline algae has been reported in many species, primarily from temperate and polar regions. Similar to tree rings, skeletal banding can provide information on growth rate, age, and longevity; as well as records of past environmental conditions and the coralline alga's growth responses to such changes. The aim of this study was to explore the presence and characterise the nature of banding in the tropical coralline alga Porolithon onkodes, an abundant and key reef-building species on the Great Barrier Reef (GBR) Australia, and the Indo-Pacific in general. To achieve this we employed various methods including X-ray diffraction (XRD) to determine seasonal mol% magnesium (Mg), mineralogy mapping to investigate changes in dominant mineral phases, scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS), and micro-computed tomography (micro-CT) scanning to examine changes in cell size and density banding, and UV light to examine reproductive (conceptacle) banding. Seasonal variation in the Mg content of the skeleton did occur and followed previously recorded variations with the highest mol% MgCO3 in summer and lowest in winter, confirming the positive relationship between seawater temperature and mol% MgCO3. Rows of conceptacles viewed under UV light provided easily distinguishable bands that could be used to measure vertical growth rate (1.4 mm year-1) and age of the organism. Micro-CT scanning showed obvious banding patterns in relation to skeletal density, and mineralogical mapping revealed patterns of banding created by changes in Mg content. Thus, we present new evidence for seasonal banding patterns in the tropical coralline alga P. onkodes. This banding in the P. onkodes skeleton can provide valuable information into the present and past life history of this important reef-building species, and is essential to assess and predict the response of these organisms to future climate and environmental changes.

Kirdyashkin Anatoly, Kirdyashkin Alexey, Gurov Vladimir

The results of experimental and theoretical modeling of free-convection flows in the melt of the plume conduit and in the mushroom-shaped head are presented. It was shown that the plumes with the mushroom-shaped heads can be responsible for the batholith formation. The main parameters of such plumes are estimated.

M. K. Pavićević, F. Bosch, G. Amthauer et al.

LOREX (LORandite EXperiment) addresses the determination of the solar (pp) neutrino flux during the last four million years by exploiting the reaction  205Tl+νe→ 205Pb+e- with an incomparably low-energy threshold of 50 keV for the capture of solar neutrinos. The ratio of 205Pb/205Tl atoms in the Tl-bearing mineral lorandite provides, if corrected for the cosmic-ray induced background, the product of the flux of solar neutrinos and their capture probability by 205Tl, averaged over the age of lorandite. To get the mean solar neutrino flux itself, four problems have to be addressed: (1) the geological age of lorandite, (2) the amount of background cosmic-ray-induced 205Pb atoms which strongly depends on the erosion rate of the lorandite-bearing rocks, (3) the capture probability of solar neutrinos by 205Tl and (4) the extraction of lorandite and the appropriate technique to “count” the small number of 205Pb atoms in relation to the number of 205Tl atoms. This paper summarizes the status of items 1 (age) and 3 (neutrino capture probability) and presents in detail the progress achieved most recently concerning the items 2 (background/erosion) and 4 (“counting” of 205Pb atoms in lorandite).

İbrahim S.Al, Nazar M. S. NUMAN

Su kaynaklarındaki kıtlık, nüfusu, artan ihtiyaçlarını karşılamak için kendi kuıyularını açmaya ve yer altı suyunu çekmeye zorlamıştır. Çalışma alanı, Irak’ta buğday, arpa, mercimek ve sebze gibi ürünlerin ekildiği ve büyükbaş hayvan yetiştiriciliğinin yapıldığı başlıca zirai alanlardan biridir. Yer altı suyu örneklerinin kimyasal özelliklerinin incelenmesinin önemi, litolojik birimlerin ve suyun karşılıklı etkileşiminin ve, doğal çözülme süreç­leri yüzünden artan doğal çözünmüş tuz konsantrasyonlarının bilinmesi açısından önemlidir. Telkaif bölgesin­den alınan yer altı suyu örneklerinin kimyasal özellikleri, ev içi ve zirai kullanım için özelliklerinin belirlenmesi amacıyla 14 örnekte incelenmiştir. Yeraltı suyu örneklerinin elektrik iletkenliği (Ec), pH, toplam çözünmüş katilar (TDS), Na+, K+, Ca+2, Mg+2, HC03_1, S04-2, N03_1,CM konsantrasyonları ve toplam sertlik (TH) gibi fiziksel ve kimyasal özellikleri belirlenmiştir. Piper diyagramı kullanılarak, yeraltı sularının uygunluğu, türü ve jeokimyasal gelişmelerinin gösterilmesi için grafik olarak hidrokimyasal parametreleri de analiz edilmiştir. Yer altı suyunun sulama için uygunluğunun gösterilmesi için Richard (1954) ve Wilcox (1955) sınıflamaları da kullanılmıştır. Çalışma alanına yayılmış olan kuyulardan Al-Fatha, Injana litolojik birimleri ve Kuvaterner akiferler tanımlanmış ve incelenmiştir. Bölgedeki yer altı suları yağmur sularından ve suyu toplama havzalarına ulaştıran vadilerden beslenmektedir, inceleme alanının yer altı suyu kimyası yeraltı suyu örneklerinin çoğunun CaHC03 and CaS04 türünde sular olduğunu göstermekte; örneklerde toplam sertlik (TH) ve toplam çözünmüş katilar (TDS) yüksek olup bunlar genellikle düşük alkali değerlerine sahiptir

P. Voudouris, M. Tarkian, K. Arikas

V. Breskovska, M. Tarkian